Trichinella spiralis in Iowa Wildlife during the Years 1953 to 1961

Abstract

Studies have been made on the sylvatic occurrence of T. spiralis in wildlife of Iowa. During the 1953-61 period examinations were made of 7,078 wildlife specimens, representing approximately 44 species. Trichinae have been found in 14 species, namely rat, mink, fox, opossum, raccoon, striped skunk, spotted skunk, coyote, badger, beaver, least weasel, wolverine, fox squirrel, and horned owl. Two or more infected species have been obtained from 11 of 12 primary sampling areas with a maximum of seven reservoir species from a central Iowa area. The sylvatic occurrence of Trichinella spiralis is an important aspect of the epidemiology and epizootiology of trichiniasis. Increasing attention has been given to the determination of wildlife reservoirs and their possible role in the trichiniasis cycle. The purpose of this report is to summarize the results of studies which have extended over a period of 8 years, 1953 to 1961. Some of the data summarized herein have been reported in earlier papers, namely Zimmermann, Schwarte, and Biester (1956), Zimmermann, Hubbard, and Biester (1959), and Zimmermann et al. (1960). T. spiralis larvae were reported from nine species of Iowa wildlife, viz. rat, mink, fox, striped skunk, spotted skunk, opossum, raccoon, coyote, and badger. Robinson and Olsen (1960) reported trichinae infections in 17.8 per cent of 472 rats from a Colorado dump. Olsen (1960) reported a prevalence of 1 per cent in bobcats, 0.5 per cent in coyotes, and 3 per cent in foxes. Rausch et al. (1956) reported T. spiralis from 11.7 per cent of 2,433 Alaskan mammals. Larvae of T. spiralis were found in 23 of 42 species. MATERIALS AND METHODS During the 8-year period, 1953-61, 7,078 wildlife specimens representing approximately 44 species were examined for Trichinella spiralis. Nearly all specimens were obtained during the hunting and trapping seasons which extended from November through March. These specimens were Received for publication 2 October 1961. *Supported in part by research grant E-606 (C5) from the National Institutes of Health, U. S. Public Health Service. Published as paper N.S. 621, Veterinary Medical Research Institute, College of Veterinary Medicine, Iowa State University of Science and Technology, Ames, Iowa. obtained mainly from 12 primary sampling areas with only limited specimens being obtained from other areas. In addition, a number of specimens were obtained from the State Conservation Commission of Iowa. Tissues selected for examination were the diaphragm, tongue, and leg muscle of larger mammals while the entire skinned and eviscerated carcasses were used from rats, mice, and other small mammals. Breast muscle was used from birds. Forty-five g samples (0.1 lb) of ground tissue were examined by the artificial digestion-Baermann technique as described previously, Zimmermann, Schwarte, and Biester, 1961.