An attempt was made to control phlebotomine sand flies
biting indoors in a rural community near Cali, Colombia,
using the residual insecticide 'K-Othrine' (deltamethrin)
sprayed on the inside wails of houses. Twelve houses were
divided into matched pairs based on physical
characteristics, one house in each pair being left
untreated while the inside walls of the other were sprayed
with 1% deltamethrin at a concentration of 500 mg a.i/m.
Sand flies were sampled each week using protected human
bait and sticky trap collections for four months after
spraying. The number of sand flies (Lutzomyia youngi)
collected on sticky traps was significantly lower (P=
0.004) in the untreated houses than in the treated ones
with which they were matched This difference was not
significant for L. columbiana; the other anthropophilic
species were not present in large numbers. The numbers
collected on human bait in treated and untreated houses
were not significantly different for either species.
Activity of the insecticide as determined by contact
bioassays remained high throughout the study and failure to
control the insects was attributed to two factors: the
tendency of sandflies to bite before making contact with
the insecticide and the fact that the number of sand flies
that entered houses represented a relatively small
proportion of the population in the wooded areas
surrounding the settlement in the study.
