Tsetse Research Articles

Parasitological investigation of bovine Trypanosomosis, vector distribution and tsetse flies infection rate study, Dabo Hana District, Buno Bedelle Zone, Southwest Ethiopia

A cross-sectional study was conducted to explore the prevalence of Trypanosome infections in cattle and within the tsetse flies from December 2020 to May 2021 in Dabo Hana district, Buno Bedelle Zone, Southwest Ethiopia. A total of 415 blood samples were examined utilizing Buffy coat and Giemsa-stained thin blood smear techniques. Vector distribution and tsetse fly infection rate were studied by deploying 60 traps in four purposively chosen villages of the district. The prevalence of Trypanosomes was 10.6% and 6.5% in cattle and in tsetse flies, respectively. Trypanosoma congolense (59.1%) in cattle and T. vivax (62.5%) in tsetse flies, were the foremost common species distinguished in the area. A significant difference (P ≤ 0.05) was observed in the prevalence of bovine Trypanosomosis between body condition scores of cattle. However, differences were not significant between coat color, sex, and age categories (P > 0.05). The mean PCV values of Trypanosome-infected cattle (22.6 ± 0.6) were significantly (P < 0.05) lower than those of non-infected cattle (25.6 ± 0.3). Out of 1441 flies caught, 1242 (86.2%) were Glossina, 113 (7.84%) were Stomoxys, and 86 (5.97%) were Tabanus. Of 1242 Glossina, 85% were G. tachinoides and the remaining 15% were G. m. sub-morsitans. This finding revealed that, three Trypanosoma species are circulating in cattle as well as in tsetse flies. It is recommended that, sustainable and integrated tsetse and Trypanosomosis control practices should be implemented to foster live stock health and agricultural development in the district. Other sensitive methods should be employed to determine the true picture of infection in the area.

Lymphatic filariasis knowledge, attitude and practice among households in Kano metropolis North-Western Nigeria

Common to most neglected tropical diseases worldwide is little published data of knowledge, attitude and practice of lymphatic filariasis (LF) in regions where the disease is endemic, despite the fact that such data is needed for preparations and plans for integrated management and control of the diseases. A cross-sectional study using structured questionnaire was conducted to assess; demography, socio-economic information, household knowledge, attitude and practice on LF in Kano metropolis North-western Nigeria. A total of 400 respondents participated in the study; 247 were males and 157 females aged 18-78 years. The study confirms the presence of LF in the study area with 33% of the participants mentioning to have seen people infected with LF in the metropolis. Although, 43% of the participant have heard about LF, only 15.6% mentioned mosquitoes as vectors while 72.0% had no idea how it is transmitted. Some of the respondents believed that it is transmitted through; the use of contaminated water (8.4%), drug abuse (1.2%) and Tsetse fly bite (1.2%). Pearson Chi-square test reveals knowledge of LF among participants to be significantly (P&lt;0.05) associated with age rather than level of education. However, 99.6% used variety of methods to control mosquitoes. Elusive data and paucity of knowledge are threats to control of infectious disease as such it is necessary they are addressed through; creating awareness, research and publications.

Towards elimination of human African trypanosomiasis

Human African Trypanosomiasis (HAT) is caused by Trypanosoma brucei which is transmitted by the tsetse fly insect vector (Glossina spp). It is one of the 20 Neglected Tropical Diseases (NTD) listed by the WHO. These diseases affect the poorest and most vulnerable communities, for which the WHO has established a dedicated 2021-2030 roadmap. At the time of Alphonse Laveran, HAT devastated the African continent. In the 1960s, the disease was nearly under control, but it strongly re-emerged in the 1990s. A coordinated effort of all stakeholders, with national control programs as the main actors, a strong contribution of research and important donations by the private sector, allowed to decrease the HAT burden significantly. Since 2018, less than 1000 cases are detected annually. We here review new diagnostics, treatments and vector control tools that have been implemented jointly and successfully in several endemic countries.The next key challenge will be to sustain the gains. Newly emerging research questions include long-term carriage of trypanosomes and adaptation of tools to low prevalence contexts. Challenges out of the research area comprise the continued need of funding, maintenance of dedicated human resources, and the key question of access. Sustainable elimination as "interruption of transmission", which is the 2030 NTD roadmap target, can be reached, if these challenges are solved. We stress the importance of continuing to combine the efforts in the fight against the disease, because sustainable elimination of HAT is the best long-term prevention strategy against re-emergence. As such, HAT elimination can serve as an example for other infectious diseases.

