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African animal trypanosomiasis (AAT) is one of the major constraints to animal health and production in sub-Saharan Africa. To inform AAT control in Uganda and help advance along the progressive control pathway (PCP), we characterized AAT prevalence among eight host species in Uganda and explored factors that influence the prevalence variation between studies. We retrieved AAT prevalence publications (n = 2232) for Uganda (1980-2022) from five life sciences databases, focusing on studies specifying AAT detection methods, sample size, and the number of trypanosome-positive animals. Following PRISMA guidelines, we included 56 publications, and evaluated publication bias by the Luis Furuya-Kanamori (LFK) index. National AAT prevalence under DNA diagnostic methods for cattle, sheep and goats was 22.15%, 8.51% and 13.88%, respectively. Under DNA diagnostic methods, T. vivax was the most common Trypanosoma sp. in cattle (6.15%, 95% CI: 2.91-10.45) while T. brucei was most common among small ruminants (goats: 8.78%, 95% CI: 1.90-19.88, and sheep: 8.23%, 95% CI: 4.74-12.50, respectively). Northern and Eastern regions accounted for the highest AAT prevalence. Despite the limitations of this study (i.e., quality of reviewed studies, underrepresentation of districts/regions), we provide insights that could be used for better control of AAT in Uganda and identify knowledge gaps that need to be addressed to support the progressive control of AAT at country level and other regional endemic countries with similar AAT eco-epidemiology.

Abstract Background Tsetse flies, the biological vectors of African trypanosomes, have established symbiotic associations with different bacteria. Their vector competence is suggested to be affected by bacterial endosymbionts. The current study provided the prevalence of three tsetse symbiotic bacteria and trypanosomes in Glossina species from Burkina Faso. Results A total of 430 tsetse flies were captured using biconical traps in four different collection sites around Bobo-Dioulasso (Bama, Bana, Nasso, and Peni), and their guts were removed. Two hundred tsetse were randomly selected and their guts were screened by PCR for the presence of Sodalis glossinidius, Spiroplasma sp., Wolbachia and trypanosomes. Of the 200 tsetse, 196 (98.0%) were Glossina palpalis gambiensis and 4 (2.0%) Glossina tachinoides. The overall symbiont prevalence was 49.0%, 96.5%, and 45.0%, respectively for S. glossinidius, Spiroplasma and Wolbachia. Prevalence varied between sampling locations: S. glossinidius (54.7%, 38.5%, 31.6%, 70.8%); Spiroplasma (100%, 100%, 87.7%, 100%); and Wolbachia (43.4%, 38.5%, 38.6%, 70.8%), respectively in Bama, Bana, Nasso and Peni. Noteworthy, no G. tachnoides was infected by S. glossinidius and Wolbachia, but they were all infected by Spiroplasma sp. A total of 196 (98.0%) harbored at least one endosymbionts. Fifty-five (27.5%) carried single endosymbiont. Trypanosomes were found only in G. p. gambiensis, but not G. tachinoides. Trypanosomes were present in flies from all study locations with an overall prevalence of 29.5%. In Bama, Bana, Nasso, and Peni, the trypanosome infection rate was respectively 39.6%, 23.1%, 8.8%, and 37.5%. Remarkably, only Trypanosoma grayi was present. Of all trypanosome-infected flies, 55.9%, 98.3%, and 33.9% hosted S. glossinidius, Spiroplasma sp and Wolbachia, respectively. There was no association between Sodalis, Spiroplasma and trypanosome presence, but there was a negative association with Wolbachia presence. We reported 1.9 times likelihood of trypanosome absence when Wolbachia was present. Conclusion This is the first survey reporting the presence of Trypanosoma grayi in tsetse from Burkina Faso. Tsetse from these localities were highly positive for symbiotic bacteria, more predominantly with Spiroplasma sp. Modifications of symbiotic interactions may pave way for disease control.

Background: Tsetse flies, the biological vectors of African trypanosomes, have established symbiotic associations with different bacteria. Their vector competence is suggested to be affected by bacterial endosymbionts. The current study provided the prevalence of three tsetse symbiotic bacteria and trypanosomes in Glossina species from Burkina Faso. Results: A total of 430 tsetse flies were captured using biconical traps in four different collection sites around Bobo-Dioulasso (Bama, Bana, Nasso, and Peni), and their guts were removed. Two hundred tsetse were randomly selected and their guts were screened by PCR for the presence of Sodalis glossinidius, Spiroplasma sp., Wolbachia and trypanosomes. Of the 200 tsetse, 196 (98.0%) were Glossina palpalis gambiensis and 4 (2.0%) Glossina tachinoides. The overall symbiont prevalence was 49.0%, 96.5%, and 45.0%, respectively for S. glossinidius, Spiroplasma and Wolbachia. Prevalence varied between sampling locations: S. glossinidius (54.7%, 38.5%, 31.6%, 70.8%); Spiroplasma (100%, 100%, 87.7%, 100%); and Wolbachia (43.4%, 38.5%, 38.6%, 70.8%), respectively in Bama, Bana, Nasso and Peni. Noteworthy, no G. tachnoides was infected by S. glossinidius and Wolbachia, but they were all infected by Spiroplasma sp. A total of 196 (98.0%) harbored at least one endosymbionts. Fifty-five (27.5%) carried single endosymbiont. Trypanosomes were found only in G. p. gambiensis, but not G. tachinoides. Trypanosomes were present in flies from all study locations with an overall prevalence of 29.5%. In Bama, Bana, Nasso, and Peni, the trypanosome infection rate was respectively 39.6%, 23.1%, 8.8%, and 37.5%. Remarkably, only Trypanosoma grayi was present. Of all trypanosome-infected flies, 55.9%, 98.3%, and 33.9% hosted S. glossinidius, Spiroplasma sp and Wolbachia, respectively. There was no association between Sodalis, Spiroplasma and trypanosome presence, but there was a negative association with Wolbachia presence. We reported 1.9 times likelihood of trypanosome absence when Wolbachia was present. Conclusion: This is the first survey reporting the presence of Trypanosoma grayi in tsetse from Burkina Faso. Tsetse from these localities were highly positive for symbiotic bacteria, more predominantly with Spiroplasma sp. Modifications of symbiotic interactions may pave way for disease control. [ABSTRACT FROM AUTHOR]

Diurnal biting flies are strongly attracted to blue objects. This behaviour is widely exploited for fly control, but its functional significance is debated. It is hypothesized that blue objects resemble animal hosts; blue surfaces resemble shaded resting places; and blue attraction is a by-product of attraction to polarized light. We computed the fly photoreceptor signals elicited by a large sample of leaf and animal integument reflectance spectra, viewed under open/cloudy illumination and under woodland shade. We then trained artificial neural networks (ANNs) to distinguish animals from leaf backgrounds, and shaded from unshaded surfaces, in order to find the optimal means of doing so based upon the sensory information available to a fly. After training, we challenged ANNs to classify blue objects used in fly control. Trained ANNs could make both discriminations with high accuracy. They discriminated animals from leaves based upon blue-green photoreceptor opponency and commonly misclassified blue objects as animals. Meanwhile, they discriminated shaded from unshaded stimuli using achromatic cues and never misclassified blue objects as shaded. We conclude that blue-green opponency is the most effective means of discriminating animals from leaf backgrounds using a fly's sensory information, and that blue objects resemble animal hosts through such mechanisms.

Landscape, climate, and culture can all structure human populations, but few existing methods are designed to simultaneously disentangle among a large number of variables in explaining genetic patterns. We developed a machine learning method for identifying the variables which best explain migration rates, as measured by the coalescent-based program MAPS that uses shared identical by descent tracts to infer spatial migration across a region of interest. We applied our method to 30 human populations in eastern Africa with high-density single nucleotide polymorphism array data. The remarkable diversity of ethnicities, languages, and environments in this region offers a unique opportunity to explore the variables that shape migration and genetic structure. We explored more than 20 spatial variables relating to landscape, climate, and presence of tsetse flies. The full model explained ∼40% of the variance in migration rate over the past 56 generations. Precipitation, minimum temperature of the coldest month, and elevation were the variables with the highest impact. Among the three groups of tsetse flies, the most impactful was fusca which transmits livestock trypanosomiasis. We also tested for adaptation to high elevation among Ethiopian populations. We did not identify well-known genes related to high elevation, but we did find signatures of positive selection related to metabolism and disease. We conclude that the environment has influenced the migration and adaptation of human populations in eastern Africa; the remaining variance in structure is likely due in part to cultural or other factors not captured in our model.

