136 results on '"Njiokou, F."'
Search Results
2. Urban malaria in sub-Saharan Africa: dynamic of the vectorial system and the entomological inoculation rate
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Doumbe-Belisse, P., Kopya, E., Ngadjeu, C. S., Sonhafouo-Chiana, N., Talipouo, A., Djamouko-Djonkam, L., Awono-Ambene, H. P., Wondji, C. S., Njiokou, F., and Antonio-Nkondjio, C.
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- 2021
- Full Text
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3. Trypanosoma vivax, T. congolense 'forest type' and T. simiae: prevalence in domestic animals of sleeping sickness foci of Cameroon
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Nimpaye H., Njiokou F., Njine T., Njitchouang G.R., Cuny G., Herder S., Asonganyi T., and Simo G.
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T. vivax ,T. congolense “forest type” ,T. simiae ,PCR ,pig ,goat ,sheep ,dog ,Infectious and parasitic diseases ,RC109-216 - Abstract
In order to better understand the epidemiology of Human and Animal trypanosomiasis that occur together in sleeping sickness foci, a study of prevalences of animal parasites (Trypanosoma vivax, T. congolense “forest type”, and T. simiae) infections was conducted on domestic animals to complete the previous work carried on T. brucei gambiense prevalence using the same animal sample. 875 domestic animals, including 307 pigs, 264 goats, 267 sheep and 37 dogs were sampled in the sleeping sickness foci of Bipindi, Campo, Doumé and Fontem in Cameroon. The polymerase chain reaction (PCR) based method was used to identify these trypanosome species. A total of 237 (27.08%) domestic animals were infected by at least one trypanosome species. The prevalence of T. vivax, T. congolense “forest type” and T. simiae were 20.91%, 11.42% and 0.34% respectively. The prevalences of T. vivax and T. congolense “forest type” differed significantly between the animal species and between the foci (p < 0.0001); however, these two trypanosomes were found in all animal species as well as in all the foci subjected to the study. The high prevalences of T. vivax and T. congolense “forest type” in Bipindi and Fontem-Center indicate their intense transmission in these foci.
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- 2011
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4. Domestic animals as potential reservoir hosts of Trypanosoma brucei gambiense in sleeping sickness foci in Cameroon
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Njiokou F., Nimpaye H., Simo G., Njitchouang G.R., Asonganyi T., Cuny G., and Herder S.
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HTA ,reservoir ,domestic animal ,Trypanosoma brucei s.l. ,T. b. gambiense group 1 ,PCR ,CATT ,QBC ,sheep ,goats ,pigs ,dogs ,south-Cameroon ,Infectious and parasitic diseases ,RC109-216 - Abstract
An explanation of the endemic nature and/or the resurgence of Human African Trypanosomiasis (HAT) in the historic foci in West and Central Africa may be the existence of an animal reservoir. In some HAT foci, pigs were found infected by Trypanosoma brucei gambiense but the implication of the other domestic animals was not quite evaluated. This study aims to determine the prevalence of T. b. gambiense in domestic animal species (goat, sheep, pig and dog) commonly found in the four active HAT foci in Cameroon (Bipindi, Fontem, Campo and Doumé). Blood samples were collected from 307 pigs, 264 goats, 267 sheep and 37 dogs and used for parasitological (QBC), immunological (LiTat 1.3 CATT) and molecular (PCR) analyses. QBC detected trypanosomes in 3.88 % domestic animals while 22.7 % were sero-positive with LiTat 1.3 CATT tests. Of the 875 animals analysed, 174 (19.88 %) harboured T. brucei s.l. DNA, found in each of the four types of animal and in the four localities. The infection rate significantly differed among the animal species (p < 0.0001) and localities (p < 0.0001). The PCR also revealed T. b. gambiense group 1 DNA in 27 (3.08 %) domestic animals. The specific infection rates were as follows: sheep (6.74 %), goats (3.08 %), pigs (0.32 %) and dogs (0 %). T. b. gambiense was found in 8 (3.92 %) animals from Bipindi, 15 (4.83 %) from Campo, 4 (2.59 %) from Fontem-Center and none from Doumé. The infection rates significantly differed between the localities, and correlated with the intensity of HAT transmission in the foci.
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- 2010
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5. Identification of trypanosomes in wild animals from Southern Cameroon using the polymerase chain reaction (PCR)
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Herder S., Simo G., Nkinin S., and Njiokou F.
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sleeping sickness ,wild animal ,reservoir ,PCR ,T. b. gambiense ,forest belt ,Cameroon ,Infectious and parasitic diseases ,RC109-216 - Abstract
One possible explanation of the maintenance of many historical foci of sleeping sickness in Central Africa could be the existence of a wild animal reservoir. In this study, PCR was used to detect the different trypanosome species present in wild animal captured by hunters in the southern forest belt of Cameroon (Bipindi). Trypanosomes were also detected by a parasitological method (Quantitative buffy coat : QBC). Parasite could not be isolated in culture medium (Kit for in vitro isolation : KIVI). Specific primers of T. brucei s.l., T. congolense forest type, T. congolense savannah type, T. vivax, T. simiae and T. b. gambiense group 1 were used to identify parasites in the blood of 164 animals belonging to 24 different species including ungulates, rodents, pangolins, carnivores, reptiles and primates. Of the 24 studied species, eight were carrying T. b. gambiense group 1. Those parasites pathogenic to man were found in monkeys (Cercocebus torquatus and Cercopithecus nictitans), in ungulates (Cephalophus dorsalis and C. monticola), in carnivores (Nandinia binotata and Genetta servalina) and in rodents (Cricetomys gambianus and Atherurus africanus). 13 species (54 %) were carrying T. brucei s.l. identified as non-gambiense group 1.
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- 2002
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- View/download PDF
6. Prevalence of symbionts and trypanosome infections in tsetse flies of two villages of the 'Faro and Deo' division of the Adamawa region of Cameroon
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Kame-Ngasse, G. I., Njiokou, F., Melachio-Tanekou, T. T., Farikou, O., Simo, G., Geiger, Anne, Abd-Alla A.M.M (ed.), Tsiamis G. (ed.), and Boucias D.G. (ed.)
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"Faro and Deo" division ,Trypanosoma spp ,fungi ,parasitic diseases ,Tsetse flies ,Cameroon ,Symbionts ,Tripartite interactions ,Animal African trypanosomiasis - Abstract
Background: Tsetse flies are vectors of human and animal African trypanosomiasis. In spite of many decades of chemotherapy and vector control, the disease has not been eradicated. Other methods like the transformation of tsetse fly symbionts to render the fly refractory to trypanosome infection are being evaluated. The aim of the present study was to evaluate the association between trypanosome infections and the presence of symbionts in these tsetse species. Tsetse flies were trapped in two villages of the "Faro and Deo" Division of the Adamawa region of Cameroon. In the field, tsetse fly species were identified and their infection by trypanosomes was checked by microscopy. In the laboratory, DNA was extracted from their midguts and the presence of symbionts (Sodalis glossinidius and Wolbachia sp.) and trypanosomes was checked by PCR. Symbionts/trypanosomes association tests were performed. Results: Three tsetse fly species including Glossina tachinoides (90.1%), Glossina morsitans submorsitans (9.4%) and Glossina fuscipes fuscipes (0.5%) were caught. In all the population we obtained an occurrence rate of 37.2% for Sodalis glossinidius and 67.6% for Wolbachia irrespective to tsetse flies species. S. glossinidius and Wolbachia sp. occurrence rates were respectively 37 and 68% for G. tachinoides and 28.6 and 59.5% for G. m. submorsitans. Between Golde Bourle and Mayo Dagoum significant differences were observed in the prevalence of symbionts. Prevalence of trypanosomes were 34.8% for Glossina tachinoides and 40.5% for Glossina morsitans submorsitans. In G. tachinoides, the trypanosome infection rates were 11, 2.6 and 13.7%, respectively, for T. brucei s.l., T. congolense forest type and T. congolense savannah type. In G. m. submorsitans, these infection rates were 16.7, 9.5 and, 2.4% respectively, for T. brucei s.l., T. congolense forest type and T. congolense savannah type. Conclusions: The rate of tsetse fly infection by trypanosomes was low compared to those obtained in HAT foci of south Cameroon, and this rate was not statistically linked to the rate of symbiont occurrence. This study allowed to show for the first time the presence of Wolbachia sp. in the tsetse fly sub-species Glossina morsitans submorsitans and Glossina tachinoides.
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- 2018
7. Special issue on enhancing vector refractoriness to trypanosome infection-foreword
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Kariithi, H. M., Meki, I. K., Schneider, D. I., De Vooght, L., Khamis, F. M., Geiger, Anne, Demirbas-Uzel, G., Vlak, J. M., Ince, I. A., Kelm, S., Njiokou, F., Wamwiri, F. N., Malele, II, Weiss, B. L., Abd-Alla, A. M. M., Abd-Alla, A.M.M (ed.), Tsiamis, G. (ed.), and Boucias, D.G. (ed.)
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Glossina ,Paratransgenesis ,Microbiota ,Trypanosoma-refractoriness ,sterile insect technique ,Hytrosaviridae ,Vector competence - Abstract
With the absence of effective prophylactic vaccines and drugs against African trypanosomosis, control of this group of zoonotic neglected tropical diseases depends the control of the tsetse fly vector. When applied in an area-wide insect pest management approach, the sterile insect technique (SIT) is effective in eliminating single tsetse species from isolated populations. The need to enhance the effectiveness of SIT led to the concept of investigating tsetse-trypanosome interactions by a consortium of researchers in a five-year (2013-2018) Coordinated Research Project (CRP) organized by the Joint Division of FAO/IAEA. The goal of this CRP was to elucidate tsetse-symbiome-pathogen molecular interactions to improve SIT and SIT-compatible interventions for trypanosomoses control by enhancing vector refractoriness. This would allow extension of SIT into areas with potential disease transmission. This paper highlights the CRP's major achievements and discusses the science-based perspectives for successful mitigation or eradication of African trypanosomosis.
