Trichinella isolates from polar bears in Svalbard. Freeze resistance and infectivity in rats and swine.

The author isolated Trichinella strains from five polar bears in Svalbard (the high arctic region of Norway). Based on infectivity experiments with white mice (BOM:NMR), the freeze resistance limits of the Trichinella strains are outlined. Further experiments showed that white rats (MOL:WIST) and pigs (sus scrofa domestica) are almost refractory to these Trichinella strains. The infectivity of Svalbard isolates in the above mentioned test animals was compared, in parallel experiments, with that of T. spiralis (Owen). The latter showed a very high infectivity to the same species of test animals. It is thus probable that the arctic Trichinella found in the polar bear is biologically distinct from both T. spinalis (Owen) and T. nativa ( Britov and Boev ).