Tsetse Fly Species Research Articles

Hunting and the re-emergence of Human African Trypanosomiasis (HAT) in Bipindi (South Cameroon)

Background: Hunting activities play an important role in the survival and subsistence of the population. During hunting activities, trappers go into the bush and end up in the same biotopes with wild animals and flies, vectors of various diseases; they can accidently get involved in the wild transmission cycle of diseases maintained by vectors and wild animal, potential reservoir hosts. Many researchers reported a tight link between hunting activities and the emergence of some infectious diseases in forest areas. In order to investigate the role of hunting in the re-emergence human African trypanosomiasis (HAT), five active hunters have been followed during their hunting activities for one year; while G. palpalis palpalis were trapped in the same habitats. Methods and materials: 127 households in the Bipindi subdivision were systematically interviewed about their forest-related activities and 5 active trappers were selected according to trapping zones, hunting methods, snare trail length, trapping seasons, the time spent in each trapping zones per day to set traps, fences or renew traps and followed daily in their activities. Moreover, concerning entomological survey, 225 Vavoua traps were set up year-round in all trapping zones to inventory, determine the distribution and densities of tsetse flies. Results: The results showed that there are two hunting techniques used in the Bipindi area: foot snares mainly set in the undisturbed forest and neck snares mostly used on fences in farmlands. The total time spent by hunters in farmlands for neck snare trapping was higher compared to other trapping zones; while the time employed in foot snare trapping in the undisturbed forest was higher compared to other habitats. The mean snare trail length varied significantly between trapping sites (χ2 = 15.421; p = 0.001) and seasons (χ2 = 39.897; p = 0.0001) and Glossina palpalis palpalis the most abundant tsetse fly species recorded in the Bipindi area occurred in all trapping zones with an apparent density although unsignificantly different between trapping zones (χ2 = 5.956; p = 0.051) was highest in farmlands. Conclusion: Hunters are exposed to the bites of probable infective G. palpalis palpalis in all trapping zones although farmlands are the most risky transmission zones of sleeping sickness for trappers.

Expansions of chemosensory gene orthologs among selected tsetse fly species and their expressions in Glossina morsitans morsitans tsetse fly.

Tsetse fly exhibit species-specific olfactory uniqueness potentially underpinned by differences in their chemosensory protein repertoire. We assessed 1) expansions of chemosensory protein orthologs in Glossina morsitans morsitans, Glossina pallidipes, Glossina austeni, Glossina palpalis gambiensis, Glossina fuscipes fuscipes and Glossina brevipalpis tsetse fly species using Café analysis (to identify species-specific expansions) and 2) differential expressions of the orthologs and associated proteins in male G. m. morsitans antennae and head tissues using RNA-Seq approaches (to establish associated functional molecular pathways). We established accelerated and significant (P<0.05, λ = 2.60452e-7) expansions of gene families in G. m. morsitans Odorant receptor (Or)71a, Or46a, Ir75a,d, Ionotropic receptor (Ir) 31a, Ir84a, Ir64a and Odorant binding protein (Obp) 83a-b), G. pallidipes Or67a,c, Or49a, Or92a, Or85b-c,f and Obp73a, G. f. fuscipes Ir21a, Gustatory receptor (Gr) 21a and Gr63a), G. p. gambiensis clumsy, Ir25a and Ir8a, and G. brevipalpis Ir68a and missing orthologs in each tsetse fly species. Most abundantly expressed transcripts in male G. m. morsitans included specific Or (Orco, Or56a, 65a-c, Or47b, Or67b, GMOY012254, GMOY009475, and GMOY006265), Gr (Gr21a, Gr63a, GMOY013297 and GMOY013298), Ir (Ir8a, Ir25a and Ir41a) and Obp (Obp19a, lush, Obp28a, Obp83a-b Obp44a, GMOY012275 and GMOY013254) orthologs. Most enriched biological processes in the head were associated with vision, muscle activity and neuropeptide regulations, amino acid/nucleotide metabolism and circulatory system processes. Antennal enrichments (>90% of chemosensory transcripts) included cilium-associated mechanoreceptors, chemo-sensation, neuronal controlled growth/differentiation and regeneration/responses to stress. The expanded and tsetse fly species specific orthologs includes those associated with known tsetse fly responsive ligands (4-methyl phenol, 4-propyl phenol, acetic acid, butanol and carbon dioxide) and potential tsetse fly species-specific responsive ligands (2-oxopentanoic acid, phenylacetaldehyde, hydroxycinnamic acid, 2-heptanone, caffeine, geosmin, DEET and (cVA) pheromone). Some of the orthologs can potentially modulate several tsetse fly species-specific behavioral (male-male courtship, hunger/host seeking, cool avoidance, hygrosensory and feeding) phenotypes. The putative tsetse fly specific chemosensory gene orthologs and their respective ligands provide candidate gene targets and kairomones for respective downstream functional genomic and field evaluations that can effectively expand toolbox of species-specific tsetse fly attractants, repellents and other tsetse fly behavioral modulators.

