In Vivo Verification of the Effect of Low-Temperature Treatment on the Enterotoxicity of Sarcocystis fayeri

Sarcocystis fayeri is a foodborne, pathogenic protozoan. As the enterotoxicity of S. fayeri to the host has been reported to be inactivated by low-temperature treatment due to loss of viability, regulations on horse meat stipulate that it is to be frozen before distribution in Japan. However, inactivation of S. fayeri enterotoxicity by freezing horse meat has not yet been verified in vivo . We analyzed the effect of low-temperature treatment on the enterotoxicity of S. fayeri in rabbit intestinal loop tests using the treated S. fayeri bradyzoites. The viability of S. fayeri decreased with lower treatment temperature and longer treatment time. The bradyzoites treated at 4°C developed fluid retention in the rabbit ileal loop, while those treated at –20°C and –80°C did not. This study suggests that the enterotoxicity of S. fayeri may be caused by factors or mechanisms that are inhibited at temperatures lower than –20°C.