Pathogen exposure surveillance in Southern Ocean pinnipeds

Abstract

An increased pressure of human activities that can introduce new infectious agents and therefore alter host-pathogen interactions, resulting in epizootics and biodiversity loss, challenges the Southern Ocean. Health status information and the potential effect of disease outbreaks in the Southern Ocean fauna is scare and evaluating the susceptibility to new infectious agents is decisive for its conservation. Herein we assess the exposure of Antarctic fur seals (AFS, Arctocephalus gazella) and Southern elephant seals (SES, Mirounga leonina) to pathogens known to be present in pinnipeds elsewhere. AFS (n = 65) serum and swab samples and SES (n = 13) serum samples from the sub-Antarctic island of Bouvet (54º41’S, 03º29’E) were collected in two austral summers (2014-2015, 2017-2018). Three PCR protocols for parapoxvirus DNA detection amplifying the DNA polymerase, B2L and GIF genomic regions were performed. The genomic region encoding for glycoprotein B (gB) was targeted to detect Phocine herpes virus-1 (PhHV-1) viral DNA. Sera were assayed for Toxoplasma gondii and smooth Brucella spp. antibodies with indirect enzyme linked immunosorbent assays (iELISAs). PCR amplicons of the expected size were generated for parapoxvirus in two of the 29 AFS pups (nasal swabs, 2014-2015), for the B2L (n=2) and DNA polymerase (n=1) genes, whereas the GIF PCR did not amplify relevant sequences. Sequencing of the PCR amplicons was carried out and blasted in GenBank finding most homology with a seal parapoxvirus, confirming the presence of the virus in AFS for the first time. Antibodies against T. gondii or smooth Brucella spp. were not detected, and no PhHV-1 amplicons were generated. Overall, our data indicate that these seals are not threatened by being exposed to the pathogens tested, although parapoxvirus infections may cause severe disease in young and stressed individuals. These data contribute to the baseline for the evaluation and management of these seal populations.