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Vector-borne diseases

Lymphatic filariasis

Infection with lymphatic filariasis, commonly known as elephantiasis, occurs when thread-like, filarial parasites are transmitted to humans through mosquitoes.

Lymphatic filariasis is transmitted by different types of mosquitoes, for example by the Culexmosquito, widespread across urban and semi-urban areas; Anopheles, mainly in rural areas; and Aedes, mainly in the Pacific Islands and parts of the Philippines. It is also transmitted by 3 types of parasite (Wuchereria bancrofti, responsible for 90% of cases, Brugia malayi and B. timori).

Microscopic parasitic worms lodge in the lymphatic system and disrupt the immune system. They live for 6–8 years and, during their lifetime, produce millions of microfilariae (tiny larvae) that circulate in the blood.

More than 120 million people are currently infected with lymphatic filariasis, about 40 million of them are disfigured and incapacitated by the disease. Lymphatic filariasis afflicts more than 25 million men with genital disease and more than 15 million people with lymphoedema.

The majority of infections have no symptoms but silently cause damage to the lymphatic system and the kidneys as well as alter the body’s immune system. Acute episodes of local inflammation involving skin, lymph nodes and lymphatic vessels often accompany chronic lymphoedema (tissue swelling).

Approximately 65% of those infected live in the WHO South-East Asia Region, 30% in the African Region, and the rest in other tropical areas.

Recommended treatment to clear the parasites from the bloodstream is a single dose of albendazole given together with either diethylcarbamazine or ivermectin. Interruption of transmission of infection can be achieved if at least 65% of the population at risk is treated over 5 years.