Epidemiology of tsetse flies in the transmission of trypanosomiasis: technical review of The Gambia experience

Climate change has posed serious health threats on both man and animals. This ranges from effects of progressive temperature rises from global warming to extreme weather events and anthropogenic activities and this has affected insect-vector distributions worldwide. Tsetse fly species transmit Trypanosomes but relative significance depends largely on the strength of their interactions with susceptible hosts. Tsetse flies are the main vectors of Trypanosomiasis and their existence pose a threat to the survival of cattle, small ruminates and equines in The Gambia. It is known to be one of the most vital parasitic diseases affecting livestock productivity in The Gambia and equines are very susceptible. Central River Region is mainly infested with the tsetse fly Glossina morsitan submorsitan a major vector of Trypanosomiasis among animals in the country and it is mainly found in dry, canopied, savannah woodland. Glossina palpalis is also present, but are more limited to riverine vegetation in the area. This work seeks to show the havoc caused by trypanosomiasis and the urgency for more studies to investigate the patterns of transmission of this disease especially in the context of climate change in other for a better control program for this zoonosis in The Gambia.Keywords: Climate Change, Glossina, Trypanosome, Cattle, Equine.

Serological examination of trypanosomes infestation in cattle reared in Keffi, Nasarawa State, Nigeria.

Cattle population is relatively dense in Nasarawa State (Nigeria) particularly in Keffi and its environs, where there are more Hausa/Fulani settlers whose main occupation is farming and herding. Unfortunately, the area is purportedly described as a "horde of tsetse fly species" which transmits trypanosomes that cause severe disease in humans, livestock and wildlife species. This study was targeted at examining trypanosome species prevalent among cattle breeds reared in Keffi metropolis. A total of 110 cattle, purely based on availability were screened within five working days for trypanosomes infestation using haematocrit centrifugation technique and buffy coat technique. The breeds of cattle examined included White Fulani (64), Sokoto Gudali (26), N'dama (16) and Muturu (4); reared in Jarmai, Gauta and Keffi North districts of Keffi Local Government Area, Nasarawa State, Nigeria. Data collected were analysed using simple descriptive statistics. It was observed that 18 (16.4%) out of 110 cattle screened were infested with 5 (4.55%) Trypanosoma con- golense and 13 (11.82%) T. vivax. The T. congolense positive cases were 4 (3.64%) in White Fulani and 1(0.91%) in Sokoto Gudali breeds whereas, T. vivax occurrence was 9 (8.18%) in White Fulani breed and 4 (3.64%) in Sokoto Gudali breed. The N'dama and Muturu breeds were absolutely not infested and no mixed infestation was recorded in any of the breeds. Trypanosoma vivax and T. congolense are the predominant trypanosome species in the study area affecting mainly Sokoto Gudali and White Fulani breeds. Since, N'dama and Muturu breeds were observed to be trypano-tolerant; intensive breeding strategy, strain upgrading mechanisms and genetic modifications could be adopted to ensure other cattles' survival and prevent disease transmission in the area and beyond.