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- 2018
8. Tracking zoonotic pathogens using bloodsucking flies as 'flying syringes'
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Bitome-Essono, P. Y., Ollomo, B., Arnathau, C., Durand, P., Mokoudoum, N. D., Yacka-Mouele, L., Okouga, A. P., Boundenga, L., Mve-Ondo, B., Obame-Nkoghe, J., Mbehang-Nguema, P., Njiokou, F., Makanga, B., Wattier, R., Ayala, Diego, Ayala, F. J., Prugnolle, F., and Paupy, Christophe
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fungi - Abstract
About 60% of emerging infectious diseases in humans are of zoonotic origin. Their increasing number requires the development of new methods for early detection and monitoring of infectious agents in wildlife. Here, we investigated whether blood meals from hematophagous flies could be used to identify the infectious agents circulating in wild vertebrates. To this aim, 1230 blood-engorged flies were caught in the forests of Gabon. Identified blood meals (30%) were from 20 vertebrate species including mammals, birds and reptiles. Among them, 9% were infected by different extant malaria parasites among which some belonged to known parasite species, others to new parasite species or to parasite lineages for which only the vector was known. This study demonstrates that using hematophagous flies as 'flying syringes' constitutes an interesting approach to investigate blood-borne pathogen diversity in wild vertebrates and could be used as an early detection tool of zoonotic pathogens.
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- 2017
9. Phylogeography of the heavily poached African common pangolin (Pholidota, Manis tricuspis) reveals six cryptic lineages as traceable signatures of Pleistocene diversification
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Gaubert, Philippe, Njiokou, F., Ngua, G., Afiademanyo, K., Dufour, S., Malekani, J., Bi, S. G., Tougard, C., Olayemi, A., Danquah, E., Djagoun, C. A, M. S., Kaleme, P., Mololo, C. N., Stanley, W., Luo, S. J., and Antunes, A.
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trade monitoring ,evolutionary significant units ,tropical Africa ,molecular tracing ,pangolins ,Pleistocene diversification - Abstract
Knowledge on faunal diversification in African rainforests remains scarce. We used phylogeography to assess (i) the role of Pleistocene climatic oscillations in the diversification of the African common pangolin (Manis tricuspis) and (ii) the utility of our multilocus approach for taxonomic delineation and trade tracing of this heavily poached species. We sequenced 101 individuals for two mitochondrial DNA (mtDNA), two nuclear DNA and one Y-borne gene fragments (totalizing 2602 bp). We used a time-calibrated, Bayesian inference phylogenetic framework and conducted character-based, genetic and phylogenetic delineation of species hypotheses within African common pangolins. We identified six geographic lineages partitioned into western Africa, Ghana, the Dahomey Gap, western central Africa, Gabon and central Africa, all diverging during the Middle to Late Pleistocene. MtDNA (cytochrome b + control region) was the sole locus to provide diagnostic characters for each of the six lineages. Tree-based Bayesian delimitation methods using single-and multilocus approaches gave high support for 'species' level recognition of the six African common pangolin lineages. Although the diversification of African common pangolins occurred during Pleistocene cyclical glaciations, causative correlation with traditional rainforest refugia and riverine barriers in Africa was not straightforward. We conclude on the existence of six cryptic lineages within African common pangolins, which might be of major relevance for future conservation strategies. The high discriminative power of the mtDNA markers used in this study should allow an efficient molecular tracing of the regional origin of African common pangolin seizures.
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- 2016
10. Bovine trypanosomiasis in tsetse-free pastoral zone of the Far-North region, Cameroon
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Suh, PF, primary, Njiokou, F, additional, Mamoudou, A, additional, Ahmadou, TM, additional, Mouhaman, A, additional, and Garabed, R, additional
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- 2017
- Full Text
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11. Identification and genetic characterization of Trypanosoma congolense in domestic animals of Fontem in the South-West region of Cameroon
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Simo, G., Sobgwi, P. F., Njitchouang, G. R., Njiokou, F., Kuiate, J. R., Cuny, Gérard, and Asonganyi, T.
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trypanosomiasis ,Trypanosoma congolense ,Genotypes ,Animal African ,Microsatellite - Abstract
To understand the circulation and the spread of Torpanosoma congolense genotypes in animals of Fontem in the southwest region of Cameroon, T. congolense forest and T. congolense savannah were investigated in 397 domestic animals in eight villages. Out of the 397 domestic animals, 86 (21.7%) were found infected by trypanosomes, using the capillary tube centrifugation test. The PCR with specific primers identified 163 (41.1%) and 81(20.4%) animals infected by T. congolense forest and T. congolense savannah, respectively; showing for the first time the circulation of T. congolense savannah in the Fontem region. No infection with T. congolense savannah was found in pigs whereas goats and sheep were infected by T. congolense forest and/or T. congolense savannah. The prevalence of trypanosomes varied significantly amongst villages and animal species. The genotyping of T. congolense forest positive samples using microsatellites markers showed that multiple genotypes occurred in 27.2% (44/163) of animals sampled, whereas single genotypes were found in 73.8% (119/163) of samples. Some alleles were found in all animal species as well as in all villages and were responsible for major genotypes, whereas others (rare alleles) were identified only in some animals of few villages. These rare alleles were characteristic of specific genotypes, assimilated to minor genotypes which can be spread in the region through tsetse flies. The microsatellite markers show a low genetic variability and an absence of sub-structuration within T. congolense forest. The analysis of the microsatellite data revealed a predominant clonal reproduction within T. congolense forest. Pigs were the animal species with the highest number of different genotypes of T. congolense forest. They seem to play an important epidemiological role in the propagation and spread of different genotypes of T. congolense.
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- 2013
12. Single nucleotide polymorphisms in beta-tubulin selected in Onchocerca volvulus following repeated ivermectin treatment : possible indication of resistance selection
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Nana-Djeunga, H., Bourguinat, C., Pion, Sébastien, Kamgno, J., Gardon, Jacques, Njiokou, F., Boussinesq, Michel, and Prichard, R. K.
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Onchocerca volvulus ,Ivermectin ,parasitic diseases ,beta-tubulin ,SNP ,Genetic selection ,Resistance marker - Abstract
The control of onchocerciasis or river blindness by mass treatment of the population with ivermectin (IVM) has been a great success until now, so that in certain foci its elimination has become feasible. However, after more than 20 years of repeated IVM mass treatment, the disease still persists in many endemic countries. Sub-optimal responses and genetic changes have been reported in Onchocerca volvulus populations under high IVM pressure but more work is needed to determine whether resistance is developing. The situation needs to be urgently clarified to preserve the achievements of onchocerciasis control programs. In this study, O. volvulus adult worms were collected from the same individuals, before IVM exposure and following three years of annual or three-monthly treatments at 150 mu g/kg or 800 mu g/kg. Four single nucleotide polymorphisms (SNPs) occurring in the beta-tubulin gene of these parasites were investigated. We found changes in genotype frequencies in O. volvulus beta-tubulin gene associated with IVM treatments. The SNP at position 1545 (A/G) showed a significant increase in frequency of the less common nucleotide in the female worms following treatment. After 13 three-monthly treatments, female worm homozygotes with the less common genotype, prior to treatment, increased in frequency. The selected homozygotes, as well as heterozygotes, appeared to be less fertile (without or with very few embryonic stages in their uteri) than the wild-type homozygotes. These results provide additional evidence for genetic selection and strengthen the warning that selection for IVM resistance may be occurring in some O. volvulus populations.
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- 2012
13. Colloque bilan des projets financés dans le cadre du programme SEST 2006
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Boussinesq, Michel, Bourguinat, C., Cabaret, J., Charvet, C., Kamgno, J., Nana-Djeunga, H., Njiokou, F., Pion, Sébastien, Prichard, R.K., and Wanji, S.
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TRAITEMENT MEDICAL ,SENSIBILITE RESISTANCE ,IVERMECTINE ,ONCHOCERCOSE ,PROGRAMME DE RECHERCHE ,PHENOTYPE ,BIOLOGIE DU PARASITE ,ANALYSE STATISTIQUE - Published
- 2011
14. Tripartite interactions between tsetse flies, Sodalis glossinidius and trypanosomes-An epidemiological approach in two historical human African Trypanosomiasis foci in Cameroon
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Farikou, O., Njiokou, F., Mbida, J. A. M., Njitchouang, G. R., Djeunga, H. N., Asonganyi, T., Simarro, P. P., Cuny, Gérard, and Geiger, Anne
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Nagana ,Glossina ,fungi ,Human African trypanosomiasis ,Trypanosome species ,Cameroon ,Historical foci ,Sodalis glossinidius ,Vector competence - Abstract
Epidemiological surveys were conducted in two historical human African trypanosomiasis foci in South Cameroon, Bipindi and Campo. In each focus, three sampling areas were defined. In Bipindi, only Glossina palpalis was identified, whereas four species were identified in Campo, G. palpalis being highly predominant (93%). For further analyses, 75 flies were randomly chosen among the flies trapped in each of the six villages. Large and statistically significant differences were recorded between both (I) the prevalence of Sodalis glossinidius (tsetse symbiont) and the prevalence of trypanosome infection of the major fly species G. p. palpalis and (2) the respective prevalence of symbiont and infection between the two foci. Despite these differences, the rate of infected flies harbouring the symbiont was very similar (75%) in both foci, suggesting that symbionts favour fly infection by trypanosomes. This hypothesis was statistically tested and assessed, showing that S. glossinidius is potentially an efficient target for controlling tsetse fly vectorial competence and consequently sleeping sickness.
- Published
- 2010
15. Diversity and spatial distribution of vectors and hosts of T. brucei gambiense in forest zones of, Southern Cameroon : epidemiological implications
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Massussi, J. A., Mbida, J. A. M., Djieto-Lordon, C., Njiokou, F., Laveissiere, Claude, and van der Ploeg, J. D.
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Reservoir host ,Human African trypanosomiasis ,Habitat types ,distribution ,G. palpalis palpalis ,Vector distribution ,Bipindi - Abstract
Host and vector distribution of Trypanosoma brucei gambiense was studied in relation to habitat types and seasons. Six (19.35%) of the 31 mammal species recorded in Bipindi were reservoir hosts. Cercopithecus nictitans was confined to the undisturbed forest and the low intensive shifting cultivation zones, while Cephalophus monticola, Cephalophus dorsalis. Cricetomys gambianus, Atherurus africanus and Nandinia binotata occurred in all the habitat types. As for vectors of human African trypanosomiasis (HAT), Glossina palpalis palpalis, was the most abundant (99.13%) among tsetse fly species. It occurs in all biotopes with its highest density recorded in the village-adjacent forest. The village-adjacent forest is therefore the most risky transmission zone for HAT mainly during the short rainy season when G. palpalis palpails density is highest (2.91); while, the high and low intensive shifting cultivation zones are the most important contact zones between humans, G. palpalis palpalis and wild mammals in all seasons.
