The absence of eosinophilia in rats infected with radiated Trichinella spiralis

By appropriate roentgen radiation, the reproductive capacity of T. spiralis larvae could be destroyed without eliminating their infectivity. The larvae were irradiated with 12,000, 16,000, or 20,000 r at a rate of 785 r per min. In contrast to rats infected with 6000 nonirradiated larvae, a similar number of larvae irradiated at the 2 lower doses failed to elicit eosinophilia, which was evident in the nonirradiated group on the 5th or 6th day after infection. Rats infected with larvae irradiated with 20,000 r developed eosinophilia on the l4th day. Moreover, larvae were recovered from muscle of the latter group of rats (but not from muscle of rats given larvae irradiated at the lower doses), indicating failure of radiation to cause reproductive sterilization at the 20,000-r level. This paradoxical finding may have resulted from an error in the irradiation technique.