Molecular Screening of Trypanosoma spp. in Glossina, Stomoxys and Tabanids in the Moukalaba Doudou National Park (South-West, Gabon)

Studies on the knowledge of the pathogens responsible for trypanosomosis remain insufficient in Gabon, particularly in protected areas, such as the Moukalaba Doudou National Park (MDNP). In order to uphold ecotourism in the Moukalaba Doudou National Park (MDNP), an entomological and parasitological study was carried out during the rainy season, from February to March 2017, to identify the trypanosome species harbored by tsetse, stable fly and tabanid vectors in this protected area. Fly collection was carried out using Vavoua and Nzi traps. Trypanosome infections in the flies were detected using the polymerase chain reaction (PCR). In total, seven species of tabanids, five species of tsetse flies and two species of stable flies were collected. These vectors harboured six species of trypanosomes, namely Trypanosoma simiae Tsavo (48%), T. theileri (17%), T. simiae (14%), T. brucei s.l. (10%), T. congolense (9%) and T. vivax (2%). The trypanosome infection rate (IR) varied somewhat among sites. It was 82% in the forest, 92% in settled areas and 95% in the savanna. The high prevalence of trypanosomes in this area raises the possibility of some trypanosomosis transmission risk to humans and animals, but the risk appears to be very low given the low frequency of T. brucei s.l. Studies on the blood meals typing could be done to identify sources and estimate the real risk of infection.

Prevalence of symbionts and trypanosome infections in tsetse flies of two villages of the \u201cFaro and D\xe9o\u201d division of the Adamawa region of Cameroon

BackgroundTsetse flies are vectors of human and animal African trypanosomiasis. In spite of many decades of chemotherapy and vector control, the disease has not been eradicated. Other methods like the transformation of tsetse fly symbionts to render the fly refractory to trypanosome infection are being evaluated. The aim of the present study was to evaluate the association between trypanosome infections and the presence of symbionts in these tsetse species. Tsetse flies were trapped in two villages of the “Faro and Déo” Division of the Adamawa region of Cameroon. In the field, tsetse fly species were identified and their infection by trypanosomes was checked by microscopy. In the laboratory, DNA was extracted from their midguts and the presence of symbionts (Sodalis glossinidius and Wolbachia sp.) and trypanosomes was checked by PCR. Symbionts/trypanosomes association tests were performed.ResultsThree tsetse fly species including Glossina tachinoides (90.1%), Glossina morsitans submorsitans (9.4%) and Glossina fuscipes fuscipes (0.5%) were caught. In all the population we obtained an occurrence rate of 37.2% for Sodalis glossinidius and 67.6% for Wolbachia irrespective to tsetse flies species. S. glossinidius and Wolbachia sp. occurrence rates were respectively 37 and 68% for G. tachinoides and 28.6 and 59.5% for G. m. submorsitans. Between Golde Bourle and Mayo Dagoum significant differences were observed in the prevalence of symbionts. Prevalence of trypanosomes were 34.8% for Glossina tachinoides and 40.5% for Glossina morsitans submorsitans. In G. tachinoides, the trypanosome infection rates were 11, 2.6 and 13.7%, respectively, for T. brucei s.l., T. congolense forest type and T. congolense savannah type. In G. m. submorsitans, these infection rates were 16.7, 9.5 and, 2.4% respectively, for T. brucei s.l., T. congolense forest type and T. congolense savannah type.ConclusionsThe rate of tsetse fly infection by trypanosomes was low compared to those obtained in HAT foci of south Cameroon, and this rate was not statistically linked to the rate of symbiont occurrence. This study allowed to show for the first time the presence of Wolbachia sp. in the tsetse fly sub-species Glossina morsitans submorsitans and Glossina tachinoides.

Variations in the Peritrophic Matrix Composition of Heparan Sulphate from the Tsetse Fly, Glossina morsitans morsitans.

Tsetse flies are the principal insect vectors of African trypanosomes—sleeping sickness in humans and Nagana in cattle. One of the tsetse fly species, Glossina morsitans morsitans, is host to the parasite, Trypanosoma brucei, a major cause of African trypanosomiasis. Precise details of the life cycle have yet to be established, but the parasite life cycle involves crossing the insect peritrophic matrix (PM). The PM consists of the polysaccharide chitin, several hundred proteins, and both glycosamino- and galactosaminoglycan (GAG) polysaccharides. Owing to the technical challenges of detecting small amounts of GAG polysaccharides, their conclusive identification and composition have not been possible until now. Following removal of PMs from the insects and the application of heparinases (bacterial lyase enzymes that are specific for heparan sulphate (HS) GAG polysaccharides), dot blots with a HS-specific antibody showed heparan sulphate proteoglycans (HSPGs) to be present, consistent with Glossina morsitans morsitans genome analysis, as well as the likely expression of the HSPGs syndecan and perlecan. Exhaustive HS digestion with heparinases, fluorescent labeling of the resulting disaccharides with BODIPY fluorophore, and separation by strong anion exchange chromatography then demonstrated the presence of HS for the first time and provided the disaccharide composition. There were no significant differences in the type of disaccharide species present between genders or between ages (24 vs. 48 h post emergence), although the HS from female flies was more heavily sulphated overall. Significant differences, which may relate to differences in infection between genders or ages, were evident, however, in overall levels of 2-O-sulphation between sexes and, for females, between 24 and 48 h post-emergence, implying a change in expression or activity for the 2-O-sulphotransferase enzyme. The presence of significant quantities of disaccharides containing the monosaccharide GlcNAc6S contrasts with previous findings in Drosophila melanogaster and suggests subtle differences in HS fine structure between species of the Diptera.

