Ecology of mechanical vectors in tsetse-free areas

Stable flies and tabanids are cosmopolitan hematophagous flies that, in tsetse-free area, act as mechanical vectors of blood pathogens. Information on these vectors is scarce, albeit essential to prepare and implement vector control programs at the national level. COMBAT will assess the species, apparent density, seasonality and infective status of hematophagous flies in tsetse-free areas, that is, in the project context, the semi-arid areas at the fringes of the Sahara Desert.

Vector competence of stable flies

Stable flies (Stomoxys) can act as mechanical vectors of animal trypanosomosis. Although infectivity is short-lived in these vectors, multiple bites due to interrupted feeding allow intra-herd transmission. During the blood-meal, the blood can be directed towards the gut or towards the crop. In the second case, trypanosomes can survive up to three days in the crop, allowing an inter-herd transmission.  This phenomenon has been described in experimental conditions, but investigations are needed to determine vector competence. COMBAT will assess the conditions for delayed mechanical transmission, i.e. factors directing blood towards the crop, blood volume, trypanosomes survival time in the crop, and regurgitation process, using laboratory reared Stomoxys and rodents experimentally infected by T. evansi as a model.