Determination of insecticides’ lethal concentrations and metabolic enzyme levels in Triatoma dimidiata

Abstract

Objective. The feasibility of the use of WHO impregnated paper and biochemical assays to determine lethal concentra­tions (LC50 and LC99) and insecticide metabolic enzyme levels of Triatoma dimidiata. Materials and methods. LC50 and LC99 were calculated with WHO papers impregnated at differ­ent concentrations of malathion, propoxur and deltamethrin; the percentage of insensitive acetylcholinesterase (iAChE); and the levels of esterases, glutathione S-transferases, and monooxygenases in laboratory nymphs of the first stage (5 to 7 days), were undertaken using the WHO biochemical assays. Results. Respectively the LC50 and LC99 μg/cm2 obtained for malathion were 43.83 and 114.38, propoxur 4.71 and 19.29, and deltamethrin 5.80 and 40.46. A 30% of the population had an iAChE, and only a few individuals had high P450 and β-eterase levels. Conclusion. Impregnated papers and bio­chemical tests developed by WHO for other insects, proved to be feasible methods in monitoring insecticide resistance and metabolic enzymes involved in T. dimidiata.

Keywords

• triatoma dimidiata
• lethal concentrations
• ace¬tylcholinesterase
• cytochromes p450
• esterases
• glutathione s-transferase