Travel Health Service Filariasis
Travel related diseases


What is Filariasis?

Filariasis is a parasitic disease caused by roundworms. The roundworm normally lives in the lymphatic in infected people. The female worms produce microfilariae which evade the blood stream and cause symptoms. The disease includes Lymphatic Filariasis and Onchocerciasis (river blindness).

Lymphatic Filariasis occurs throughout sub-Saharan Africa and in much of South-East Asia, in the Pacific islands and in smaller foci in South America. The incubation period averages 10-12 months. Symptoms include fever, lymphadenitis, and swelling of limbs and scrotum.

River Blindness occurs mainly in western and central Africa, and also in Central and South America. The incubation period averages 1 year. Symptoms include dermatitis and nodules under the skin. The microfilariae often reach the eye and cause blindness, and because the vector blackfly breeds in rivers and valleys, thus the name of the illness.

How does it spread?

Lymphatic Filariasis is transmitted by the bite of infected female mosquito. River blindness is transmitted by the bite of infected female blackfly.

How can you prevent it?

Prevention of Lymphatic Filariasis and river blindness is by avoiding exposure to the bites of mosquitoes and blackflies in the endemic areas respectively. The following measures should be employed when travelling in the endemic areas:

While indoor

  • Stay in air-conditioned rooms or those protected by screen

  • Use bed net during sleeping

While outdoor

  • Wear long-sleeved clothing to cover arms and legs

  • Use insect repellents containing DEET on exposed skin and clothings. For further information about insect repellents, please refer to Frequently Asked Questions.

How is it treated?

Treatment of lymphatic filariasis includes anti-parasitic drug, diethylcarbamazine (DEC) while treatment of river blindness includes anti-parasitic drug, ivermectin. Reconstructive surgery may be needed to remove unsightly tissue in some patients.