The Trypanosoma brucei MISP family of invariant proteins is co-expressed with BARP as triple helical bundle structures on the surface of salivary gland forms, but is dispensable for parasite development within the tsetse vector.

Trypanosoma brucei spp. develop into mammalian-infectious metacyclic trypomastigotes inside tsetse salivary glands. Besides acquiring a variant surface glycoprotein (VSG) coat, little is known about the metacyclic expression of invariant surface antigens. Proteomic analyses of saliva from T. brucei-infected tsetse flies identified, in addition to VSG and Brucei Alanine-Rich Protein (BARP) peptides, a family of glycosylphosphatidylinositol (GPI)-anchored surface proteins herein named as Metacyclic Invariant Surface Proteins (MISP) because of its predominant expression on the surface of metacyclic trypomastigotes. The MISP family is encoded by five paralog genes with >80% protein identity, which are exclusively expressed by salivary gland stages of the parasite and peak in metacyclic stage, as shown by confocal microscopy and immuno-high resolution scanning electron microscopy. Crystallographic analysis of a MISP isoform (MISP360) and a high confidence model of BARP revealed a triple helical bundle architecture commonly found in other trypanosome surface proteins. Molecular modelling combined with live fluorescent microscopy suggests that MISP N-termini are potentially extended above the metacyclic VSG coat, and thus could be tested as a transmission-blocking vaccine target. However, vaccination with recombinant MISP360 isoform did not protect mice against a T. brucei infectious tsetse bite. Lastly, both CRISPR-Cas9-driven knock out and RNAi knock down of all MISP paralogues suggest they are not essential for parasite development in the tsetse vector. We suggest MISP may be relevant during trypanosome transmission or establishment in the vertebrate's skin.

Population genetics of Glossina fuscipes fuscipes from southern Chad

In Subsaharan Africa, tsetse flies (genus Glossina) are vectors of trypanosomes causing Human African Trypanosomiasis (HAT) and Animal African Trypanosomosis (AAT). Some foci of HAT persist in Southern Chad, where a program of tsetse control was started against the local vector Glossina fuscipes fuscipes in the Mandoul focus in 2014, and in Maro in 2018. Flies were also sampled in 2018 in Timbéri and Dokoutou. We analyzed the population genetics of G. fuscipes fuscipes from the four tsetse-infested zones. The trapping samples were characterized by a strong female biased sex-ratio, except in Timbéri and Dokoutou that had high tsetse densities. Apparent density and effective population density appeared smaller in the main foci of Mandoul and Maro and the average dispersal distance (within the spatial scale of each zone) was as large as or larger than the total length of each respective zone. The genetic signature of a population bottleneck was found in the Mandoul and Timbéri area, suggesting a large ancient interconnected metapopulation that underwent genetic subdivision into small, isolated pockets due to adverse environmental conditions. The long-range dispersal and the existence of genetic outliers suggest a possibility of migration from remote sites such as the Central African Republic in the south (although the fly situation remains unknown there) and/or a genetic signature of recent exchanges. Due to likely isolation, an eradication strategy may be considered for sustainable HAT control in Mandoul focus. Another strategy will probably be required in Maro focus, which probably experiences much more exchanges with its neighbors.

Feeding frequency and its associated effects on the production and survival rate of Glossina fuscipes fuscipes

