Abstract

Each year, several hundred pinnipeds are admitted to marine mammal rehabilitation centers in the United States, and suspected poxvirus infections are observed in these animals. Poxvirus infections are especially common among juvenile hospitalized pinnipeds and they appear to be hospital-acquired. This potential for nosocomial infection prompted a 3 year study into the etiology, treatment and epidemiology of poxvirus infections in pinnipeds. The main objectives of this study were to gain the information needed for the veterinary management of poxvirus epizootics in marine mammal rehabilitation centers and to determine the threat affected animals pose to the free-ranging pinniped populations. Based on our findings, a list of practical recommendations for the prevention and management of poxvirus epizootics in marine mammal rehabilitation centers was developed. Most significant findings included that poxviruses from Atlantic pinnipeds are distinct from those of Pacific pinnipeds. Quarantine procedures should therefore be put in place to avoid the introduction of novel poxvirus strains into naïve wild populations when pinnipeds, such as animals unsuitable for release, are transferred between facilities on the Atlantic and Pacific coast. Poxviruses are not commonly transmitted between free-ranging phocids and otariids. However, some parapoxvirus strains are capable of infecting multiple host species within a phylogenetic family but may be able to infect host species belonging to different phylogenetic families as well. At least some poxvirus infections that are observed in rehabilitation centers are acquired while in the rehabilitation center. Poxviruses appear endemic in wild California sea lion populations. Therefore, the release of captive sea lions infected with locally endemic parapoxvirus strain into the wild should not increase the risk of an outbreak in wild populations, and the presence of pox lesions in fully rehabilitated California sea lions should not preclude their return to the wild.