Susceptibility of Swine to Sylvatic Trichinella Spiralis Isolates

Worley, David

Abstract

The primary objective of the proposed research is to determine the susceptibility of swine to a series of sylvatic strains of Trichinella spiralis and to evaluate the kinetics of the infection, including seroconversion rates using a standard ELISA immunodiagnostic procedure. Data on the prevalence of trichinosis in Montana pigs examined during the past year indicated a natural infection rate of about 1.2%, based on the presence of tissue larvae in six of 470 animals (unpublished data, MBRS Subproject 19, 1988). None of the infected pigs was detected with a standard enzyme-linked immunosorbent assay (Eisenstein et al., 1985), suggesting that the excretory-secretory antigen used in the test was unable to """"""""recognize"""""""" antibody present in the sera of infected pigs, or that titers were insufficient to react with the test antigen at the dilutions tested. Conversely, occasional pig sera testing positive via ELISA yielded negative results by digestion. An experimental approach to evaluate infectivity of sylvatic Trichinella isolates in pigs and determine their persistence in tissues over time will be used to evaluate the ability of the pig to serve as a suitable host for non-domestic strains of this parasite. A second aspect involves characterization of sylvatic T. spiralis isolates by DNA profiling to distinguish wild strains from each other and compare them with a domestic strain used for reference purposes. Current work in our laboratory using restriction fragment length polymorphisms (RFLP) as genetic markers has proved to be a useful means of distinguishing Trichinella isolates from the gray wolf, grizzly bear, bobcat, and pig (Worley et al., 1988). Additional use of RFLP analysis is projected to compare genomic DNA from other sylvatic strains currently being maintained in rodents at MSU: lynx, cougar, marten, fisher, black bear, and wolverine. Use of infectivity characteristics in pigs and genetic polymorphisms of tissue stages reared in rodents will be evaluated as methods for characterizing sylvatic T. spiralis biotypes existing in the U.S. and for determining their relationships to domestic pig isolates and to each other.