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- 2010
16. Phylogenetic analysis reveals the presence of the Trypanosoma cruzi clade in African terrestrial mammals
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Hamilton, P. B., Adams, E. R., Njiokou, F., Gibson, W. C., Cuny, Gérard, and Herder, Stéphane
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Trypanosoma ,Evolution ,GAPDH ,parasitic diseases ,Ribosomal RNA gene ,Molecular dating ,Biodiversity ,FFLB ,Barcoding - Abstract
Despite the impact of some trypanosome species on human and livestock health, the full diversity of trypanosomes in Africa is poorly understood. A recent study examined the prevalence of trypanosomes among a wide variety of wild vertebrates in Cameroon using species-specific PCR tests, but six trypanosome isolates remained Unidentified. Here they have been re-examined using fluorescent fragment length barcoding (FFLB) and phylogenetic analysis of glycosomal glyceraldehyde phosphate dehydrogenase gGAPDH and 18S ribosomal RNA (rDNA) genes. Isolates from a monkey (Cercopithecus nictitans) and a palm civet (Nandinia binotata) belonged to the Tryponosoma cruzi clade, known previously only from New World and Australian terrestrial mammals, and bats from Africa, Europe and South America. Of the Four other isolates, three from antelope were identified as Tryponosoma theileri, and one from a crocodile as T grayi. This is the first report of trypanosomes of the T cruzi clade in African terrestrial mammals and expands the clade's known global distribution in terrestrial mammals. Previously it has been hypothesized that African and New World trypanosomes diverged after continental separation, dating the divergence to around 100 million years ago. The new evidence instead suggests that intercontinental transfer occurred well after this, possibly via bats or rodents, allowing these trypanosomes to establish and evolve in African terrestrial mammals, and questioning the validity of calibrating trypanosome molecular trees using continental separation. Crown Copyright (c) 2008 Published by Elsevier Ltd. All rights reserved.
- Published
- 2009
17. Distributions écologiques et spatiales d'Aedes aegypti et d'Aedes albopictus dans l'environnement urbain au Cameroun (Afrique centrale)
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Kamgang, Basile, Youta Happi, J., Njiokou, F., Simard, Frédéric, Hervé, Jean-Pierre, and Paupy, Christophe
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VECTEUR ,BIOGEOGRAPHIE ,ARBOVIROSE ,ECOLOGIE ,MILIEU URBAIN ,GITE LARVAIRE ,HABITAT URBAIN - Published
- 2009
18. Distribution et écologie des vecteurs de la trypanosomose humaine africaine de type savanicole en zone de forêt dégradée au sud Cameroun : cas du foyer de Doumé
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Mbida Mbida, J.A., Mimpfoundi, R., Njiokou, F., Manga, L., and Laveissière, Claude
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PIEGEAGE ,LUTTE INTEGREE ,VECTEUR ,FOYER EPIDEMIOLOGIQUE ,TRYPANOSOMIASE HUMAINE ,DIVERSITE SPECIFIQUE ,REPARTITION GEOGRAPHIQUE ,ZONE HUMIDE ,ECOLOGIE ,CONTACT FORET SAVANE - Published
- 2009
19. Maladie du sommeil : le renouveau
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Grébaut, Pascal, Bodo, J.M., Assona, A., Foumane Ngane, V., Njiokou, F., Ollivier, G., Soula, G., and Laveissière, Claude
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EPIDEMIOLOGIE ,FORET ,CHASSE ,DEPISTAGE ,TRANSMISSION ,VECTEUR ,ENQUETE ,TRYPANOSOMIASE HUMAINE ,FACTEUR DE RISQUE ,CONTACT HOMME VECTEUR ,TRYPANOSOMIASE HUMAINE AFRICAINE ,PARASITE ,FOYER ENDEMIQUE - Published
- 2001
20. Aspects épidémiologiques d'un foyer de maladie du sommeil mal connu : le foyer de Bipindi au Cameroun
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Grébaut, Pascal, Wang, S., Bodo, J.M., Ebo'o Eyenga, V., Binzouli, J.J., Ndong Ngoé, C., Nomo, E., Nkinin, S., Njiokou, F., Ollivier, G., Foumane, V., and Bureau, P.
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EMERGENCE ,EPIDEMIOLOGIE ,MIGRATION ,TRANSMISSION ,ETUDE REGIONALE ,TRYPANOSOMIASE HUMAINE ,SURVEILLANCE EPIDEMIOLOGIQUE ,MALADIE DU SOMMEIL ,HISTOIRE ,VILLAGE ,ENDEMIE ,FOYER ENDEMIQUE - Abstract
Pour la première fois, une équipe de prospection médicale a effectué une campagne de dépistage dans le foyer de trypanosomiase humaine de Bipindi au Cameroun, plus connu sous le nom de "foyer de Lolodorf". Si l'histoire nous apporte des éléments qui pourraient expliquer l'installation de la trypanosomiase humaine dans la région depuis la fin du siècle dernier, au travers de plusieurs vagues de migrations, elle nous apprend aussi que ce foyer n'a jamais connu de flambée épidémique. La découverte de 44 malades lors de deux prospections médicales réalisées fin 1998 et début 1999, pose le problème du maintien à bas bruit de l'endémie et des conditions de son émergence. (Résumé d'auteur)
- Published
- 2000
21. Cinétique de Trypanosoma brucei gambiense en culture sur milieux KIVI et Cunningham
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Kohagne, T.L., Nkinin, S.W., Grébaut, Pascal, Njiokou, F., and Penchenier, Laurent
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DENSITE ,CULTURE IN VITRO ,ISOLEMENT ,CROISSANCE ,KIVI.KIT FOR IN VITRO ISOLATION ,TRYPANOSOMIASE HUMAINE ,ETUDE EXPERIMENTALE ,PARASITE ,TRYPANOSOMIASE ANIMALE ,MILIEU DE CUNNINGHAM - Abstract
Dans le but d'optimiser l'utilisation de la méthode d'isolement "in vitro" des trypanosomes sanguicoles par le "kit for in vitro isolation" (KIVI), une étude a été réalisée sur 14 KIVI positifs obtenus à partir de malades du foyer de Campo au Cameroun. Une estimation de la densité parasitaire par comptage régulier a été effectuée du jour où les KIVI ont été déclarés positifs à celui où les trypanosomes ont complètement disparu du milieu. Après application des analyses statistiques, nous avons pu observer que les trypanosomes se multiplient activement dans le KIVI et atteignent leur pic optimal de croissance après 26 jours plus or minus 1 (risque 5%) en moyenne. Il existe une corrélation linéaire significative (p=0.03) entre la quantité de parasites présents dans le KIVI le jour de son ensemencement et le jour où les parasites dans ce KIVI atteignent leur pic optimal de croissance. Ainsi, le nombre maximal de jours mis par les trypanosomes pour atteinde le pic optimal de croissance est significativement d'autant plus bas que la densité parasitaire de départ est élevée. Après ensemencement, un KIVI a besoin d'être surveillé pendant 40 jours avant d'être déclaré négatif. La durée pendant laquelle un KIVI positif conserve les trypanosomes dépasse 50 jours mais elle est variable selon les souches. La recherhce nécessite de grandes quantités de trypanosomes que le KIVI ne peut fournir. Il faut donc passer par une culture de masse sur le milieu de Cunnigham. Les repiquages effectués sur ce milieu avant J22 aboutissent à des densités élevées de trypanosomes (1200 x 10(exp 6) parasites/ml). Tous les repiquages effectués après J34 donnent des densités parasitaires faibles (200x10exp6 parasites/ml), insuffisantes pour la recherche. Il ressort de cette étude que le KIVI est un outil très utile pour l'isolement des trypanosomes sur le terrain... (D'après résumé d'auteur)
- Published
- 2000
22. Le foyer de trypanosomose humaine de Campo (Cameroun) : historique et situation de l'endémie en 1998
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Penchenier, Laurent, Grébaut, Pascal, Ebo'o Eyenga, V., Bodo, J.M., Njiokou, F., Binzouli, J.J., Simarro, P., Soula, G., Herder, Stéphane, and Laveissière, Claude
- Subjects
PARASITOLOGIE ,TEST ,EVALUATION ,DEPISTAGE ,ETUDE REGIONALE ,TRYPANOSOMIASE HUMAINE ,CATT.CARD AGGLUTINATION TEST TRYPANOSOMIASIS ,ENDEMIE ,SEROLOGIE ,FOYER ENDEMIQUE ,PREVALENCE ,PROSPECTION ,ANIMAL RESERVOIR - Abstract
Pour la première fois depuis 13 ans, le foyer de trypanosomose humaine de Campo, à cheval sur la frontière entre Cameroun et Guinée équatoriales, a été prospecté. Le depistage s'est fait en juin 1998, simultanément des deux côtés de la frontière. L'étude de ce foyer connu depuis près d'un siècle, toujours actif, est particulièrement intéressante car il n'a jamais fait l'objet de flambée épidémique : le trypanosome y persiste à bas bruit. Selon les dépistages passifs signalés, la prévalence estimée se situe entre 0,2 et 0,5%. Dans la partie camerounaise du foyer, 5255 personnes ont été examinées (90,6% de la population rencensée) et 405 en Guinée équatoriale (71,3% de la population recensée). Le dépistage sérologique a été effectué avec le CATT 1.3 qui est le CATT classiquement utilisé lors des prospections, et avec le CATT latex. La recherche de trypanosomes a été faite par examen du suc ganglionnaire en cas de présence d'adénopathies, et, dans le sang, par Quantitative Buffy Coat (QBC) par la mini colonne échangeuse d'anions (mAEC), ainsi que par la mise en culture in vitro du sang des suspects sériologiques. Alors que 16 malades ont été dépistés au Cameroun, aucun ne l'a été en Guinée équatoriale. Les résultats obtenus montrent que le foyer de Campo est un foyer strictement camerounais, centré sur le village d'Ipono avec une faible prévalence (0,3%). La persistance de l'endémie est liée à la présence à Ipono d'un réservoir porcin de #Trypanosoma brucei gambiense$ qui a été mise en évidence lors de cette étude. Les données épidémiologiques recueillies permettent d'envisager une action concertée, médicale et entomologique, limitée au seul village d'Ipono, afin d'éradiquer l'affection. Lors de cette prospection, le CATT latex s'est avéré plus intéressant que le CATT 1.3 puisqu'à résultat égal, il diminue d'au moins 8 fois la charge de travail pour un coût moindre. Ce point reste à confirmer dans un foyer hyperendémique. (Résumé d'auteur)
- Published
- 1999
23. Le foyer de trypanosomiase humaine de Campo (Cameroun) en 1998 : aspects épidémiologiques, état de l'endémie et comparaison des CATT 1.3 et CATT Latex dans le dépistage de masse
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Penchenier, Laurent, Grébaut, Pascal, Bodo, J.M., Ebo'o Eyenga, V., Njiokou, F., Simo, S., Nkinin, S.W., Ndong Asumu, P., Simarro, P., Herder, Stéphane, and Soula, G.
