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Ovine toxoplasmosis is a major cause of abortion and placentitis. Lambs with congenital infection are born with encephalitis. Abortions occurred between May and August 2006 in an estate in Três Palmeiras, southern Brazil. This study aimed to assess the frequency of abortion associated with toxoplasmosis among ewes in southern Brazil using indirect hemagglutination and pathoanatomical and immunohistochemical analyses. Blood samples were collected from nine animals for indirect hemagglutination. One fetus underwent necropsy and histopathological and immunohistochemical analyses. Three samples, one of which belonged to the necropsied animals mother, were positive on the serological test. The necropsy revealed pale foci in the liver, lungs with a marbled appearance, heart with severe pallor and brain and cerebellar congestion. Fragments of all organs were collected, fixed in 10% buffered formalin, processed, and stained with hematoxylin-eosin. Microscopically, there were cysts and tachyzoites in the brain in areas of malacia with microgliosis and lymphoplasmacytic infiltration, suggesting toxoplasmic encephalitis. There was also interstitial pneumonia, centrolobular necrosis with structures compatible with tachyzoites, focal lymphocytic myocarditis and acute tubular nephrosis. The immunohistochemical test was positive for Toxoplasma gondii. The results allowed diagnosing the ovine toxoplasmosis.

To identify pathologic alterations, sixteen cows, in the last 3 months of gestation, all cross-breed, Holstein x Zebu, serum positive for Sarcocystis, were selected and divided into four groups of four animals each. The first group was considered as control and the other three groups were experimentally infected with 1x10(4) (2nd group), 5x10(4) (3rd group) and 1x10(5) (4th group) sporocysts obtained from dog's feces. The gross lesions in the cows were consisted of pale mucous membranes, paleness of the skeletal striated muscle and enlargement of lymph nodes, heart, liver, spleen and lungs. In the aborted fetus, the most prominent gross lesion were excess of fluid in peritoneal and thoracic cavities, and petecheas in the surface of intercostal muscles, thymus and spleen. On histological sections, no parasitic form was found in the tissues of the fetus, placenta or uterine tissue of the exposed cows. However, meronts, young and mature cysts of S. cruzi were observed in striated muscle. In the aborted fetus, hemorrhage, was the main histological lesion observed in brain, cerebellum and kidneys.