Detection and identification of pathogenic trypanosome species in tsetse flies along the Comoé River in Côte d'Ivoire

Application of biomolecular techniques on tsetse fly puparia for species identification at larvipostion sites

Puparia are commonly found in tsetse fly larviposition sites during studies on larval ecology. This chitinous shell is representative of past or ongoing exploitation of these sites by tsetse flies. The morphological characteristics of the puparium are not sufficiently distinctive to allow identification of the species. This study explores the applicability of biomolecular techniques on empty puparia for tsetse fly species identification. Five techniques were compared for DNA extraction from tsetse fly puparia, 1/Chelex® 100 Resin, 2/CTAB, 3/Livak's protocol, 4/DEB + proteinase K and 5/QIAamp® DNA Mini kit, using two homogenisation methods (manual and automated). Using a combination of two primer pairs, Chelex, CTAB, and DEB + K proved the most efficient on fresh puparia with 90, 85, and 70% samples identified, respectively. Shifting from fresh to one- to nine-month-old puparia, the Chelex method gave the best result allowing species identification on puparia up to seven months old. The subsequent testing of the Chelex extraction protocol identified 152 (60%) of 252 field-collected puparia samples at species level. The results show that reliable genetic identification of tsetse flies species can be performed from empty puparia, what can prove of great interest for future ecological studies on larviposition sites. The Chelex technique was the most efficient for DNA extraction, though the age-limit of the samples stood at seven months, beyond which DNA degradation probably compromises the genetic analysis.

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.

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.

Molecular epidemiological survey of pathogenic trypanosomes in naturally infected cattle in northern Côte d'ivoire

Bovine trypanosomiasis is a significant health concern for livestock intensification in Côte d'Ivoire. This study aimed to determine the prevalence and distribution of pathogenic trypanosomes and identify the most infected cattle breed in northern Côte d&apos;Ivoire. We examined 700 cattle and found that polymerase chain reaction (PCR) was more sensitive (12.3%) than microscopic observation (5.6%). Among the trypanosome species detected in naturally infected cattle, Trypanosoma vivax was 7.3%, Trypanosoma simiae tsavo was 6.7%, and Trypanosoma congolense was 0.4%. The overall prevalence of trypanosome infection in all cattle breeds was 12.3%, while the prevalence in individual breeds was 14.8%, 7.3%, 10.6%, and 12.3% for N'Dama, Baoule, Zebu, and Mere breed, respectively. The infected animals had low packed cell volume, influencing the prevalence. Our findings indicate that bovine trypanosomes are prevalent in Côte d'Ivoire, and their prevalence varies by region and breed. These pathogens include T. vivax, T. simiae tsavo, and T. congolense.

Prevalence of bovine trypanosomiasis in Côte d'Ivoire: Systematic review and meta-analysis

Bovine trypanosomiasis is a parasitic disease caused by protozoans of the genus Trypanosoma. The disease cause economic losses in livestock production. In order to determine the status of research on this disease in Côte d'Ivoire, we used the systematic review method and meta-analysis. Three electronics databases, namely Google Scholar, PubMed and CrossRef were used to search for publications on trypanosomiasis prevalence that met our inclusion criteria. Twenty five articles were identified, 11 of which met the inclusion criteria. Bovine trypanosomiasis prevalence of 2.99% (95% confidence interval [CI]: 2.96% - 3.01%) to 25.28% (95% CI: 25.17% - 25.38%) were recorded between 1960 and 2021. The analyses showed that the most infected regions were the Bagoue 11.26% (95% CI: 11.25% - 11.27%), Bounkani 14.94% (95% CI: 14.93% - 14.95%), Gbeke 10.34% (95% CI: 10.33% - 10.35%), Marahoue 13.79% (95% CI: 13.78% - 13.80%), Poro 8.50% (95% CI: 8.49% - 8.51%), and Tchologo 11.83% (95% CI: 11.82% - 11.84%).The most sensitive diagnostic method used was the polymerase chain reaction (PCR). The species of trypanosomes diagnosed were Typanosoma vivax 4.99% (95% CI: 4.97% - 5.01%), T. congolense 1.51% (95% CI: 1.49% - 1.52%), and T. brucei 0.61% (95% CI: 0.59% - 0.62%). Despite some variation, the prevalence of bovine trypanosomiasis in Côte d'Ivoire caused mainly by T. vivax has increased in the years between 1977 and 2017. Efforts to control tsetse and other mechanical vectors should also be put in place to minimize its transmission.Contribution: The authors studied the prevalence of bovine trypanosomiasis using the systematic review method and MA in order to determine the status of research on this disease in Côte d'Ivoire.