Tsetse flies are large blood-sucking flies of the genus Glossina, which are exclusively found in Africa. They are important vectors of Trypanosomes, which cause sleeping sickness in humans and African Animal Trypanosomosis (AAT) in livestock. Due to the lack of effective vaccines to control this disease, vector control has been an ideal strategy. There are many vector control methods developed so far. Sterile Insect Technique (SIT) is one of such method which depends on the mass production of male flies in the laboratory, sterilization, and release of these flies in the target area. The study was conducted to evaluate the effect of different feeding frequencies on the production and survival rate of Glossina fuscipes fuscipes to identify the best feeding frequency that could optimize the production and minimize the cost of production in a massrearing insectary facility at Kaliti Tsetse Fly Mass Rearing and Irradiation Centre, Addis Ababa, Ethiopia. Three experimental groups were established based on feeding frequency regimes. The first group was fed three times per week, the second four times per week, and the third group five times per week. Parameters that are routinely used for assessing colony performance such as; survival rate, fecundity, pupae per initial females (PPIF), and pupal quality were evaluated for each treatment group and statistical comparisons were made between the groups. The results revealed that feeding frequency had a crucial effect on fly production and survival. The lowest results for all parameters were obtained in flies fed three times per week and relatively the best results were obtained in the four-times-per-week feeding regime. Therefore, we recommend a further study on aspects that are not addressed in this study, such as emergency rate and progeny quality, to apply the four times per week feeding regime as it will have a positive economic impact that could enable more resources to be re-injected into the insectary compared to five or more feeding regimes which are currently in use in the study site.

Vector competence of sterile male Glossina fuscipes fuscipes for Trypanosoma brucei brucei: implications for the implementation of the sterile insect technique in a sleeping sickness focus in Chad

BackgroundHuman African trypanosomiasis (HAT) is a neglected tropical disease caused by Trypanosoma brucei gambiense transmitted by tsetse flies in sub-Saharan West Africa. In southern Chad the most active and persistent focus is the Mandoul focus, with 98% of the reported human cases, and where African animal trypanosomosis (AAT) is also present. Recently, a control project to eliminate tsetse flies (Glossina fuscipes fuscipes) in this focus using the sterile insect technique (SIT) was initiated. However, the release of large numbers of sterile males of G. f. fuscipes might result in a potential temporary increase in transmission of trypanosomes since male tsetse flies are also able to transmit the parasite. The objective of this work was therefore to experimentally assess the vector competence of sterile males treated with isometamidium for Trypanosoma brucei brucei.MethodsAn experimental infection was set up in the laboratory, mimicking field conditions: the same tsetse species that is present in Mandoul was used. A T. b. brucei strain close to T. b. gambiense was used, and the ability of the sterile male tsetse flies fed on blood with and without a trypanocide to acquire and transmit trypanosomes was measured.ResultsOnly 2% of the experimentally infected flies developed an immature infection (midgut) while none of the flies developed a metacyclic infection of T. b. brucei in the salivary glands. We did not observe any effect of the trypanocide used (isometamidium chloride at 100 mg/l) on the development of infection in the flies.ConclusionsOur results indicate that sterile males of the tested strain of G. f. fuscipes were unable to cyclically transmit T. b. brucei and might even be refractory to the infection. The data of the research indicate that the risk of cyclical transmission of T. brucei by sterile male G. f. fuscipes of the strain colonized at IAEA for almost 40 years appears to be small.Graphical

A volatile sex attractant of tsetse flies.

Tsetse flies transmit trypanosomes-parasites that cause devastating diseases in humans and livestock-across much of sub-Saharan Africa. Chemical communication through volatile pheromones is common among insects; however, it remains unknown if and how such chemical communication occurs in tsetse flies. We identified methyl palmitoleate (MPO), methyl oleate, and methyl palmitate as compounds that are produced by the tsetse fly Glossina morsitans and elicit strong behavioral responses. MPO evoked a behavioral response in male-but not virgin female-G. morsitans. G. morsitans males mounted females of another species, Glossina fuscipes, when they were treated with MPO. We further identified a subpopulation of olfactory neurons in G. morsitans that increase their firing rate in response to MPO and showed that infecting flies with African trypanosomes alters the flies' chemical profile and mating behavior. The identification of volatile attractants in tsetse flies may be useful for reducing disease spread.

Chemical notes of tsetse fly mating

Volatile pheromones offer a means to control flies that spread disease.

Structural similarities between the metacyclic and bloodstream form variant surface glycoproteins of the African trypanosome.

