- Loa loa
- The eye worm, a parasite that lives in humans and other primates. People contract the parasite when bitten by infected deer flies. The larvae of the worm enter the bloodstream and later develop into adult worms. Symptoms may not appear for months or years after the bite of the fly. The worms migrate through the skin causing local inflammatory reactions called Calabar swellings. The worms can often be seen migrating across the conjunctiva and cornea of the eye. Hence, the name "eye worm." The worm sometimes enters the brain causing encephalitis. The microfilarial (tiny thread-like) form of the worm is found in blood and lymphatic fluid during the day and in the lungs at night. The insect vector (that carries the parasite) is the deer fly Chrysops which lives in swampy areas of the forest, principally in the Congo River region, Sudan, and Ethiopia. Diagnosis is by detection of the microfilariae in the blood. Protective measures against the flies include the use of a repellent, long-sleeved shirts and long pants, and the use of bednets when sleeping. Treatment is with diethylcarbamazine (DEC) or ivermectin (Stromectol). DEC can also be used for prophylaxis. The disease caused by loa loa is called loiasis or lymphatic filariasis. .
* * *The African eye worm, a species of the family Onchocercidae (superfamily Filarioidea) that is indigenous to the western part of equatorial Africa, especially in the region of the Congo River, and is the causal agent of loiasis. Adult worms are white or gray-white, cylindroid, and threadlike, the males averaging 25–35 by 0.3–0.4 mm (with a curved tail) and the females ranging from 50–60 by 0.4–0.6 mm; microfilariae are ensheathed, with nuclei extending to the tip of the tail. The life cycle is somewhat similar to that of Wuchereria species; humans are the only known definitive host, and parasites are transmitted by Chrysops flies (family Tabanidae); infective larvae from the latter require 3 years or more to mature in humans, and the adult forms may persist in a human host for as long as 17 years. SEE ALSO: loiasis.
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* * *a threadlike species 2.5 to 5 cm long found in West and Central Africa, the cause of loiasis. The immature forms or microfilariae are diurnal, being found in the peripheral circulation in greatest concentrations during the day. Flies of the genus Chrysops are the intermediate hosts and vectors.
Loa loa. (A), Adult worm in eye; (B), tail of adult male, with spicules typical of the species.
Medical dictionary. 2011.