Effect of Rainfall on the Prevalence of Fascioliasis in Puerto Rico

Abstract

Extraordinary numbers of Lymnaea cubensis snails were noted in the Dorado area of Puerto Rico in February 1971, coincident with heavy rainfall from October through December 1970. Fasciola hepatica occurred in snails at a modal rate of 4%, assuring vast numbers of infected snails and metacercariae. A snail density determination was made for subsequent comparison, and six of 19 herds of cattle examined previously (1970) were reexamined to determine changes in occurrence of fascioliasis. By May 1971, most of the snails were decimated and had not reoccurred by September 1972. Frequency of Fasciola hepatica and egg counts doubled after the snail bloom, but returned to normal by mid-1972. The need for long term epidemiological research on fascioliasis in Puerto Rico is indicated.