Immunohistological and serological investigations of morbillivirus infection in Black Sea harbour porpoises (Phocoena phocoena)

In the present study the occurrence of morbillivirus infection in harbour porpoises (Phocoena phocoena) from the Black Sea was investigated. Blood and tissue specimens of lung, brain and spleen from 73 stranded or by-caught harbour porpoises derived from the three Black Sea subregions such as Bulgaria, Georgia and Ukraine were collected between 1997 and 1999 and processed for histology, immunohistochemistry and serology. Age determination was performed according to dental growth layers and body length. The age of the investigated population ranged from neonates to a 12-year-old animal. Morbillivirus-specific neutralizing antibodies were detected in 53% of harbour porpoises. Generally, titres were very low and ranged from 20 to 270. There was no correlation between age, geographical origin and titre levels. The most common histological finding (97%) consisted of a mild to severe granulomatous bronchopneumonia due to lung worm infection. There were no changes indicative of a morbillivirus infection. Using immunohistology none of the animals were positive for morbillivirus antigen. However, the serological data are suggestive of a continuously circulating morbillivirus among harbour porpoises from the Black Sea indicating that harbour porpoises may serve as carriers for fatal diseases in susceptible cetacean species.