Estudo da distribuição de Neospora caninum em caprinos machos naturalmente infectados

Abstract

Neosporosis is a parasitic disease caused by Neospora caninum, responsible for abortions and reproductive failure in goats. The aim of this study was to evaluate the distribution of N. caninum by histopathology, immunohistochemistry (IHC) and PCR in different tissues of male fetuses, young and adult goats congenitally infected and without clinical signs of neosporosis. The 12 goats were congenitally infected by endogenous transplacental transmission. Microscopic lesions compatible with neosporosis were observed in skeletal muscle, heart and central nervous system (CNS).The most frequent finding in skeletal muscle and myocardial was the lymphoplasmacytic inflammation and sometimes it was associated with calcification and macrophages, besides giant cells in the myocardial. Cysts were seen by IHC, in skeletal muscle of two fetuses and in the heart of a four -monthold male, tachyzoites were observed in the tongue of one fetus. The lesions in the CNS are consistent with neosporosis and were more severe in one fetus and one adult, the IHC was positive for N. caninum in three fetuses and two adults. Of the 171 PCR positive samples for N. caninum, 73.1% were from groups of skeletal muscles, heart and nervous system. The highest percentage of PCR detection was observed in fetuses and in two young and adults goats. N. caninum had 5.6 times more chances to be present in fetal tissues than in young and adults. In fetuses, N. caninum had predilection for skeletal muscle than the heart; in skeletal muscle there was predilection for thoracoabdominal muscles; it was more likely to detect DNA of N. caninum in skeletal muscle than in the nervous and reproductive systems and other organs (lung, liver, kidney, spleen, mesenteric lymph node, thymus, adrenal and skin). Young and adult goats had all heart samples positive in PCR. Statistically, there was a higher chance of N. caninum occur in the heart when compared to all other analyzed tissues. Greater were the chances of N. caninum also occur in skeletal muscles in relation to the reproductive system and other organs. In all goats, telencephalon was the nervous system portion with more positive results by PCR (58.3%). The findings achieved with this study showed that the N. caninum DNA was more likely to be found in fetal tissues than in young and adult goats. The best tissues for diagnosis of neosporosis were the skeletal muscles, heart and CNS. The reproductive system was the tissue group with the lowest rate of positive PCR samples, indicating that venereal transmission may not be important in goats.