- Subjects
EPIDEMIOLOGIE ,DIAGNOSTIC ,TEST ,TECHNIQUE ,DEPISTAGE ,EVALUATION ,ETUDE COMPARATIVE ,TRYPANOSOMIASE HUMAINE ,ENDEMIE ,SEROLOGIE ,FOYER ENDEMIQUE ,PORC ,ANIMAL RESERVOIR - Abstract
Pour la première fois depuis 13 ans, le foyer de trypanosomiase humaine de Campo, à cheval sur la frontière entre Cameroun et Guinée Equatoriale, a été prospecté. Le dépistage s'est fait conjointement des 2 côtés de la frontière. Nous avons profité de cette occasion pour comparer le Card Agglutination Test for Trypanosomiasis (CATT) de type antigénique LiTat 1.3 classiquement utilisé dans les prospections, au CATT Latex, qui consiste en une suspension lyophilisée de latex couvert d'antigènes de surface variables de formes sanguicoles de #Trypanosoma brucei gambiense$ de types antigéniques LiTat 1.3, 1.5, 1.6. Nous avons également recherché l'existence de réactions sérologiques croisées entre trypanosomes, d'une part, et #plasmodium$ et microfilaires, d'autre part. Les résultats obtenus montrent que le foyer de Campo est un foyer Camerounais centré sur le village d'Ipono et de faible prévalence (0,3%). La persistance de l'endémie pourrait être liée à la présence d'un réservoir porcin à Ipono. Le CATT Latex a présenté, à la dilution de 1/4, une spécificité nettement supérieure (76,5%) à celle du CATT 1.3 au seuil de 1+ (42,8%). Au seuil de 1/8ème la spécificité du CATT Latex était de 93,8%. Pour les 2 CATT la sensibilité était de 100%. L'utilisation du CATT Latex en place du CATT 1.3 diminuerait, au seuil de 1/8ème, la charge de travail de près de 8 fois et le coût de 3 fois. Il n'y avait pas de réaction croisée avec les $plasmodium$ et les microfilaires. Il reste à le confirmer et à valider le seuil de détection dans un foyer de forte prévalence. (Résumé d'auteur)
- Published
- 1998
24. Stratégies de Lutte et de Surveillance dans le Paludisme et les Trypanosomiases
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Njiokou, F., Samé-Ekobo, A., Njoha S., Oskam, L., Cuny, Gérard, and Herder, Stéphane
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ONCHOCERCOSE ,VARIABILITE GENETIQUE ,SPECIATION ,LOCUS DIAGNOSTIC - Published
- 1997
25. Stratégies de Lutte et de Surveillance dans le Paludisme et les Trypanosomiases
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Bouchité, Bernard, Njiokou, F., Demanou, M., and Brutus, Laurent
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VARIATION SAISONNIERE ,TRANSMISSION ,ENTOMOLOGIE MEDICALE ,ENQUETE ,PALUDISME ,MILIEU URBAIN ,FACTEUR ANTHROPIQUE ,GITE LARVAIRE - Published
- 1997
26. Trypanosoma vivax,T. congolense“forest type” andT. simiae: prevalence in domestic animals of sleeping sickness foci of Cameroon
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Nimpaye, H., primary, Njiokou, F., additional, Njine, T., additional, Njitchouang, G.R., additional, Cuny, G., additional, Herder, S., additional, Asonganyi, T., additional, and Simo, G., additional
- Published
- 2011
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27. Domestic animals as potential reservoir hosts ofTrypanosoma brucei gambiensein sleeping sickness foci in Cameroon
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Njiokou, F., primary, Nimpaye, H., additional, Simo, G., additional, Njitchouang, G.R., additional, Asonganyi, T., additional, Cuny, G., additional, and Herder, S., additional
- Published
- 2010
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28. International congress of parasitology
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Bellec, Christian, Njiokou, F., Jarne, P., Bosseno, Marie-France, Finot, Luc, N'Goran, E., Yapi, Y., Sellin, Bertrand, and Delay, B.
- Subjects
SCHISTOSOMIASE ,EPIDEMIOLOGIE ,REPRODUCTION ,HOTE ,ENZYME ,ELECTROPHORESE ,VECTEUR ,DYNAMIQUE DE POPULATION ,BIOLOGIE ,GENETIQUE ,MOLLUSQUE ,VARIABILITE INTRASPECIFIQUE - Published
- 1990
29. Population genetic structure of the schistosome-vector snail Bulinus globosus: examining the role of genetic drift, migration and human activities
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Njiokou, F, primary, Delay, B, additional, Bellec, C, additional, N'Goran, E K, additional, Yapi, G Yapi, additional, and Jarne, P, additional
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- 1994
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30. Trypanosoma vivax, T. congolense“forest type” and T. simiae: prevalence in domestic animals of sleeping sickness foci of Cameroon
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Nimpaye, H., Njiokou, F., Njine, T., Njitchouang, G.R., Cuny, G., Herder, S., Asonganyi, T., and Simo, G.
- Abstract
In order to better understand the epidemiology of Human and Animal trypanosomiasis that occur together in sleeping sickness foci, a study of prevalences of animal parasites (Trypanosoma vivax, T. congolense“forest type”, and T. simiae) infections was conducted on domestic animals to complete the previous work carried on T. brucei gambienseprevalence using the same animal sample. 875 domestic animals, including 307 pigs, 264 goats, 267 sheep and 37 dogs were sampled in the sleeping sickness foci of Bipindi, Campo, Doumé and Fontem in Cameroon. The polymerase chain reaction (PCR) based method was used to identify these trypanosome species. A total of 237 (27.08%) domestic animals were infected by at least one trypanosome species. The prevalence of T. vivax, T. congolense“forest type” and T. simiaewere 20.91%, 11.42% and 0.34% respectively. The prevalences of T. vivaxand T. congolense“forest type” differed significantly between the animal species and between the foci (p < 0.0001); however, these two trypanosomes were found in all animal species as well as in all the foci subjected to the study. The high prevalences of T. vivaxand T. congolense“forest type” in Bipindi and Fontem-Center indicate their intense transmission in these foci.
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- 2011
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31. Domestic animals as potential reservoir hosts of Trypanosoma brucei gambiensein sleeping sickness foci in Cameroon
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Njiokou, F., Nimpaye, H., Simo, G., Njitchouang, G.R., Asonganyi, T., Cuny, G., and Herder, S.
- Abstract
An explanation of the endemic nature and/or the resurgence of Human African Trypanosomiasis (HAT) in the historic foci in West and Central Africa may be the existence of an animal reservoir. In some HAT foci, pigs were found infected by Trypanosoma brucei gambiensebut the implication of the other domestic animals was not quite evaluated. This study aims to determine the prevalence of T. b. gambiensein domestic animal species (goat, sheep, pig and dog) commonly found in the four active HAT foci in Cameroon (Bipindi, Fontem, Campo and Doumé). Blood samples were collected from 307 pigs, 264 goats, 267 sheep and 37 dogs and used for parasitological (QBC), immunological (LiTat 1.3 CATT) and molecular (PCR) analyses. QBC detected trypanosomes in 3.88 % domestic animals while 22.7 % were sero-positive with LiTat 1.3 CATT tests. Of the 875 animals analysed, 174 (19.88 %) harboured T. bruceis.l. DNA, found in each of the four types of animal and in the four localities. The infection rate significantly differed among the animal species (p < 0.0001) and localities (p < 0.0001). The PCR also revealed T. b. gambiensegroup 1 DNA in 27 (3.08 %) domestic animals. The specific infection rates were as follows: sheep (6.74 %), goats (3.08 %), pigs (0.32 %) and dogs (0 %). T. b. gambiensewas found in 8 (3.92 %) animals from Bipindi, 15 (4.83 %) from Campo, 4 (2.59 %) from Fontem-Center and none from Doumé. The infection rates significantly differed between the localities, and correlated with the intensity of HAT transmission in the foci.
- Published
- 2010
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32. Genetic tracing of the illegal trade of the white-bellied pangolin (Phataginus tricuspis) in western Central Africa.
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Din Dipita A, Missoup AD, Aguillon S, Lecompte E, Momboua BR, Chaber AL, Abernethy K, Njiokou F, Tindo M, Ntie S, and Gaubert P
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- Animals, Africa, Central, Genetics, Population, Gene Frequency, Commerce, Genotype, Cameroon, Genetic Variation, Pangolins genetics, Microsatellite Repeats genetics
- Abstract
The white-bellied pangolin is subject to intense trafficking, feeding both local and international trade networks. In order to assess its population genetics and trace its domestic trade, we genotyped 562 pangolins from local to large bushmeat markets in western central Africa. We show that the two lineages described from the study region (WCA and Gab) were overlapping in ranges, with limited introgression in southern Cameroon. There was a lack of genetic differentiation across WCA and a significant signature of isolation-by-distance possibly due to unsuspected dispersal capacities involving a Wahlund effect. We detected a c. 74.1-82.5% decline in the effective population size of WCA during the Middle Holocene. Private allele frequency tracing approach indicated up to 600 km sourcing distance by large urban markets from Cameroon, including Equatorial Guinea. The 20 species-specific microsatellite loci provided individual-level genotyping resolution and should be considered as valuable resources for future forensic applications. Because admixture was detected between lineages, we recommend a multi-locus approach for tracing the pangolin trade. The Yaoundé market was the main hub of the trade in the region, and thus should receive specific monitoring to mitigate pangolins' domestic trafficking. Our study also highlighted the weak implementation of CITES regulations at European borders., (© 2024. The Author(s).)
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- 2024
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33. Significant reduction of blackfly densities in persistent onchocerciasis area following pilot implementation of an environment friendly approach (Slash and Clear).
