Morbillivirus and Toxoplasma Exposure and Association with Hematological Parameters for Southern Beaufort Sea Polar Bears: Potential Response to Infectious Agents in a Sentinel Species

Abstract

Arctic temperatures are increasing in response to greenhouse gas forcing and polar bears have already responded to changing conditions. Declines in body stature and vital rates have been linked to warming-induced loss of sea-ice. As food webs change and human activities respond to a milder Arctic, exposure of polar bears and other arctic marine organisms to infectious agents may increase. Because of the polar bear's status as arctic ecosystem sentinel, polar bear health could provide an index of changing pathogen occurrence throughout the Arctic, however, exposure and monitoring protocols have yet to be established. We examine prevalence of antibodies to Toxoplasma gondii, and four morbilliviruses (canine distemper [CDV], phocine distemper [PDV], dolphin morbillivirus [DMV], porpoise morbillivirus [PMV]) including risk factors for exposure. We also examine the relationships between antibody levels and hematologic values established in the previous companion article. Antibodies to Toxoplasma gondii and morbilliviruses were found in both sample years. We found a significant inverse relationship between CDV titer and total leukocytes, neutrophils, monocytes, and eosinophils, and a significant positive relationship between eosinophils and Toxoplasma gondii antibodies. Morbilliviral prevalence varied significantly among age cohorts, with 1-2 year olds least likely to be seropositive and bears aged 5-7 most likely. Data suggest that the presence of CDV and Toxoplasma gondii antibodies is associated with polar bear hematologic values. We conclude that exposure to CDV-like antigen is not randomly distributed among age classes and suggest that differing behaviors among life history stages may drive probability of specific antibody presence.

Cross-species transmission of canine distemper virus—an update

“…There is marked serological evidence that various species of bears have been exposed to CDV including American black bears ( Ursus americanus ) [76], Asian black bears ( Ursus tibethanus ) [66], polar bears ( Ursus maritimus ) [77], grizzly bears ( Ursus arctos horribilis ) [32] and Marsican brown bears ( Ursus arctos marsicanus ) [78]. However, clinicopathological manifestation of distemper in ursids is rare.…”

Qualitative risk assessment of impact of Toxoplasma gondii on health of beluga whales, Delphinapterus leucas from the Eastern Beaufort Sea, Northwest Territories

“…Morbilliviruses have not been documented in EBS beluga, but have been reported from other marine mammals from the Beaufort Sea (Kirk et al 2010) and in ringed seals in the northwestern Canadian Arctic (Duignan et al 1997). In two stranded beluga whales from the SLE with pathology associated with T. gondii, concomitant morbillivirus infection was not detected (Mikaelian et al 2000).…”

Infectious diseases of Antarctic penguins: current status and future threats

“…In Norway, a fulminant infection in a closely monitored herd of musk ox (Ovibos moschatus) caused by P. multocida resulted in the deaths of a significant number of these animals during unusually warm and humid summer weather (Ytrehus et al 2008). Polar bears (Ursus maritimus) are also thought to be at increased risk of exposure to infectious diseases through increasingly closer contacts with multiple sources, driven by the warming climate (Kirk et al 2010 (Lynch et al 2010). Such observations are of concern since decreased chick rearing success, and poor body condition has been associated with high tick infestation in other penguin species (e.g., king penguins in the Crozet Archipelago; Mangin et al 2003).…”