STUDIES ON PATHOGENESIS, TISSUE INFECTION AND CONGENITAL TRANSMISSIONIN COWS EXPERIMENTALLY INFECTED WITH SARCOCYSTIS-CRUZI BY VARIOUS ROUTES

A group of nine cows, naturally infected with Sarcocystis, were challe nged with Sarcocystis cruzi: three intrarumenally with sporocysts, two intrarumenally with water (controls), two intravenously with merozoit es grown in vitro and two intravenously with saline solution (controls ). The animals intrarumenally challenged with sporocysts developed acu te sarcocystiosis and produced stillborn calves, whereas those intrave nously challenged with merozoites suffered from subclinical sarcocysti osis with premature births. No parasites were found in calves from cow s challenged with sporocysts; however, a meront of Sarcocystis was fou nd within a macrophage in the cerebrospinal fluid of a calf from a cow intravenously inoculated with merozoites of S. cruzi. This is the fir st time that merozoites of S. cruzi grown in vitro have been demonstra ted to retain the ability to infect their natural intermediate host an d complete their life cycle.