Modular nanotheranostic agents for protistan parasitic diseases: Magic bullets with tracers

Protistan parasitic infections contribute significantly to morbidity and mortality, causing more than 2 billion human infections annually. However, current treatments are often limited; due to ineffective drugs and drug resistance, thus better options are urgently required. In the present context, theranostics agents are those that offer simultaneous detection, diagnosis and even treatment of protistan parasitic diseases. "Nanotheranostics" is the term used to describe such agents, that are around 100 nm or less in size. Anti-parasitic activity of nanoparticles (NPs) has been reported, and many have useful intrinsic imaging properties, but it is perhaps their multifunctional nature that offers the greatest potential. NPs may be used as adapters onto which various subunits with different functions may be attached. These subunits may facilitate targeting parasites, coupled with toxins to eradicate parasites, and probe subunits for detection of particles and/or parasites. The modular nature of nano-platforms promises a "mix and match" approach for the construction of tailored agents by using combinations of these subunits against different protistan parasites. Even though many of the subunits have shown promise alone, these have not yet been put together convincingly enough to form working theranostics against protistan parasites. Although the clinical application of nanotheranostics to protistan parasitic infections in humans requires more research, we conclude that they offer not just a realisation of Paul Ehrlich's long imagined "magic bullet" concept, but potentially are magic bullets combined with tracer bullets.

Prevalence of trypanosomes and selected symbionts in tsetse species of eastern Zambia

Insect symbionts have attracted attention for their potential use as anti-parasitic gene products in arthropod disease vectors. While tsetse species of the Luangwa valley have been extensively studied, less is known about the prevalence of symbionts and their interactions with the trypanosome parasite. Polymerase chain reaction was used to investigate the presence of Wolbachia and Sodalis bacteria, in tsetse flies infected with trypanosomes (Trypanosoma vivax, Trypanosoma congolense and Trypanosoma brucei). Out of 278 captured tsetse flies in eastern Zambia, 95.3% (n = 265, 95% CI = 92.8–97.8) carried endosymbionts: Wolbachia (79.1%, 95% CI 73.9–83.8) and Sodalis (86.3%, 95% CI 81.7–90.1). Overall, trypanosome prevalence was 25.5% (n = 71, 95% CI = 20.4–30.7), 10.8% (n = 30, 95% CI 7.1–14.4) for T. brucei, 1.4% (n = 4, 95% CI = 0.4–3.6) for both T. congolense and T. vivax, and 0.7% (n = 2, 95% CI 0.1–2.6) for T. b. rhodesiense. Out of 240 tsetse flies that were infected with Sodalis, trypanosome infection was reported in 40 tsetse flies (16.7%, 95% CI = 12.0–21.4) while 37 (16.8%, 95% CI 11.9–21.8) of the 220 Wolbachia infected tsetse flies were infected with trypanosomes. There was 1.3 times likelihood of T. brucei infection to be present when Wolbachia was present and 1.7 likelihood of T. brucei infection when Sodalis was present. Overall findings suggest absence of correlation between the presence of tsetse endosymbionts and tsetse with trypanosome infection. Lastly, the presence of pathogenic trypanosomes in tsetse species examined provided insights into the risk communities face, and the importance of African trypanosomiasis in the area.

Prevalence of Trypanosoma and Sodalis in wild populations of tsetse flies and their impact on sterile insect technique programmes for tsetse eradication

The sterile insect technique (SIT) is an environment friendly and sustainable method to manage insect pests of economic importance through successive releases of sterile irradiated males of the targeted species to a defined area. A mating of a sterile male with a virgin wild female will result in no offspring, and ultimately lead to the suppression or eradication of the targeted population. Tsetse flies, vectors of African Trypanosoma, have a highly regulated and defined microbial fauna composed of three bacterial symbionts that may have a role to play in the establishment of Trypanosoma infections in the flies and hence, may influence the vectorial competence of the released sterile males. Sodalis bacteria seem to interact with Trypanosoma infection in tsetse flies. Field-caught tsetse flies of ten different taxa and from 15 countries were screened using PCR to detect the presence of Sodalis and Trypanosoma species and analyse their interaction. The results indicate that the prevalence of Sodalis and Trypanosoma varied with country and tsetse species. Trypanosome prevalence was higher in east, central and southern African countries than in west African countries. Tsetse fly infection rates with Trypanosoma vivax and T. brucei sspp were higher in west African countries, whereas tsetse infection with T. congolense and T. simiae, T. simiae (tsavo) and T. godfreyi were higher in east, central and south African countries. Sodalis prevalence was high in Glossina morsitans morsitans and G. pallidipes but absent in G. tachinoides. Double and triple infections with Trypanosoma taxa and coinfection of Sodalis and Trypanosoma were rarely observed but it occurs in some taxa and locations. A significant Chi square value (< 0.05) seems to suggest that Sodalis and Trypanosoma infection correlate in G. palpalis gambiensis, G. pallidipes and G. medicorum. Trypanosoma infection seemed significantly associated with an increased density of Sodalis in wild G. m. morsitans and G. pallidipes flies, however, there was no significant impact of Sodalis infection on trypanosome density.

