Occurrence, diversity and distribution of Trypanosoma infections in cattle around the Akagera National Park, Rwanda

BackgroundAfrican Trypanosomiases threaten the life of both humans and animals. Trypanosomes are transmitted by tsetse and other biting flies. In Rwanda, the AAT endemic area is mainly around the tsetse-infested Akagera National Park (NP). The study aimed to identify Trypanosoma species circulating in cattle, their genetic diversity and distribution around the Akagera NP. MethodologyA cross-sectional study was carried out in four districts, where 1,037 cattle blood samples were collected. The presence of trypanosomes was determined by microscopy, immunological rapid test VerY Diag and PCR coupled with High-Resolution Melt (HRM) analysis. Parametrical tests (ANOVA) were used to compare the mean Packed cell Volume (PCV) and trypanosomes occurrence. The Cohen Kappa test was used to compare the level of agreement between the diagnostic methods. FindingsThe overall prevalence of trypanosome infections was 5.6%, 7.1% and 18.7% by thin smear, Buffy coat technique and PCR/HRM respectively. Microscopy showed a low sensitivity while a low specificity was shown by the rapid test (VerY Diag). Trypanosoma (T.) congolense was found at a prevalence of 10.7%, T. vivax 5.2%, T. brucei brucei 2% and T. evansi 0.7% by PCR/HRM. This is the first report of T.evansi in cattle in Rwanda. The non-pathogenic T. theileri was also detected. Lower trypanosome infections were observed in Ankole x Friesian breeds than indigenous Ankole. No human-infective T. brucei rhodesiense was detected. There was no significant difference between the mean PCV of infected and non-infected animals (p>0.162). ConclusionsOur study sheds light on the species of animal infective trypanosomes around the Akagera NP, including both pathogenic and non-pathogenic trypanosomes. The PCV estimation is not always an indication of trypanosome infection and the mechanical transmission should not be overlooked. The study confirms that the area around the Akagera NP is affected by AAT, and should, therefore, be targeted by the control activities. AAT impact assessment on cattle production and information on the use of trypanocides are needed to help policymakers prioritise target areas and optimize intervention strategies. Ultimately, these studies will allow Rwanda to advance in the Progressive Control Pathway (PCP) to reduce or eliminate the burden of AAT. Author summaryAfrican Trypanosomiasis is a major neglected tropical disease associated with rural areas in low resource settings. The socio-economic and health impact of the disease on humans and livestock is often found at the edge of tsetse-infested protected wildlife areas. Trypanosomiasis is reported around Akagera region of Rwanda at the border with Tanzania, where it is not well documented. This work was the first large-scale study to map Trypanosoma occurrence in cattle around the tsetse-infested Akagera National Park. The study determined the genetic diversity and distribution of trypanosomes circulating in cattle blood by using microscopy, immunological rapid tests and molecular techniques. We found animal pathogenic trypanosomes (i.e. T. brucei brucei, T. congolense savannah, T. evansi and T. vivax) and the non-pathogenic T. theileri. We did not find human-infective T. b. rhodesiense causing sleeping sickness. This new knowledge contributes to a better understanding of the epidemiology of animal Trypanosomiasis and it will inform the setting of adequate and more focused control of the disease in the area. The findings are expected to promote the progressive reduction or the elimination of the Animal African Trypanosomiasis burden in the area and inform the process for validation of rhodesiense Human African Trypanosomiasis (rHAT) elimination.