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Domche A, Nana Djeunga HC, Nwane PB, Njitchouang GR, Nono Fesuh B, Njiokou F, Jacob B, Pion SD, and Kamgno J
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- Animals, Humans, Insect Vectors, Cameroon, Rivers, Onchocerciasis prevention & control, Simuliidae
- Abstract
The effectiveness of the "Slash and Clear" method in reducing blackfly populations in low transmission areas is established, but its impact in high transmission settings with large rivers and dense vectors is yet to be proven. A community-based intervention study was conducted in the Mbam Valley, Centre Cameroon, involving two sites: Bayomen (control) and Biatsota (intervention). In each arm, baseline blackfly densities were collected over one year using the human landing method. The intervention consisted of destroying the trailing vegetation where blackflies breed. Blackfly densities were collected post-intervention to assess the impact of the intervention. Post-intervention data showed a 50.8% reduction in blackfly density in Biatsota (mean number of collected blackflies from 1936 to 953), while a reduction of 26.7% was observed in Bayomen (mean number of collected blackflies from 2418 to 1774). The reduction rate attributable to the intervention was 32.9%. Statistical analysis confirmed that the reduction in blackfly density was significantly greater in the intervention site. This study demonstrates the feasibility and significant impact of the "Slash and Clear" method in high transmission areas. However, further research is required to assess its long-term effects and determine how this strategy can be scaled up and sustained until onchocerciasis elimination is achieved., (© 2024. The Author(s).)
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- 2024
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34. Geographical emergence of sulfadoxine-pyrimethamine drug resistance-associated P. falciparum and P. malariae alleles in co-existing Anopheles mosquito and asymptomatic human populations across Cameroon.
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Nkemngo FN, Raissa LW, Nguete DN, Ndo C, Fru-Cho J, Njiokou F, Wanji S, and Wondji CS
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- Animals, Humans, Pyrimethamine pharmacology, Pyrimethamine therapeutic use, Sulfadoxine pharmacology, Sulfadoxine therapeutic use, Alleles, Cameroon epidemiology, Drug Combinations, Plasmodium falciparum, Drug Resistance genetics, Tetrahydrofolate Dehydrogenase genetics, Anopheles genetics, Antimalarials pharmacology, Antimalarials therapeutic use, Malaria, Falciparum drug therapy, Malaria, Falciparum epidemiology, Malaria, Falciparum genetics, Malaria drug therapy, Malaria epidemiology, Malaria genetics
- Abstract
Malaria molecular surveillance remains critical in detecting and tracking emerging parasite resistance to anti-malarial drugs. The current study employed molecular techniques to determine Plasmodium species prevalence and characterize the genetic diversity of Plasmodium falciparum and Plasmodium malariae molecular markers of sulfadoxine-pyrimethamine resistance in humans and wild Anopheles mosquito populations in Cameroon. Anopheles mosquito collections and parasitological survey were conducted in villages to determine Plasmodium species infection, and genomic phenotyping of anti-folate resistance was accomplished by sequencing the dihydrofolate-reductase ( dhfr ) and dihydropteroate-synthase ( dhps ) genes of naturally circulating P. falciparum and P. malariae isolates. The malaria prevalence in Elende was 73.5% with the 5-15 years age group harboring significant P. falciparum (27%) and P. falciparum + P. malariae (19%) infections. The polymorphism breadth of the pyrimethamine-associated Pfdhfr marker revealed a near fixation (94%) of the triple-mutant -A
16 I51 R59 N108 I164 . The Pfdhps backbone mediating sulfadoxine resistance reveals a high frequency of the V431 A436 G437 K540 A581 A613 alleles (20.8%). Similarly, the Pmdhfr N50 K55 L57 R58 F59 S114 F168 I170 haplotype (78.4%) was predominantly detected in the asexual blood stage. In contrast, the Pmdhps - S436 A F437 occured at 37.2% frequency. The combined quadruple N50 K55 L57 R58 S59 S114 F168 I170 _ S436 G437 K540 A581 A613 (31.9%) was the major circulating haplotype with similar frequency in humans and mosquitoes. This study highlights the increasing frequency of the P. malariae parasite mostly common in asymptomatic individuals with apparent P. falciparum infection. Interventions directed at reducing malaria transmission such as the scaling-up of SP are favoring the emergence and spread of multiple drug-resistant alleles between the human and mosquito host systems., Competing Interests: The authors declare no conflict of interest.- Published
- 2023
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35. Impact of a small-scale tsetse fly control operation with deltamethrin impregnated "Tiny Targets" on tsetse density and trypanosomes' circulation in the Campo sleeping sickness focus of South Cameroon.
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Melachio Tanekou TT, Bouaka Tsakeng CU, Tirados I, Acho A, Bigoga J, Wondji CS, and Njiokou F
- Subjects
- Animals, Cameroon epidemiology, Trypanosomiasis, African epidemiology, Trypanosomiasis, African prevention & control, Tsetse Flies, Trypanosoma
- Abstract
Background: Significant progress has been made towards African sleeping sickness elimination in the last decade. Indeed, the World Health Organization (WHO) global goal of eliminating the chronic form of the disease as a public health problem was achieved in 2020 (i.e., < 2,000 new cases per year). Vector control has played an important role in achieving this goal. In this study, we evaluated the impact of the insecticide impregnated Tiny Targets on tsetse fly densities and their infection rates with Trypanosoma spp in the Campo sleeping sickness focus of South Cameroon., Methods: The study site was divided into two areas: (i) the south-west experimental area, which included vector control, and (ii) the eastern part as the non-intervention area. After compiling the baseline entomological data (tsetse densities and trypanosome infection rates), around 2000 Tiny Targets were deployed in the South-West area and replaced every six months for two years. Post-intervention surveys were conducted every six months to determine tsetse densities and levels of trypanosome infections with PCR-based methods., Results: Following the intervention, tsetse mean catches decreased by 61% after six months, and up to 73% after twelve months (pre-intervention: 2.48 flies/trap/day, 95%CI [1.92-3.14]; 12-months post-intervention: 0.66 tsetse/trap/day, 95%CI [0.42-0.94]). This decrease was not sustained after 18 months, and the mean catch doubled compared to that after 12 months. After 24 months, the mean catches still increased by 17% (18 months: 1.45 tsetse/trap/day, 95%CI [1.07-1.90] and 24 months: 1.71 tsetse/trap/day, 95%CI [1.27-2.24]). In the non-intervention area, a variation in tsetse catches was observed during the two years, with a general increase from 2.43 [0.73-5.77] to 3.64 [1.47-7.70] tsetse/trap/day. In addition, trypanosome infection rates dropped by 75% in both areas (P-value < 0.001) from 21.20% to 5.06% and from 13.14% to 3.45% in intervention and control areas respectively., Conclusion: Tiny targets have proven useful in reducing tsetse population densities and trypanosome infection rates, providing evidence for the integration of this tool in current strategies towards trypanosomiasis elimination in Campo. The non-sustained decrease of tsetse densities after one year may indicate reinvasions from neighbouring breeding sites or that the intervention area was not large enough. Our results show the need to scale up by accessing difficult breeding sites and extend the tiny targets to the whole transborder focus., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2023 Melachio Tanekou et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)
- Published
- 2023
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36. Pangolin Genomes Offer Key Insights and Resources for the World's Most Trafficked Wild Mammals.
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Heighton SP, Allio R, Murienne J, Salmona J, Meng H, Scornavacca C, Bastos ADS, Njiokou F, Pietersen DW, Tilak MK, Luo SJ, Delsuc F, and Gaubert P
- Subjects
- Animals, Genome, Phylogeny, Genomics, Pangolins genetics, Mammals genetics
- Abstract
Pangolins form a group of scaly mammals that are trafficked at record numbers for their meat and purported medicinal properties. Despite their conservation concern, knowledge of their evolution is limited by a paucity of genomic data. We aim to produce exhaustive genomic resources that include 3,238 orthologous genes and whole-genome polymorphisms to assess the evolution of all eight extant pangolin species. Robust orthologous gene-based phylogenies recovered the monophyly of the three genera and highlighted the existence of an undescribed species closely related to Southeast Asian pangolins. Signatures of middle Miocene admixture between an extinct, possibly European, lineage and the ancestor of Southeast Asian pangolins, provide new insights into the early evolutionary history of the group. Demographic trajectories and genome-wide heterozygosity estimates revealed contrasts between continental versus island populations and species lineages, suggesting that conservation planning should consider intraspecific patterns. With the expected loss of genomic diversity from recent, extensive trafficking not yet realized in pangolins, we recommend that populations be genetically surveyed to anticipate any deleterious impact of the illegal trade. Finally, we produce a complete set of genomic resources that will be integral for future conservation management and forensic endeavors for pangolins, including tracing their illegal trade. These comprise the completion of whole-genomes for pangolins through the hybrid assembly of the first reference genome for the giant pangolin (Smutsia gigantea) and new draft genomes (∼43x-77x) for four additional species, as well as a database of orthologous genes with over 3.4 million polymorphic sites., Competing Interests: Conflict of interest statement. The authors declare no competing/conflict of interests., (© The Author(s) 2023. Published by Oxford University Press on behalf of Society for Molecular Biology and Evolution.)
- Published
- 2023
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37. High efficacy of chlorfenapyr-based net Interceptor ® G2 against pyrethroid-resistant malaria vectors from Cameroon.
