Article: Filariasis

Lymphatic Filariasis is a parasitic and infectious tropical disease, caused by the thread-like parasitic filarial worms, Wuchereria bancrofti, Brugia malayi, and Brugia timori, all transmitted by mosquitoes. It is extremely rare in Western countries. Loa loa is another filarial parasite of humans, transmitted by the deer fly.

In 1866, Otto Wucherer demonstrated the presence of microfilariae, or filarial larvae, in urine. In 1871, Timoth Lewis discovered the presence of microfilariae in peripheral blood; later, in 1876, Joseph Bancroft discovered the adult form. Finally in 1878, Patrick Manson observed the development of W. bancrofti in mosquitoes.

Filariasis is endemic in tropical regions of Asia, Africa, Central and South America.

The most spectacular symptom of lymphatic filariasis is elephantiasis (thickening of the skin and underlying tissues), which was the first disease discovered to be transmitted by insects. Elephantiasis is caused when the parasites lodge in the lymphatic system.

Elephantiasis affects above all the lower extremities, whereas ears, mucus membranes, and amputation stumps are rarely affected; however, it depends on the species of filaria. W. bancrofti can affect the legs, arms, vulva, breasts, while Brugia timori rarely affects the genitals. Infection by Onchocerca volvulus and the migration of its microfilariae through the cornea is a major cause of blindness (Onchocerciasis).