Estudo da distribuição do Neospora Caninum em tecidos de cabras naturalmente infectadas

Abstract

Neospora caninum is an intracellular protozoan considered one of the main agents responsible for abortion and stillborn fetuses in goats and other animal species. Systematic studies about the distribution of N. caninum in tissues of natural infected animals, during its latent period, are not found. This study investigated the distribution of the lesions and the presence of N. caninum in various tissues, with emphasis on skeletal muscles and central nervous system, of healthy and naturally infected goats that transmitted the parasite to their offspring. For this purpose 368 tissues samples from eight goats (46 tissues from each animal), were collected and submitted to histopathological, immunohistochemical (IHC) and molecular analysis. Microscopic lesions of discrete to moderate non-suppurative myositis were found in four goats; in the central nervous system perivascular cuffing were seen in five goats, and mild to moderate gliosis in three. In one goat tachyzoites were seen in the cerebral cortex, that was, also, positive in the polymerase chain reaction (PCR) test for N. caninum. By the IHQ test, parasitic structures were not visualized in the tissues. By PCR test, 37% of the collected samples were positive for N. caninum. Among skeletal muscles, 42.8 % of the samples were positive and there was no preference of the parasite for a muscle group. However, the muscles cleido-occipital, triceps and semimembranosus had a higher proportion of positive samples (62.5 %). In the central nervous system 44.4 % of samples were positive, with the cervical segment of the spinal cord been the most affected region (62.5 %). The groups, heart, digestive system, reproductive system and other tissues, were respectively 25 %, 25,6 %, 28,6 % and 29,7 % positive for N. caninum by PCR. All skin samples were negative in the PCR. The statistical chi- square test showed that N. caninum has 1.6 more chance to be located in skeletal muscle than in other tissues. The findings in this study reinforce that the central nervous system and skeletal muscles, specially the muscles cleido-occipital, triceps and semimembranosus, are the main locations of the protozoan in adult animals and these tissues should be collected for the diagnosis of neosporosis.