- Author
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Tchouakui M, Thiomela RF, Nchoutpouen E, Menze BD, Ndo C, Achu D, Tabue RN, Njiokou F, Joel A, and Wondji CS
- Subjects
- Animals, Cameroon, Mosquito Vectors, Anopheles, Malaria prevention & control
- Abstract
Background: The increasing reports of resistance to pyrethroid insecticides associated with reduced efficacy of pyrethroid-only interventions highlight the urgency of introducing new non-pyrethroid-only control tools. Here, we investigated the performance of piperonyl-butoxide (PBO)-pyrethroid [Permanet 3.0 (P3.0)] and dual active ingredients (AI) nets [Interceptor G2 (IG2): containing pyrethroids and chlorfenapyr and Royal Guard (RG): containing pyrethroids and pyriproxyfen] compared to pyrethroid-only net Royal Sentry (RS) against pyrethroid-resistant malaria vectors in Cameroon., Methods: The efficacy of these tools was firstly evaluated on Anopheles gambiae s.l. and Anopheles funestus s.l. from Gounougou, Mibellon, Mangoum, Nkolondom, and Elende using cone/tunnel assays. In addition, experimental hut trials (EHT) were performed to evaluate the performance of unwashed and 20 times washed nets in semi-field conditions. Furthermore, pyrethroid-resistant markers were genotyped in dead vs alive, blood-fed vs unfed mosquitoes after exposure to the nets to evaluate the impact of these markers on net performance. The XLSTAT software was used to calculate the various entomological outcomes and the Chi-square test was used to compare the efficacy of various nets. The odds ratio and Fisher exact test were then used to establish the statistical significance of any association between insecticide resistance markers and bed net efficacy., Results: Interceptor G2 was the most effective net against wild pyrethroid-resistant An. funestus followed by Permanet 3.0. In EHT, this net induced up to 87.8% mortality [95% confidence interval (CI): 83.5-92.1%) and 55.6% (95% CI: 48.5-62.7%) after 20 washes whilst unwashed pyrethroid-only net (Royal Sentry) killed just 18.2% (95% CI: 13.4-22.9%) of host-seeking An. funestus. The unwashed Permanet 3.0 killed up to 53.8% (95% CI: 44.3-63.4%) of field-resistant mosquitoes and 47.2% (95% CI: 37.7-56.7%) when washed 20 times, and the Royal Guard 13.2% (95% CI: 9.0-17.3%) for unwashed net and 8.5% (95% CI: 5.7-11.4%) for the 20 washed net. Interceptor G2, Permanet 3.0, and Royal Guard provided better personal protection (blood-feeding inhibition 66.2%, 77.8%, and 92.8%, respectively) compared to pyrethroid-only net Royal Sentry (8.4%). Interestingly, a negative association was found between kdrw and the chlorfenapyr-based net Interceptor G2 (χ
2 = 138; P < 0.0001) with homozygote-resistant mosquitoes predominantly found in the dead ones., Conclusions: The high mortality recorded with Interceptor G2 against pyrethroid-resistant malaria vectors in this study provides first semi-field evidence of high efficacy against these major malaria vectors in Cameroon encouraging the implementation of this novel net for malaria control in the country. However, the performance of this net should be established in other locations and on other major malaria vectors before implementation at a large scale., (© 2023. National Institute of Parasitic Diseases.)- Published
- 2023
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38. Trends in black fly density, parity and infection rates from riverside to villages of the Bafia Health District in Cameroon: implication for onchocerciasis vector control.
- Author
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Domche A, Nana-Djeunga HC, Nwane PB, Njitchouang GR, Dzune-Fossouo DC, Fesuh BN, Njiokou F, and Kamgno J
- Subjects
- Animals, Female, Humans, Cameroon epidemiology, Insect Vectors, Onchocerciasis epidemiology, Onchocerciasis prevention & control, Simuliidae
- Abstract
Background: Reducing contact between humans and black flies can lead to interruption of onchocerciasis transmission. The Esperanza Window Trap (EWT) has been shown to be an effective tool for reducing black fly densities. Several shape-based improvements to this trapping system have been made to optimise its effectiveness, but optimisation of this trapping system has been based most often on the shape of the trap, collection in areas of high black fly density and the addition of attractants, without considering transmission potentials and parity rates. This study aims to investigate the differences in biting rates and transmission potential between three catch points along a transect to guide the choice of EWT placement., Methods: Monthly black fly collection was carried out over a 1-year study period using the human landing method at three catch points along a transect from the riverside toward the centre of two first-line villages (Biatsota and Bayomen), in the Mbam valley in Cameroon. All female black flies caught were counted and dissected, and entomological indicators were computed and compared between the catch points and villages., Results: A total of 80,732 black flies were caught, of which 57,517 were dissected; of the latter, 2743 (4.8%) were parous and 44 (1.6%) were infective. Regarding the distance to the river, a vector density gradient was observed, with the highest annual biting rates being recorded at the riverside. The highest annual transmission potentials were also recorded at the riverside (165 vs 255 infective larvae/man/year in Bayomen and Biatsota, respectively). Overall, the highest parity rates were recorded at the riverside in Biatsota (5.1%) where various human activities are frequent and at the centre of Bayomen village (6.3%)., Conclusion: The results of this study reveal that entomological parameters were the highest at the riverside catch sites and indicate that riverside locations should be prioritised for EWTs or other trapping systems to achieve optimal performance in onchocerciasis control., (© 2023. BioMed Central Ltd., part of Springer Nature.)
- Published
- 2023
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39. Epidemiology of malaria, schistosomiasis, and geohelminthiasis amongst children 3-15 years of age during the dry season in Northern Cameroon.
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Nkemngo FN, W G Raissa L, Nebangwa DN, Nkeng AM, Kengne A, Mugenzi LMJ, Fotso-Toguem YG, Wondji MJ, Shey RA, Nguiffo-Nguete D, Fru-Cho J, Ndo C, Njiokou F, Webster JP, Wanji S, and Wondji CS
- Subjects
- Male, Animals, Humans, Child, Preschool, Child, Adolescent, Cross-Sectional Studies, Cameroon epidemiology, Seasons, Schistosoma mansoni, Prevalence, Feces parasitology, Soil parasitology, Schistosomiasis diagnosis, Schistosomiasis epidemiology, Schistosomiasis complications, Helminthiasis parasitology, Malaria complications, Malaria, Falciparum epidemiology, Anemia epidemiology, Anemia complications
- Abstract
Background: The double burden of malaria and helminthiasis in children poses an obvious public health challenge, particularly in terms of anemia morbidity. While both diseases frequently geographically overlap, most studies focus on mono-infection and general prevalence surveys without molecular analysis. The current study investigated the epidemiological determinants of malaria, schistosomiasis, and geohelminthiasis transmission among children in the North Region of Cameroon., Methodology: School and pre-school children aged 3-15 year-of-age were enrolled from three communities in March 2021 using a community cross-sectional design. Capillary-blood samples were obtained, and each was examined for malaria parasites using rapid-diagnostic-test (RDT), microscopy, and PCR while hemoglobin level was measured using a hemoglobinometer. Stool samples were analyzed for Schistosoma mansoni, S. guineensis, and soil-transmitted-helminthiasis (STH) infections using the Kato Katz method, and urine samples were assessed for the presence of S. haematobium eggs (including hybrids) using the standard urine filtration technique., Result: A malaria prevalence of 56% (277/495) was recorded by PCR as opposed to 31.5% (156/495) by microscopy and 37.8% (186/495) by RDT. Similarly, schistosomiasis was observed at prevalence levels of up to 13.3% (66/495) overall [S. haematobium (8.7%); S. mansoni (3.8%); mixed Sh/Sm (0.6%); mixed Sh/Sm/Sg (0.2%). Both infections were higher in males and the 3-9 year-of-age groups. A high frequency of PCR reported P. falciparum mono-infection of 81.9% (227/277) and mixed P. falciparum/P. malariae infection of 17.3% (48/277) was observed. Malaria-helminths co-infections were observed at 13.1% (65/495) with marked variation between P. falciparum/S. haematobium (50.8%, 33/65); P. falciparum/S. mansoni (16.9%, 11/65) and P. falciparum/Ascaris (9.2%, 6/65) (χ2 = 17.5, p = 0.00003). Anemia prevalence was 32.9% (163/495), categorically associated with P. falciparum (45.8%, 104/227), Pf/Sh (11.5%, 26/227), and Pf/Sm (3.9%, 9/227) polyparasitism., Conclusion: Polyparasitism with malaria and helminth infections is common in school-aged children despite periodic long-lasting insecticide-treated nets (LLINs) distribution and regular school-based praziquantel (for schistosomiasis) and albendazole (for STH) campaigns. Co-existence of Plasmodium parasites and helminths infections notably Schistosoma species among children may concurrently lead to an increase in Plasmodium infection with an enhanced risk of anemia, highlighting the necessity of an integrated approach for disease control interventions., Competing Interests: he authors have declared that no competing interests exist., (Copyright: © 2023 Nkemngo et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)
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- 2023
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40. Association between polymorphisms of IL4, IL13, IL10, STAT6 and IFNG genes, cytokines and immunoglobulin E levels with high burden of Schistosoma mansoni in children from schistosomiasis endemic areas of Cameroon.
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Mewamba EM, Noyes H, Tiofack AAZ, Kamga RMN, Kamdem CN, Mengoue LET, Ofon E, Ngassam RIK, Nyangiri O, Bucheton B, Njiokou F, Womeni MH, Matovu E, MacLeod A, and Simo G
- Subjects
- Animals, Humans, Child, Schistosoma mansoni genetics, Interleukin-13 genetics, Interleukin-10 genetics, Interleukin-4 genetics, Cytokines genetics, Cameroon epidemiology, Antigens, Helminth genetics, Sensitivity and Specificity, Polymorphism, Genetic, Prevalence, Immunoglobulin E, Feces, Schistosomiasis mansoni epidemiology, Schistosomiasis mansoni genetics, Schistosomiasis
- Abstract
Eliminating schistosomiasis as a public health problem by 2030 requires a better understanding of the disease transmission, especially the asymmetric distribution of worm burden in individuals living and sharing the same environment. It is in this light that this study was designed to identify human genetic determinants associated with high burden of S. mansoni and also with the plasma concentrations of IgE and four cytokines in children from two schistosomiasis endemic areas of Cameroon. In school-aged children of schistosomiasis endemic areas of Makenene and Nom-Kandi of Cameroon, S. mansoni infections and their infection intensities were evaluated in urine and stool samples using respectively the Point-of-care Circulating Cathodic Antigen test (POC-CCA) and the Kato Katz (KK) test. Thereafter, blood samples were collected in children harbouring high burden of schistosome infections as well as in their parents and siblings. DNA extracts and plasma were obtained from blood. Polymorphisms at 14 loci of five genes were assessed using PCR-restriction fragment length polymorphism and amplification-refractory mutation system. The ELISA test enabled to determine the plasma concentrations of IgE, IL-13, IL-10, IL-4 and IFN-γ. The prevalence of S. mansoni infections was significantly higher (P < 0.0001 for POC-CCA; P = 0.001 for KK) in Makenene (48.6% for POC-CCA and 7.9% for KK) compared to Nom-Kandi (31% for POC-CCA and 4.3% for KK). The infection intensities were also higher (P < 0.0001 for POC-CCA; P = 0.001 for KK) in children from Makenene than those from Nom-Kandi. The allele C of SNP rs3024974 of STAT6 was associated with an increased risk of bearing high burden of S. mansoni both in the additive (p = 0.009) and recessive model (p = 0.01) while the allele C of SNP rs1800871 of IL10 was protective (p = 0.0009) against high burden of S. mansoni. The alleles A of SNP rs2069739 of IL13 and G of SNP rs2243283 of IL4 were associated with an increased risk of having low plasma concentrations of IL-13 (P = 0.04) and IL-10 (P = 0.04), respectively. This study showed that host genetic polymorphisms may influence the outcome (high or low worm burden) of S. mansoni infections and also the plasma concentrations of some cytokines., Competing Interests: Declaration of Competing Interest The authors declare that they have no conflict of interest., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)
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- 2023
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41. Trypanosome Infections and Anemia in Cattle Returning from Transhumance in Tsetse-Infested Areas of Cameroon.
