Estudo histopatológico, imuno-histoquímico e molecular de casos fatais de diarreia bovina na Microrregião de Lavras, Minas Gerais

Abstract

Diarrhea is a syndrome of complex etiology that affects several animal species. The infectious agents that are often associated are bovine coronavirus (BCoV), rotavirus, Bovine Viral Diarrhea virus (BVDV), Salmonella spp., Escherichia coli, Cryptosporidium spp., among others. In the first part of this study, an outbreak of winter dysentery in adult cows during the summer was presented. Clinical and pathological features of affected cattle were disclosed and a nested RT-PCR and immunohistochemistry was performed to confirm the involvement of bovine coronavirus in the outbreak. Out of 30 bovine, 15 cows presented diarrhea and, among these, one died. At necropsy, the main change was observed in the spiral loop of the ascending colon, characterized by mucosal erosions and haemorrhage in the mucosa and a large amount of blood in the lumen and, in histopathology, necrosis of intestinal cypts in this area. The findings were consistent with BCoV infection, as confirmed by the presence of viral antigens in lesions and genetic material in faecal sample. The nested RT-PCR was also positive in four faecal samples from co-inhabitants diarrheic cows. All samples tested in paired serology for BVDV and in immunohistochemistry for Salmonella spp. of the necropsied cow were negative. It is highlighted in this coronavirus outbreak in adult cattle the occurrence in the warmer season and the simultaneous involvement of the virus in the respiratory and gastrointestinal tracts. In the second part of this work, was performed a morphological, immunohistochemical and molecular investigation of spontaneous fatal cases of bovine diarrhea, from 2007 to 2012, in the Southern region of Minas Gerais. In this research were evaluated 32 animals of different ages and an acute to sub-acute necrotizing enteritis/colitis was the predominant morphologic diagnosis in bovine diarrhea (17/32). There was positive immunostaining for Salmonella spp. and BVDV in 9.4% (3/32) and 6.25% (2/32) of cases, respectively. The nested RT-PCR for BCoV resulted positive in four samples (4/9). The present results emphasize that diarrhea is a syndrome of complex etiology and that the research of fatal cases of this disorder through morphological, immunohistochemical and molecular techniques can provide important informations for diarrhea diagnosis, treatment and control.