RESUMO
This study reports the clinicopathological, immunohistochemical, and molecular findings from two cases of systemic toxoplasmosis in pigs showing apathy and dyspnea. In the post-mortem examination, severe diffuse necrotizing bronchointerstitial pneumonia with numerous intralesional tachyzoites of Toxoplasma gondii was observed. The lungs had not collapsed but were diffusely reddened, and the parenchyma showed friable whitish subpleural nodules with multifocal to coalescent distribution and diameters of 0.5-1.0 cm. The histopathological findings comprised mononuclear inflammation and multifocal areas of necrosis in alveolar septa (cases 1 and 2). In addition, esophagitis and ulcerations in the mucosa of the stomach and the small and large intestines were observed (case 1). Immunohistochemical analysis using anti-T. gondii antibodies on lung tissue in both cases revealed strong immunolabeling of free tachyzoites and tachyzoites in the cytoplasm of histiocytes and in cysts. Nested PCR targeting a 155-bp fragment of the B1 gene of T. gondii was positive for the DNA extracted from lung fragments from the two pigs. Genotyping of the samples by means of PCR-RFLP (10 markers) and by means of microsatellites (15 of them) revealed that these animals were infected with T. gondii that was molecularly characterized as the non-archetypal genotype Chinese 1. This presents worldwide circulation, but it had not previously been described in Brazil. The microsatellite analysis showed that the animals were infected with the same T. gondii isolate circulating in the environment.