Question
Bancroftian filariasis.
Answer
Bancroftian filariasis is lymphatic filariasis caused by Wuchereria bancrofti, the predominant cause of lymphatic filariasis worldwide, transmitted by Culex quinquefasciatus mosquitoes.
Life cycle: infective third-stage larvae are transmitted by mosquito bite, migrate to and mature within lymphatic vessels/lymph nodes (particularly lower limbs and, in men, the genital region) into adult worms, which mate and produce microfilariae that circulate in peripheral blood, typically with nocturnal periodicity (matching the night-biting habit of Culex), completing the cycle when a mosquito ingests circulating microfilariae.
Clinical features: asymptomatic microfilaraemia (common); acute adenolymphangitis (recurrent fever with painful, inflamed lymphatics); chronic manifestations — lymphoedema and elephantiasis (typically lower limbs), and in men, hydrocele; Tropical Pulmonary Eosinophilia — a hypersensitivity syndrome without demonstrable microfilaraemia.
Laboratory diagnosis: peripheral blood smear (thick smear, Giemsa) for microfilariae, timed to nocturnal periodicity; circulating filarial antigen (CFA) test — not periodicity-dependent; ultrasonography showing the “filarial dance sign.”
Treatment: diethylcarbamazine (DEC), often combined with albendazole; management of chronic lymphoedema and hydrocelectomy for established disease.