Abstract

In recent decades, morbilliviruses have been responsible for major epizootics among marine mammals. Histopathology can provide a simple means for the recognition of disease due to morbilliviruses. However, determination of the exact virus is often problematic. This is caused by: (1) the often autolyzed state of the carcasses making virus isolation difficult, (2) the similarity of the histopathologic lesions and (3) the overlapping host ranges of these viruses. The use of specific immunohistochemical tests for the diagnosis of marine mammal morbilliviruses was tested as a means to differentiate these viruses. Four monoclonal antibodies made against phocine distemper virus (PDV) and three monoclonal antibodies made against cetacean morbillivirus (CMV) were tested on formalin-fixed, paraffin-embedded tissues from confirmed cases of PDV, CMV, and canine distemper virus (CDV). All four anti-PDV antibodies stained both PDV and CDV but not CMV. Of the three anti-CMV antibodies, two were positive for CMV and negative for CDV and PDV. One anti-CMV antibody was positive for CMV and CDV, but was negative for PDV. Application of these antibodies to histopathologic samples having lesions consistent with morbillivirus infection provide a diagnostic means for distinguishing between infection of PDV (or CDV) and CMV.