Simple Summary: Arthropods are a large and diverse group of animals, some of which are pests, while others transmit human and livestock diseases as they bite them to feed on blood. Chemical-based vector and pest control for decades has made many arthropods resistant to the chemicals used. So, there is a need to investigate other control agents, such as the biological, arthropod-killing fungus Metarhizium anisopliae, for the ability to infect and kill human and livestock disease-transmitting arthropods. In this study, we tested if the fungus M. anisopliae infects and kills mosquitoes, tsetse flies, and ticks. This was performed by finding out how long mosquitoes lived after being infected with fungus spores, as well as the amount of fungus spores suitable to lead to their death. The same optimal concentration of fungus that killed mosquitoes also successfully killed tsetse flies and ticks. We recommend that the fungus be formulated in a suitable concentration of 109 spores/mL and its ability to kill mosquitoes, tsetse flies, and ticks be confirmed in the field. This would lead to the development of a fungal formulation that can be sprayed on livestock such as cattle, for the exposure of multiple blood-feeding and disease-transmitting arthropods at the same time, to impact their survival. Arthropod vectors are responsible for a multitude of human and animal diseases affecting poor communities in sub-Saharan Africa. Their control still relies on chemical agents, despite growing evidence of insecticide resistance and environmental health concerns. Biorational agents, such as the entomopathogenic fungus Metarhizium anisopliae, might be an alternative for vector control. Recently, the M. anisopliae isolate ICIPE 7 has been developed into a commercial product in Kenya for control of ticks on cattle. We were interested in assessing the potential of controlling not only ticks but also disease-transmitting mosquitoes and tsetse flies using cattle as blood hosts, with the aim of developing a product for integrated vector management. Laboratory bioassays were carried out with M. anisopliae, isolate ICIPE 7 and isolate ICIPE 30, to compare efficacy against laboratory-reared Anopheles arabiensis. ICIPE 7 was further tested against wild Glossina fuscipes and Rhipicephalus spp. Dose–response tests were implemented, period of mosquito exposure was evaluated for effects on time to death, and the number of spores attached to exposed vectors was assessed. Exposure to 109 spores/mL of ICIPE 7 for 10 min resulted in a similar mortality of An. arabiensis as exposure to ICIPE 30, albeit at a slower rate (12 vs. 8 days). The same ICIPE 7 concentration also resulted in mortalities of tsetse flies (LT50: 16 days), tick nymphs (LT50: 11 days), and adult ticks (LT50: 20 days). Mosquito mortality was dose-dependent, with decreasing LT50 of 8 days at a concentration of 106 spores/mL to 6 days at 1010 spores/mL. Exposure period did not modulate the outcome, 1 min of exposure still resulted in mortality, and spore attachment to vectors was dose-dependent. The laboratory bioassays confirmed that ICIPE 7 has the potential to infect and cause mortality to the three exposed arthropods, though at slower rate, thus requiring further validation under field conditions. [ABSTRACT FROM AUTHOR]

We report 4 cases of human African trypanosomiasis that occurred in Ethiopia in 2022, thirty years after the last previously reported case in the country. Two of 4 patients died before medicine became available. We identified the infecting parasite as Trypanosoma brucei rhodesiense. Those cases imply human African trypanosomiasis has reemerged.

This overview initially describes insect immune reactions and then brings together present knowledge of the interactions of vector insects with their invading parasites and pathogens. It is a way of introducing this Special Issue with subsequent papers presenting the latest details of these interactions in each particular group of vectors. Hopefully, this paper will fill a void in the literature since brief descriptions of vector immunity have now been brought together in one publication and could form a starting point for those interested and new to this important area. Descriptions are given on the immune reactions of mosquitoes, blackflies, sandflies, tsetse flies, lice, fleas and triatomine bugs. Cellular and humoral defences are described separately but emphasis is made on the co-operation of these processes in the completed immune response. The paper also emphasises the need for great care in extracting haemocytes for subsequent study as appreciation of their fragile nature is often overlooked with the non-sterile media, smearing techniques and excessive centrifugation sometimes used. The potential vital role of eicosanoids in the instigation of many of the immune reactions described is also discussed. Finally, the priming of the immune system, mainly in mosquitoes, is considered and one possible mechanism is presented. [ABSTRACT FROM AUTHOR]

Tsetse flies are major arthropod vectors of trypanosomes that cause debilitating African animal trypanosomiasis. The emergence of drug-resistant trypanosomes is a common problem in sub-Saharan Africa. This study aimed to identify tsetse flies’ seasonal variation in apparent densities and their infection rates and the occurrence of drug-resistant trypanosomes. Tsetse flies were collected from Lambwe, Kenya, during May and September 2021. Genomic DNA was extracted from them, and the ITS1 gene was amplified to detect Trypanosoma infection with subsequent species determination. Transporter genes DMT, E6M6, TbAT/P2, and TcoAde2 were targeted to detect polymorphisms associated with drug-resistance, using sequencing and comparison to drug-sensitive trypanosome species referenced in Genbank. A total of 498 tsetse flies and 29 non-tsetse flies were collected. The apparent density of flies was higher in wet season 6.2 fly per trap per density (FTD) than in the dry season 2.3 FTD (P = 0.001), with n = 386 and n = 141 flies caught in each season, respectively. Male tsetse flies (n = 311) were more numerous than females (n = 187) (P = 0.001). Non-tsetse flies included Tabanids and Stomoxys spp. Overall, Trypanosoma infection rate in tsetse was 5% (25/498) whereby Trypanosoma vivax was 4% (11/25), Trypanosoma congolense 36% (9/25), and Trypanosoma brucei 20% (5/25) (P = 0.186 for the distribution of the species), with infections being higher in females (P = 0.019) and during the wet season (P < 0.001). Numerous polymorphisms and insertions associated with drug resistance were detected in DMT and E6M6 genes in two T. congolense isolates while some isolates lacked these genes. T. brucei lacked TbAT/P2 genes. TcoAde2 sequences in three T. congolense isolates were related to those observed in trypanosomes from cattle blood in our previous study, supporting tsetse fly involvement in transmission in the region. We report Trypanosoma associated with trypanocidal drug-resistance in tsetse flies from Lambwe, Kenya. Female tsetse flies harbored more Trypanosoma infections than males. Tsetse transmission of trypanosomes is common in Lambwe. Risk of trypanosome infection would seem higher in the wet season, when tsetse flies and Trypanosoma infections are more prevalent than during the dry season. More efforts to control animal trypanosome vectors in the region are needed, with particular focus on wet seasons. [ABSTRACT FROM AUTHOR]

BackgroundGlossina species (tsetse flies), the sole vectors of African trypanosomes, maintained along their long evolutionary history a unique reproductive strategy, adenotrophic viviparity. Viviparity reduces their reproductive rate and, as such, imposes strong selective pressures on males for reproductive success. These species live in sub-Saharan Africa, where the distributions of the main sub-genera Fusca, Morsitans, and Palpalis are restricted to forest, savannah, and riverine habitats, respectively. Here we aim at identifying the evolutionary patterns of the male reproductive genes of six species belonging to these three main sub-genera. We then interpreted the different patterns we found across the species in the light of viviparity and the specific habitat restrictions, which are known to shape reproductive behavior.ResultsWe used a comparative genomic approach to build consensus evolutionary trees that portray the selective pressure acting on the male reproductive genes in these lineages. Such trees reflect the long and divergent demographic history that led to an allopatric distribution of the Fusca, Morsitans, and Palpalis species groups. A dataset of over 1700 male reproductive genes remained conserved over the long evolutionary time scale (estimated at 26.7 million years) across the genomes of the six species. We suggest that this conservation may result from strong functional selective pressure on the male imposed by viviparity. It is noteworthy that more than half of these conserved genes are novel sequences that are unique to the Glossina genus and are candidates for selection in the different lineages.ConclusionsTsetse flies represent a model to interpret the evolution and differentiation of male reproductive biology under different, but complementary, perspectives. In the light of viviparity, we must take into account that these genes are constrained by a post-fertilization arena for genomic conflicts created by viviparity and absent in ovipositing species. This constraint implies a continuous antagonistic co-evolution between the parental genomes, thus accelerating inter-population post-zygotic isolation and, ultimately, favoring speciation. Ecological restrictions that affect reproductive behavior may further shape such antagonistic co-evolution.

