SARCOCYSTIS SINGAPORENSIS - STUDIES ON HOST-SPECIFICITY, PATHOGENICITY, AND POTENTIAL USE AS A BIOCONTROL AGENT OF WILD RATS

Host specificity and pathogenicity of Sarcocystis singaporensis were i nvestigated as a prerequisite to a subsequent application of the paras ite as a biocontrol agent of wild rats in Egypt. After inoculation of 7 snake species comprising the families Elapidae, Viperidae, Colubrida e, and Boidae with sarcocysts, sporocyst development was only observed in a reticulated python. Among amphibians, reptiles, and rodents that orally received various sporocyst doses in the laboratory, 2 x 10(4) sporocysts or more were lethal to roof rats Rattus rattus frugivorous, brown rats Rattus norvegicus, and bandicoot rats Nesokia indica. Sarc ocysts developed in Rattus spp. and Nile grass rats Arvicanthis niloti cus. Subsequently, the pathogenicity of S. singaporensis was tested un der natural control situations offering bait pellets containing high a mounts of sporocysts to a free-living population of roof rats, which w as monitored by indirect census baiting commonly used in rodenticide e valuation. Ten days after consumption of the bait pellets, the infecte d population collapsed, leading to a control success of 73%. A negativ e control population, which received a placebo, remained stable. These data demonstrate for the first time that S. singaporensis can be used as a biocontrol agent of wild rats. However, an immunization experime nt with roof rats in the laboratory showed that these are capable of m ounting a rapid specific immune response resulting in survival of acut e sarcocystosis.