After controlling Triatoma infestans
other species of triatomine that were considered minor in the transmission of Chagas disease became important. The persistence of
in Northeastern Brazil,
associated with reinfection of domestic environments recently sprayed with pyrethroids, may be a signal of susceptibility
alteration of this species to this insecticide. Specimens of T. brasiliensis
from the municipality of Tauá, state of Ceará,
were captured before and one year after spraying. They were submitted to bioassays using deltamethrin. The LD50
0.19-0.33 ng of deltamethrin/nymph. The resistance ratio among samples from Tauá varied from 1.16-1.79 in the samples captured before
the spraying and 1.00-1.74 in the samples captured one year after spraying, demonstrating that the two populations were equally susceptible
to deltamethrin. The small difference in susceptibility between the two captures suggests that T. brasiliensis
obtained in the
second capture are from new invasions of the domestic environment and that the insecticide did not select resistant individuals.
Therefore, it is suggested that T. brasiliensis
control be carried out supplementing the regular use of pyrethroids with
complementary measures, such as improvement of the dwellings and health education.