Abstract Background Tsetse flies are cyclical vectors of African trypanosomiasis (AT). The flies have established symbiotic associations with different bacteria that influence certain aspects of their physiology. Vector competence of tsetse flies for different trypanosome species is highly variable and is suggested to be affected by bacterial endosymbionts amongst other factors. Symbiotic interactions may provide an avenue for AT control. The current study provided prevalence of three tsetse symbionts in Glossina species from Cameroon, Chad and Nigeria. Results Tsetse flies were collected and dissected from five different locations. DNA was extracted and polymerase chain reaction used to detect presence of Sodalis glossinidius, Spiroplasma species and Wolbachia endosymbionts, using species specific primers. A total of 848 tsetse samples were analysed: Glossina morsitans submorsitans (47.52%), Glossina palpalis palpalis (37.26%), Glossina fuscipes fuscipes (9.08%) and Glossina tachinoides (6.13%). Only 95 (11.20%) were infected with at least one of the three symbionts. Among infected flies, six (6.31%) had Wolbachia and Spiroplasma mixed infection. The overall symbiont prevalence was 0.88, 3.66 and 11.00% respectively, for Sodalis glossinidius, Spiroplasma species and Wolbachia endosymbionts. Prevalence varied between countries and tsetse fly species. Neither Spiroplasma species nor S. glossinidius were detected in samples from Cameroon and Nigeria respectively. Conclusion The present study revealed, for the first time, presence of Spiroplasma species infections in tsetse fly populations in Chad and Nigeria. These findings provide useful information on repertoire of bacterial flora of tsetse flies and incite more investigations to understand their implication in the vector competence of tsetse flies.

Trypanosomosis is a vector-borne zoonotic disease transmitted by the tsetse fly (Glossina species). The condition is caused by protozoa known as Trypanosomes. In 2009, large-scale aerial spraying with deltamethrin at 0.26-0.3 g/ha, was undertaken in 5000 km2 covering parts of the Sesheke and Shang’ombo districts to control tsetse flies animal trypanosomosis in cattle in the area. Cattle were sampled for prevalence and incidence of trypanosomosis before, during, and, after aerial spraying as a circuitous way of detecting the presence of the primary vector (tsetse flies). Buffy coats, thick and thin dry smears were applied in the parasitological tests. In the baseline survey, 1,866 cattle were presented, and 25.7% (n = 481) were sampled and examined. Trypanosoma spp. was detected in 1.9% (n = 9) of animals. Six sentinel herds (four treatments and two controls) with 20 animals per herd were monitored for the incidence of AAT during and after aerial spraying, and prevalence was compared among the three phases. The results showed that no new case of trypanosomosis was detected in the treatment herd during the aerial spraying and three months into the postaerial spraying period except 0.83% (n = 1) in the control herd [Mid-P exact; p-value = 0.167 (1-tailed)]. This suggests an association between deltamethrin aerial spraying and trypanosomosis. In conclusion, there was a significant reduction in trypanosomosis prevalence following the aerial spraying operation. This indicates that aerial spraying significantly reduced the tsetse population and subsequently reduced disease transmission to cattle in the area. Furthermore, it indicates that aerial spraying was an effective method of controlling trypanosomosis in cattle. There is a need to extend this operation to other tsetse-infested areas in the country.

Simple Summary: Insect vectors are responsible for transmitting a range of diseases, leading to significant mortality rates annually. Their behavior and physiology can undergo shifts due to complex molecular interactions during mating and feeding. In this review, we provide an exhaustive overview of the current "omics" knowledge—spanning genomics, transcriptomics, proteomics, and metabolomics—across various vector species. We highlight potential molecular targets for vector control and outline the advancements and gaps in our understanding, which could pave the way for innovative and effective strategies to curb disease transmission. Female insects belonging to the genera Anopheles, Aedes, Glossina, and Rhodnius account for the majority of global vector-borne disease mortality. In response to mating, these female insects undergo several molecular, physiological, and behavioral changes. Studying the dynamic post-mating molecular responses in these insects that transmit human diseases can lead to the identification of potential targets for the development of novel vector control methods. With the continued advancements in bioinformatics tools, we now have the capability to delve into various physiological processes in these insects. Here, we discuss the availability of multiple datasets describing the reproductive physiology of the common blood-feeding insects at the molecular level. Additionally, we compare the male-derived triggers transferred during mating to females, examining both shared and species-specific factors. These triggers initiate post-mating genetic responses in female vectors, affecting not only their reproductive success but also disease transmission. [ABSTRACT FROM AUTHOR]

Tsetse flies (Glossina spp.) house a population-dependent assortment of microorganisms that can include pathogenic African trypanosomes and maternally transmitted endosymbiotic bacteria, the latter of which mediate numerous aspects of their host's metabolic, reproductive, and immune physiologies. One of these endosymbionts, Spiroplasma, was recently discovered to reside within multiple tissues of field captured and laboratory colonized tsetse flies grouped in the Palpalis subgenera. In various arthropods, Spiroplasma induces reproductive abnormalities and pathogen protective phenotypes. In tsetse, Spiroplasma infections also induce a protective phenotype by enhancing the fly's resistance to infection with trypanosomes. However, the potential impact of Spiroplasma on tsetse's viviparous reproductive physiology remains unknown. Herein we employed high-throughput RNA sequencing and laboratory-based functional assays to better characterize the association between Spiroplasma and the metabolic and reproductive physiologies of G. fuscipes fuscipes (Gff), a prominent vector of human disease. Using field-captured Gff, we discovered that Spiroplasma infection induces changes of sex-biased gene expression in reproductive tissues that may be critical for tsetse's reproductive fitness. Using a Gff lab line composed of individuals heterogeneously infected with Spiroplasma, we observed that the bacterium and tsetse host compete for finite nutrients, which negatively impact female fecundity by increasing the length of intrauterine larval development. Additionally, we found that when males are infected with Spiroplasma, the motility of their sperm is compromised following transfer to the female spermatheca. As such, Spiroplasma infections appear to adversely impact male reproductive fitness by decreasing the competitiveness of their sperm. Finally, we determined that the bacterium is maternally transmitted to intrauterine larva at a high frequency, while paternal transmission was also noted in a small number of matings. Taken together, our findings indicate that Spiroplasma exerts a negative impact on tsetse fecundity, an outcome that could be exploited for reducing tsetse population size and thus disease transmission.

Background: Tsetse flies are cyclical vectors of African trypanosomiasis (AT). The flies have established symbiotic associations with different bacteria that influence certain aspects of their physiology. Vector competence of tsetse flies for different trypanosome species is highly variable and is suggested to be affected by bacterial endosymbionts amongst other factors. Symbiotic interactions may provide an avenue for AT control. The current study provided prevalence of three tsetse symbionts in Glossina species from Cameroon, Chad and Nigeria. Results: Tsetse flies were collected and dissected from five different locations. DNA was extracted and polymerase chain reaction used to detect presence of Sodalis glossinidius, Spiroplasma species and Wolbachia endosymbionts, using species specific primers. A total of 848 tsetse samples were analysed: Glossina morsitans submorsitans (47.52%), Glossina palpalis palpalis (37.26%), Glossina fuscipes fuscipes (9.08%) and Glossina tachinoides (6.13%). Only 95 (11.20%) were infected with at least one of the three symbionts. Among infected flies, six (6.31%) had Wolbachia and Spiroplasma mixed infection. The overall symbiont prevalence was 0.88, 3.66 and 11.00% respectively, for Sodalis glossinidius, Spiroplasma species and Wolbachia endosymbionts. Prevalence varied between countries and tsetse fly species. Neither Spiroplasma species nor S. glossinidius were detected in samples from Cameroon and Nigeria respectively. Conclusion: The present study revealed, for the first time, presence of Spiroplasma species infections in tsetse fly populations in Chad and Nigeria. These findings provide useful information on repertoire of bacterial flora of tsetse flies and incite more investigations to understand their implication in the vector competence of tsetse flies. [ABSTRACT FROM AUTHOR]

Tsetse flies (Glossina spp.) act as the sole vectors of the African trypanosome species that cause Human African Trypanosomiasis (HAT or African Sleeping Sickness) and Nagana in animals. These flies have undergone a variety of specializations during their evolution including an exclusive diet consisting solely of vertebrate blood for both sexes as well as an obligate viviparous reproductive biology. Alongside these adaptations, Glossina species have developed intricate relationships with specific microbes ranging from mutualistic to parasitic. These relationships provide fundamental support required to sustain the specializations associated with tsetse's biology. This chapter provides an overview on the knowledge to date regarding the biology behind these relationships and focuses primarily on four bacterial species that are consistently associated with Glossina species. Here their interactions with the host are reviewed at the morphological, biochemical and genetic levels. This includes: the obligate symbiont Wigglesworthia, which is found in all tsetse species and is essential for nutritional supplementation to the blood-specific diet, immune system maturation and facilitation of viviparous reproduction; the commensal symbiont Sodalis, which is a frequently associated symbiont optimized for survival within the fly via nutritional adaptation, vertical transmission through mating and may alter vectorial capacity of Glossina for trypanosomes; the parasitic symbiont Wolbachia, which can manipulate Glossina via cytoplasmic incompatibility and shows unique interactions at the genetic level via horizontal transmission of its genetic material into the genome in two Glossina species; finally, knowledge on recently observed relations between Spiroplasma and Glossina is explored and potential interactions are discussed based on knowledge of interactions between this bacterial Genera and other insect species. These flies have a simple microbiome relative to that of other insects. However, these relationships are deep, well-studied and provide a window into the complexity and function of host/symbiont interactions in an important disease vector.

