ZOONOTIC FILARIASIS

Filariae of animals, especially those of mammals, often infect humans and typically produce cryptic infections. These ''zoonotic'' infection s have been reported from virtually all parts of the world including t emperate zones. Infections may be symptomatic or not, and the parasite s are found in surgical tissue biopsy specimens or, more rarely, are r emoved intact from superficial sites such as the orbit or conjuctivae. Typically, these worms tend to occupy tissue sites similar to those o ccupied in the natural animal host, with the exception of the eyes. Ma ny kinds of filariae have been isolated from humans, including species of Dirofilaria, Brugia, Onchocerca, Dipetalonema, Loaina and Meningon ema. Worms have been found in subcutaneous tissues, the heart and lung s, lymphatics, the eye, and the central nervous system. Specific ident ification of these filariae is based on their morphological features i n histologic sections. Unfortunately, some of these worms cannot be id entified even at the generic level. There are other species of filaria e, presumed to be zoonotic, which produce patent infections in humans but are poorly and incompletely known. These include Microfilaria semi clarum and Microfilaria bolivarensis. It is probable that almost any f ilaria parasitizing animals can, under proper circumstance, infect hum ans and undergo some degree of development. Undoubtedly, additional sp ecies of filariae will continue to be isolated from humans in the futu re.