Thioester-containing proteins in the tsetse fly (Glossina) and their response to trypanosome infection.

Thioester‐containing proteins (TEPs) are conserved proteins with a role in innate immune immunity. In the current study, we characterized the TEP family in the genome of six tsetse fly species (Glossina spp.). Tsetse flies are the biological vectors of several African trypanosomes, which cause sleeping sickness in humans or nagana in livestock. The analysis of the tsetse TEP sequences revealed information about their structure, evolutionary relationships and expression profiles under both normal and trypanosome infection conditions. Phylogenetic analysis of the family showed that tsetse flies harbour a genomic expansion of specific TEPs that are not found in other dipterans. We found a general expression of all TEP genes in the alimentary tract, mouthparts and salivary glands. Glossina morsitans and Glossina palpalis TEP genes display a tissue‐specific expression pattern with some that are markedly up‐regulated when the fly is infected with the trypanosome parasite. A different TEP response was observed to infection with Trypanosoma brucei compared to Trypanosoma congolense, indicating that the tsetse TEP response is trypanosome‐specific. These findings are suggestive for the involvement of the TEP family in tsetse innate immunity, with a possible role in the control of the trypanosome parasite.

English

Ethiopia is one of African country with nine regions and two city administration of which five regions were infected with more than one species of tsetse flies. Known species in Ethiopia are five in number namely Glossina pallidipes, G .morsitans, G. fuscipes, G. tachinoides and G. longipennis. Most tsetse transmission is cyclic and begins when blood from a trypanosome-infected animal is ingested by the fly. The clinical feature of the disease follows the level or burdens of tsetse challenge species. The main feature is anemia results in a progressive drop in packed cell volume, a non-specific but useful indicator in endemic areas. The most sensitive rapid method is examining a wet mount of the buffy coat area of a PCV tube after centrifugation, looking for motile parasites. The prevalence of trypanosomosis in enzootic area can be reduced by parasite control, vector control, host resistance protection prophylactic treatment and good husbandry management system. The methods of tsetse fly control involved bush clearing, elimination of game animals on which tsetse feed, and the sterile male technique (sterile insect techniques). Since female tsetse only mates once in a lifetime, this technique is theoretically able to eradicate a targeted tsetse species. Trypanotolerant animals are very important in tsetse fly challenging areas, but most countries did not accept them due to their low production of milk than indigenous breed. In conclusion, prevalence of trypanosomosis is devastating diseases of cattle in Ethiopia with both direct and indirect economic losses. Key words: Bovine, trypanosomosis, nagana, tsetse fly, protozoa.

Comparative genomics identifies male accessory gland proteins in five Glossina species.

Accessory gland proteins (ACPs) are important reproductive proteins produced by the male accessory glands (MAGs) of most insect species. These proteins are essential for male insect fertility, and are transferred alongside semen to females during copulation. ACPs are poorly characterized in Glossina species (tsetse fly), the principal vector of the parasite that causes life-threatening Human African Trypanosomiasis and Animal trypanosomiasis in endemic regions in Africa. The tsetse fly has a peculiar reproductive cycle because of the absence of oviposition. Females mate once and store sperm in a spermathecal, and produce a single fully developed larva at a time that pupates within minutes of exiting their uterus. This slow reproductive cycle, compared to other insects, significantly restricts reproduction to only 3 to 6 larvae per female lifespan. This unique reproductive cycle is an attractive vector control strategy entry point. We exploit comparative genomics approaches to explore the diversity of ACPs in the recently available whole genome sequence data from five tsetse fly species ( Glossina morsitans, G. austeni, G. brevipalpis, G. pallidipes and G. fuscipes). We used previously described ACPs in Drosophila melanogaster and Anopheles gambiae as reference sequences. We identified 36, 27, 31, 29 and 33 diverse ACP orthologous genes in G. austeni, G. brevipalpis, G. fuscipes, G. pallidipes and G. morsitans genomes respectively, which we classified into 21 functional classes. Our findings provide genetic evidence of MAG proteins in five recently sequenced Glossina genomes. It highlights new avenues for molecular studies that evaluate potential field control strategies of these important vectors of human and animal disease.

