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a family of parasitic nematodes. Filariids are long and filamentous or hairlike. Some, for example, the female of the tropical African species Onchocerca (Filaria) volvulus, may measure as much as 45 cm in length and as little as 0.33 mm in width. Adults live in the body cavity, subcutaneous tissue, lymph and blood vessels, and heart of vertebrates, including man. The presence of the larvae (microfilaria) in the host’s blood is a striking evidence of infestation.
Blood-sucking insects and, occasionally, ticks and mites are the intermediate hosts. They become infested with the larvae by sucking the blood of the primary host and, in turn, may infest other vertebrates, including man. There are more than 80 genera of Filariidae, comprising 380 species. Ten species parasitize man, causing filariases (seeBANCROFT’S FILARIA).