Infectivity of isolates of Trichinella and the ability of an arctic isolate to survive freezing temperatures in the raccoon, Procyon lotor, under experimental conditions.

The objectives of this study were to determine if the raccoon was a useful experimental animal for infections of Trichinella and to determine if the ability of Trichinella to survive freezing conditions, known to occur in wild animals, could be duplicated under laboratory conditions. The isolates of Trichinella used in this study were from pigs, polar bear, wolverine, arctic fox and T. spiralis var. pseudospiralis originally isolated from a raccoon in the USSR. The raccoon was found to be a useful experimental host for Trichinella as it was easily maintained under experimental conditions and was readily infected. Infectivity indices were lower in raccoons than in laboratory mice. Those isolates of Trichinella with the longest association with laboratory mice had the lowest infectivity indices. The isolate of Trichinella from an arctic fox retained its ability to survive freezing temperatures when introduced into raccoons held under experimental conditions. The type of host, method of passing the parasite and perhaps a special genetic characteristic of arctic isolates seem to be important factors influencing their ability to survive freezing temperatures.