Serologic Investigation of Leptospira spp., Sarcocystis neurona, and Toxoplasma gondii in Guadalupe Fur Seals (Arctocephalus townsendi) from Guadalupe Island, Mexico.

The Guadalupe fur seal (GFS; Arctocephalus townsendi) is susceptible to the ecologic impacts of anomalous ocean warming events, which have led to prey scarcity that, in turn, affects its feeding habits, nutritional condition, and survival at Guadalupe Island, Mexico. Concurrently, ocean warming has also caused increased outbreaks of zoonotic diseases in North Pacific pinnipeds. This study assessed the exposure to zoonotic disease agents (Leptospira spp., Sarcocystis neurona, and Toxoplasma gondii) in GFS on Guadalupe Island (2016, 2017, and 2020), during a period of persistent ocean warming and unusual strandings in Mexico and the USA. Blood samples were collected from 129 GFS (82 females and 47 males) at Guadalupe Island. All tested GFS were seronegative for Leptospira spp. and S. neurona, whereas 17/129 (13%) tested seropositive for T. gondii, predominantly pups (1 yr) of both sexes. Although T. gondii was only detected in a relatively small proportion of GFS at Guadalupe Island, the parasite is frequently reported in pinniped populations inhabiting coastal ecosystems worldwide. Currently, the GFS population is increasing, which may promote range expansion and increase interaction with other marine mammals that may carry zoonotic pathogens along the coastal ecosystems of the northeastern Pacific Ocean. Only GFS pups were seropositive for T. gondii, which may reflect a passive transfer of maternal antibodies during lactation. However, the low prevalence observed may also indicate limited environmental exposure or other ecologic factors. As on other islands, exotic invasive species are reported in Guadalupe Island, which cannot be discounted as a possible source of exposure of GFS to pathogens and parasites such as T. gondii.