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En depit des methodes de lutte developpees contre le paludisme, l’apparition de la resistance d’Anopheles gambiae s.l. aux insecticides constitue une menace susceptible de conduire a l’echec de la lutte contre cette pathologie. Une etude recapitulative a ete realisee afin de montrer la dynamique spatio-temporelle de la resistance d’Anopheles gambiae s.l. a quelques insecticides utilises au Congo de 2002 a 2018. Les tests de sensibilite ont ete realises avec des femelles adultes âgees de un a cinq jours. Les insecticides testes appartiennent a 4 familles : (1) organochlores : DDT 4%; (2) organophosphores : malathion 5%, pirimiphos-methyl 1,25% ; (3) pyrethrinoides : permethrine 0,75%, deltamethrine 0,05% et 0,5%, European Scientific Journal, ESJ ISSN: 1857-7881 (Print) e - ISSN 1857-7431 January 2021 edition Vol.17, No.3 www.eujournal.org 245 lambdacyhalothrine 0,05 %; (4) carbamates : bendiocarbe 0,1% et 0,5%. Les tests ont ete faits avec les synergistes, l’effet knock-down a ete evalue pendant 60 minutes et la mortalite observee 24 heures apres. Cette etude a montre un developpement de la resistance au DDT, aux pyrethrinoides, l’apparition de la resistance au bendiocarbe et au pirimiphosmethyl et la sensibilite au malathion. Les mutations knockdown resistance (kdr) (L1014F) et (L1014S) sont percues comme responsables de la resistance au DDT et aux pyrethrinoides. Le retablissement de la sensibilite des anopheles a la deltamethrine apres exposition aux synergistes implique une resistance metabolique. L'etude a confirme l’existence de la resistance au DDT, aux pyrethrinoides, au bendiocarbe et au pirimiphos-methyl dans plusieurs departements du pays. Pour garantir l’efficacite des insecticides, il est primordial de surveiller la dynamique de la resistance aux insecticides et eventuellement, identifier les mecanismes impliques dans la resistance. Despite control methods developed against malaria, the emergence of Anopheles gambiae s.l. resistance to insecticides constitutes a threat that could lead to the failure of the fight against this pathology. A summary study was carried out in order to show the spatio-temporal dynamic of resistance of European Scientific Journal, ESJ ISSN: 1857-7881 (Print) e - ISSN 1857-7431 January 2021 edition Vol.17, No.3 www.eujournal.org 246 Anopheles gambiae s.l. to some insecticides used in Congo from 2002 to 2018. Sensitivity tests were carried out with two to five days old adult females. The insecticides tested belonged to 4 families: (1) organochlorines: DDT 4%; (2) organophosphates: malathion 5%, pirimiphos-methyl 1.25%; (3) pyrethroids: permethrin 0.75%, deltamethrin 0.05% and 0.5%, lambdacyhalothrin 0.05%; (4) carbamates: bendiocarb 0.1% and 0.5%. Tests were done with synergists. The knock-down effect was evaluated for 60 minutes and mortality 24 hours later. This study showed the existence of resistance to DDT, pyrethroids, development of resistance to bendiocarb and pirimiphos-methyl and sensitivity to malathion in several departments of the country. The knockdown resistance (kdr) mutations (L1014F) and (L1014S) are responsible for DDT resistance. Restoration of Anopheles' sensitivity to deltamethrin after exposure to synergists involves metabolic resistance. The study confirmed the development susceptibility to DDT, pyrethroids, bendiocarb and pirimiphos-methyl. To ensure the effectiveness of insecticides, it is essential to monitor the periodically susceptibility tests to insecticides and to identify the possible resistance mechanisms involved.