Comparative genomics identifies male accessory gland proteins in five Glossina species

Accessory gland proteins (ACPs) are important reproductive proteins produced by the male accessory glands (MAGs) of most insect species. These proteins are essential for male insect fertility, and are transferred alongside semen to females during copulation. ACPs are poorly characterized in Glossina species (tsetse fly), the principal vector of the parasite that causes life-threatening Human African Trypanosomiasis and Animal trypanosomiasis in endemic regions in Africa. The tsetse fly has a peculiar reproductive cycle because of the absence of oviposition. Females mate once and store sperm in a spermathecal, and produce a single fully developed larva at a time that pupates within minutes of exiting their uterus. This slow reproductive cycle, compared to other insects, significantly restricts reproduction to only 3 to 6 larvae per female lifespan. This unique reproductive cycle is an attractive vector control strategy entry point. We exploit comparative genomics approaches to explore the diversity of ACPs in the recently available whole genome sequence data from five tsetse fly species ( Glossina morsitans, G. austeni, G. brevipalpis, G. pallidipes and G. fuscipes). We used previously described ACPs in Drosophila melanogaster and Anopheles gambiae as reference sequences. We identified 36, 27, 31, 29 and 33 diverse ACP orthologous genes in G. austeni, G. brevipalpis, G. fuscipes, G. pallidipes and G. morsitans genomes respectively, which we classified into 21 functional classes. Our findings provide genetic evidence of MAG proteins in five recently sequenced Glossina genomes. It highlights new avenues for molecular studies that evaluate potential field control strategies of these important vectors of human and animal disease.

Patterns of tsetse abundance and trypanosome infection rates among habitats of surveyed villages in Maasai steppe of northern Tanzania

BackgroundChanges of land cover modify the characteristics of habitat, host-vector interaction and consequently infection rates of disease causing agents. In this paper, we report variations in tsetse distribution patterns, abundance and infection rates in relation to habitat types and age in the Maasai Steppe of northern Tanzania. In Africa, Tsetse-transmitted trypanosomiasis negatively impacted human life where about 40 million people are at risk of contracting the disease with dramatic socio-economical consequences, for instance, loss of livestock, animal productivity, and manpower.MethodsWe trapped tsetse flies in dry and wet seasons between October 2014 and May 2015 in selected habitats across four villages: Emboreet, Loiborsireet, Kimotorok and Oltukai adjacent to protected areas. Data collected include number and species of tsetse flies caught in baited traps, PCR identification of trypanosome species and extraction of monitored Normalized Difference Vegetation Index (NDVI) data from Moderate Resolution Imaging Spectrometer (MODIS).ResultsOur findings demonstrate the variation of tsetse fly species abundance and infection rates among habitats in surveyed villages in relation to NDVI and host abundance. Results have shown higher tsetse fly abundance in Acacia-swampy ecotone and riverine habitats for Emboreet and other villages, respectively. Tsetse abundance was inconsistent among habitats in different villages. Emboreet was highly infested with Glossina swynnertoni (68%) in ecotone and swampy habitats followed by G. morsitans (28%) and G. pallidipes (4%) in riverine habitat. In the remaining villages, the dominant tsetse fly species by 95% was G. pallidipes in all habitats. Trypanosoma vivax was the most prevalent species in all infected flies (95%) with few observations of co-infections (with T. congolense or T. brucei).ConclusionsThe findings of this study provide a framework to mapping hotspots of tsetse infestation and trypanosomiasis infection and enhance the communities to plan for effective control of trypanosomiasis.

Comparative genomics identifies male accessory gland proteins in five Glossina species.

