Histopathological Myocardial Changes and CPV-2 DNA Detection in Young Dogs: A Retrospective Study

Canine parvovirus type 2 (CPV-2) remains an important cause of morbidity and mortality in young dogs worldwide. Although the enteric form of the disease is well characterized, myocardial involvement associated with CPV-2 infection remains incompletely understood. The present retrospective study aimed to investigate myocardial lesions in young dogs and to evaluate their association with CPV-2 DNA detection using histopathological examination and PCR-based molecular analysis of formalin-fixed paraffin-embedded (FFPE) cardiac tissue. A total of 27 dogs aged between 3 and 11 months, submitted for diagnostic necropsy between 2019 and 2021, were included in the study. Histopathological evaluation was performed on myocardial tissue sections stained with hematoxylin and eosin, while conventional PCR targeting the VP1/VP2 region was used for the detection of CPV-2 DNA. Associations between PCR positivity and histopathological findings were assessed using Fisher's exact test. Myocardial abnormalities were identified in all examined cases (27/27, 100%), with myocarditis consistently observed throughout the study population. Cardiomyocyte necrosis and myocardial fibrosis were identified in 9/27 (33.3%) and 14/27 (51.9%) cases, respectively. CPV-2 DNA was detected in 9/27 myocardial tissue samples (33.3%). Cardiomyocyte necrosis was significantly more frequent in CPV-2-positive dogs than in PCR-negative animals (77.8% vs. 11.1%; p ≈ 0.001). Similarly, myocardial fibrosis was identified more frequently in CPV-2-positive cases (100.0% vs. 27.8%; p ≈ 0.001). Myocarditis was present in all examined animals and therefore could not be evaluated statistically according to PCR status. The detection of CPV-2 DNA in myocardial tissues exhibiting histopathological lesions supports a possible association between CPV-2 infection and myocardial injury in young dogs. However, the retrospective design, limited sample size, and the use of conventional PCR do not allow conclusions regarding causality or direct viral involvement in lesion development. Further studies incorporating larger case series and complementary diagnostic techniques are needed to clarify the pathogenesis and clinical significance of CPV-2-associated myocardial lesions.