Detecção de anticorpos contra Sarcocystis spp. e investigação da ocorrência de transmissão vertical por Sarcocystis neurona em equinos

Abstract

The equine protozoal mieloencefalite (EPM) is caused mainly by Sarcocystis neurona. It s definitive host is the opossum (Didelphis spp.), which becomes infected by ingesting sporocysts from tissues of intermediate hosts, that belong to different species. Clinical manifestations occur with neurologic signs, which vary according to the area of the nervous system affected. Clinical disease is not common, however cases of immunosuppression as senility, stress, use of corticosteroids may lead to development of clinical signs. From an epidemiological standpoint, it is interesting to determine the distribution of the protozoa in order to know the areas where animals were exposed to S. neurona through serological tests, in order to consider EPM in differential diagnosis of neurological diseases and guide the treatment. In the U.S. it is estimated that half of the horses are reagents for S. neurona, in Brazil there are not many reports about prevalence of seropositive horses. The transplacental infection has been described for other species of Sarcocystis, however there is no evidence of intrauterine infection by S. neurona, only some studies suggesting the vertical transmission as another way of agent maintenance, which could be confirmed by detecting antibodies in sera from neonates before colostrum ingestion. While S. neurona is the primary agent of equine mieloencefalite, S. cruzi is related to losses in cattle. Although parasites present similar life cycle, but with different definitive hosts, horses were exposed to both species of Sarcocystis, and these two species may infect horses and spread concurrently in herds. Therefore, this study aimed to detect the occurrence of transplacental transmission by S. neurona in horses and compare the prevalence of flocks against S. neurona and S. cruzi. Results were arranged in two chapters. In chapter one, we investigated the occurrence of transplacental infection of S. neurona in horses. For this, blood was collected from mares and their newborns for antibodies against S. neurona. In the second chapter, we compared, by indirect immunofluorescence, serum samples from 189 mares for the presence of antibodies against Sarcocystis spp. using as antigen S. neurona and S. cruzi. The analysis of the results revealed the majority of animals responding to antigens of S. cruzi and a third of seropositive animals reacted to antigens of both species.