Prevalence of Trichinella spiralis in Wild Animals on Two Illinois Swine Farms

Abstract

Various wild animal species on two Illinois swine farms were studied for evidence of Trichinella spiralis infection. On one farm only grain and commercial supplement were utilized as swine feed. Of 239 wild animals examined from this farm, only a Norway rat (Rattus norvegicus) and a white-footed mouse (Peromyscus leucopus) were found infected with T. spiralis. This is believed to be the first report of natural T. spiralis infection in P. leucopus. Cooked garbage was fed to swine on the second farm. Of the 250 wild animals examined from this farm, only two Norway rats (R. norvegicus) were found infected with T. spiralis. Gould (1945), and Zimmermann and Hubbard (1963), have reviewed the literature on specific wildlife hosts of Trichinella spiralis, and Zimmermann and Hubbard (1963), found that 324 (3.9%) of 8,308 wildlife specimens collected in Iowa from 1953 to 1963 were infected with T. spiralis. However, the role of wildlife in swine infections and the effects of interacting wild animal populations on maintenance of the parasite remain unresolved. Previously, other workers (Kerr, 1942; Schwartz, 1952, 1960), and more recently Zimmermann and Brandly (1965), have demonstrated that the prevalence of T. spiralis infection in garbage-fed pigs is higher than rates in farm-raised swine as a group. One may hypothesize that wild animals living on a swine farm that utilizes garbage as feed would have a higher prevalence of T. spiralis Received for publication 11 October 1967. * Dr. Martin, at the time of this study, was assigned by the National Communicable Disease Center, Atlanta, Georgia, to the Illinois Department of Public Health, Springfield. He is currently regional public health veterinarian with the department. t Dr. Schnurrenberger is chief public health veterinarian, Illinois Department of Public Health, Springfield, and senior member of the Center for Zoonoses Research. + Dr. Andersen, at the time of this study, was assistant professor of veterinary pathology and hygiene, University of Illinois College of Veterinary Medicine, and associate member of the Center for Zoonoses Research. He is currently associate professor of zoology, Brigham Young University, Provo, Utah. ? Mr. Hsu is a research assistant in veterinary pathology and hygiene, University of Illinois College of Veterinary Medicine. infection than wild animals from a farm that does not use garbage for swine feed. This study was designed to determine the prevalence of trichinelliasis in wild animal species on two Illinois swine farms, one that feeds garbage to swine and one that does not. MATERIALS AND METHODS Farm S, in northeastern Illinois, is a square area of 1,100 acres, with a swine-breeding herd of approximately 40 sows. The farm is divided almost equally between cropland and pasture. The swine are fed locally grown corn with commercial supplement. Farm G, in east central Illinois, is a rectangular area of approximately 20 acres. Cooked garbage is fed to the offspring of 10 to 12 sows. All the farm area except for the dwelling and the hog lots was used until May 1966, as an open dump by the owner who hauls trash commercially. Samples of diaphragm from 20 swine raised on Farm G were collected and examined by the United States Department of Agriculture in 1964, as part of a nationwide survey of garbage-fed swine (Jefferies, 1966). Two of the 20 swine were found infected with T. spiralis larvae at that time. Wild animals were trapped on Farm S in August 1964 and 1965, and in March, May, and August 1966 (Table I). Animals were collected on Farm G in November 1965 and March, July, and November 1966 (Table II). The species, age, sex, and location of capture were recorded for each animal. The whole muscular part of the diaphragm was taken from each of the small mammals; approximately half of the diaphragm muscle was collected from each of the larger mammals. From birds, 5 to 10 g of breast muscle was collected. Small rodent identification was confirmed by Dr. Richard D. Andrews, Department of Zoology, Eastern Illinois University, Charleston, Illinois. All samples were examined under the trichinoscope or digested in 1% pepsin and 0.5% HC1 for 12 hr. Digested sediment was examined under the trichinoscope or microscope with 10 X magnification. Samples collected from Farm S in August