Distribuição do Parvovírus canino nos tecidos e caracterização do subtipo circulante em Minas Gerais

Abstract

The canine Parvovirus type 2 (CPV-2) is responsible for hemorrhagic gastroenteritis in dogs and, more rarely, non-suppurative myocarditis in puppies. The diagnosis in necropsied dogs is mainly made by intestinal lesions, but when there are intestinal post-mortem alterations or nonspecific lesions, immunohistochemistry (IHC) has been used to detect the virus in other tissues. Three antigenic variants of CPV-2; CPV-2a, CPV-2b and CPV-2c, have been identified in many countries by molecular testing and may be associated with different epidemiological pictures and severity of lesions. Thus, the aim of this study is to describe the distribution of canine parvovirus in tissues by IHC and to characterize the circulating strain(s) in Minas Gerais by molecular analysis and sequencing. Ten dogs with gross lesions suggestive of canine parvovirosis and five negative controls were necropsied at the Veterinary Pathology Sector of the Federal University of Lavras in the 2020-2021 period. Tissues from these dogs were submitted to histological, immunohistochemical, and molecular analysis. The most frequent gross lesions were hyperemic small intestinal serosa, reddish and rough mucosa, with evident Peyer's patches, increased and reddish retropharyngeal and mesenteric lymph nodes. Microscopically, atrophy and fusion of the intestinal villi (7/10), dilated crypts (5/10), necrosis (9/10), and desquamation of epithelial cells into the lumen (8/10) were visualized. Lymphoid necrosis and cellular rarefaction were more pronounced in tonsils (6/10) and retropharyngeal lymph nodes (6/10). The tissues more often positive on IHC for CPV-2 were tongue (88,89%); tonsil, retropharyngeal lymph nodes (77,78%); ileum (70%) and bone marrow (57,14%). All ten dogs were positive for CPV-2 in the polymerase chain reaction (PCR). Nucleotide sequencing reveaed a high nucleotide identity to VP2 and a consistent mutation at amino acid 426 (aspartic acid), characterizing the occurrence of the CPV-2b subtype. Negative controls were negative by IHC and PCR tests for CPV-2. This study contributed to a better knowledge of canine Parvovirus distribution in tissues, being tongue, tonsil, retropharyngeal lymph node, ileum and bone marrow the tissues with the highest frequency of immunolabeling, therefore for IHQ diagnosis of canine parvovirus infection. The results also demonstrate that the CPV-2b subtype circulates in the canine population of Minas Gerais.