During infection of mammalian hosts, African trypanosomes thwart immunity using antigenic variation of the dense Variant Surface Glycoprotein (VSG) coat, accessing a large repertoire of several thousand genes and pseudogenes, and switching to antigenically distinct copies. The parasite is transferred to mammalian hosts by the tsetse fly. In the salivary glands of the fly, the pathogen adopts the metacyclic form and expresses a limited repertoire of VSG genes specific to that developmental stage. It has remained unknown whether the metacyclic VSGs possess distinct properties associated with this particular and discrete phase of the parasite life cycle. We present here three novel metacyclic form VSG N-terminal domain crystal structures (mVSG397, mVSG531, and mVSG1954) and show that they mirror closely in architecture, oligomerization, and surface diversity the known classes of bloodstream form VSGs. These data suggest that the mVSGs are unlikely to be a specialized subclass of VSG proteins, and thus could be poor candidates as the major components of prophylactic vaccines against trypanosomiasis.

Whole blood transcriptome profiles of trypanotolerant and trypanosusceptible cattle highlight a differential modulation of metabolism and immune response during infection by Trypanosoma congolense

Animal African trypanosomosis, caused by blood protozoan parasites transmitted mainly by tsetse flies, represents a major constraint for millions of cattle in sub-Saharan Africa. Exposed cattle include trypanosusceptible indicine breeds, severely affected by the disease, and West African taurine breeds called trypanotolerant owing to their ability to control parasite development, survive and grow in enzootic areas. Until now the genetic basis of trypanotolerance remains unclear. Here, to improve knowledge of the biological processes involved in trypanotolerance versus trypanosusceptibility, we identified bovine genes differentially expressed in five West African cattle breeds during an experimental infection by Trypanosoma congolense and their biological functions. To this end, whole blood genome-wide transcriptome of three trypanotolerant taurine breeds (N’Dama, Lagune and Baoulé), one susceptible zebu (Zebu Fulani) and one African taurine x zebu admixed breed (Borgou) were profiled by RNA sequencing at four time points, one before and three during infection. As expected, infection had a major impact on cattle blood transcriptome regardless of the breed. The functional analysis of differentially expressed genes over time in each breed confirmed an early activation of the innate immune response, followed by an activation of the humoral response and an inhibition of T cell functions at the chronic stage of infection. More importantly, we highlighted overlooked features, such as a strong disturbance in host metabolism and cellular energy production that differentiates trypanotolerant and trypanosusceptible breeds. N’Dama breed showed the earliest regulation of immune response, associated with a strong activation of cellular energy production, also observed in Lagune, and to a lesser extent in Baoulé. Susceptible Zebu Fulani breed differed from other breeds by the strongest modification in lipid metabolism regulation. Overall, this study provides a better understanding of the biological mechanisms at work during infection, especially concerning the interplay between immunity and metabolism that seems differentially regulated depending on the cattle breeds.

Design, synthesis and biological evaluations of quinolone amides against African trypanosomiasis with improved solubility

The human African trypanosomiasis is a devastating parasitic infection, which is caused by the protozoan Trypanosoma brucei and transmitted by the bite of the tsetse fly. An untreated infection usually results in death and only few drugs with significant drawbacks are currently available for treatment. Previous investigations revealed the quinolone amide MB007 as a lead compound with an excellent selectivity for T. b. brucei. Here, new quinolone amides were synthesized for deeper insights into the structure-activity relationship. Furthermore, the aqueous solubility of the compounds was analyzed, as the poor solubility of previous quinolone amides impeded in vivo studies for target identification. The biological evaluation led to the new lead structure 9f, which exhibits a promising in vitro activity against T. b. brucei (IC50 = 22 nM) and showed no cytotoxicity against macrophages. Moreover, compounds 10b and 10c were discovered, which possessed an improved solubility combined with a decent selectivity.

Prevalence and Association of Trypanosomes and Sodalis glossinidius in Tsetse Flies from the Kafue National Park in Zambia

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.

Suitability of Raycell MK2 Blood X-ray Irradiator for the Use in the Sterile Insect Technique: Dose Response in Fruit Flies, Tsetse Flies and Mosquitoes.

The sterile insect technique (SIT) is based on the inundatory field release of a target pest following their reproductive sterilization via exposure to radiation. Until recently, gamma irradiation from isotopic sources has been the most widely used in SIT programs. As isotopic sources are becoming increasingly expensive, especially for small programs, and regulations surrounding their procurement and shipment increasingly strict, irradiation capacity is one of the limiting factors in smaller or newly developing SIT projects. For this reason, the possibility of using X-ray irradiators has been evaluated in the recent decade. The availability of "off-the-shelf" blood X-ray irradiators that meet the technical requirements for insect irradiation can provide irradiation capacity for those SIT projects in which the acquisition of gamma ray irradiators is not feasible. Following the recent technical characterization of a Raycell MK2 X-ray blood irradiator, it was found in this study, that MK2 instruments were suitable for the sterilization of fruit flies, tsetse flies and mosquitoes, inducing comparable, even slightly higher, sterility levels compared to those achieved by gamma ray irradiation. This, together with its estimated processing efficiency, shows that MK2 irradiators are suitable for small- to mid-sized SIT programs.

