The filaria is any of various slender roundworms that inhabit tropical regions of the world. Filariae are parasites of backboned animals, including man. Several kinds of filariae cause serious diseases, such as filariasis and elephantiasis.
The life cycle of a filaria requires two different hosts: animal and insect. Filariae grow into adults in the body of a backboned animal, where the female lays many small eggs. The eggs hatch into tiny larvae in the animal's bloodstream. When a bloodsucking insect, such as a mosquito, bites the infected animal, it sucks up many larvae along with the blood. Inside the insect the larvae may grow and eventually move into the salivary glands near the insect's mouth. If the infected insect bites another backboned animal, the larvae in its saliva are transferred to the new victim. As the larvae move through the animal's blood, they mature into adults, sometimos reaching a length of 16 inches.
The kind of disease produced by filariae depends on the tissue or organ in which they settle to mature. For example, a filaria living in blood vessels of the eye may cause blindness. Filariae in the lymph vessels of the leg may block the flow of lymph and cause swelling.
Filariae are classified in the phylum Nematoda.