Accessory gland proteins (ACPs) are important reproductive proteins produced by the male accessory glands (MAGs) of most insect species. These proteins are essential for male insect fertility, and are transferred alongside semen to females during copulation. ACPs are poorly characterized in Glossina species (tsetse fly), the principal vector of the parasite that causes life-threatening Human African Trypanosomiasis and Animal trypanosomiasis in endemic regions in Africa. The tsetse fly has a peculiar reproductive cycle because of the absence of oviposition. Females mate once and store sperm in a spermathecal, and produce a single fully developed larva at a time that pupates within minutes of exiting their uterus. This slow reproductive cycle, compared to other insects, significantly restricts reproduction to only 3 to 6 larvae per female lifespan. This unique reproductive cycle is an attractive vector control strategy entry point. We exploit comparative genomics approaches to explore the diversity of ACPs in the recently available whole genome sequence data from five tsetse fly species ( Glossina morsitans, G. austeni, G. brevipalpis, G. pallidipes and G. fuscipes). We used previously described ACPs in Drosophila melanogaster and Anopheles gambiae as reference sequences. We identified 36, 27, 31, 29 and 33 diverse ACP orthologous genes in G. austeni, G. brevipalpis, G. fuscipes, G. pallidipes and G. morsitans genomes respectively, which we classified into 21 functional classes. Our findings provide genetic evidence of MAG proteins in five recently sequenced Glossina genomes. It provides new avenues for molecular studies that evaluate potential field control strategies of these important vectors of human and animal disease.

Remarkable richness of trypanosomes in tsetse flies (Glossina morsitans morsitans and Glossina pallidipes) from the Gorongosa National Park and Niassa National Reserve of Mozambique revealed by fluorescent fragment length barcoding (FFLB)

Trypanosomes of African wild ungulates transmitted by tsetse flies can cause human and livestock diseases. However, trypanosome diversity in wild tsetse flies remains greatly underestimated. We employed FFLB (fluorescent fragment length barcoding) for surveys of trypanosomes in tsetse flies (3086) from the Gorongosa National Park (GNP) and Niassa National Reserve (NNR) in Mozambique (MZ), identified as Glossina morsitans morsitans (GNP/NNR=77.6%/90.5%) and Glossina pallidipes (22.4%/9.5%). Trypanosomes were microscopically detected in 8.3% of tsetse guts. FFLB of gut samples revealed (GNP/NNR): Trypanosoma congolense of Savannah (27%/63%), Kilifi (16.7%/29.7%) and Forest (1.0%/0.3%) genetic groups; T. simiae Tsavo (36.5%/6.1%); T. simiae (22.2%/17.7%); T. godfreyi (18.2%/7.0%); subgenus Trypanozoon (20.2%/25.7%); T. vivax/T. vivax-like (1.5%/5.2%); T. suis/T. suis-like (9.4%/11.9%). Tsetse proboscises exhibited similar species composition, but most prevalent species were (GNP/NNR): T. simiae (21.9%/28%), T. b. brucei (19.2%/31.7%), and T. vivax/T. vivax-like (19.2%/28.6%). Flies harboring mixtures of trypanosomes were common (~ 64%), and combinations of more than four trypanosomes were especially abundant in the pristine NNR. The non-pathogenic T. theileri was found in 2.5% while FFLB profiles of unknown species were detected in 19% of flies examined. This is the first report on molecular diversity of tsetse flies and their trypanosomes in MZ; all trypanosomes pathogenic for ungulates were detected, but no human pathogens were detected. Overall, two species of tsetse flies harbor 12 species/genotypes of trypanosomes. This notable species richness was likely uncovered because flies were captured in wildlife reserves and surveyed using the method of FFLB able to identify, with high sensitivity and accuracy, known and novel trypanosomes. Our findings importantly improve the knowledge on trypanosome diversity in tsetse flies, revealed the greatest species richness so far reported in tsetse fly of any African country, and indicate the existence of a hidden trypanosome diversity to be discovered in African wildlife protected areas.

Seasonal variation of tsetse fly species abundance and prevalence of trypanosomes in the Maasai Steppe, Tanzania.

