Mucosal disease associated with BVDV-1b and BVDV-1e in cattle in Southern Brazil.

Bovine viral diarrhea virus (BVDV) is an important pathogen of the global cattle industry. Fetal infection during the period of immunotolerance may result in the birth of persistently infected (PI) animals. In such animals, the emergence of or superinfection with cytopathic variants may trigger mucosal disease (MD). The objective of this study was to characterize the anatomopathological and virological aspects of two cases of MD. Animal 1, a 24-month-old presented with diarrhea, weight loss, lameness, sialorrhea, and oral and cutaneous lesions. Animal 2, a four-month-old, exhibited weight loss, intermittent diarrhea, and dehydration. Both animals were submitted to necropsy, and tissue samples from all organs were collected for histopathological evaluation. For BVDV detection, serum samples were subjected to RT-PCR and amplified products were submitted to Sanger sequencing and phylogenetic analysis. Liver and spleen fragments were used for viral isolation in MDBK cell cultures. Immunohistochemistry using the panpestiviral monoclonal antibody 15C5 was performed to detect BVDV antigen. Anatomopathological examination of Animal 1 revealed ulcerative glossitis, erosive stomatitis, erosive and ulcerative esophagitis as well as erosive and ulcerative rumenitis, erosive abomasitis, and ulcerative and crusting dermatitis affecting the nasal planum and the distal limb region. In Animal 2, ulcerative rumenitis, erosive abomasitis, and lymphoid depletion in the ileal Peyer's patches were observed. Both animals were positive for BVDV in immunohistochemistry and classified as BVDV-1e and BVDV-1b based on phylogenetic analysis. Viral isolates from both cases induced cytopathic effect between 48 and 96 h post-inoculation. This study demonstrates distinct lesion patterns in unrelated cases of MD associated with BVDV-1e and BVDV-1b in cattle, constitutes the first report of typical MD associated with these subgenotypes in Brazil.