Lethality of triatomines (Hemiptera: Reduviiae), vectors of Chagas' disease, feeding on blood baits containing synthetic insecticides, under laboratory conditions

Abstract

A laboratory study was conducted to test the toxicity of synthetic insecticides added to defibrinated sheep blood kept at room temperature and offered as food to the following triatomine species: Triatoma infestans, Panstrongylus megistus, Triatoma vitticeps, Triatoma pseudomaculata, Triatoma brasiliensis and Rhodnius prolixus. The insecticides used, at a concentration of 1 g/l, were: HCH, DDT, Malathion and Trichlorfon, and the lethalithy observed at the end of a 7-day period varied according to the active principle of each. HCH was the most effective by the oral route, killing 100% of the insects, except P. megistus (95.7%) and T. pseudomaculata (94.1%). Trichlorfon killed the insects at rates ranging from 71.8% (T. vitticeps) to 98% (R. prolixus). Malathion was slightly less efficient, killing the insects at rates from 56.8% (T. vitticeps) to 97% (T. brasiliensis). DDT was the least effective, with a killing rate of 10% (T. vitticeps) to 75% (T. brasiliensis). Since the tests were performed at room temperature, we suggest that baits of this type should be tried for the control of triatomines in the field.

Dynamics of evolution and resistance to starvation of Triatoma vitticeps (Stal 1859) (Reduviidae: Triatominae), submitted to two different regimens of food deprivation

“…If their survivors manage to feed at this stage, 50% of them will pass on to the adult phase and will survive long enough to reproduce (10% of the adults can survive up to 160 days). Lima et al (1991) tested experimentally the toxicity of several synthetic insecticides (hexachlorocyclohexane, DDT, triclorfon, malathion, cypermetrin, deltametrin and permetrin). She added them to the food intake of six triatomine species (Panstrongylus megistus, T. infestans, T. pseudomaculata, T. vitticeps, T. brasiliensis and Rhodnius prolixus) and, among all these species, T. vitticeps demonstrated the largest level of resistance to any tested insecticide, except for HCH in concentration of 1 g/l, in spite of the fact that T. vitticeps is not a household species.…”

Laboratory and field studies for the control of Chagas disease vectors using the fungus Metarhizium anisopliae

“…When this study was done, in Brazil, the principal method to reduce triatomine populations infesting human dwellings was with chemical insecticides of prolonged residual action, such as hexachlorocyclohexane (BHC; Coura, 1993; Lima et al, 1991; Marsden, 1984; Silva et al, 1998). According to Marsden (1984), when organochlorines were banned in many developed countries, Brazil imported supplies from South Africa and used 474,000 tons of BHC in 1979.…”

Desenvolvimento de Rhodnius pictipes Stal, 1872 alimentado através de membrana de silicone e em camundongos (Hemiptera, Reduviidae, Triatominae)

“…A alimentação artificial supre as necessidades nutricionais desses insetos, sem os inconvenientes da manutenção de hospedeiros vivos, além de minimizar efeitos de características individuais dos hospedeiros nos estudos de transmissão do Trypanosoma cruzi. Este método foi também utilizado como isca em medidas de controle, conforme demonstrado por Lima et al (1991Lima et al ( , 1992 e Lima (1994); para manutenção de colônias em laboratório (Garcia et al 1975), além da utilização no xenodiagnóstico artificial. Neste último caso torna-se ainda mais indicado, já que podem ocorrer casos de reações alérgicas cutâneas às picadas desses insetos (Mott et al 1980, Costa et al 1981.…”