Bancroftian filariasis in the Igwun basin, Nigeria: an epidemiological, parasitological, and clinical study in relation to the transmission dynamics.

Abstract

A 12-months study on bancroftian filariasis was carried out in the Igwun basin, Nigeria. A total of 1,418 individuals (768 males, and 650 females) were examined for microfilaremia and clinical filarial stigmata. There were 14.3% and 11.1% male and female point prevalence rates, respectively, and an overall prevalence of 12.8%. Prevalence rates and microfilarial density increased with age. The highest mff density of 35 mff/20 ml blood occurred in the 40-49 year old male individuals. Disease rates of 55.5 and 65.3% were recorded for males and females respectively. Chyluria (9.3% males, 16.7% females), hydrocele (17.8%), elephantiasis (15.9% males, 29.2% females), and enlarged groin glands (16.4% males, 19.4% females) were the major clinical signs, all associated with microfilaremia. Anopheles gambiae and Cules pipiens were the principal vectors. The estimated mean daily, weekly, and monthly per capita biting densities were 26, 161, and 753 respectively. The overall infection rate of mosquitoes was 22.3%, with a mean mff density of approximately 5 mff/mosquito. These vector parameters were indicative of active transmission in the area, and may be responsible for the high prevalence of infection, the diversity of clinical signs, and high morbidity rates.