Laboratory-reared Xenopsylla brasiliensis and X. cheopis obtained from several parts of Tanzania were tested with 0.5% malathion, using the standard WHO test kit.
Two strains of Xenopsylla brasiliensis (Mbulu and Amani) were more susceptible as 100% mortality was obtained after 12 hr exposure. With the remaining populations, 100% mortality was obtained after 24 hr exposure. LT50 of X. brasiliensis were 3.1, 3.3 and 4.5 hr for Mbulu, Tawalani and Amani strains respectively. Similarly, LT50 of X. cheopis were 8.1, 7 and 5.4 hr for Chunya, Amani and Tawalani strains respectively.
It was generally concluded that malathion was a suitable insecticide for use in flea and consequently plague control in Tanzania as X. brasiliensis and X. cheopis are the commonest flea vectors of the disease in the country. Moreover, the insecticide is locally available and it has limited toxicity on non-target organisms and little persistence in the environment.
