Background: Toxoplasmosis is a worldwide disease that affects virtually all species of warm-blooded animals. The felids, domestic and wild, are considered the definitive hosts of the protozoan. In Brazil, Toxoplasma gondii infection has been diagnosed in horses, goats, primates, dogs and cats. In the backlands of Paraiba, the disease has been sporadically reported affecting dogs with canine distemper and swine, but cases of systemic toxoplasmosis in cats have not yet been described. The aim of the present study was to describe the main epidemiological, clinical and anatomopathological aspects of two cases of systemic toxoplasmosis in kittens. Cases: Two kittens were affected with three (cat 1) and six (cat 2) months old, females, and crossbreed. The kittens had not been vaccinated or dewormed, and were raised with other cats in a peridomiciliary regime in a rural area in the backlands of Paraiba. Cat 1 was thin, apathetic, dehydrated, tachypneic and with pale mucous membranes. Cat 2, showed inappetence, apathy, jaundice, fever, dehydration, dyspnea and abdominal breathing pattern. At necropsy, non-collapsed, shiny, reddish lungs with multifocal whitish areas, punctuated or nodular, measuring from 0.1 to 0.3 cm in diameter, were found on the pleural surface and parenchyma. The livers were pale, with lobular pattern accentuation, and reddish depressed multifocal areas randomly distributed on the capsular surface. Histologically, multifocal to coalescent areas of necrosis, moderate (cat 1) or marked (cat 2), associated with intralesional bradyzoites and tachyzoites and variable lymphoplasmacytic infiltrate were observed. In cat 2, numerous bradyzoites were visualized in the gray matter of the left cerebral hemisphere (temporal and parietal lobes), sometimes associated with a moderate lymphoplasmacytic inflammatory infiltrate. In the perivascular spaces of the cerebral cortex, discrete inflammatory lymphoplasmacytic infiltrate (perivascular cuffs) were observed. Immunohistochemistry for T. gondii revealed strong immunolabelling of the parasitic organisms. Discussion: The diagnosis of systemic toxoplasmosis was established based on anatomopathological findings and histomorphological characteristics of the agent, being confirmed by immunohistochemistry. The systemic disease occurs most often in young animals, especially immunocompromised or immunologically immature neonates. In these kittens, it was not possible to determine the presence of an intercurrent immunosuppressive condition; however, both animals were kept in the peridomiciliary regime and were in contact with other cats, which may have acted as a source of infection. Besides, both kittens were raised in rural environments, condition that associated with the usual predatory behavior of this species may have favored the ingestion of infected intermediate hosts. The clinical signs of the disease vary considerably depending on the location and severity of the lesions. Infection in cats usually is asymptomatic or promotes self-limiting diarrhea as a result of protozoal enteroepithelial replication; but in some cases the protozoan can spread to other tissues, determining the occurrence of necrotic processes, dysfunction and clinical manifestations. Systemic toxoplasmosis occurs sporadically in kittens in the backlands of Paraiba, with pulmonary and hepatic clinical manifestations. The histopathological findings are characterized by tissue necrosis and lymphoplasmacytic inflammation associated with intralesional protozoa. The diagnosis can be established based on the histomorphologic characteristics of the agent and confirmed by immunohistochemistry.