Bovine trypanosomosis in upstream and downstream of Ghibe-III hydroelectric dam: parasitological and entomological study, southern Ethiopia

Two-point cross-sectional study design in dry and rainy seasons was employed near Ghibe-III Dam from December 2018 to July 2019. Trypanosomosis prevalence comparison between downstream (Kindodidaye) and upstream (Loma districts), associated risk factors, vector dispersion, identification and vector infection rate considered. Blood sample collected from 1280 cattle from two districts during dry and rainy seasons; the assumed risk factors recorded. Samples were examined using heamatological and parasitological techniques. In this study 9.1% (116/1280) trypanosomosis prevalence recorded. Prevalence was significantly (p < 0.05) different between Kindodidaye (11.7%) and Loma (6.4%). Most of the infections were due to T. congolense (79.3%) followed by T. vivax (17.2%) and T. brucei (2.6%) and one mixed infection recorded. Significant (p < 0.05) difference observed in season, within district and between districts. Among the assumed risk factors: district, season, Kebele and body condition score showed significant (p < 0.05) difference; whereas sex, age, color weren't significantly (p > 0.05) different. Significantly (p < 0.05) low mean PCV observed in infected group, dry season and Kindodidaye district. Entomological survey revealed 1030 tsetse spp. (G. pallidipes and G. fuscipes) and 2045 biting flies mainly Stomoxysis and Tabanus, and other unidentified spp. recorded. Tsetse apparent density were significantly (p < 0.05) high in Kindodidaye and rainy season with value of 5.3 and 7.1 F/T/D, respectively. Out of 182 tsetse fly dissected twenty seven (14.6%) of them were infected. A proportion of 23.0%, 30.8% and 46.2% infection rate recorded in proboscis, salivary gland and mid gut, respectively. The study shows Kindodidaye and rainy season had high trypanosomosis and tsetse apparent density than Loma. The difference might be associated with water reserve created due to Ghibe III hydroelectric dam and this could be a golden opportunity in the area to contribute tsetse control program. Stakeholders' need to aware to use this opportunity before tsetse adapts itself into new environment or niche for their survival.

Rapid diagnosis of parasitic diseases: current scenario and future needs

BACKGROUND

Parasitic diseases are one of the world's most devastating and prevalent infections, causing millions of morbidities and mortalities annually. In the past, many of these infections have been linked predominantly to tropical or subtropical areas. Nowadays, however, climatic and vector ecology changes, a significant increase in international travel, armed conflicts, and migration of humans and animals have influenced the transmission of some parasitic diseases from 'book pages' to reality in developed countries. It has also been noted that many patients who have never travelled to endemic areas suffer from blood-borne infections caused by protozoa. In the light of existing knowledge, this new trend can be explained by the fact that in the process of migration a large number of asymptomatic carriers become a part of the blood bank donor and transplant donor populations. Accurate and rapid diagnosis represents the crucial weapon in the fight against parasitic infections.

AIMS

To review old and new approaches for rapid diagnosis of parasitic infections.

SOURCES

Data for this review were obtained through searches of PubMed using combinations of the following terms: parasitological diagnostics, microscopy, lateral flow assays, immunochromatographic assays, multiplex-PCR, and transplantation.

CONTENT

In this review, we provide a brief account of the advantages and limitations of rapid methods for diagnosis of parasitic diseases and focus our attention on current and future research in this area. The approximate costs associated with the use of different techniques and their applicability in endemic and non-endemic areas are also discussed.

IMPLICATIONS

Microscopy remains the cornerstone of parasitological diagnostics, especially in the field and low-resource settings, and provides epidemiological assessment of parasite burden. However, increased use and availability of point-of-care tests and molecular assays in modern era allow more rapid and accurate diagnoses and increased sensitivity in the identification of parasitic infections.

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.

Prevalence of trypanosome infection in tsetse flies from Oji River and Emene axis of Enugu State, Nigeria: A preliminary report

INTRODUCTION

Trypanosomes are protozoan parasites of vertebrates transmitted by blood-sucking tsetse fly. Trypanosomes remain a constant threat to the lives of humans and animals throughout large regions of Africa.

