Background and Objective: Lushoto district has been an active focus of plague disease since 1980 and
many pesticides were used to control rodents and fleas from 1980 to 2003 when outbreaks occurred
yearly. For over seven years ago commercial Carbaryl 5% powder has been used for controlling fleas in the
area. However, there is no current research to substantiate its effectiveness either in the laboratory or in
the field.
Methods: Immature stages of
Xenopsylla brasiliensis
were collected from two villages in Lushoto and
transported to Sokoine University of Agriculture (SUA), Morogoro and reared in an insectary to stock
colony. Known weights of commercial Carbaryl 5% powder were thoroughly mixed with known weights of
clean fine sand as to obtain a final concentration of 0.05% (WW) of Carbaryl/sand mixture. The same
concentration was suspended in 50cc distilled water and pieces of filter paper were soaked in the solution,
left at room temperature until the suspension was fully adsorbed and the papers were left to dry. Adult
fleas of mixed ages and of both sexes were obtained from the stock colony and exposed to both
Carbaryl/sand mixture and Carbaryl-adsorbed filter papers for various periods of time. Field trials were
carried out at Manolo and Viti villages where house and rodent flea indices were determined before and
after dusting with commercial Carbaryl 5% powder.
Results: In the laboratory tests, 100% mortality occurred at 90 minutes exposure in Carbaryl/sand mixture
experiments and at 35 minutes exposure to Carbaryl-adsorbed filter papers. LT
50 in both sets of exposure
was 48.2 min and 23.1 min in Carbaryl/sand mixture and Carbaryl-coated filter papers tests respectively. In
field trials,
X. brasiliensis and
Pulex irritans
were the most abundant flea species. Post-dusting flea
populations were significantly lower in treated than in control houses (p=0.028). House flea indices
dropped from 7.7 to 0.33 and 37.8 to 0 in Viti and Manolo villages respectively at 3 months post-dusting.
Conclusion: Commercial Carbaryl 5% powder in current use was still effective against potential flea vectors
in Lushoto.
