filariase

Filariasis, also known as filariase, is a group of parasitic diseases caused by filarial nematodes transmitted by blood-sucking arthropods. The most well-known forms are lymphatic filariasis and onchocerciasis, but the term also covers loiasis and other filarial infections such as mansonellosis. Endemic in tropical and subtropical regions, the disease burden is highest in parts of sub-Saharan Africa, Asia, and the Pacific.

Etiology and transmission: Lymphatic filariasis is caused mainly by Wuchereria bancrofti, Brugia malayi, and Brugia timori. Onchocerciasis is caused by Onchocerca volvulus; loiasis by Loa loa. Vectors include mosquitoes for lymphatic filariasis and blackflies for onchocerciasis; loiasis is transmitted by deer flies. After a vector bite, larvae mature and migrate to their preferred tissues. Microfilariae circulate in the blood or reside in the skin and are taken up by vectors to continue the cycle.

Clinical features: Lymphatic disease can cause chronic limb swelling, lymphedema, and hydrocele. Onchocerciasis leads to severe itching, skin changes, and potential vision loss. Loa loa can cause transient swelling and migratory ocular worms. Many infections are asymptomatic; some patients have inflammatory episodes during microfilaremia.

Diagnosis and treatment: Diagnosis relies on microfilariae detection in blood or skin, serology, or molecular tests. Treatments vary by species and region and often include albendazole with ivermectin or diethylcarbamazine; doxycycline can target Wolbachia endosymbionts in some species. Morbidity management emphasizes limb and skin care; hydrocele surgery where indicated. Prevention centers on vector control, bed nets, and periodic mass drug administration to reduce transmission.