Tsetse fly ecology and risk of transmission of African trypanosomes related to a protected forest area at a military base in the city of Abidjan, Côte d'Ivoire.

African trypanosomoses, whose pathogens are transmitted by tsetse flies, are a threat to animal and human health. Tsetse flies observed at the military base of the French Forces in Côte d'Ivoire (FFCI base) were probably involved in the infection and death of military working dogs. Entomological and parasitological surveys were carried out during the rainy and dry seasons using "Vavoua" traps to identify tsetse fly species, their distribution, favorable biotopes and food sources, as well as the trypanosomes they harbor. A total of 1185 Glossina palpalis palpalis tsetse flies were caught, corresponding to a high average apparent density of 2.26 tsetse/trap/day. The results showed a heterogeneous distribution of tsetse at the FFCI base, linked to more or less favorable biotopes. No significant variation in tsetse densities was observed according to the season. The overall trypanosomes infection rate according to microscopic observation was 13.5%. Polymerase chain reaction (PCR) analyses confirmed the presence of Trypanosoma vivax and T. congolense forest type, responsible for African animal trypanosomosis. Our findings suggest that there is a risk of introduction and transmission of T. brucei gambiense, responsible for human African trypanosomiasis, on the study site. This risk of transmission of African trypanosomes concerns not only the FFCI base, but also inhabited peripheral areas. Our study confirmed the need for vector control adapted to the eco-epidemiological context of the FFCI base.

Prevalence of Spiroplasma and interaction with wild Glossina tachinoides microbiota.

Tsetse flies (Diptera: Glossinidae) are vectors of the tropical neglected diseases sleeping sickness in humans and nagana in animals. The elimination of these diseases is linked to control of the vector. The sterile insect technique (SIT) is an environment-friendly method that has been shown to be effective when applied in an area-wide integrated pest management approach. However, as irradiated males conserve their vectorial competence, there is the potential risk of trypanosome transmission with their release in the field. Analyzing the interaction between the tsetse fly and its microbiota, and between different microbiota and the trypanosome, might provide important information to enhance the fly's resistance to trypanosome infection. This study on the prevalence of Spiroplasma in wild populations of seven tsetse species from East, West, Central and Southern Africa showed that Spiroplasma is present only in Glossina fuscipes fuscipes and Glossina tachinoides. In G. tachinoides, a significant deviation from independence in co-infection with Spiroplasma and Trypanosoma spp. was observed. Moreover, Spiroplasma infections seem to significantly reduce the density of the trypanosomes, suggesting that Spiroplasma might enhance tsetse fly's refractoriness to the trypanosome infections. This finding might be useful to reduce risks associated with the release of sterile males during SIT implementation in trypanosome endemic areas.

Prevalence of bovine trypanosomosis and apparent density of tsetse flies in Hawa Gelan district, West Oromia, Ethiopia

Across sectional study was conducted from October to November 2021 to determine the prevalence of bovine trypanosomosis and the apparent density of tsetse flies in six peasant association of hawa gelan district. For the prevalence study, dark phase contrast buffy coat examination and giemsa stained thin blood smears were used. Whereas for entomological survey to determine apparent density of flies, traps were deployed. The entomological survey indicated that four species of glossina were the fly species caught in the study area. Apparent tsetse flies density of 5.34 flies/trap/day was recorded in the district and the highest FTD was recorded Mender 16 village. For the prevalence study, out of total of 532 cattle examined, 19(3.57%) were found infected with trypanosomes. Out of infected animals highest prevalence was recorded in cattle with poor body condition (52.63%) followed by medium (31.58%) and good (15.79%).The overall mean PCV value of examined cattle is 29.29± 4.813 and the overall mean PCV value of non infected cattle was slightly higher (29.30%) than that of infected animals (28.3%).Among the species of trypanosomes isolated, Trypanosoma vivax was identified to the major causes of trypanosomosis in the study area accounting for 63.16% of total infections observed followed by trpanosoma congolense (36.84%) respectively. Taken as a whole, the present work evidenced that tsetse and trypanosomosis has continued to pose aconsiderable threat to cattle of the study area warranting an integrated control to safeguard cattle production and productivity.

