Pilot whales (Globicephala melas) mortality due to morbillivirus in Mediterranean sea

Abstract

Morbilliviruses have emerged as significant pathogens of cetaceans and pinnipeds worldwide. Two cetacean morbilliviruses have been identified and named porpoise morbillivirus (PMV) and dolphin morbillivirus (DMV). PMV was isolated from harbor porpoises that died along the Irish coast. DMV was first identified in striped dolphins from the Mediterranean. Although, morbillivirus outbreaks have not been previously reported in pilot whales, antibodies to morbilliviruses have been reported in 86% of two species of pilot whales (Globicephala melas and macrorrhynchus) in the western Atlantic. Barrett et al. (1995) found that 93% of stranded long-finned pilot whales (Globicephala melas) were morbillivirus seropositive, providing further evidence that cetacean morbilliviruses are widespread. Interestingly, molecular evidences from one pilot whale stranded in New Jersey (USA), which died with encephalitis, suggested that the long-finned pilot whale is host of a different, novel type of cetacean morbillivirus (called pilot whale morbillivirus or PWMV), and distinct from both PMV and DMV. During a period of six months (November 2006-April 2007) more than 25 long finned pilot whales (G. melas) died alog the southern Spanish Mediterranean coast and Balearic Islands. Nine pilot whales were fresh or moderate autolytic and they were completely or partially necrosied and sampled. A histological, immunohistochemical and virological study was performed on frozen and formalin fixed tissues. RT-PCR detection of cetacean morbillivirus (CetMV) was carried out on samples of brain, lung, spleen, lymph nodes, liver and kidneys, from 7 pilot whales. We report the first epizootic event of lethal morbilliviral infection in longfinned pilot whales (G. melas) that occurred in the Mediterranean Sea. Sequence analysis of a 426 bp conserved fragment of the morbillivirus phosphoprotein (P) gene suggests that the virus involved in this whale mortality event is phylogenetically more closely related to DMV rather to the novel PWMV identified by Taubenberger in a pilot whale.