Serosurvey of Parainfluenza Virus (TtPIV1) Antibodies in Two Bottlenose Dolphin (Tursiops truncatus) Populations
Abstract
Evidence of exposure to parainfluenza viruses in wild, terrestrial mammalian populations is common throughout the world, including bison in Alaska (67%)6, chamois in the central Italian Alps (17%)2, pampas deer in Argentina (43%)5, pronghorns in Alberta (49%)3, rhinoceros in South Africa (25%)1 and white-tailed deer in Quebec (82-84%).4
An indirect enzyme-linked immunosorbent assay (ELISA) was developed as a tool to study the epidemiological features of a novel parainfluenza virus (tentatively named TtPIV1) of bottlenose dolphins. In the absence of more than one positive control case, the positive:negative cut-off value with associated sensitivity and specificity parameters could not be calculated for this assay. Instead, the convalescent serum sample of the positive control case with the highest mean optical density (MAN3-3-00) and a serum sample of a neonate bottlenose dolphin before first nursing were included on each plate as, respectively, positive and negative reference sera. The mean optical density (OD405) of each sample was divided by the OD405 of positive reference serum MAN3-3-00. Samples for which the OD405 ratio was > 1.0 were considered to contain antibodies against TtPIV1 (positive or exposed), whereas samples for which the corrected OD405 was = 0.0 were considered not to contain detectable antibodies against TtPIV1 (negative or unexposed). Samples with OD405 ratios > 0.0 but < 1.0 were considered inconclusive.
Serum samples from 114 dolphins were tested, including 58 dolphins managed by the U.S. Navy Marine Mammal Program in San Diego, California (July through October 2006) and 56 free-ranging wild bottlenose dolphins in Sarasota, Florida (June 2003 through June 2005). The mean OD405 ratio among all study samples was 0.4 (SD=0.4; median=0.2, range 0.0-2.8). A total of 13 (11.4%) dolphins were positive, 34 (29.8%) were negative, and 67 (58.8%) were inconclusive. When comparing the two dolphin populations, there were no significant differences in mean OD405 ratio (p=0.6) or percentages of animals characterized as negative, positive, or inconclusive (p=0.5).
Similar to many terrestrial mammalian species, evidence of exposure to parainfluenza virus was not uncommon in both managed and wild healthy bottlenose dolphin populations located on west and east coasts of the United States. A formal risk assessment is being conducted to further characterize the relevance of this virus to marine mammals.
Acknowledgements
The authors would like to thank Dr. Pam Yochem at Hubbs-SeaWorld Research Institute and Dr. Judy St. Leger at SeaWorld San Diego for their co-leadership in establishing the Center for Marine Veterinary Virology. This work was funded by research grant No. N00014-06-1-0250 to HN from the Office of Naval Research. Dolphin Quest support of health assessment operations in Sarasota Bay provided access to samples from wild dolphins. All sample collection protocols were approved by the University of Florida Institutional Animal Care and Use Committee (IACUC# C233). Field sampling was conducted under National Marine Fisheries Service Scientific Research Permit No. 522-1569, issued to Wells.
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