Novel adenovirus detected in captive bottlenose dolphins (Tursiops truncatus) suffering from self-limiting gastroenteritis

Abstract

Background: Adenoviruses are common pathogens in vertebrates, including humans. In marine mammals, adenovirus has been associated with fatal hepatitis in sea lions. However, only in rare cases have adenoviruses been detected in cetaceans, where no clear correlation was found between presence of the virus and disease status. Case presentation: A novel adenovirus was identified in four captive bottlenose dolphins with self-limiting gastroenteritis. Viral detection and identification were achieved by: PCR-amplification from fecal samples; sequencing of partial adenovirus polymerase (pol) and hexon genes; producing the virus in HeLa cells, with PCR and immunofluorescence detection, and with sequencing of the amplified pol and hexon gene fragments. A causative role of this adenovirus for gastroenteritis was suggested by: 1) we failed to identify other potential etiological agents; 2) the exclusive detection of this novel adenovirus and of seropositivity for canine adenoviruses 1 and 2 in the four sick dolphins, but not in 10 healthy individuals of the same captive population; and 3) the virus disappeared from feces after clinical signs receded. The partial sequences of the amplified fragments of the pol and hexon genes were closest to those of adenoviruses identified in sea lions with fatal adenoviral hepatitis, and to a Genbank-deposited sequence obtained from a harbour porpoise. Conclusion: These data suggest that adenovirus can cause self-limiting gastroenteritis in dolphins. This adenoviral infection can be detected by serology and by PCR detection in fecal material. Lack of signs of hepatitis in sick dolphins may reflect restricted tissue tropism or virulence of this adenovirus compared to those of the adenovirus identified in sea lions. Gene sequence-based phylogenetic analysis supports a common origin of adenoviruses that affect sea mammals. Our findings suggest the need for vigilance against adenoviruses in captive and wild dolphin populations.

Postmortem Findings in Cetaceans Found Stranded in the Pelagos Sanctuary, Italy, 2007–14

“…The diagnosed septicemia caused by E. coli was an interesting finding, given that E. coli infections have been mainly described in pinnipeds (Howard et al 1983;Cowan 2002). Adenovirus was detected in one animal in the absence of related lesions, and confirmed the lack of correlation between presence of the virus and disease, as reported in a previous study (Rubio-Guerri et al 2015).…”

Emerging viruses in marine mammals.

“…Sea lion adenoviruses (OtAdV-1, OtAdV-2) were isolated from California sea lions while similar adenoviruses were found in liver samples or faeces from pinnipeds including South African and South American fur seals, a South American sea lion and a Hawaiian monk seal [98,166]. Adenoviruses have also been isolated from northern elephant seals (PhAdV-1), Pacific harbour seal (PhAdV-2), bottlenose dolphins (Tursiops adenovirus-1), sei whales (Balaenoptera borealis), bowhead whales, beluga whales, harbour porpoises and polar bears (U. maritimus) [98,126,[164][165][166][167][168][169][170][171][172][173]. In otters, canine adenovirus-1 and a novel adenovirus have infected captive Eurasian otters (Lutra lutra) and southern sea otters, respectively [100,174].…”

Novel Divergent Polar Bear-Associated Mastadenovirus Recovered from a Deceased Juvenile Polar Bear

“…Difficulties that were encountered in both cell culture isolation attempts and identifying PbAdV-1 using electron microscopy have proven troublesome for previous studies such as the identification of the bottlenose dolphin adenovirus ( 21 ). The virus was believed to have replicated to some extent in the HeLa cells; however, electron microscopy could not give conclusive results on identifying adenovirus particles in the infected cells similar to PbAdV-1.…”