Trichinella spiralis, T. britovi, and T. nativa: Infectivity, larval distribution in muscle, and antibody response after experimental infection of pigs

The infectivity of Trichinella spiralis, T. nativa, and T. britovi was experimentally compared in pigs. Blood sampling was performed weekly, and muscle juices were obtained at slaughter 10 weeks after inoculation. Muscle larvae were found in all of four pigs inoculated with T. spiralis [mean 190 larvae per gram (lpg)] and in three of four pigs inoculated with T. britovi (mean 7 lpg). No larvae were found in pigs inoculated with T. nativa. For T. spiralis and T. britovi, the neck muscle (m. splenius) appears to be a predilection site in addition to the tongue, the diaphragm, and the jaw. High antibody responses were found in all experimental groups, independent of the antigen used, and even in pigs in which no muscle larvae were recovered. The strong and consistent antibody response found with meat juice indicates the usefulness of this material where a blood sample is not obtainable, e.g. meat samples from wild animals. Immunoblotting (Western blots) on slaughter sera revealed no species specificity when comparing homologous versus heterologous staining. 1995; Pozio et al. 1992, 1996). In some regions these species are sympatric. The host infectivity of different Trichinella species has previously been shown to differ (Britov and Boer 1972; Garkavi 1972; Dick and Chadee 1983; Penkova et al. 1985; Murrell et al. 1986; Dame et al. 1987). Concurrent infection with Trichinella species has been found in nature (Pozio et al. 1995). Thus, to evaluate the role of the different European Trichinella species in transmission between sylvatic and domestic biotopes, which would aid in developing effective control strategies, it is important to know the infectivity levels for pigs of well-characterized sylvatic Trichinella species. Routine Trichinella control in most European countries is based on the physical detection of muscle larvae during meat inspection. Serological testing of live animals (e.g. for breeding) and samples from wildlife may, however, become an additional valuable tool due to the liberalization of animal trade within the European Union and the necessity for established trichinellosis-free areas to maintain that status. The present paper describes observations on pigs experimentally infected with the three Trichinella species found in Europe which represent potential threats to the human food chain, and the adequacy of routine parasitological methods for their detection.