Concomitant transmission of human and animal trypanosomoses: Mandoul focus in Chad

Trypanosomosis is a vector-borne disease which affects both humans and animals. It is cyclically transmitted by tsetse flies and is caused by Trypanosoma sp. Although the disease is mainly endemic where its vectors are present, endemic areas where transmission of both forms of the disease coexist have seldom been studied. During our study, epidemiological and entomological surveys were carried out, followed by the analysis of collected samples by the polymerase chain reaction (PCR). Out of 13,410 persons examined, 132 sleeping sickness cases were diagnosed. After examination of 144 cattle samples by PCR, 33 were found infected by either Trypanosoma brucei (39%) or T. vivax (55%), or exhibited a co-infection (two animals). Three insect families were trapped at variable densities (Glossinidae, Stomoxyinae, and Tabanidae). Glossina fuscipes fuscipes was only caught in the southern part of the focus, and the highest apparent density per trap per day (ADT) of 0.56 was found in the gallery forest bordering the villages where the highest number of human African trypanosomosis was diagnosed. Tabanids were caught in all investigated areas but the highest ADT, i.e. 15.55, was observed in the northern part of the focus. No Stomoxys sp. was found in the prospected area located farthest from the river. The identification of trypanosomes in people and in cattle, and the presence of the cyclical vector as well as mechanical vectors, confirmed endemic human and animal trypanosomoses in the focus. Combatting vectors with a strategy common to both forms of the disease is crucial to control them sustainably