Immunohistochemical identification of a malignant catarrhal fever virus in cattle with renal diseases from Paraná state, Southern Brazil: a retrospective epidemiological study.

Malignant catarrhal fever (MCF) is a viral infectious disease caused by specific members of the Macavirus genus that are referred to as the MCF virus (MCFV) complex group. This study determined the prevalence of MCFV-associated infections in cattle within the mesoregions of the state of Paraná, Southern Brazil, by analyzing the histopathologic patterns of renal lesions in association with positive immunoreactivity to intralesional antigens of MCFV. Intracytoplasmic MCFV antigens were identified in 41.7% (48/115) of the kidneys of cattle evaluated. Lymphocytic interstitial nephritis, vascular degeneration, and ballooning degeneration of the renal tubules were the principal histopathological findings associated with positive immunoreactivity to MCFV. The results indicate that MCFV infections are endemic within the state of Paraná and suggest that the kidney can be of diagnostic value in suspected cases of MCF-associated infections in cattle. Furthermore, the utilization of an in situ diagnostic technique resulted in the detection of a greater number of cases of infections by MCFV than previously identified using other diagnostic methods. Additionally, degenerative vascular lesions of the kidney should be considered during the establishment of a histological diagnosis of MCFV-induced infections in cattle in the absence of fibrinoid change or necrotizing vasculitis.