Background Invasive mosquito species, such as Aedes albopictus in Congo can affect the distribution of native species, changing the vector composition and pattern of disease transmission. Here, we comparatively establish the geographical distribution and larval habitat preference of Ae. aegypti and Ae. albopictus and the risk of arbovirus disease outbreaks using Stegomyia indices in the city of Brazzaville, the capital of the Republic of the Congo. Methods Human dwelling surveys of water-holding containers for immature stages of Aedes was carried out in December 2017 in Brazzaville through a random cluster sampling method. A total of 268 human dwellings distributed in 9 boroughs and 27 neighbourhoods were surveyed across the city. Results Overall, 455 potential larval habitats were surveyed. Both Ae. aegypti and Ae. albopictus were collected across the city with an overall high prevalence of Ae. aegypti (53.1%) compared to Ae. albopictus (46.9%). Geographical distribution analysis showed that Ae. aegypti was more abundant (mean = 6.6 ± 1.4) in neighbourhoods located in downtown, while the abundance of Ae. albopictus was low (mean = 3.5 ± 0.6) in suburbs. Peridomestic containers, especially discarded tanks, were the most strongly colonized productive larval habitat for both mosquito species with the prevalence of 56.4% and 53.1% for Ae. aegypti and Ae. albopictus, respectively. Globally, the house index (HI), Breteau index (BI) and container index (CI) were high for Ae. aegypti (26.6%, 38.4% and 22.6%) and Ae. albopictus (33.3%, 49.6% and 26.6%) compared to the transmission risk threshold (5%, 5% and 20%) established by the WHO/PAHO. Overall, pupae-based indices (the pupae index and the pupae per person index) were not significantly different between Ae. aegypti (273.4% and 23.2%) and Ae. albopictus (228.8% and 19.5%). Conclusions The findings of this study suggest a high risk for transmission of arbovirus diseases in Brazzaville and call for an urgent need to implement vector control strategies against these vectors in the Republic of the Congo.

Background In the Republic of Congo, with two massive outbreaks of chikungunya observed this decade, little is known about the insecticide resistance profile of the two major arbovirus vectors Aedes aegypti and Aedes albopictus. Here, we established the resistance profile of both species to insecticides and explored the resistance mechanisms to help Congo to better prepare for future outbreaks. Methods Immature stages of Ae. aegypti and Ae. albopictus were sampled in May 2017 in eight cities of the Republic of the Congo and reared to adult stage. Larval and adult bioassays, and synergist (piperonyl butoxide [PBO]) assays were carried out according to WHO guidelines. F1534C mutation was genotyped in field collected adults in both species and the polymorphism of the sodium channel gene assessed in Ae. aegypti. Results All tested populations were susceptible to temephos after larval bioassays. A high resistance level was observed to 4% DDT in both species countrywide (21.9–88.3% mortality). All but one population (Ae. aegypti from Ngo) exhibited resistance to type I pyrethroid, permethrin, but showed a full susceptibility to type II pyrethroid (deltamethrin) in almost all locations. Resistance was also reported to 1% propoxur in Ae. aegypti likewise in two Ae. albopictus populations (Owando and Ouesso), and the remaining were fully susceptible. All populations of both species were fully susceptible to 1% fenitrothion. A full recovery of susceptibility was observed in Ae. aegypti and Ae. albopictus when pre-exposed to PBO and then to propoxur and permethrin respectively. The F1534C kdr mutation was not detected in either species. The high genetic variability of the portion of sodium channel spanning the F1534C in Ae. aegypti further supported that knockdown resistance probably play no role in the permethrin resistance. Conclusions Our study showed that both Aedes species were susceptible to organophosphates (temephos and fenitrothion), while for other insecticide classes tested the profile of resistance vary according to the population origin. These findings could help to implement better and efficient strategies to control these species in the Congo in the advent of future arbovirus outbreaks.

Background Malaria in pregnancy is associated with considerable morbidity and mortality. Regular surveillance of artemisinin-based combination therapy tolerance, or molecular makers of resistance, is vital for effective malaria treatment, control and eradication programmes. Plasmodium falciparum multiple drug resistance-1 gene (Pfmdr1) N86Y mutation is associated with reduced susceptibility to lumefantrine. This study assessed the prevalence of Pfmdr1 N86Y in Brazzaville, Republic of Congo. Methods A total 1001 of P. falciparum-infected blood samples obtained from asymptomatic malaria pregnant women having a normal child delivery at the Madibou Integrated Health Centre were analysed. Pfmdr1 N86Y genotyping was conducted using PCR-restriction fragment length polymorphism. Results The wild type Pfmdr1 N86 allele was predominant (> 68%) in this study, whereas a few isolates carrying the either the mutant allele (Pfmdr1 86Y) alone or both alleles (mixed genotype). The dominance of the wildtype allele (pfmdr1 N86) indicates the plausible decline P. falciparum susceptibility to lumefantrine. Conclusion This study gives an update on the prevalence of Pfmdr1 N86Y alleles in Brazzaville, Republic of Congo. It also raises concern on the imminent emergence of resistance against artemether–lumefantrine in this setting. This study underscores the importance to regular artemether–lumefantrine efficacy monitoring to inform the malaria control programme of the Republic of Congo.

