An insight into the epidemiology of dolphin morbillivirus worldwide

Serum samples from 288 cetaceans representing 25 species and originating fr om II different countries were collected between 1995 and 1999 and examined for the presence of dolphin morbillivirus (DMV)-specific antibodies by an indirect ELISA (iELISA) (N = 267) or a plaque reduction assay (N = 21). A t otal of 35 odontocetes were seropositive: three harbour porpoises (Phocoena phocoena) and a common dolphin (Delphinus delphis) from the Northeastern ( NE) Atlantic, a bottlenose dolphin (Tursiops truncatus) from Kent (England) , three striped dolphins (Stenella coeruleoalba), two Risso's dolphins (Gra mpus griseus) and a bottlenose dolphin from the Mediterranean Sea, one comm on dolphin from the Southwest (SW) Indian Ocean, three Eraser's dolphins (L agenodelphis hosei) from the SW Atlantic, 18 long-finned pilot whales (Glob icephala melas) and a bottlenose dolphin from the SW Pacific as well as a c aptive bottlenose dolphin (Tursiops aduncus) originally from Taiwan. The pr esence of morbillivirus antibodies in 17 of these animals was further exami ned in other iELISAs and virus neutralization tests. Our results indicate t hat DMV infects cetaceans worldwide. This is the first report of DMV-seropo sitive animals from the SW Indian, SW Atlantic and West Pacific Oceans. Pre valence of DMV-seropositives was 85.7% in 21 pilot whales from the SW Pacif ic and both sexually mature and immature individuals were infected. This in dicates that DMV is endemic in these animals, The same situation may occur among Eraser's dolphins from the SW Atlantic. The prevalence of DMV-seropos itives was 5.26% and 5.36% in 19 common dolphins and 56 harbour porpoise fr om the NE Atlantic, respectively, and 18.75% in 16 striped dolphins from th e Mediterranean. Prevalence varied significantly with sexual maturity in ha rbour porpoises and striped dolphins; all DMV-seropositives being mature an imals. The prevalence of seropositive harbour porpoise and striped dolphins appeared to have decreased since previous studies. These data suggest that DMV is not endemic within these populations, that they are losing their hu moral immunity against the virus and that they may be vulnerable to new epi demics. (C) 2001 Elsevier Science B.V. All rights reserved.