Clinical, pathological, and immunohistochemistry characterization of toxoplasmosis in dogs with distemper in the semiarid region of Paraíba, Brazil

The objective of this study was to describe the clinical, pathological, and immunohistochemistry characteristics of five cases of toxoplasmosis, an infection often associated with distemper in dogs. From January 2000 to December 2012, a retrospective study was performed analyzed dogs with distemper in the semiarid region of Paraíba. We evaluated this sample to focus on individuals who presented with concomitant structures in protozoa characteristics, and performed immunohistochemistry (IHC) tests using polyclonal anti-Toxoplasma gondii antibody. In all cases, the clinical signs were similar including digestive changes, as well as respiratory, neurological, and ocular lesions, suggesting an infection of canine distemper virus. The diagnosis of distemper was confirmed on histopathological analysis depending on the presence of intranuclear and intracytoplasmic eosinophilic inclusion bodies in different tissues. Histopathological examination also revealed the characteristic presence of parasitic cysts T. gondii in the brain in four cases, and in the lung in one case. The brain cysts were associated with multifocal areas of malacia and lung there was alveolar septa thickening due to infiltration of macrophages, lymphocytes, and plasma cells, with moderate proliferation of type II pneumocytes and coalescing multifocal areas of necrosis. These cysts are characterized by round and strongly basophilic structures, measuring approximately 5 to 70 ?m, delimited by thin wall, stained by hematoxylin and eosin, and immunomarked as brown by immunohistochemistry (IHC) using the chromogen DAB. The diagnosis of toxoplasmosis associated with infection by canine distemper virus in the five case studied was based on microscopic findings and confirmed by immunohistochemistry. Toxoplasmosis should be included in the differential diagnosis of dogs with severe progressive systemic signs, especially when respiratory and neurological involvement is suspected.