Filariasis is a parasitical and infectious tropical disease, caused by the thread-like parasitic filarial worms, Wuchereria bancrofti, Brugia malayi, and B. timori , all transmitted by mosquitoes. It is extremely rare in Western countries.

The most spectacular symptom of filariasis is elephantiasis (swelling in the genitals or limbs), which was the first disease discovered to be transmitted by insects. Elephantiasis is caused when the parasites lodge in the lymphatic system.

In 1866, Otto Wecherer demonstrated the presence of filaria, or filaria larva, in urine. In 1871, Timoth Lewis discovered the presence of microfilaria in peripheral blood; later, in 1876, Joseph Bancroft discovered the adult form. Finally in 1878, Patrick Manson observed the development of Wuchereria bancrofti in mosquitos.

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

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. Wuchereria 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).

Video of filariasis: [1]