AIMS AND OBJECTIVES

This study investigated the presence, prevalence, and species of trypanosome parasite in tsetse flies caught in two areas of no previous documented history of trypanosome infection.

MATERIALS AND METHODS

For this purpose, 63 and 77 nonterenal tsetse flies were collected from Oji River and Emene areas of Enugu State Nigeria, respectively. Genomic DNA was isolated from the whole tsetse fly using genomic DNA extraction kit. Identification and characterization of trypanosome were done using two approaches: the amplification of internal transcribed spacer 1 of ribosomal DNA and the use of primers specific to Trypanozoon.

RESULTS

In Oji River, of 63 tsetse flies collected, the identification of trypanosome parasite was done on 57 flies and 6 (10.71%) tsetse flies were infected with trypanosome parasite. Six flies were infected with Trypanosoma Congolense, 2 with Trypanosoma Vivax, and 1 with Trypanosoma brucei. Two mixed infections of T. vivax and T. congolense and 1 mixed infection of T. brucei and T. congolense was also identified. In Emene, of 77 tsetse flies collected, the identification of trypanosome parasite was done on 66 flies and 11 (16.6%) tsetse flies were infected with trypanosome parasite. Nine flies were infected with T. congolense, 2 with T. vivax, and 3 with T. brucei. Mixed infections identified include 2 mixed infections of T. brucei and T. congolense and 1 mixed infections of T. vivax and T. brucei. None of the subspecies of T. brucei were detected using species specific primers.

DISCUSSION

This study shows the parasitological evidence on the occurrence of animal African trypanosomiasis and also demonstrated that there is likely no active transmission of human African trypanosomiasis in the study areas.

CONCLUSION

This study shows that there is likely no active transmission of human African trypanosomiasis going on in these localities since no human infective form of the parasite was detected.

A systematic review and meta-analysis of trypanosome prevalence in tsetse flies

Background

The optimisation of trypanosomosis control programs warrants a good knowledge of the main vector of animal and human trypanosomes in sub-Saharan Africa, the tsetse fly. An important aspect of the tsetse fly population is its trypanosome infection prevalence, as it determines the intensity of the transmission of the parasite by the vector. We therefore conducted a systematic review of published studies documenting trypanosome infection prevalence from field surveys or from laboratory experiments under controlled conditions. Publications were screened in the Web of Science, PubMed and Google Scholar databases. Using the four-stage (identification, screening, eligibility and inclusion) process in the PRISMA statement the initial screened total of 605 studies were reduced to 72 studies. The microscopic examination of dissected flies (dissection method) remains the most used method to detect trypanosomes and thus constituted the main focus of this analysis. Meta-regression was performed to identify factors responsible for high trypanosome prevalence in the vectors and a random effects meta-analysis was used to report the sensitivity of molecular and serological tests using the dissection method as gold standard.

Results

The overall pooled prevalence was 10.3% (95% confidence interval [CI] = 8.1%, 12.4%) and 31.0% (95% CI = 20.0%, 42.0%) for the field survey and laboratory experiment data respectively. The country and the year of publication were found to be significantly factors associated with the prevalence of trypanosome infection in tsetse flies. The alternative diagnostic tools applied to dissection positive samples were characterised by low sensitivity, and no information on the specificity was available at all.

Conclusion

Both temporal and spatial variation in trypanosome infection prevalence of field collected tsetse flies exists, but further investigation on real risk factors is needed how this variation can be explained. Improving the sensitivity and determining the specificity of these alternative diagnostic tools should be a priority and will allow to estimate the prevalence of trypanosome infection in tsetse flies in high-throughput.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-017-1012-9) contains supplementary material, which is available to authorized users.

High Frequency of Trypanosoma congolense Savannah Type (Kinetoplastida: Trypanosomatidae) Among Tsetse Flies (Diptera: Glossinidae) in a Historic Trypanosoma Foci in North-Eastern Gabon: Preliminary Study [corrected]