Tsetse flies (genus Glossina) transmit deadly trypanosomes to human populations and domestic animals in sub-Saharan Africa. Some foci of Human African Trypanosomiasis due to Trypanosoma brucei gambiense (g-HAT) persist in southern Chad, where a program of tsetse control was implemented against the local vector Glossina fuscipes fuscipes in 2018 in Maro. We analyzed the population genetics of G. f. fuscipes from the Maro focus before control (T0), one year (T1), and 18 months (T2) after the beginning of control efforts. Most flies captured displayed a local genetic profile (local survivors), but a few flies displayed outlier genotypes. Moreover, disturbance of isolation by distance signature (increase of genetic distance with geographic distance) and effective population size estimates, absence of any genetic signature of a bottleneck, and an increase of genetic diversity between T0 and T2 strongly suggest gene flows from various origins, and a limited impact of the vector control efforts on this tsetse population. Continuous control and surveillance of g-HAT transmission is thus recommended in Maro. Particular attention will need to be paid to the border with the Central African Republic, a country where the entomological and epidemiological status of g-HAT is unknown.

BackgroundTsetse flies (Glossina sp.) are the vectors of human and animal trypanosomiasis throughout sub-Saharan Africa. Tsetse flies are distinguished from other Diptera by unique adaptations, including lactation and the birthing of live young (obligate viviparity), a vertebrate blood-specific diet by both sexes, and obligate bacterial symbiosis. This work describes the comparative analysis of six Glossina genomes representing three sub-genera: Morsitans (G. morsitans morsitans, G. pallidipes, G. austeni), Palpalis (G. palpalis, G. fuscipes), and Fusca (G. brevipalpis) which represent different habitats, host preferences, and vectorial capacity.ResultsGenomic analyses validate established evolutionary relationships and sub-genera. Syntenic analysis of Glossina relative to Drosophila melanogaster shows reduced structural conservation across the sex-linked X chromosome. Sex-linked scaffolds show increased rates of female-specific gene expression and lower evolutionary rates relative to autosome associated genes. Tsetse-specific genes are enriched in protease, odorant-binding, and helicase activities. Lactation-associated genes are conserved across all Glossina species while male seminal proteins are rapidly evolving. Olfactory and gustatory genes are reduced across the genus relative to other insects. Vision-associated Rhodopsin genes show conservation of motion detection/tracking functions and variance in the Rhodopsin detecting colors in the blue wavelength ranges.ConclusionsExpanded genomic discoveries reveal the genetics underlying Glossina biology and provide a rich body of knowledge for basic science and disease control. They also provide insight into the evolutionary biology underlying novel adaptations and are relevant to applied aspects of vector control such as trap design and discovery of novel pest and disease control strategies.

The unicellular parasite Trypanosoma brucei is transmitted between mammals by tsetse flies. Following the discovery that flagellar phosphodiesterase PDEB1 is required for trypanosomes to move in response to signals in vitro (social motility), we investigated its role in tsetse flies. Here we show that PDEB1 knockout parasites exhibit subtle changes in movement, reminiscent of bacterial chemotaxis mutants. Infecting flies with the knockout, followed by live confocal microscopy of fluorescent parasites within dual-labelled insect tissues, shows that PDEB1 is important for traversal of the peritrophic matrix, which separates the midgut lumen from the ectoperitrophic space. Without PDEB1, parasites are trapped in the lumen and cannot progress through the cycle. This demonstrates that the peritrophic matrix is a barrier that must be actively overcome and that the parasite's flagellar cAMP signaling pathway facilitates this. Migration may depend on perception of chemotactic cues, which could stem from co-infecting parasites and/or the insect host.

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Female insects belonging to the genera Anopheles, Aedes, Glossina, and Rhodnius account for the majority of global vector-borne disease mortality. In response to mating, these female insects undergo several molecular, physiological, and behavioral changes. Studying the dynamic post-mating molecular responses in these insects that transmit human diseases can lead to the identification of potential targets for the development of novel vector control methods. With the continued advancements in bioinformatics tools, we now have the capability to delve into various physiological processes in these insects. Here, we discuss the availability of multiple datasets describing the reproductive physiology of the common blood-feeding insects at the molecular level. Additionally, we compare the male-derived triggers transferred during mating to females, examining both shared and species-specific factors. These triggers initiate post-mating genetic responses in female vectors, affecting not only their reproductive success but also disease transmission.

Abstract This article presents an overview of paratransgenesis as a strategy to control pathogen transmission by insect vectors. It first briefly summarises some of the disease-causing pathogens vectored by insects and emphasises the need for innovative control methods to counter the threat of resistance by both the vector insect to pesticides and the pathogens to therapeutic drugs. Subsequently, the state of art of paratransgenesis is described, which is a particularly ingenious method currently under development in many important vector insects that could provide an additional powerful tool for use in integrated pest control programmes. The requirements and recent advances of the paratransgenesis technique are detailed and an overview is given of the microorganisms selected for genetic modification, the effector molecules to be expressed and the environmental spread of the transgenic bacteria into wild insect populations. The results of experimental models of paratransgenesis developed with triatomines, mosquitoes, sandflies and tsetse flies are analysed. Finally, the regulatory and safety rules to be satisfied for the successful environmental release of the genetically engineered organisms produced in paratransgenesis are considered. Graphical Abstract

BackgroundTsetse flies (Diptera, Glossinidae) display unique reproductive biology traits. Females reproduce through adenotrophic viviparity, nourishing the growing larva into their modified uterus until parturition. Males transfer their sperm and seminal fluid, produced by both testes and male accessory glands, in a spermatophore capsule transiently formed within the female reproductive tract upon mating. Both sexes are obligate blood feeders and have evolved tight relationships with endosymbionts, already shown to provide essential nutrients lacking in their diet. However, the partnership between tsetse and its symbionts has so far been investigated, at the molecular, genomic and metabolomics level, only in females, whereas the roles of microbiota in male reproduction are still unexplored.ResultsHere we begin unravelling the impact of microbiota on Glossina m. morsitans (G. morsitans) male reproductive biology by generating transcriptomes from the reproductive tissues of males deprived of their endosymbionts (aposymbiotic) via maternal antibiotic treatment and dietary supplementation. We then compared the transcriptional profiles of genes expressed in the male reproductive tract of normal and these aposymbiotic flies. We showed that microbiota removal impacts several male reproductive genes by depressing the activity of genes in the male accessory glands (MAGs), including sequences encoding seminal fluid proteins, and increasing expression of genes in the testes. In the MAGs, in particular, the expression of genes related to mating, immunity and seminal fluid components' synthesis is reduced. In the testes, the absence of symbionts activates genes involved in the metabolic apparatus at the basis of male reproduction, including sperm production, motility and function.ConclusionsOur findings mirrored the complementary roles male accessory glands and testes play in supporting male reproduction and open new avenues for disentangling the interplay between male insects and endosymbionts. From an applied perspective, unravelling the metabolic and functional relationships between tsetse symbionts and male reproductive physiology will provide fundamental information useful to understanding the biology underlying improved male reproductive success in tsetse. This information is of particular importance in the context of tsetse population control via Sterile Insect Technique (SIT) and its impact on trypanosomiasis transmission.

