filariasis

Filariasis is a group of diseases caused by parasitic nematodes in the superfamily Filarioidea. The main forms are lymphatic filariasis, onchocerciasis (river blindness), and loiasis. Causative species include Wuchereria bancrofti and Brugia spp. for lymphatic filariasis; Onchocerca volvulus for onchocerciasis; and Loa loa for loiasis. Transmission occurs via biting insects: mosquitoes for lymphatic filariasis, blackflies for onchocerciasis, and deer flies for loiasis.

In the life cycle, adult worms inhabit the lymphatic system (lymphatic filariasis) or subcutaneous tissues (onchocerciasis, loiasis). They produce microfilariae that circulate in blood or skin. When a vector ingests microfilariae, they develop into infective larvae and are transmitted to another person.

Clinical features vary by form. Lymphatic filariasis can cause chronic swelling of limbs and genitals (elephantiasis). Onchocerciasis may cause intense itching, skin changes, and can lead to blindness. Loiasis can produce Calabar swellings and migratory subcutaneous nodules; ocular involvement may occur.

Diagnosis relies on detecting microfilariae, parasite antigens, or DNA in appropriate specimens, aided by species-specific timing and serology. Imaging can assist in assessing lymphatic or ocular involvement.

Treatment depends on the species and disease stage. Anthelmintic regimens commonly use diethylcarbamazine, ivermectin, and albendazole in combination; doxycycline can target Wolbachia endosymbionts and reduce transmission. Loiasis requires careful drug choice due to potential adverse reactions. Supportive care for lymphedema and skin disease is important.

Prevention includes vector control and mass drug administration programs in endemic areas, along with personal protective measures.