Human African trypanosomiasis became a neglected disease after the 1960s, when case numbers dropped dramatically. It again became a public health problem in sub-Saharan Africa at the end of the 1990s, when new cases were reported, notably in Central Africa, and specifically in Gabon, where historic foci existed and new cases have been reported. Therefore, the present study reports on an entomological survey conducted in May 2012 to determine the pathogenic trypanosome infection rate in tsetse flies and characterize the diversity of Trypanosoma species in the Ivindo National Park (INP) in northeastern Gabon. Nine Vavoua traps were used to catch tsetse over a 7-days period. All tsetse flies captured were identified to species, dissected, and trypanosome species identified using polymerase chain reaction (PCR). In total, 160 tsetse flies were analyzed, including Glossina palpalis palpalis, Glossina fusca congolense, and Glossina tachinoïdes The trypanosome infection rate of the flies was 6.3 and 31.9% using microscopy and PCR, respectively. The species identified were Trypanosoma congolense savannah type, Trypanosoma brucei brucei, Trypanosoma brucei gambiense, Trypanosoma vivax, and Trypanosoma congolense forest type. Trypanosoma risk index was 0.75 and 7.05 for humans and for animals, respectively. This study illustrates the diversity of Trypanosoma species infecting the tsetse flies in the INP. The simultaneous occurrence of Trypanosoma and tsetse from the palpalis group may suggest that the reservoirs of African animal trypanosomiasis should be carefully monitored in this area.

Trypanosome infection rates in tsetse flies in the "silent" sleeping sickness focus of Bafia in the Centre Region in Cameroon

Background

The Bafia sleeping sickness focus of Cameroon is considered as “silent” with no case reported for about 20 years despite medical surveys performed during the last decades. In this focus, all epidemiological factors that can contribute to trypanosomes transmission are present. To update our knowledge on the current risks of Human and Animal African trypanosomiases, different trypanosome species were identified in midguts of tsetse flies captured in the Bafia focus.

Methods

Tsetse flies were trapped using pyramidal traps. Each tsetse fly was identified and live flies were dissected and their midguts collected. DNA was extracted from each midgut and thereafter, blood meals and different trypanosome species were identified with molecular tools. The biological data were transported onto maps in order to have their distribution.

Results

Of the 98 traps set up, 461 Glossina palpalis palpalis were captured; 322 (69.8 %) tsetse flies were dissected and 49 (15.2 %) teneral flies identified. The average apparent density of tsetse flies per day was 1.18. Of the 35 (10.9 %) blood meals collected, 82 % were taken on pigs and 17.6 % on humans. Eighty two (25.5 %) trypanosome infections were identified: 56 (17.4 %) T. congolense savannah, 17 (5.3 %) T. congolense forest, 5 (1.6 %) T. vivax and 4 (1.2 %) T. brucei s.l. No infection of T. simiae and T. b. gambiense was identified. Sixty seven (81.7 %) infections were single and 15 (18.3 %) mixed involving one triple infection (T. congolense forest, T. brucei and T. vivax) and 14 double infections: 11 T. congolense forest and T. congolense savannah, two T. congolense savannah and T. brucei, and one of T. brucei and T. vivax. The generated maps show the distribution of tsetse flies and trypanosome infections across the focus.

Conclusion

This study has shown that animal trypanosomes remain an important problem in this region. Meanwhile, it is very likely that HAT does not seem anymore to be a public health problem in this focus. The generated maps enabled us to define high risk transmission areas for AAT, and where disease control must be focused in order to improve animal health as well as the quantity of animal proteins.

A Spatio-temporal Model of African Animal Trypanosomosis Risk

BACKGROUND

African animal trypanosomosis (AAT) is a major constraint to sustainable development of cattle farming in sub-Saharan Africa. The habitat of the tsetse fly vector is increasingly fragmented owing to demographic pressure and shifts in climate, which leads to heterogeneous risk of cyclical transmission both in space and time. In Burkina Faso and Ghana, the most important vectors are riverine species, namely Glossina palpalis gambiensis and G. tachinoides, which are more resilient to human-induced changes than the savannah and forest species. Although many authors studied the distribution of AAT risk both in space and time, spatio-temporal models allowing predictions of it are lacking.

METHODOLOGY/PRINCIPAL FINDINGS

We used datasets generated by various projects, including two baseline surveys conducted in Burkina Faso and Ghana within PATTEC (Pan African Tsetse and Trypanosomosis Eradication Campaign) national initiatives. We computed the entomological inoculation rate (EIR) or tsetse challenge using a range of environmental data. The tsetse apparent density and their infection rate were separately estimated and subsequently combined to derive the EIR using a "one layer-one model" approach. The estimated EIR was then projected into suitable habitat. This risk index was finally validated against data on bovine trypanosomosis. It allowed a good prediction of the parasitological status (r2 = 67%), showed a positive correlation but less predictive power with serological status (r2 = 22%) aggregated at the village level but was not related to the illness status (r2 = 2%).

CONCLUSIONS/SIGNIFICANCE

The presented spatio-temporal model provides a fine-scale picture of the dynamics of AAT risk in sub-humid areas of West Africa. The estimated EIR was high in the proximity of rivers during the dry season and more widespread during the rainy season. The present analysis is a first step in a broader framework for an efficient risk management of climate-sensitive vector-borne diseases.