Arthropod vectors have multiple physical and immunological barriers that impede the development and transmission of parasites to new vertebrate hosts. These barriers include the peritrophic matrix (PM), a chitinous barrier that separates the blood bolus from the midgut epithelia and modulates vector-pathogens interactions. In tsetse flies, a sleeve-like PM is continuously produced by the cardia organ located at the fore- and midgut junction. African trypanosomes, Trypanosoma brucei, must bypass the PM twice; first to colonize the midgut and secondly to reach the salivary glands (SG), to complete their transmission cycle in tsetse. However, not all flies with midgut infections develop mammalian transmissible SG infections-the reasons for which are unclear. Here, we used transcriptomics, microscopy and functional genomics analyses to understand the factors that regulate parasite migration from midgut to SG. In flies with midgut infections only, parasites fail to cross the PM as they are eliminated from the cardia by reactive oxygen intermediates (ROIs)-albeit at the expense of collateral cytotoxic damage to the cardia. In flies with midgut and SG infections, expression of genes encoding components of the PM is reduced in the cardia, and structural integrity of the PM barrier is compromised. Under these circumstances trypanosomes traverse through the newly secreted and compromised PM. The process of PM attrition that enables the parasites to re-enter into the midgut lumen is apparently mediated by components of the parasites residing in the cardia. Thus, a fine-tuned dialogue between tsetse and trypanosomes at the cardia determines the outcome of PM integrity and trypanosome transmission success.

Tsetse flies are important vectors of human and animal trypanosomiasis. Ability to reduce tsetse populations is an effective means of disease control. Lactation is an essential component of tsetse's viviparous reproductive physiology and requires a dramatic increase in the expression and synthesis of milk proteins by the milk gland organ in order to nurture larval growth. In between each gonotrophic cycle, tsetse ceases milk production and milk gland tubules undergo a nearly two-fold reduction in width (involution). In this study, we examined the role autophagy plays during tsetse fly milk gland involution and reproductive output. Autophagy genes show elevated expression in tissues associated with lactation, immediately before or within two hours post-parturition, and decline at 24-48h post-parturition. This expression pattern is inversely correlated with that of the milk gland proteins (lactation-specific protein coding genes) and the autophagy inhibitor fk506-bp1. Increased expression of Drosophila inhibitor of apoptosis 1, diap1, was also observed in the milk gland during involution, when it likely prevents apoptosis of milk gland cells. RNAi-mediated knockdown of autophagy related gene 8a (atg8a) prevented rapid milk gland autophagy during involution, prolonging gestation, and reducing fecundity in the subsequent gonotrophic cycle. The resultant inhibition of autophagy reduced the recovery of stored lipids during the dry (non-lactating) periods by 15-20%. Ecdysone application, similar to levels that occur immediately before birth, induced autophagy, and increased milk gland involution even before abortion. This suggests that the ecdysteroid peak immediately preceding parturition likely triggers milk gland autophagy. Population modeling reveals that a delay in involution would yield a negative population growth rate. This study indicates that milk gland autophagy during involution is critical to restore nutrient reserves and allow efficient transition between pregnancy cycles. Targeting post-birth phases of reproduction could be utilized as a novel mechanism to suppress tsetse populations and reduce trypanosomiasis.

Many emerging infectious diseases originate from wild animals, so there is a profound need for surveillance and monitoring of their pathogens. However, the practical difficulty of sample acquisition from wild animals tends to limit the feasibility and effectiveness of such surveys. Xenosurveillance, using blood‐feeding invertebrates to obtain tissue samples from wild animals and then detect their pathogens, is a promising method to do so. Here, we describe the use of tsetse fly blood meals to determine (directly through molecular diagnostic and indirectly through serology), the diversity of circulating blood‐borne pathogens (including bacteria, viruses and protozoa) in a natural mammalian community of Tanzania. Molecular analyses of captured tsetse flies (182 pools of flies totalizing 1728 flies) revealed that the blood meals obtained came from 18 different vertebrate species including 16 non‐human mammals, representing approximately 25% of the large mammal species present in the study area. Molecular diagnostic demonstrated the presence of different protozoa parasites and bacteria of medical and/or veterinary interest. None of the six virus species searched for by molecular methods were detected but an ELISA test detected antibodies against African swine fever virus among warthogs, indicating that the virus had been circulating in the area. Sampling of blood‐feeding insects represents an efficient and practical approach to tracking a diversity of pathogens from multiple mammalian species, directly through molecular diagnostic or indirectly through serology, which could readily expand and enhance our understanding of the ecology and evolution of infectious agents and their interactions with their hosts in wild animal communities. [ABSTRACT FROM AUTHOR]

Introduction: Human African trypanosomiasis (HAT) is a neglected tropical disease still endemic in the Republic of Congo. Despite the continuous detection of HAT cases in the country, there is still not enough data on trypanosome infections in tsetse flies, trypanosome species and tsetse flies' species distribution in endemic foci. The present study was intended to fill this gap and improve understanding of trypanosome circulation in three active foci in the centre and south of Congo. Methods: Pyramid traps were set in various places in villages to collect tsetse flies both during the rainy and dry seasons. Once collected, tsetse flies were identified using morphological keys. DNA extracted from flies was processed by PCR for species identification and for detection of trypanosome presence. A second PCR was run for different trypanosome species identification. Results: A total of 1291 tsetse flies were collected. The average apparent density of flies per day was 0.043 in Mpouya, 0.73 in Ngabé and 2.79 in Loudima. Glossina fuscipes quazensis was the predominant tsetse fly collected in Ngabé and Mpouya, while Glossina palpalis palpalis was the only tsetse fly found in Loudima. A total of 224 (17.7%) flies were detected infected by trypanosomes; 100 (7.91%) by Trypanosoma congolense savannah, 22 (1.74%) by Trypanosoma congolense forest, 15 (1.19%) by Trypanosoma vivax, 83 (6.56%) by Trypanosoma brucei (s.l.) and 2 (0.16%) undetermined species. No T Trypanosoma brucei gambiense was found. A total of 57 co-infections between T. brucei (s.l.) and T. congolense savannah or T. brucei (s.l.) and T. congolense forest were found only in G. p. palpalis. Loudima recorded the highest number of infected tsetse flies. Conclusion: The study provided updated information on the distribution of tsetse fly populations as well as on Trypanosoma species circulating in tsetse flies in the different active HAT foci in Congo. These data suggested a high risk of potential transmission of animal trypanosomes in these foci, thus stressing the need for active surveillance in this endemic area. [ABSTRACT FROM AUTHOR]

Tsetse flies are vectors of the parasite trypanosoma that cause the neglected tropical diseases human and animal African trypanosomosis. Semiochemicals play important roles in the biology and ecology of tsetse flies. Previous reviews have focused on olfactory-based attractants of tsetse flies. Here, we present an overview of the identification of repellents and their development into control tools for tsetse flies. Both natural and synthetic repellents have been successfully tested in laboratory and field assays against specific tsetse fly species. Thus, these repellents presented as innovative mobile tools offer opportunities for their use in integrated disease management strategies., (© 2024. The Author(s).)

Introduction: Tsetse flies ( Glossina ) transmit Trypanosoma brucei gambiense , which causes gambiense human African trypanosomiasis (gHAT). As part of national efforts to eliminate gHAT as a public health problem, Uganda implemented a large-scale programme of deploying Tiny Targets, which comprise panels of insecticide-treated material which attract and kill tsetse. At its peak, the programme was the largest tsetse control operation in Africa. Here, we quantify the impact of Tiny Targets and environmental changes on the spatial and temporal patterns of tsetse abundance across North-Western Uganda., Methods: We leverage a 100-month longitudinal dataset detailing Glossina fuscipes fuscipes catches from monitoring traps between October 2010 and December 2019 within seven districts in North-Western Uganda. We fitted a boosted regression tree (BRT) model assessing environmental suitability, which was used alongside Tiny Target data to fit a spatiotemporal geostatistical model predicting tsetse abundance across our study area (~16 000 km 2 ). We used the spatiotemporal model to quantify the impact of Tiny Targets and environmental changes on the distribution of tsetse, alongside metrics of uncertainty., Results: Environmental suitability across the study area remained relatively constant over time, with suitability being driven largely by elevation and distance to rivers. By performing a counterfactual analysis using the fitted spatiotemporal geostatistical model, we show that deployment of Tiny Targets across an area of 4000 km 2 reduced the overall abundance of tsetse to low levels (median daily catch=1.1 tsetse/trap, IQR=0.85-1.28). No spatial-temporal locations had high (>10 tsetse/trap/day) numbers of tsetse compared with 18% of locations for the counterfactual., Conclusions: In Uganda, Tiny Targets reduced the abundance of G. f. fuscipes and maintained tsetse populations at low levels. Our model represents the first spatiotemporal geostatistical model investigating the effects of a national tsetse control programme. The outputs provide important data for informing next steps for vector control and surveillance., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY. Published by BMJ.)