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Farikou O, Simo G, Njiokou F, Kamé Ngassé GI, Achiri Fru M, and Geiger A
- Abstract
The objective of this work was to assess the anemic status and the use of an immunological test and PCR-based methods to determine the infection rates of trypanosomes species. Transhumance aims to provide cattle with greener pastures and greater water resources than in the Djerem region during the dry season. Two criteria were used to assess the health status of the animals, the prevalence of trypanosomiasis and the level of anemia. In addition, we have evaluated the effectiveness, in trypanosomiasis detection, of the Very Diag Kit (CEVA Santé animale), a Rapid diagnosis test (RDT) based on immunological identification of T. congolense s.l. and T. vivax , responsible for AAT. Four trypanosome species ( Trypanosoma congolense savannah type (Tcs), T. congolense forest type (Tcf), T. brucei s.l. (Tbr) and T. vivax (Tvx)) were identified in cattle sampled in four villages. The overall infection rate determined by PCR (68.6%) was much higher than those generally reported in cattle from the Adamawa region (35 to 50%). Infections (including mixed infections) by Tc s.l. (Tcs + Tcf) were predominant (45.7%). The infection rates were also determined using the Very Diag Kit allowing us to identify Tc s.l. and Tvx in the field in less than 20 min. This method provided, for the global infection, a higher rate (76.5%) than that determined by PCR (68.6%), although it is supposed to be less sensitive than PCR. Tc s.l. infection rate (37.8%) was similar to that (38.8%) determined by PCR (Tcs + Tcf single infections). In contrast, the prevalence of Tvx single infections measured by RDT (18%) was nearly two-fold higher than that (9.4%) measured by PCR. Thus, further comparative analyses seem to be needed in order to more accurately assess the sensitivity and specificity of the Very Diag test under our conditions of use on blood samples. The mean PCVs in trypanosome-infected as well as in uninfected cattle were below 25%, the threshold below which an animal is considered anemic. Our study shows that cattle return from transhumance in poor health. It raises questions about its real benefit, especially since the herds are themselves likely to become vectors of trypanosomiasis and possibly of other diseases. At least, effective measures have to be undertaken to treat all cattle coming back from transhumance.
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- 2023
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42. Genetic Diversity of Cytochrome P450s CYP6M2 and CYP6P4 Associated with Pyrethroid Resistance in the Major Malaria Vectors Anopheles coluzzii and Anopheles gambiae from Yaoundé, Cameroon.
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Fotso-Toguem Y, Tene-Fossog B, Mugenzi LMJ, Wondji MJ, Njiokou F, Ranson H, and Wondji CS
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- Animals, Permethrin pharmacology, Cameroon, Insecticide Resistance genetics, Mosquito Vectors genetics, Cytochrome P-450 Enzyme System genetics, Cytochrome P-450 Enzyme System metabolism, Genetic Variation genetics, Insecticides pharmacology, Pyrethrins pharmacology, Anopheles genetics, Anopheles metabolism, Malaria genetics
- Abstract
Assessing the genetic diversity of metabolic resistance genes, such as cytochrome P450s, helps to understand the dynamics and evolution of resistance in the field. Here, we analyzed the polymorphisms of CYP6M2 and CYP6P4, associated with pyrethroid resistance in Anopheles coluzzii and Anopheles gambiae , to detect potential resistance markers. Field-caught resistant mosquitos and susceptible lab strains were crossed, and F4 was exposed to permethrin for 15 min and 90 min to discriminate highly susceptible (HS) and highly resistant (HR) mosquitos, respectively. Significant permethrin mortality reduction was observed after pre-exposure to PBO, suggesting the gene involvement of P450s. qPCR analysis revealed significant overexpression of CYP6M2 ( FC = 19.57 [95% CI 13.96-25.18] for An. coluzzii ; 10.16 [7.86-12.46] for An. gambiae ) and CYP6P4 ( FC = 6.73 [6.15-7.30] An. coluzzii ; 23.62 [26.48-20.76] An. gambiae ). Full-gene and ≈1 kb upstream were sequenced. For CYP6M2, the upstream region shows low diversity in HR and HS (overall Hd = 0.49, π = 0.018), whereas the full-gene shows allelic-variation but without evidence of ongoing selection. CYP6P4 upstream region showed a lower diversity in HR (Hd = 0.48) than HS (Hd = 0.86) of An. gambiae . These results highlighted that CYP6P4 -associated resistance is potentially driven by modification in upstream region. However, further work is needed to determine the real causative variants that will help design rapid detection tools.
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- 2022
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43. Spatial distribution and insecticide resistance profile of Aedes aegypti and Aedes albopictus in Douala, the most important city of Cameroon.
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Yougang AP, Keumeni CR, Wilson-Bahun TA, Tedjou AN, Njiokou F, Wondji C, and Kamgang B
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- Animals, Insecticide Resistance genetics, Permethrin, Cameroon, Mosquito Vectors genetics, Aedes, Insecticides pharmacology, Pyrethrins pharmacology
- Abstract
Prevention and control of Aedes-borne viral diseases such as dengue rely on vector control, including the use of insecticides and reduction of larval sources. However, this is threatened by the emergence of insecticide resistance. This study aimed to update the spatial distribution, the insecticide resistance profile of A. aegypti and A. albopictus and the potential resistant mechanisms implicated in the city of Douala. Immature stages of Aedes were collected in August 2020 in eight neighbourhoods in Douala and reared to adult stages. Adult bioassays, and piperonyl butoxide (PBO) synergist assays were carried out according to World Health Organization recommendations. Expression of some candidate metabolic genes including Cyp9M6F88/87, Cyp9J28a, Cyp9J10 and Cyp9J32 in A. aegypti, and Cyp6P12 in A. albopictus were assessed using qPCR. A. aegypti adults G0 were screened using real time melting curve qPCR analyses to genotype the F1534C, V1016I and V410L Aedes kdr mutations. Overall, A. aegypti is the predominant Aedes species, but analyses revealed that both A. albopictus and A. aegypti coexist in all the prospected neighbourhoods of Douala. High level of resistance was observed to three pyrethroids tested in both Aedes species. In A. aegypti a lower mortality rate was reported to permethrin (5.83%) and a higher mortality rate to deltamethrin (63.74%). Meanwhile, for A. albopictus, lower (6.72%) and higher (84.11%) mortality rates were reported to deltamethrin. Similar analysis with bendiocarb, revealed for A. aegypti a loss of susceptibility. However, in A. albopictus samples, analyses revealed a susceptibility in Logbessou, and confirmed resistance in Kotto (59.78%). A partial recovery of mortality was found to insecticides after pre-exposure to PBO. Cyp6P12 was found significantly overexpressed in A. albopictus permethrin resistant and Cyp9M6F88/87 for A. aegypti deltamethrin resistant. F1534C, V1016I and V410L mutations were detected in A. aegypti from different neighbourhoods and by considering the combination of these three kdr 14 genotypes were found. These findings provide relevant information which should be capitalised in the implementation of arbovirus vector control strategies and insecticide resistance management., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2022 Yougang et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)
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- 2022
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44. Knowledge, attitudes, and practices regarding malaria control among communities living in the south Cameroon forest region.
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Bamou R, Tchuinkam T, Kopya E, Awono-Ambene P, Njiokou F, Mwangangi J, and Antonio-Nkondjio C
- Abstract
Objective: This study assessed knowledge, attitudes, and practices (KAP) regarding malaria among communities living in the equatorial forest region of south Cameroon., Methods: The study was conducted in Olama and Nyabessan. Interviews were undertaken using a semi-structured questionnaire for data collection on KAP, while malaria rapid diagnostic testing, using SD BIOLINE kits, was employed for malaria parasite detection., Results: In total, 186 heads of households (HoH), comprising 105 (56.45%) males and 81 (43.45%) females, were interviewed. The majority of HoH demonstrated good knowledge of malaria (86.56%; n = 161) and control measures, with a high proportion of long-lasting insecticidal net (LLIN) ownership (96.8%; n = 180). More than two-thirds (81.1%; n = 151) of households owned at least one LLIN for two people. The majority of HoH (85.40%) declared visiting hospitals or clinics in cases of suspected malaria. Malaria parasite prevalence was high in the two study sites (63.9% in Nyabessan and 48.65% in Olama), and varied according to age, house type, and sleeping time., Conclusion: The study indicated that despite good knowledge of malaria, high possession and utilization of control measures by population, transmission of malaria still persist in the area. The study stress the need for implementing additional control measures to improve the fight against malaria in the area., (© 2022 The Author(s).)
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- 2022
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45. Fine-scale mapping of Schistosoma mansoni infections and infection intensities in sub-districts of Makenene in the Centre region of Cameroon.
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Mewamba EM, Tiofack AAZ, Kamdem CN, Tchounkeu EY, Tatang RJA, Mengoue LET, Mbagnia MCT, Njiokou F, Casacuberta-Partal M, Womeni HM, and Simo G
- Subjects
- Child, Animals, Humans, Praziquantel therapeutic use, Cameroon epidemiology, Antigens, Helminth, Sensitivity and Specificity, Schistosoma mansoni, Feces, Prevalence, Schistosomiasis mansoni prevention & control, Schistosomiasis, Schistosomatidae
- Abstract
Background: Schistosomiasis control relies mainly on mass drug administration of Praziquantel (PZQ) to school aged children (SAC). Although precision mapping has recently guided decision making, the sub-districts and the epidemiological differences existing between bio-ecological settings in which infected children come from were not taken into consideration. This study was designed to fill this gap by using POC-CCA and KK to comparatively determine the prevalence and infection intensities of Schistosoma mansoni (S. mansoni) and to perform fine-scale mapping of S. mansoni infections and its infection intensities with the overarching goal of identifying sub-districts presenting high transmission risk where control operations must be boosted to achieve schistosomiasis elimination., Methodology: During a cross- sectional study conducted in Makenene, 1773 stool and 2253 urine samples were collected from SAC of ten primary schools. S. mansoni infections were identified using the point of care circulating cathodic antigen (POC-CCA) and Kato-Katz (KK) test respectively on urine and stool samples. Geographical coordinates of houses of infected SAC were recorded using a global position system device. Schistosome infections and infection intensities were map using QGIS software., Results: The prevalence of S. mansoni inferred from POC-CCA and KK were 51.3% and 7.3% respectively. Most infected SAC and those bearing heavy infections intensities were clustered in sub-districts of Baloua, Mock-sud and Carrière. Houses with heavily-infected SAC were close to risky biotopes., Conclusion: This study confirms the low sensitivity of KK test compared to POC-CCA to accurately identify children with schistosome infection and bearing different schistosome burden. Fine-scale mapping of schistosome infections and infection intensities enabled to identify high transmission sub-districts where control measures must be boosted to reach schistosomiasis elimination., Competing Interests: The authors have declared that no competing interests exist.
