A new tactic for Triatoma infestans control: fabrics impregnated with beta-cypermethrin.

Triatoma infestans is the most important vector of Chagas' disease in Argentina. Experiences from Argentine national campaigns have shown indoor spraying to control triatomine bugs is both expensive and difficult. An alternative control method may be the use of pyrethroid-impregnated fabrics (PIFs), which could be both a practical and cheap complement to conventional control measures. In this study, a formulation of emulsifiable concentrate of beta-cypermethrin [alpha-cyano-3-phenoxybenzyl-3-(2,2-dichlorovinyl)-2,2- dimethylcyclopropanecarboxilate] pyrethroid was used to impregnate different fabrics. The fabrics were then tested for their efficacy and persistence in killing Triatoma infestans. Insects attempting to penetrate or grasp the fabric in search of blood meals were poisoned by the exposure to the absorbed pyrethroid. Laboratory bioassays showed that the insecticidal effect of the PIFs with a dosage of 0.2 g/m2 lasted longer on wool than on cotton or rayon. Eight months after impregnation, a residual efficacy of 100% was found for wool, 80% for rayon-cotton fabrics, and 50% for rayon-polyester fabrics. In addition, beta-cypermethrin-impregnated fabrics showed a better repellency effect than did fabrics impregnated with either deltamethrin or cypermethrin. For field trials, fabrics were impregnated either in the laboratory or "in situ" at a dosage of 1 g beta-cypermethrin/m2 and then dried. The PIFs were placed inside homes, either under the roof or under the bed mattress. The field trials showed the PIF approach to be very effective in keeping dwellings free of triatomine bugs for at least one year and found a high degree of acceptability among the houses' residents.

Synthesis and bioactivity of new phosphorodithioates derived from N-substituted maleamic esters.

1. A new series of organophosphorus compounds derived from N-substituted maleamic esters by reaction with dimethyl and diethyl phosphorodithioic acid was synthesized. 2. Two isomers, with chemical structures analogous to malathion were obtained for each maleamic ester assayed. 3. They were characterized, and their toxicity against a resistant strain of Musca domestica (strain G), a susceptible one (strain RAC) and Triatoma infestans (vector of Chagas' disease) were measured. 4. The structural chemical modification introduced by replacing a carboxyester group for a N-substituted amido one, reverted the resistance obtained for malathion. 5. Replacement of methyl by ethyl dithiophosphoric acid did not introduce significative differences. 6. In the case of Triatoma infestans, the synthesized compounds were less active than malathion.

Toxicity of methyl bromide and other gaseous insecticides to Triatoma infestans.

Cuticular penetration of lipid soluble substances in Triatoma infestans is very poor (less than 1% in 24 hr), while the respiratory route is particularly efficient (28% in 5 min). Accordingly, several noxious gases killed the insect at short periods of time. CH3Br and SO2 were particularly effective and they also evidenced ovicide action. With the former compound this effect is also observed at low concentrations. The CH3Br hydrolysis products or its metabolites were not similarly effective, while other methylating agent, diazomethane, was very active. The irreversible binding of 14CH3Br to proteins and lipids of T. infestans, as well as the decrease in the sulfhydryl groups content of the proteins of the insect provoked by CH3Br suggest that this compound kills the insect because of its alkylating properties. The use of gaseous insecticides in the chemical control of T. infestans is discussed.

Toxicity of methyl bromide and other gaseous insecticides to Triatoma infestans.

Cuticular penetration of lipid soluble substances in Triatoma infestans is very poor (less than 1

in 24 hr), while the respiratory route is particularly efficient (28

in 5 min). Accordingly, several noxious gases killed the insect at short periods of time. CH3Br and SO2 were particularly effective and they also evidenced ovicide action. With the former compound this effect is also observed at low concentrations. The CH3Br hydrolysis products or its metabolites were not similarly effective, while other methylating agent, diazomethane, was very active. The irreversible binding of 14CH3Br to proteins and lipids of T. infestans, as well as the decrease in the sulfhydryl groups content of the proteins of the insect provoked by CH3Br suggest that this compound kills the insect because of its alkylating properties. The use of gaseous insecticides in the chemical control of T. infestans is discussed.

Toxicity of methyl bromide and other gaseous insecticides to Triatoma infestans

Cuticular penetration of lipid soluble substances in Triatoma infestans is very poor (less than 1

in 24 hr), while the respiratory route is particularly efficient (28

in 5 min). Accordingly, several noxious gases killed the insect at short periods of time. CH3Br and SO2 were particularly effective and they also evidenced ovicide action. With the former compound this effect is also observed at low concentrations. The CH3Br hydrolysis products or its metabolites were not similarly effective, while other methylating agent, diazomethane, was very active. The irreversible binding of 14CH3Br to proteins and lipids of T. infestans, as well as the decrease in the sulfhydryl groups content of the proteins of the insect provoked by CH3Br suggest that this compound kills the insect because of its alkylating properties. The use of gaseous insecticides in the chemical control of T. infestans is discussed.