Tsetse flies, the vectors of trypanosomiasis, represent a threat to public health and economy in sub-Saharan Africa. Despite these concerns, information on temporal and spatial dynamics of tsetse and trypanosomes remain limited and may be a reason that control strategies are less effective. The current study assessed the temporal variation of the relative abundance of tsetse fly species and trypanosome prevalence in relation to climate in the Maasai Steppe of Tanzania in 2014-2015. Tsetse flies were captured using odor-baited Epsilon traps deployed in ten sites selected through random subsampling of the major vegetation types in the area. Fly species were identified morphologically and trypanosome species classified using PCR. The climate dataset was acquired from the African Flood and Drought Monitor repository. Three species of tsetse flies were identified: G. swynnertoni (70.8%), G. m. morsitans (23.4%), and G.pallidipes (5.8%). All species showed monthly changes in abundance with most of the flies collected in July. The relative abundance of G. m. morsitans and G. swynnertoni was negatively correlated with maximum and minimum temperature, respectively. Three trypanosome species were recorded: T. vivax (82.1%), T. brucei (8.93%), and T. congolense (3.57%). The peak of trypanosome infections in the flies was found in October and was three months after the tsetse abundance peak; prevalence was negatively correlated with tsetse abundance. A strong positive relationship was found between trypanosome prevalence and temperature. In conclusion, we find that trypanosome prevalence is dependent on fly availability, and temperature drives both tsetse fly relative abundance and trypanosome prevalence.

Variation of tsetse fly abundance in relation to habitat and host presence in the Maasai Steppe, Tanzania.

Human activities modify ecosystem structure and function and can also alter the vital rates of vectors and thus the risk of infection with vector-borne diseases. In the Maasai Steppe ecosystem of northern Tanzania, local communities depend on livestock and suitable pasture that is shared with wildlife, which can increase tsetse abundance and the risk of trypanosomiasis. We monitored the monthly tsetse fly abundance adjacent to Tarangire National Park in 2014-2015 using geo-referenced, baited epsilon traps. We examined the effect of habitat types and vegetation greenness (NDVI) on the relative abundance of tsetse fly species. Host availability (livestock and wildlife) was also recorded within 100×100 m of each trap site. The highest tsetse abundance was found in the ecotone between Acacia-Commiphora woodland and grassland, and the lowest in riverine woodland. Glossina swynnertoni was the most abundant species (68%) trapped throughout the entire study, while G. pallidipes was the least common (4%). Relative species abundance was negatively associated with NDVI, with greatest abundance observed in the dry season. The relationship with the abundance of wildlife and livestock was more complex, as we found positive and negative associations depending on the host and fly species. While habitat is important for tsetse distribution, hosts also play a critical role in affecting fly abundance and, potentially, trypanosomiasis risk.

Spatial distribution and trypanosome infection of tsetse flies in the sleeping sickness focus of Zimbabwe in Hurungwe District.

BackgroundIn Zimbabwe, cases of human African trypanosomiasis (HAT) are caused by the unicellular protozoan Trypanosoma brucei, sub-species T. b. rhodesiense. They are reported from the tsetse-infested area in the northern part of the country, broadly corresponding to the valley of the Zambezi River. Tsetse-transmitted trypanosomes, in particular T. congolense and T. vivax, also cause morbidity and mortality in livestock, thus generating poverty and food insecurity. Two species of tsetse fly, Glossina morsistans morsitans and G. pallidipes, are known to be present in the Zambezi Valley, although their distributional patterns and densities have not been investigated in detail. The present study tries to address this gap by providing some insight into the dynamics of trypanosomiasis in humans and livestock.MethodsTsetse distribution and trypanosome infections were studied using traps and fixed fly rounds located at 10 km intervals along a 110 km long transect straddling the southern escarpment of the Zambezi Valley. Three km long fly rounds were conducted on 12 sites, and were repeated 11 times over a 7-month period. Additional traps were deployed and monitored in selected sites. Microscopic examination of 2092 flies for trypanosome infections was conducted.ResultsSurveys confirmed the presence of G. morsitans morsitans and G. pallidipes in the Zambezi Valley floor. Moving south, the apparent density of tsetse flies appears to peak in the vicinity of the escarpment, then drops on the highlands. Only one fly was caught south of the old game fence separating protected and settled areas. A trypanosome infection rate of 6.31% was recorded in tsetse flies dissected. Only one infection of the T. brucei-type was detected.ConclusionsTsetse fly distribution in the study area appears to be driven by ecological factors such as variation in land use and altitude-mediated climatic patterns. Although targeted control of tsetse flies have played a role in determining distribution, no major control operations have been implemented in the area for 15 years. Trypanosome infections in tsetse flies are consistent with HAT epidemiological data, which considers the situation to be generally ‘low risk’. Nonetheless, underreporting is likely to conceal the true epidemiological picture, and efforts are needed to strengthen the diagnostic capacities of health facilities.

