Tabanids as vectors of disease agents

The Tabanidae are the least studied of the major dipteran pests of man and animals but active research projects on them are few, numbering no more than 50 in taxonomy and distribution, 15 in economic entomology and 5 in disease transmission. In this article, factors governing the vectorial roles of Tabanidae are discussed briefly, emphasising the reasons which make them important mechanical vectors. Recent research on tabanid transmission of viral, bacterial, protozoal and filarial pathogens, chiefly of veterinary importance, is then reviewed. These include equine infectious anaemia virus, bovine leukaemia virus [bovine/type C oncovirus], vesicular stomatitis virus, hog cholera virus [swine fever virus], Bacillus anthracis, Francisella tularensis, Anaplasma marginale, Borrelia burgdorferi, Besnoitia besnoiti, Haemoproteus metchnikovi (of turtles), Megatrypanum (of deer), Trypanosoma theileri, T. evansi and T. vivax (the latter in cattle in Colombia, transmitted by Cryptotylus unicolor), and filariae, all cyclo-developmentally transmitted: Loa loa of man and Loa of other primates (transmitted by Chrysops spp.), Dirofilaria roemeri of kangaroos (by Dasybasis spp.) and the arterial worm Elaeophora schneideri of North American ruminants (for which there is circumstantial evidence of transmission by Tabanus and Hybomitra spp.). A further 5 viral, 10 bacterial, 5 protozoal and 1 filarial pathogens of man or animals and their associated tabanid vectors are listed.