Decline of brugian filariasis in Cherthala taluk, Alappuzha district, Kerala.

A total of 4492 persons from 5 panchayats and 1 town were investigated from the Brugia malayi most endemic taluk of Cherthala, Alappuzha district of Kerala state. The urban area in Cherthala taluk only revealed mf carriers; mf rate was 0.13%. Rural areas in Cherthala taluk were free from infection. Microfilaria rate had declined by 99.5% and disease rate by 90.7% in Cherthala compared to 1934 prevalence. Shedding of sheath by B. malayi microfilariae was recorded for the first time in India. The youngest person with microfilaria and disease manifestation was 4 1/2 and 9 years respectively. All the 3 major vectors, Mansonia annulifera, Ma.uniformis and Culex quinquefasciatus were prevalent throughout. Complete disappearance of brugian filariasis from this taluk is a distinct possibility. The reasons for the drastic decline are discussed.