Abstract

Morbilliviruses have caused epizootics in different species of marine mammals and serology for morbillivirus specific antibodies disclosed a global distribution of the disease causing pathogens.

To further investigate the role of morbilliviruses as a cause of disease and death blood and tissue samples from 77 stranded or by-caught harbour porpoises from the German Baltic and North Sea, collected between 1991 and 1997, were investigated for morbillivirus infection. A virus neutralization assay for detection of canine distemper virus (CDV, Onderstepoort) and porpoise morbillivirus (PMV) specific antibodies was performed. Routine histology was done on different organs including brain, lung and lymph nodes and immunohistology for morbillivirus antigen by means of the avidin biotin peroxidase technique using a cross reactive, polyclonal antibody against CDV was performed on lung.

Neutralizing CDV and PMV antibody titers were found in 41 (53%) and 65 (84%) animals, respectively. The highest titers for CDV were 1:226 and for PMV >1:761; titers were always highest against cetacean morbillivirus. No histological lesions specific for morbillivirus infection were detected and by immunohistology all cases investigated so far were negative for morbillivirus antigen. The absence of morbillivirus antigen and the lack of characteristic morbillivirus-specific lesions shows that morbillivirus infection was not a major cause of death or illness in the investigated population. However, the high incidence of morbillivirus specific antibodies indicates a continuous spread and infection of morbillivirus among harbour porpoises from the German Baltic and North Sea.