Sleeping sickness is still prevalent in Campo, southern Cameroon, despite the efforts of World Health Organization and the National Control Programme in screening and treating cases. Reducing disease incidence still further may need the control of tsetse vectors. We update entomological and parasitological parameters necessary to guide tsetse control in Campo. Tsetse flies were trapped, their apparent densities were evaluated as the number of flies captured per trap per day and mapped using GIS tools. Polymerase chain reaction based methods were used to identify their trypanosome infection rates. Glossina palpalis palpalis was the dominant vector species representing 93.42% and 92.85% of flies captured respectively during the heavy and light dry seasons. This species presented high densities, that is, 3.87, 95% CI [3.84–3.91], and 2.51, 95% CI [2.49–2.53] flies/trap/day in the two seasons. Moreover, 16.79% (of 1054) and 20.23% (of 1132 flies) were found infected with at least 1 trypanosome species for the 2 seasons respectively, Trypanosoma congolense being the most prevalent species, and Trypanosoma. brucei gambiense identified in 4 samples. Tsetse flies are abundant in Campo and present high trypanosome infection rates. The detection of tsetse infected with human trypanosomes near the newly created palm grove show workers' exposition. Tsetse densities maps built will guide vector control with 'Tiny Targets'. [ABSTRACT FROM AUTHOR]

Tsetse flies (Glossina spp.) transmit parasitic African trypanosomes (Trypanosoma spp.), including Trypanosoma congolense, which causes animal African trypanosomiasis (AAT). AAT detrimentally affects agricultural activities in sub-Saharan Africa and has negative impacts on the livelihood and nutrient availability for the affected communities. After tsetse ingests an infectious blood meal, T. congolense sequentially colonizes the fly's gut and proboscis (PB) organs before being transmitted to new mammalian hosts during subsequent feedings. Despite the importance of PB in blood feeding and disease transmission, little is known about its molecular composition, function and response to trypanosome infection. To bridge this gap, we used RNA-seq analysis to determine its molecular characteristics and responses to trypanosome infection. By comparing the PB transcriptome to whole head and midgut transcriptomes, we identified 668 PB-enriched transcripts that encoded proteins associated with muscle tissue, organ development, chemosensation and chitin-cuticle structure development. Moreover, transcripts encoding putative mechanoreceptors that monitor blood flow during tsetse feeding and interact with trypanosomes were also expressed in the PB. Microscopic analysis of the PB revealed cellular structures associated with muscles and cells. Infection with T. congolense resulted in increased and decreased expression of 38 and 88 transcripts, respectively. Twelve of these differentially expressed transcripts were PB-enriched. Among the transcripts induced upon infection were those encoding putative proteins associated with cell division function(s), suggesting enhanced tissue renewal, while those suppressed were associated with metabolic processes, extracellular matrix and ATP-binding as well as immunity. These results suggest that PB is a muscular organ with chemosensory and mechanosensory capabilities. The mechanoreceptors may be point of PB-trypanosomes interactions. T. congolense infection resulted in reduced metabolic and immune capacity of the PB. The molecular knowledge on the composition and putative functions of PB forms the foundation to identify new targets to disrupt tsetse's ability to feed and parasite transmission.

Insects with restricted diets rely on obligate microbes to fulfil nutritional requirements essential for biological function. Tsetse flies, vectors of African trypanosome parasites, feed exclusively on vertebrate blood and harbour the obligate endosymbiont Wigglesworthia glossinidia. Without Wigglesworthia, tsetse are unable to reproduce. These symbionts are sheltered within specialized cells (bacteriocytes) that form the midgut-associated bacteriome organ. To decipher the core functions of this symbiosis essential for tsetse's survival, we performed dual-RNA-seq analysis of the bacteriome, coupled with metabolomic analysis of bacteriome and haemolymph collected from normal and symbiont-cured (sterile) females. Bacteriocytes produce immune regulatory peptidoglycan recognition protein (pgrp-lb) that protects Wigglesworthia, and a multivitamin transporter (smvt) that can aid in nutrient dissemination. Wigglesworthia overexpress a molecular chaperone (GroEL) to augment their translational/transport machinery and biosynthesize an abundance of B vitamins (specifically B1-, B2-, B3- and B6-associated metabolites) to supplement the host's nutritionally deficient diet. The absence of Wigglesworthia's contributions disrupts multiple metabolic pathways impacting carbohydrate and amino acid metabolism. These disruptions affect the dependent downstream processes of nucleotide biosynthesis and metabolism and biosynthesis of S-adenosyl methionine (SAM), an essential cofactor. This holistic fundamental knowledge of the symbiotic dialogue highlights new biological targets for the development of innovative vector control methods.

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. [ABSTRACT FROM AUTHOR]

Background: Animal African trypanosomosis (AAT) is a veterinary disease caused by trypanosomes transmitted cyclically by tsetse flies. AAT causes huge agricultural losses in sub-Saharan Africa. Both tsetse flies and trypanosomosis (T&T) are endemic in the study area inhabited by smallholder livestock farmers at the livestock-wildlife interface around Arabuko-Sokoke Forest Reserve (ASFR) in Kilifi County on the Kenyan coast. We assessed farmers’ knowledge, perceptions and control practices towards T&T. Methods: A cross-sectional study was conducted during November and December 2017 to collect data from 404 randomly selected cattle-rearing households using a structured questionnaire. Descriptive statistics were used to determine farmers’ knowledge, perceptions, and control practices towards T&T. Demographic factors associated with knowledge of T&T were assessed using a logistic regression model. Results: Participants consisted of 53% female, 77% married, 30% elderly (>55 years), and the majority (81%) had attained primary education or below. Most small-scale farmers (98%) knew the tsetse fly by its local name, and 76% could describe the morphology of the adult tsetse fly by size in comparison to the housefly’s (Musca domestica). Only 16% of the farmers knew tsetse flies as vectors of livestock diseases. Higher chances of adequate knowledge on T&T were associated with the participants’ (i) age of 15–24 years (aOR 2.88 (95% CI 1.10–7.52), (ii) level of education including secondary (aOR 2.46 (95% CI 1.43–4.24)) and tertiary (aOR 3.80 (95% CI 1.54–9.37)), and (iii) employment status: self-employed farmers (aOR 6.54 (95% CI 4.36–9.80)). Conclusions: Our findings suggest that small-scale farmers around ASFR have limited knowledge of T&T. It is envisaged that efforts geared towards training of the farmers would bridge this knowledge gap and sharpen the perceptions and disease control tactics to contribute to the prevention and control of T&T.

Male Seminal Fluid Proteins (SFPs) transferred during copulation modulate female reproductive physiology and behavior, impacting sperm storage/use, ovulation, oviposition, and remating receptivity. These capabilities make them ideal targets for developing novel methods of insect disease vector control. Little is known about the nature of SFPs in the viviparous tsetse flies (Diptera: Glossinidae), vectors of Human and Animal African trypanosomiasis. In tsetse, male ejaculate is assembled into a capsule-like spermatophore structure visible post-copulation in the female uterus. We applied high-throughput approaches to uncover the composition of the spermatophore in Glossina morsitans morsitans. We found that both male accessory glands and testes contribute to its formation. The male accessory glands produce a small number of abundant novel proteins with yet unknown functions, in addition to enzyme inhibitors and peptidase regulators. The testes contribute sperm in addition to a diverse array of less abundant proteins associated with binding, oxidoreductase/transferase activities, cytoskeletal and lipid/carbohydrate transporter functions. Proteins encoded by female-biased genes are also found in the spermatophore. About half of the proteins display sequence conservation relative to other Diptera, and low similarity to SFPs from other studied species, possibly reflecting both their fast evolutionary pace and the divergent nature of tsetse's viviparous biology.