Population Dynamics of Tsetse flies at Salt Lick B and Guruntun Areas of Yankari National Park Bauchi State Nigeria

Objective: The aim of the research was to Identity tsetse species distribution present in salt lick B and Guruntun area of Yankari National Park and to determine the apparent density of the flies, Materials and Methods: Twenty biconical traps were mounted between salt lick B area and Guruntun River side. Coordinates and GPS positions were determined for each trap set. Results: Two dominant species of tsetse flies were found mostly in the two sides, which include G. tachinoides and G. morsitan . Three thousand and forty seven (3,047) flies were collected during the period, out of which 2,827 were G. tachinoides with apparent density of 70.68, while 220 were G. morsitans with apparent density of 5.5.Out of the 2,827, G. tachinoides 2,415 were females with apparent density of 60.4 while 412 were males with apparent density of 20.6. Conclusion the patterns of fly distribution in the two locations especially the female GlossinaTachnoides showed that tsetse fly is a still a major hindrance to wild life population in Yankari National Park. There is a need for intervention in other to reduce the fly population in the two areas which serves as a major site during game viewing and research.

Animal trypanosomosis in clinically healthy cattle of north Cameroon: epidemiological implications.

BackgroundThe control of animal trypanosomosis consists, amongst other things, of the punctual treatment of new cases, primarily diagnosed by pastoralists on the basis of clinical signs. This practice suggests that many apparently healthy infected animals are left untreated. In this study animal trypanosomosis in clinically healthy zebu cattle was evaluated, the distribution of the vectors established and the epidemiological implications discussed.MethodsIn 2014 two cross-sectional surveys were carried out in the Cambeef ranch. A total of 866 blood samples were collected from cattle in different sites: 549 in the dry season and 317 in the rainy season. The blood samples were subjected to parasitological examination using the buffy coat method and to PCV determination. An entomological survey on animal trypanosomosis vectors was undertaken during tsetse flies caught were identified and the mid-gut of each living non-teneral tsetse fly was examined for infections using a microscope.ResultsAn overall trypanosomosis prevalence of 9 % was found in the cattle examined. There were significantly (P < 0.05) more trypanosome infected cattle in the dry season than the rainy season. Trypanosome-infected cattle had significantly (P < 0.05) lower Body Condition Scores (BCS) and Packed Cell Volumes (PCV) in the dry season than in the rainy season. Anemia was positively correlated with trypanosome infection. The likelihood for an animal to be parasitologically free of trypanosome infection was at least three times as high in the Gudali breed as compared with the white and red Fulani breeds. Species of trypanosomes identified were Trypanosoma vivax (73.23 %), Trypanosoma congolense (15.49 %) and Trypanosoma brucei (11.27 %). A total of 390 tsetse flies and 103 tabanids were trapped. Two species of tsetse flies were identified: Glossina tachinoides (33.59 %) and G. morsitans submorsitans (41 %). Nine of the 194 non-teneral flies were infected with trypanosomes.ConclusionCarriers of trypanosomes are present amongst apparently healthy cattle in the study site. Attempts to successfully reduce the population of reservoir trypanosomes within herds and control the disease will need to consider mass screening once every year and this should be associated with drug sensitivity tests.

Molecular screening for Anaplasmataceae in ticks and tsetse flies from Ethiopia.

Hard ticks and tsetse flies are regarded as the most important vectors of disease agents in Sub-Saharan Africa. With the aim of screening these blood-sucking arthropods for vector-borne pathogens belonging to the family Anaplasmataceae in South-Western Ethiopia, four species of tsetse flies (collected by traps) and seven species of ixodid ticks (removed from cattle) were molecularly analysed. DNA was extracted from 296 individual ticks and from 162 individuals or pools of tsetse flies. Besides known vector-pathogen associations, in Amblyomma cohaerens ticks sequences of Anaplasma marginale and A. phagocytophilum were detected, the latter for the first time in any ticks from cattle in Africa. In addition, part of the gltA gene of Ehrlichia ruminantium was successfully amplified from tsetse flies (Glossina pallidipes). First-time identification of sequences of the above pathogens in certain tick or tsetse fly species may serve as the basis of further epidemiological and transmission studies.