Apoptosis in feline panleukopenia and canine parvovirus enteritis

Tissue samples of cats and dogs with panleukopenia and parvovirus enteritis , respectively, were examined for the presence of viral antigen-positive ce lls and apoptotic cells by immunohistochemistry and by TUNEL assay (Termina l Transferase-Mediated dUTP Nick End Labelling). Compared to control animal s, infected cats and dogs generally had more TUNEL-positive cells. Cell typ es positive for parvovirus antigen, for example digestive tract epithelial and mesenchymal cells, and lymphocytes and macrophages in lymphoid tissues were also positive for TUNEL signals. Occasionally, TUNEL signal and viral antigen were present in the same tissue areas, suggesting a direct viral tr igger of apoptosis. More frequently, however, there was no complete overlap of antigen and TUNEL-positive areas. The results of this study indicate th at apoptotic cell death contributes significantly to the widespread tissue damage of parvovirus infection in cats and dogs.