Near-infrared imaging for automated tsetse pupae sex sorting in support of the sterile insect technique.

Tsetse flies are the cyclical vectors of African trypanosomes and one of several methods to manage this vector is the sterile insect technique (SIT). The ability to determine the sex of tsetse pupae with the objective to separate the sexes before adult emergence has been a major goal for decades for tsetse management programmes with an SIT component. Tsetse females develop faster and pharate females inside the pupae melanise 1-2 days before males. This earlier melanisation can be detected by infrared cameras through the pupal shell, and the newly developed Near InfraRed Pupae Sex Sorter (NIRPSS) takes advantage of this. The melanisation process is not homogeneous for all fly organs and the pupa needs to be examined ventrally, dorsally and laterally to ensure accurate classification by an image analysis algorithm. When the pupae are maturing at a constant temperature of 24°C and sorted at the appropriate age, 24 days post-larviposition for Glossina palpalis gambiensis, the sorting machine can efficiently separate the sexes. The recovered male pupae can then be sterilised for field releases of males, while the rest of the pupae can be used to maintain the laboratory colony. The sorting process with the new NIRPSS had no negative impact on adult emergence and flight ability. A mean male recovery of 62.82±3.61% was enough to provide sterile males to an operational SIT programme, while mean contamination with females (4.69±3.02%) was low enough to have no impact on the maintenance of a laboratory colony.

Development and characterization of microsatellite markers for the tsetse species Glossina brevipalpis and preliminary population genetics analyses.

Tsetse flies, the vectors of African trypanosomes are of key medical and economic importance and one of the constraints for the development of Africa. Tsetse fly control is one of the most effective and sustainable strategies used for controlling the disease. Knowledge about population structure and level of gene flow between neighbouring populations of the target vector is of high importance to develop appropriate strategies for implementing effective management programmes. Microsatellites are commonly used to identify population structure and assess dispersal of the target populations and have been developed for several tsetse species but were lacking for Glossina brevipalpis. In this study, we screened the genome of G. brevipalpis to search for suitable microsatellite markers and nine were found to be efficient enough to distinguish between different tsetse populations. The availability of these novel microsatellite loci will help to better understand the population biology of G. brevipalpis and to assess the level of gene flow between different populations. Such information will help with the development of appropriate strategies to implement the sterile insect technique (SIT) in the framework of an area-wide integrated pest management (AW-IPM) approach to manage tsetse populations and ultimately address the trypanosomoses problem in these targeted areas.

Gamma-radiation of Glossina palpalis gambiensis revisited: effect on fertility and mating competitiveness

African animal trypanosomoses are vector-borne diseases that cause enormous livestock losses in sub-Saharan Africa, with drastic socio-economic impacts. Vector control in the context of an area-wide integrated pest management program with a sterile insect technique component requires the production of high-quality sterile male tsetse flies. In our study, we evaluated the effect of irradiation on the fecundity of Glossina palpalis gambiensis to identify the optimal dose that will induce maximum sterility while maintaining biological performance as much as possible. In addition, male mating performance was evaluated in semi-field cages. The irradiation doses used were 90, 100, 110, 120, 130, 140, and 150 Gy, and untreated males were used as the control. The results showed that pupal production and emergence rates were higher in batches of females that had mated with fertile males than in those that had mated with irradiated males with any experimental dose. A dose of 120 Gy administered to male flies induced 97-99% sterility after mating with virgin females. For the semi-field cage experiments, males irradiated with 120 Gy showed good sexual competitiveness as compared to fertile males and those irradiated with 140 Gy, considering the level of filling of spermatheca and the number of pairs formed. The optimal radiation dose of 120 Gy found in this study is slightly different from the traditional dose of 110 Gy that has been used in several eradication programmes in the past. The potential reasons for this difference are discussed, and an argument is made for the inclusion of reliable dosimetry systems in these types of studies.