Studies on cross-immunity in Herpetosoma trypanosomes of Microtus, Clethrionomys and Apodemus.

Laboratory-bred rodents of three species were inoculated with heterologous Herpetosoma trypanosome species as follows: Microtus agrestis with Trypanosoma evotomys or T. grosi, Apodemus sylvaticus with T. evotomys or T. microti and Clethrionomys glareolus with T. grosi or T. microti. The three rodent species were subsequently challenged with their natural trypanosome parasite, i.e. T. microti for M. agrestis, T. grosi for A. sylvaticus and T. evotomys for C. glareolus. The parasitaemias and courses of infection that developed were followed. All challenged animals showed some degree of cross-immunity; not all became infected, and those that did had lower levels of parasitaemia and shorter patent periods than control animals. No C. glareolus previously inoculated with T. microti developed T. evotomys infections on challenge, and an infection was observed in just one of ten M. agrestis inoculated first with T. evotomys and later with T. microti.