This article presents an overview of paratransgenesis as a strategy to control pathogen transmission by insect vectors. It first briefly summarises some of the disease-causing pathogens vectored by insects and emphasises the need for innovative control methods to counter the threat of resistance by both the vector insect to pesticides and the pathogens to therapeutic drugs. Subsequently, the state of art of paratransgenesis is described, which is a particularly ingenious method currently under development in many important vector insects that could provide an additional powerful tool for use in integrated pest control programmes. The requirements and recent advances of the paratransgenesis technique are detailed and an overview is given of the microorganisms selected for genetic modification, the effector molecules to be expressed and the environmental spread of the transgenic bacteria into wild insect populations. The results of experimental models of paratransgenesis developed with triatomines, mosquitoes, sandflies and tsetse flies are analysed. Finally, the regulatory and safety rules to be satisfied for the successful environmental release of the genetically engineered organisms produced in paratransgenesis are considered. [ABSTRACT FROM AUTHOR]

Introduction: Trypanosomiasis is a parasitic infection caused by the protozoa Trypanosoma. It is exclusively associated with Glossina species habitats and, therefore, restricted to specific geographical settings. It affects a wide range of hosts, including humans. Animals may carry different Trypanosoma spp. while being asymptomatic. They are, therefore, potentially important in unpremeditated disease transmission. Aim: The aim of this study was to study the potential impact of the government tsetse fly control program, and to elucidate the role of pigs in the Trypanosoma epidemiology in the West Nile region in Uganda. Methods: A historically important human African trypanosomiasis (HAT) hotspot was selected, with sampling in sites with and without a government tsetse fly control program. Pigs were screened for infection with Trypanosoma and tsetse traps were deployed to monitor vector occurrence, followed by tsetse fly dissection and microscopy to establish infection rates with Trypanosoma. Pig blood samples were further analyzed to identify possible Trypanosoma infections using internal transcribed spacer (ITS)-PCR. Results: Using microscopy, Trypanosoma was detected in 0.56% (7/1262) of the sampled pigs. Using ITS-PCR, 114 of 341 (33.4%) pig samples were shown to be Trypanosoma vivax positive. Of the 360 dissected tsetse flies, 13 (3.8%) were positive for Trypanosoma under the microscope. The difference in captured tsetse flies in the government intervention sites in comparison with the control sites was significant (p < 0.05). Seasonality did not play a substantial role in the tsetse fly density (p > 0.05). Conclusion: This study illustrated the impact of a government control program with low vector abundance in a historical HAT hotspot in Uganda. The study could not verify that pigs in the area were carriers for the causative agent for HAT, but showed a high prevalence of the animal infectious agent T. vivax. [ABSTRACT FROM AUTHOR]

Abstract Objective Animal African trypanosomiasis (AAT) is a life-threatening vector-borne disease, caused by trypanosome parasites, which are principally transmitted by tsetse flies. In Kenya, the prevalence of drug-resistant trypanosomes in endemic regions remains poorly understood. The objective of this study was to establish AAT point prevalence, drug susceptibility of associated trypanosomes, and measure infectivity by multiple AAT mammalian hosts to tsetse flies in Shimba hills, a resource-poor region with high bovine trypanosomiasis prevalence and morbidity rates at the coast of Kenya. We collected tsetse flies using traps (1 Ngu and 2 biconical), and then sorted them on sex and species. Trypanosomes present in tsetse flies were detected by first extracting all genomic DNA, and then performing PCR reactions with established primers of the internal transcribed spacer regions. Polymorphisms associated with trypanocide resistance in the TbAT1 gene were also detected by performing PCR reactions with established primers. Results Our findings suggest low trypanosome prevalence (3.7%), low trypanocide resistance, and low infectivity by multiple mammalian hosts to tsetse flies in Shimba hills. We conclude that enhanced surveillance is crucial for informing disease management practices that help prevent the spread of drug-resistant trypanosomiasis.

Tsetse flies are obligate hematophagous vectors of animal and human African trypanosomosis. They cyclically transmit pathogenic Trypanosoma species. The endosymbiont Sodalis glossinidius is suggested to play a role in facilitating the susceptibility of tsetse flies to trypanosome infections. Therefore, this study was aimed at determining the prevalence of S. glossinidius and trypanosomes circulating in tsetse flies and checking whether an association exists between trypanosomes and Sodalis infections in tsetse flies from Kafue National Park in Zambia. A total of 326 tsetse flies were sampled from the Chunga and Ngoma areas of the national park. After DNA extraction was conducted, the presence of S. glossinidius and trypanosome DNA was checked using PCR. The Chi-square test was carried out to determine whether there was an association between the presence of S. glossinidius and trypanosome infections. Out of the total tsetse flies collected, the prevalence of S. glossinidius and trypanosomes was 21.8% and 19.3%, respectively. The prevalence of S. glossinidius was 22.2% in Glossina morsitans and 19.6% in Glossina pallidipes. In relation to sampling sites, the prevalence of S. glossinidius was 26.0% in Chunga and 21.0% in Ngoma. DNA of trypanosomes was detected in 18.9% of G. morsitans and 21.4% of G. pallidipes. The prevalence of trypanosomes was 21.7% and 6.0% for Ngoma and Chunga, respectively. The prevalences of trypanosome species detected in this study were 6.4%, 4.6%, 4.0%, 3.7%, 3.1%, and 2.5% for T. vivax, T. simiae, T. congolense, T. godfreyi, T. simiae Tsavo, and T. b. brucei, respectively. Out of 63 trypanosome infected tsetse flies, 47.6% of the flies also carried S. glossinidius, and the remaining flies were devoid of S. glossinidius. A statistically significant association was found between S. glossinidius and trypanosomes (p < 0.001) infections in tsetse flies. Our findings indicated that presence of S. glossinidius increases the susceptibility of tsetse flies to trypanosome infections and S. glossinidius could be a potential candidate for symbiont-mediated vector control in these tsetse species.

Background: Tsetse flies, the biological vectors of African trypanosomes, have established symbiotic associations with different bacteria. Their vector competence is suggested to be affected by bacterial endosymbionts. The current study provided the prevalence of three tsetse symbiotic bacteria and trypanosomes in Glossina species from Burkina Faso., Results: A total of 430 tsetse flies were captured using biconical traps in four different collection sites around Bobo-Dioulasso (Bama, Bana, Nasso, and Peni), and their guts were removed. Two hundred tsetse were randomly selected and their guts were screened byPCR for the presence of Sodalis glossinidius, Spiroplasmasp ., Wolbachia and trypanosomes. Of the 200 tsetse, 196 (98.0%) were Glossina palpalis gambiense and 4 (2.0%) Glossina tachinoides . The overall symbiont prevalence was 49.0%, 96.5%, and 45.0%, respectively for S. glossinidius, Spiroplasma and Wolbachia . Prevalence varied between sampling locations: S. glossinidius (54.7%, 38.5%, 31.6%, 70.8%); Spiroplasma (100%, 100%, 87.7%, 100%); and Wolbachia (43.4%, 38.5%, 38.6%, 70.8%),respectively in Bama, Bana, Nasso and Peni. Noteworthy, no G. tachhnoides was infected by S . glossinidius and Wolbachia , but they were all infected by Spiroplasma sp . A total of 196 (98.0 %) harbored at least one endosymbionts. Fifty-five (27.5%) carried single endosymbiont. Trypanosomes were found only in G.p. gambiense , but not G. tachinoides . Trypanosomes were present in flies from all study locations with an overall prevalence of 29.5%. In Bama, Bana, Nasso, and Peni, the trypanosome infection rate was respectively 39.6%, 23.1%, 8.8%, and 37.5%. Remarkably, only Trypanosoma grayi was present. Of all trypanosome-infected flies, 55.9%, 98.3%, and 33.9% hosted S. glossinidius, Spiroplasma sp and Wolbachia , respectively. There was no association between Sodalis , Spiroplasma and trypanosome presence, but there was a negative association with Wolbachia presence. We reported1.9 times likelihood of trypanosome absence when Wolbachia was present., Conclusion: This is the first survey reporting the presence of Trypanosoma grayi in tsetse from Burkina Faso. Tsetse from these localities were highly positive for symbiotic bacteria, more predominantly with Spiroplasma sp . Modifications of symbiotic interactions may pave way for disease control., Competing Interests: Competing interests: The authors declare that they have no competing interests.

