<i>In Vivo</i> Verification of the Effect of Low-Temperature Treatment on the Enterotoxicity of <i>Sarcocystis fayeri</i>

<i>Sarcocystis fayeri</i> is a foodborne, pathogenic protozoan. As the enterotoxicity of <i>S. fayeri</i> 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 <i>S. fayeri</i> enterotoxicity by freezing horse meat has not yet been verified <i>in vivo</i>. We analyzed the effect of low-temperature treatment on the enterotoxicity of <i>S. fayeri</i> in rabbit intestinal loop tests using the treated <i>S. fayeri</i> bradyzoites. The viability of <i>S. fayeri</i> 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 <i>S. fayeri</i> may be caused by factors or mechanisms that are inhibited at temperatures lower than -20°C.