Bruchidius atrolineatus (Pic) is a common pest infesting cowpea seeds (Vigna unguiculata Walp) in Africa. In the Sahelian zone, the adults are in reproductive diapause during the dry season. Diapause induction depends on the climatic conditions during embryonic and post-embryonic development. A strain of B. atrolineatus originating from the Niamey (13oN) was reared in different thermoperiodic and photoperiodic conditions. In the thermoperiodic regime 40:25oC, in continuous darkness, induction of diapause was dependent on the duration of the thermophase. Photoperiod could also influence diapause induction but the response depended on the temperature. When the beetles were reared in conditions of LD 12:12 h, 40:25oC, for seven generations, the proportion of diapausing adults decreased and their sensitivity to photoperiod increased. In LD 14:10 h, 40:25CC, the proportion of diapausing adults remained high regardless of the photoperiod. In these conditions, the first emerging adults were sexually active and were used for selection of a strain with a low incidence of diapause. After twelve generations, the proportion of diapausing beetles was lower than 5%. The responses of this selected strain to photo- and thermoperiods were reduced. The sensitivity of B. atrolineatus to photoperiod and thermoperiod could be controlled by genetic systems as observed in other insect species.

Bruchidius atrolineatus (Pic) (Bruchidae: Coleoptera) is a bruchid beetle infesting Vigna unguiculata (Walp). During the dry season, adults are in reproductive diapause. Studies of adult populations in a traditional store containing contaminated pods of V. unguiculata show that the reproductive diapause is induced during the first larval instars. The temperature decrease from November to January probably is the main climatic factor inducing this diapause. The percentage of diapausing adults depends on the duration of the larval development at low temperatures. Experiments in climatic boxes confirm these results. At 12 h 25 °T–12 h 20° C 11–13 LD, a high proportion of the adults emerging from the V. unguiculata seeds are in reproductive diapause and the duration of their growth is variable. L1 L2 L3 larvae probably are sensitive stages to the thermal variations and the processes allowing emergence of diapausing adults probably are induced during these larval instars. Resume Induction de la diapause reproductrice chez Bruchidius atrolineatus coleoptere bruchidae durant la saison seche en zone Sahelienne Bruchidius atrolineatus (Pic) est un Coleoptere Bruchidae se developpant en zone sahelienne aux depens d'une legumineuse Vigna unguiculata. Pendant la saison seche, les adultes sont en diapause reproductrice. Un suivi des populations d'adultes a ete realise dans un grenier traditionnel en ‘terre sechee’ contenant des gousses recoltees dans la nature et portant des œufs de B. atrolineatus. Il a permis de constater que la diapause reproductrice etait induite durant les premieres phases du developpement larvaire. La decroissance des temperatures de Novembre a Janvier avec des minima de 15 °C et des maxima de 25 °C est probablement le principal facteur permettant l'induction de cette diapause. L'introduction dans le grenier de gousses portant des œufs venant d'etre emis a differentes periodes de la saison seche montre que le pourcentage d'adultes diapausants depend de la duree du developpement larvaire aux temperatures ‘basses’. Des experiences realisees dans des etuves programmees confirment ces resultats. A 12 h 25 °T/12 h 20 °C 11–13 LD, un taux eleve d'adultes emergeant des graines est en diapause reproductrice et la duree de leur developpement post-embryonnaire est tres variable. En conditions plus chaudes 12 h 40 °C/12 h 25 °C 11–13 LD, le taux d'adultes diapausants est plus reduit et la duree du developpement plus courte. L'analyse de la croissance larvaire montre que les premiers stades larvaires sont probablement des stades sensibles aux variations thermiques. Les modifications physiologiques permettant l'emergence d'adultes diapausants ou sexuellement actifs seraient induites durant ces stades.