The impact of vector control on Triatoma dimidiata in the Guatemalan department of Jutiapa.

In 2000, a national control operation against the triatomine vectors of Trypanosoma cruzi, based on house spraying with residual pyrethroid insecticides, was initiated in Guatemala. The impact of the operation against Triatoma dimidiata in the most heavily infested department, Jutiapa, was evaluated by pre- and post-spraying surveys of the vector populations. Of the houses checked for Tri. dimidiata in the baseline surveys, 18.3% were found to be infested with the bug, and in 12.1% of the villages investigated more than half of the houses were found to be infested. The later survey was conducted after 24,250 houses and their associated peridomestic structures (in the 336 villages in which >5% of the houses had been found infested in the pre-spraying survey) had been sprayed. As a result of just this one round of spraying, the mean percentage of houses found infested in each of the villages surveyed twice fell from 36.0% to 8.9%. After the spraying, the percentage of houses infested in each sprayed village was never >50%, and the houses in 35.2% of the sprayed villages that were re-surveyed appeared to have been completely cleared of triatomine bugs. Re-infestation and colonization were mainly observed inside the houses, probably indicating that some indoor bugs survived the spraying round. If the department of Jutiapa is to be freed and kept free from domestic infestation, the efficacy of the insecticide spraying needs to be improved, spraying techniques need to be reviewed, and insecticides need to be re-applied at regular intervals. An effective vector-surveillance system (preferably one in which community participation is encouraged) is also essential.