Smaller horse fly species like this one are widely called Deer Flies. However, deer species are not found in East Africa. There are of course plenty of antelope. Only the small dik-dik are likely to be found a forest area. These are blood feeders as adults (mostly the females) so could well use people or grazing animals as hosts. Although not normally disease vectors, in some parts of the world tabanids may transmit tularemia.