Failure of vaccine or virulent strains of canine parvovirus to induce immunosuppressive effects on the immune system of the dog.

It is generally believed that canine parvovirus (CPV) is immunosuppressive and that immunosuppression plays an important role in the pathogenesis of canine parvovirus disease. However, there is little experimental evidence to support this assertion. The effects of virulent and vaccine strains of CPV on natural effector (NE) cell activity, antibody-dependent cell-mediated cytotoxicity (ADCC), chemiluminescence (CL) of neutrophils, lymphocyte response to mitogen, specific antibody response to CPV, and dermal reaction to phytohemagglutinin (PHA) were examined. Neither a virulent nor a vaccine strain of CPV significantly suppressed the immune system. The only potential effect noted was that dogs infected with the virulent strain of CPV developed a transient peripheral blood leukopenia. It was concluded that CPV does not cause immunosuppression and that immunosuppression does not play a significant role in the pathogenesis of canine parvovirus disease.