Tsetse flies are the exclusive biological vectors of African trypanosomes in Africa, which are estimated to cover about 80% of the country’s total area, hindering rearing of livestock and creating health risk to humans as well. This study was performed to determine the sex and species composition of tsetse flies from selected communities of Kagarko Local Government Area, Kaduna State, Nigeria. Sampling of flies was done using standard biconical traps according to the method of Challier and Larvessiere and were sorted into sex and species using morphological distinctions as described by Leak. The study was carried out for four (4) months, during which forty seven (47) tsetse flies were caught, 16 (34.04%) were male and 31(65.96%) were female and all forty seven (47) flies were members of the Glossina palpalis palpalis. The abundance of more female flies supports the fact that they live longer, go out more frequently in search of blood meal due to reproductive requirements and the presence of only Glossina palpalis palpalis implies that it is the dominant species, hence, transmission of trypanosomiasis as Glossina palpalis palpalis are the major vectors of trypanosomiasis in Nigeria. [ABSTRACT FROM AUTHOR]

BackgroundTranscription initiation regulation is mediated by sequence-specific interactions between DNA-binding proteins (transcription factors) and cis-elements, where BRE, TATA, INR, DPE and MTE motifs constitute canonical core motifs for basal transcription initiation of genes. Accurate identification of transcription start site (TSS) and their corresponding promoter regions is critical for delineation of these motifs. To this end, the genome scale analysis of core promoter architecture in insects has been confined to Drosophila. The recently sequenced Tsetse fly genome provides a unique opportunity to analyze transcription initiation regulation machinery in blood-feeding insects.ResultsA computational method for identification of TSS in newly sequenced Tsetse fly genome was evaluated, using TSS seq tags sampled from two developmental stages namely; larvae and pupae. There were 3134 tag clusters among which 45.4% (1424) of the tag clusters mapped to first coding exons or their proximal predicted 5'UTR regions and 1.0% (31) tag clusters mapping to transposons, within a threshold of 100 tags per cluster. These 1393 non transposon-derived core promoters had propensity for AT nucleotides. The -1/+1 and 1/+1 positions in D. melanogaster, and G. m. morsitans had propensity for CA and AA dinucleotides respectively. The 1393 tag clusters comprised narrow promoters (5%), broad with peak promoters (23%) and broad without peak promoters (72%). Two-way motif co-occurrence analysis showed that the MTE-DPE pair is over-represented in broad core promoters. The frequently occurring triplet motifs in all promoter classes are the INR-MTE-DPE, TATA-MTE-DPE and TATA-INR-DPE. Promoters without the TATA motif had higher frequency of the MTE and INR motifs than those observed in Drosophila, where the DPE motif occur more frequently in promoters without TATA motif. Gene ontology terms associated with developmental processes were overrepresented in the narrow and broad with peak promoters.ConclusionsThe study has identified different motif combinations associated with broad promoters in a blood-feeding insect. In the case of TATA-less core promoters, G.m. morsitans uses the MTE to compensate for the lack of a TATA motif. The increasing availability of TSS seq data allows for revision of existing gene annotation datasets with the potential of identifying new transcriptional units.

Introduction: Human African trypanosomiasis (HAT) is a neglected tropical disease still endemic in the Republic of Congo. Despite the continuous detection of HAT cases in the country, there is still not enough data on trypanosome infections in tsetse flies, trypanosome species and tsetse flies’ species distribution in endemic foci. The present study was intended to fill this gap and improve understanding of trypanosome circulation in three active foci in the centre and south of Congo. Methods: Pyramid traps were set in various places in villages to collect tsetse flies both during the rainy and dry seasons. Once collected, tsetse flies were identified using morphological keys. DNA extracted from flies was processed by PCR for species identification and for detection of trypanosome presence. A second PCR was run for different trypanosome species identification. Results: A total of 1291 tsetse flies were collected. The average apparent density of flies per day was 0.043 in Mpouya, 0.73 in Ngabé and 2.79 in Loudima. Glossina fuscipes quazensis was the predominant tsetse fly collected in Ngabé and Mpouya, while Glossina palpalis palpalis was the only tsetse fly found in Loudima. A total of 224 (17.7%) flies were detected infected by trypanosomes; 100 (7.91%) by Trypanosoma congolense savannah, 22 (1.74%) by Trypanosoma congolense forest, 15 (1.19%) by Trypanosoma vivax, 83 (6.56%) by Trypanosoma brucei (s.l.) and 2 (0.16%) undetermined species. No T Trypanosoma brucei gambiense was found. A total of 57 co-infections between T. brucei (s.l.) and T. congolense savannah or T. brucei (s.l.) and T. congolense forest were found only in G. p. palpalis. Loudima recorded the highest number of infected tsetse flies. Conclusion: The study provided updated information on the distribution of tsetse fly populations as well as on Trypanosoma species circulating in tsetse flies in the different active HAT foci in Congo. These data suggested a high risk of potential transmission of animal trypanosomes in these foci, thus stressing the need for active surveillance in this endemic area.

Livestock is heavily affected by trypanosomosis in Africa. Through strong selective pressure, several African indigenous breeds of cattle and small ruminants have acquired varying degrees of tolerance against this disease. In this study, we combined LFMM and PCAdapt for analyzing two datasets of goats from West-Central Africa and East Africa, respectively, both comprising breeds with different assumed levels of trypanotolerance. The objectives were (i) to identify molecular signatures of selection related to trypanotolerance; and (ii) to guide an optimal sampling for subsequent studies. From 33 identified signatures, 18 had been detected previously in the literature as being mainly associated with climatic adaptations. The most plausible signatures of trypanotolerance indicate the genes DIS3L2, COPS7B, PD5A, UBE2K, and UBR1. The last gene is of particular interest since previous literature has already identified E3-ubiquitin ligases as playing a decisive role in the immune response. For following-up on these findings, the West-Central African area appears particularly relevant because of (i) a clear parasitic load gradient related to a humidity gradient, and (ii) still restricted admixture levels between goat breeds. This study illustrates the importance of protecting local breeds, which have retained unique allelic combinations conferring their remarkable adaptations.

Background: African trypanosomiasis, which is mainly transmitted by tsetse flies (Glossina spp.), is a threat to public health and a significant hindrance to animal production. Tools that can reduce tsetse densities and interrupt disease transmission exist, but their large-scale deployment is limited by high implementation costs. This is in part limited by the absence of knowledge of breeding sites and dispersal data, and tools that can predict these in the absence of ground-truthing. Methods: In Kenya, tsetse collections were carried out in 261 randomized points within Shimba Hills National Reserve (SHNR) and villages up to 5 km from the reserve boundary between 2017 and 2019. Considering their limited dispersal rate, we used in situ observations of newly emerged flies that had not had a blood meal (teneral) as a proxy for active breeding locations. We fitted commonly used species distribution models linking teneral and non-teneral tsetse presence with satellite-derived vegetation cover type fractions, greenness, temperature, and soil texture and moisture indices separately for the wet and dry season. Model performance was assessed with area under curve (AUC) statistics, while the maximum sum of sensitivity and specificity was used to classify suitable breeding or foraging sites. Results: Glossina pallidipes flies were caught in 47% of the 261 traps, with teneral flies accounting for 37% of these traps. Fitted models were more accurate for the teneral flies (AUC = 0.83) as compared to the non-teneral (AUC = 0.73). The probability of teneral fly occurrence increased with woodland fractions but decreased with cropland fractions. During the wet season, the likelihood of teneral flies occurring decreased as silt content increased. Adult tsetse flies were less likely to be trapped in areas with average land surface temperatures below 24 °C. The models predicted that 63% of the potential tsetse breeding area was within the SHNR, but also indicated potential breeding pockets outside the reserve. Conclusion: Modelling tsetse occurrence data disaggregated by life stages with time series of satellite-derived variables enabled the spatial characterization of potential breeding and foraging sites for G. pallidipes. Our models provide insight into tsetse bionomics and aid in characterising tsetse infestations and thus prioritizing control areas. [ABSTRACT FROM AUTHOR]

Livestock is heavily affected by trypanosomosis in Africa. Through strong selective pressure, several African indigenous breeds of cattle and small ruminants have acquired varying degrees of tolerance against this disease. In this study, we combined LFMM and PCAdapt for analyzing two datasets of goats from West-Central Africa and East Africa, respectively, both comprising breeds with different assumed levels of trypanotolerance. The objectives were (i) to identify molecular signatures of selection related to trypanotolerance; and (ii) to guide an optimal sampling for subsequent studies. From 33 identified signatures, 18 had been detected previously in the literature as being mainly associated with climatic adaptations. The most plausible signatures of trypanotolerance indicate the genes DIS3L2 , COPS7B , PD5A , UBE2K , and UBR1. The last gene is of particular interest since previous literature has already identified E3-ubiquitin ligases as playing a decisive role in the immune response. For following-up on these findings, the West-Central African area appears particularly relevant because of (i) a clear parasitic load gradient related to a humidity gradient, and (ii) still restricted admixture levels between goat breeds. This study illustrates the importance of protecting local breeds, which have retained unique allelic combinations conferring their remarkable adaptations. [ABSTRACT FROM AUTHOR]