The baseline susceptibility levels of Chunya Praomys natalensis, the commonest plague reservoir and crop pest in Tanzania, to warfarin.

P. natalensis were live-trapped at Kibwawa (Chunya district) in November 1977 and November 1979. An F3 generation was raised from animals which tolerated 0.025% a.i. warfarin. All three populations were tested using the WHO standard method (WHO/VBC/75.595), with 0.025% warfarin. The populations tested were fully susceptible to the rodenticide, and the latter was well acceptable to the rodents. In this area, warfarin can be successfully used for controlling P. natalensis. Failure to obtain 100% mortality with the 1977-caught wild population was probably due to vigour tolerance. Regular seminars are recommended to train staff in the rodenticide application.