Trichinella sp. in polar bears from Svalbard, in relation to hide length and age

Abstract

Diaphragm and masseter muscles from 376 polar bears ((irsur maririmus), 252 ringed seals (Phocn hispida), 84 bearded seals (Erignarhus barbarus), and 77 arctic foxes (Alopex lagopus) from Svalbard were examined for Trichinelln. Infection rates in polar bears varied between 23 and 58%, and between 3 and 67% in arctic fox. None of the seals were infected. Trichrnella in polar bears is probably transferred through cannibalism and scavenging upon polar bear carcasses. Infection rate in arctic fox was high when they preyed upon polar bear carcasses before polar bear hunting was prohibited in 1973. A low infection rate seems more natural when such prey is not available. No difference could be found in infection rate between male and female polar bears. There is only a slight increase in infectlon rate with age, as calculatcd from hide lengths, and many adult animals remain uninfectcd. Geographlcal isolation of polar bear populations may explain differences in Trichinella infection rates between beara from arctic Amcrica and arctic Europe. Possible explanations are that discrete polar bear populations have different food habita. or that they are exposed to different Trichinella strains.