Mass administration of DEC-medicated salt for filariasis control in the endemic population of Karaikal, south India: implementation and impact assessment.

DEC (diethylcarbamazine)-medicated salt, at a concentration of 0.1 to 0.2 mg per 100 mg, was given to the entire population of Karaikal (119 978) in South India for a 4-year period from 1982. The per capita consumption of DEC in medicated salt was 13.3 grams for the entire period. The prevalence of microfilaraemia declined significantly from 4.5% in 1982 to 0.14% in 1985 and 0.4% in 1993. Vector infection declined from 0.6% in 1982 to zero after two years. The mechanism of preparation and regulated distribution of DEC-medicated salt in the locality is presented. Long-term follow-up suggests that DEC-medicated salt distribution is cheap, safe and efficient for the elimination of filariasis.