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- 2022
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46. Exposition of Intermediate Hosts of Schistosomes to Niclosamide (Bayluscide WP 70) Revealed Significant Variations in Mortality Rates: Implications for Vector Control.
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Kengne Fokam AC, Sumo L, Bagayan M, Nana-Djeunga HC, Kuete T, Nganjou GSO, Tchami Mbagnia MC, Djune-Yemeli L, Wondji CS, and Njiokou F
- Subjects
- Animals, Bulinus, Niclosamide toxicity, Schistosoma, Water, Biomphalaria, Molluscacides toxicity
- Abstract
(1) Background: Schistosomiasis remains a public health issue in Cameroon. Snail control using Niclosamide can prevent schistosome transmission. It is safe to determine lethal concentrations for the population. This study aimed at assessing the toxicity of Niclosamide on different developmental stages of snail populations; (2) Methods: Snails were collected, identified, and reared in the laboratory. Egg masses and adult snails were exposed to Niclosamide, at increasing concentrations (0.06, 0.125, 0.25, 0.5, 1 mg/L for egg embryos and 0.06, 0.08, 0.1, 0.12, 0.14, 0.16, 0.18, 0.2 mg/L for adults). After 24 h exposure, egg masses and snails were removed from Niclosamide solutions, washed with source water and observed; (3) Results: Snail susceptibility was species and population dependent. For egg embryos, Biomphalaria pfeifferi was the most susceptible (LC
50 : 0.1; LC95 : 6.3 mg/L) and Bulinus truncatus the least susceptible (LC50 : 4.035; LC95 : 228.118 mg/L). However, for adults, B. truncatus was the most susceptible (mortality rate: 100%). The LC50 and LC95 for Bi. camerunensis eggs were 0.171 mg/L and 1.102 mg/L, respectively, and were higher than those obtained for adults (0.0357 mg/L and 0.9634 mg/L); (4) Conclusion: These findings will guide the design of vector control strategies targeting these snail species in Cameroon.- Published
- 2022
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47. Reduced performance of community bednets against pyrethroid-resistant Anopheles funestus and Anopheles gambiae, major malaria vectors in Cameroon.
- Author
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Ngongang-Yipmo ES, Tchouakui M, Menze BD, Mugenzi LMJ, Njiokou F, and Wondji CS
- Subjects
- Animals, Cameroon epidemiology, Female, Insecticide Resistance, Mosquito Control methods, Mosquito Vectors genetics, Anopheles genetics, Insecticide-Treated Bednets, Insecticides pharmacology, Malaria prevention & control, Pyrethrins pharmacology
- Abstract
Background: Long-lasting insecticidal nets (LLINs) are a vital tool in the fight against malaria vectors. However, their efficacy in the field can be impacted by several factors, including patterns of usage, net age, mosquito resistance and the delayed mortality effect, all of which could influence malaria transmission. We have investigated the effectiveness of the various brands of LLINs available in markets and households in Cameroon on pyrethroid-resistant mosquitoes and assessed their post-exposure effect., Methods: Following quality control assessment on a susceptible laboratory mosquito strain, we evaluated the immediate and delayed mortality effects of exposure to LLINs (both newly bough LLINst and used ones collected from households in Elende village, Cameroon, in 2019) using standard WHO cone tests on Anopheles gambiae and Anopheles funestus populations collected from the Centre region of Cameroon. Alive female mosquitoes were genotyped for various resistance markers at different time points post-exposure to evaluate the impact of insecticide resistance on the efficacy of bednets., Results: The laboratory-susceptible strain experienced high mortality rates when exposed to all pyrethroid-only brands of purchased nets (Olyset® Net, Super Net, PermaNet® 2.0, Yorkool®, Royal Sentry®) (Mean±SEM: 68.66 ± 8.35% to 93.33 ± 2.90%). However, low mortality was observed among wild An. funestus mosquitoes exposed to the bednets (0 ± 0 to 28 ± 6.7%), indicating a reduced performance of these nets against field mosquitoes. Bednets collected from households also showed reduced efficacy on the laboratory strain (mortality: 19-66%), as well as displaying a significant loss of efficacy against the local wild strains (mortality: 0 ± 0% to 4 ± 2.6% for An. gambiae sensu lato and 0 ± 0% to 8 ± 3.2% for An. funestus). However, compared to the unexposed group, mosquitoes exposed to bednets showed a significantly reduced longevity, indicating that the efficacy of these nets was not completely lost. Mosquitoes with the CYP6P9a-RR and L119F-GSTe2 mutations conferring pyrethroid resistance showed greater longevity after exposure to the Olyset net than their susceptible counterparts, indicating the impact of resistance on bednet efficacy and delayed mortality., Conclusion: These findings show that although standard bednets drastically lose their efficacy against pyrethroid-resistant field mosquitoes, they still are able to induce delayed mortality in exposed populations. The results of this study also provide evidence of the actual impact of resistance on the quality and efficacy of LLINs in use in the community, with mosquitoes carrying the CYP6P9a-RR and L119F-GSTe2 mutations conferring pyrethroid resistance living longer than their susceptible counterparts. These results highlight the need to use new-generation nets that do not rely solely on pyrethroids., (© 2022. The Author(s).)
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- 2022
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48. Assessing the Tsetse Fly Microbiome Composition and the Potential Association of Some Bacteria Taxa with Trypanosome Establishment.
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Tsakeng CUB, Tanekou TTM, Soffack SF, Tirados I, Noutchih C, Njiokou F, Bigoga JD, and Wondji CS
- Abstract
The tsetse flies, biological vectors of African trypanosomes, harbour a variety of bacteria involved in their vector competence that may help in developing novel vector control tools. This study provides an inventory of tsetse bacterial communities in Cameroon and explores their possible associations with trypanosome establishment in Glossina palpalis palpalis . High throughput sequencing of the V3-V4 hypervariable region of the bacterial 16S rRNA gene, with subsequent metagenomic, multivariate, and association analyses, were used to investigate the levels and patterns of microbial diversity in four tsetse species. Overall, 31 bacterial genera and four phyla were identified. The primary symbiont Wigglesworthia dominated almost all the samples, with an overall relative abundance of 47.29%, and seemed to be replaced by Serratia or Burkholderia in some G. tachinoides flies. Globally, significant differences were observed in the microbiome diversity and composition among tsetse species and between teneral and non-teneral flies, or between flies displaying or not displaying mature trypanosome infections. In addition, differential abundance testing showed some OTUs, or some bacteria taxa, associated with trypanosome maturation in tsetse flies. These bacteria could be further investigated for an understanding of their mechanism of action and alternatively, transformed and used to block trypanosome development in tsetse flies.
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- 2022
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49. Knowledge translation and evidence generation to increase the impact of vector control in Burkina Faso, Cameroon and Malawi.
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Mwendera CA, Mzilahowa T, Njiokou F, N'falé S, Amegee Quach J, Thomsen E, Dabire R, Ranson H, Alhassan N, Oronje R, and Worrall E
- Subjects
- Burkina Faso, Cameroon, Humans, Malawi, Translational Science, Biomedical
- Abstract
Lack of context-specific evidence and inadequate evidence-use for decision-making contribute to poor health. This paper reports on our work aimed at addressing the knowledge translation (KT) gap between evidence generators and users. We present our experiences of strengthening KT via technical advisory groups (TAGs) in parallel with increasing evidence generation through research fellowships and operational research. Vectorborne diseases (VBDs) impose substantial health and economic burdens in sub-Saharan Africa despite being preventable with vector control. The Partnership for Increasing the Impact of Vector Control aimed to reduce the burden of VBDs in Burkina Faso, Cameroon, Malawi and at regional and global levels. TAGs can promote evidence-use in policy and practice by engaging relevant stakeholders in both research and policy processes. TAGs and related activities are best facilitated by a coordinator with skills in research and policy. Contextual factors should influence the design and governance of TAGs, which will likely evolve over time. Relevant national stakeholders should be included in TAGs and be actively involved in developing research agendas to increase the relevance and acceptability of research findings for decision-making. The countries present three differing contexts with longer-term research and evaluation necessary to draw lessons on impact., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2022. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)
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- 2022
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50. A 6.5kb Intergenic Structural Variation Exacerbates the Fitness Cost of P450-Based Metabolic Resistance in the Major African Malaria Vector Anopheles funestus .
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Tchouakui M, Mugenzi LMJ, Wondji MJ, Tchoupo M, Njiokou F, and Wondji CS
- Subjects
- Animals, Cytochrome P-450 Enzyme System genetics, Cytochrome P-450 Enzyme System metabolism, Humans, Insecticide Resistance genetics, Mosquito Vectors genetics, Anopheles genetics, Anopheles metabolism, Insecticides pharmacology, Malaria genetics, Pyrethrins metabolism, Pyrethrins pharmacology
- Abstract
Metabolic-based resistance to insecticides limit the control of medically important pests, and it is extremely detrimental in the ongoing struggle to control disease vectors. Elucidating the fitness cost of metabolic resistance in major malaria vectors is vital for successful resistance management. We established the fitness cost of the 6.5kb structural variant ( 6.5kb-sv ) between the duplicated CYP6P9a/b P450s using the hybrid strain generated from the crossing between two An. funestus laboratory strains. Furthermore, we assessed the cumulative impact of this marker with the duplicated P450 genes. We established that individuals that were homozygote for the resistant structural variant (SV) presented reduced fecundity and slow development relative to those that were homozygote for the susceptible SV. Furthermore, we observed that 6.5kb act additively with CYP6P9a and CYP6P9b to exacerbate the reduced fecundity and the increased development time of resistant mosquitoes since double/triple homozygote susceptible (SS/SS/SS) significantly laid more eggs and developed faster than other genotypes. Moreover, a restoration of susceptibility was noted over 10 generations in the insecticide-free environment with an increased proportion of susceptible individuals. This study highlights the negative impact of multiple P450-based resistance on the key physiological traits of malaria vectors. Such high fitness costs suggest that in the absence of selection pressure, the resistant individuals will be outcompeted in the field. Therefore, this should encourage future strategies based on the rotation of insecticides to reduce selection pressure and to slow the spread of pyrethroid resistance.
- Published
- 2022
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