The closest relatives of Setaria species of importance in veterinary medicine are Stephanofilaria stilesi, adults of which live in the skin of cattle, and Dipetalonema, the various species of which are found in a variety of locations in several hosts, including the subcutaneous tissues of dogs. Neither the taxonomy of the genus Setaria, nor the identities of the species in Canada, has been clearly defined.
Adult Setaria species recovered from domestic animals and wildlife in Canada are up to approximately 10 cm in length and clearly visible to the naked eye. They are usually identified on the basis of their location in the host.
Microfilariae of Setaria species are approximately 200 µm to 250 µm in length.
Host range and geographic distribution
Life cycle - indirect
Adult Setaria species live in the peritoneal cavity. Microfilariae produced by the females enter the bloodstream. The life cycle continues when these microfilariae are ingested by a mosquito (several species) or a horn fly (Haematobia irritans) intermediate host during blood feeding. Infective third-stage larvae develop in the intermediate hosts and infect the mammalian host during a subsequent feeding.