Morbillivirus infection in free-ranging Atlantic bottlenose dolphins (Tursiops truncatus) from the Southeastern United States: seroepidemiologic and pathologic evidence of subclinical infection.

From 2003 to 2007, sera (n=234) from free-ranging Atlantic bottlenose dolphins (Tursiops truncatus) inhabiting two southeast Atlantic estuarine regions, the Indian River Lagoon (IRL), FL and Charleston, SC (CHS) were tested for antibodies to cetacean morbilliviruses as part of a multidisciplinary study of individual and population health. Positive morbillivirus titers were found on initial capture in 12 of 122 (9.8%) IRL dolphins in the absence of an epizootic. All CHS dolphins were seronegative. Positive fluctuating morbillivirus titers and seroconversion were found in IRL dolphins. Seropositivity was detected in dolphins 8-13 years of age as well as in dolphins that were alive during the 1987-1988 epizootic. During the study period, pathologic and immunohistochemical findings from stranded IRL dolphins (n=14) did not demonstrate typical morbillivirus-associated lesions or the presence of morbillivirus antigen. The findings suggest that morbillivirus infections are occurring in the absence of widespread mortality in IRL dolphins.