Caspian seal die-off is caused by canine distemper virus

The primary cause of the deaths of 10·000 seals in the Caspian Sea during the spring of 2000 is now reported by an international team of scientists to be canine distemper virus 1xMass die-off of Caspian seals caused by canine distemper virus. Kennedy, S et al. Emerg. Infect. Dis. 2000; 6: 637–639Crossref | PubMedSee all References1. Caspian seals (Phoca caspica) are listed as vulnerable species (endangered) and live in the Caspian Sea bordered by Russia, Kazakhstan, Turkmenistan, Iran and Azerbaijan. The highest death rates were reported during April and May as the disease spread south from the mouth of the Ural river to the Turkmenistan coast.Animals exhibited symptoms of debilitation, muscle spasms, ocular and nasal exudation and sneezing. Necroscopies showed no consistent gross lesions but microscopic examination of various tissues showed broncho-interstitial pneumonia, encephalitis, pancreatitis and lymphocytic depletion in lymphoid tissues, among other features. The picture was characteristic of a morbillivirus infection. Morbillivirus antigen was detected in multiple tissues using a monoclonal antibody against the nucleoprotein of phocine distemper virus. The findings were characteristic of distemper in terrestrial and aquatic animals. Tissues were also examined for morbillivirus nucleic acid by RT-PCR yielding the expected products. Fragments were sequenced and subjected to phylogenetic analyses. Serum specimens were also examined for canine distemper virus-specific IgM and IgG antibodies by direct and indirect ELISA tests. The data indicated that the seals from widely separated regions of the Caspian Sea were infected by the same virus.The origin of the virus is unknown but there are suspicions of terrestrial carnivores being involved. Such suspicions were aroused by earlier reports of die-offs in pinniped populations attributed to some association with domestic dogs. The contributory role of high levels of pollutants in the Caspian Sea is also being investigated.