Biological control of rodents using Sarcocystis singaporensis

Parasites have been identified as an important factor in regulating vertebr ate populations. In replicated field experiments (plots up to 4 ha) perform ed in Thailand we tested whether commensal and field rodents could be artif ically infected and controlled with the host-restricted apicomplexan protoz oon Sarcocystis singaporensis which is endemic in Southeast Asia. When bait -pellets containing high numbers of these parasites were consumed by rodent s of three species (Rattus norvegicus, Rattus tiomanicus, Bandicota indica) in different agricultural habitats (chicken farm, oil palm plantation, ric efield), we observed a parasite-induced mortality ranging from 58% to 92%. Detection of merozoites of S. singaporensis in lung tissue samples of rats collected dead at the experimental sites using a species-specific monoclona l antibody confirmed that S. singaporensis was the causative agent of morta lity. As observed with brown rats, the parasite's effect on the host was no t related to sex. These experiments demonstrate for the first time that art ificial infection of rodents with an endemic protozoon has the potential fo r effective population control. (C) 1999 Australian Society for Parasitolog y Inc. Published by Elsevier Science Ltd. All rights reserved.