Pathogen Surveillance in Free-ranging Giant Otters (Pteronura brasiliensis) in Three Ecoregions of Brazil.

The giant otter (Pteronura brasiliensis) is the largest river otter in the world and globally classified as endangered. Little information is available regarding pathogen exposure in this species due to low densities and the challenges associated with capturing individuals in the wild. Serological assays were used to investigate exposure of 10 free-ranging giant otters from different Brazilian ecoregions to canine distemper virus (CDV), parvovirus, rabies virus, Leptospira spp., smooth Brucella, and Toxoplasma gondii. Molecular assays were conducted to assess the presence of Hepatozoon spp., Cytauxzoon spp., and Babesia spp. Serum antibodies were detected for CDV (5/10), canine parvovirus (2/10), rabies virus (1/7), Leptospira spp. (2/10), and T. gondii (3/10). None of the giant otters were exposed to smooth Brucella. Of the individuals that received molecular testing, 2/6 were positive for Hepatozoon spp., and 0/6 were positive for Babesia spp. or Cytauxzoon spp. These results provide the first data on pathogen exposure in free-ranging giant otters. Long-term monitoring of these populations is essential to determine which pathogens are endemic and which may pose a conservation threat to giant otters.