Diversity of Insecticide Resistance Profiles in Pyrethroid-resistant Triatoma infestans (Hemiptera: Reduviidae) from Argentina and Bolivia.

GERMANO, MÓNICA; VASSENA, CLAUDIA; SANTO ORIHUELA, PABLO; ZERBA, EDUARDO; PICOLLO, MARÍA INÉS

Durban

Congreso; XXIII International Entomological Congress.; 2008

Introduction: Triatoma infestans is the main vector of Chagas Disease in South América. Chemical control by insecticides has been successful for the elimination of domestic infestation and consequently the reduction of vectorial transmission. Recently, high resistance to pyrethroids was reported in northern Argentina and southern Bolivia. Additionally a decrease in the effectiveness of field treatments was found in two Andean areas of Bolivia. In this work we studied the susceptibility profile to non-pyrethroid insecticides in resistant populations from Salta (Argentina) and Yacuiba, Sucre and Mataral (Bolivia)Methods: Toxicity test were done by topical application of insecticides (0,2 µl) on first nymphs (3- 5 days old). Activity of cytochrome P-450 mono-oxygenase was measured in individual first nymphs through ethoxycoumarine-o-deethylase.Results: Resistant ratios (RRs) demonstrated lower deltamethrin resistance for Andean populations (RR Sucre 31.3; RR Mataral 17.4) than Salta (RR 133.1) and Yacuiba (RR 154.4). Moreover, remarkable differences were found in resistance profile to fipronil in Andean and non-andean populations. Sucre and mataral showed very high RRs (585.5 and 386.9 respectively) to fipronil, while Salta and Yacuiba were susceptible to this insecticide. Additional studies demonstrated that all populations were susceptible to the organophosphorus fenithrotion. Activity of mono-oxygenases showed noticeable differences in the distribution of activities between susceptible and resistant populations. The total percentage of insects below 0.48 pmol of 7-OH coumarine/m/I was lower for susceptible strain than for resistant populations (Salta, Yacuiba , Sucre and Mataral).   Conclusions: The differential pattern of susceptibility to insecticides and the relative contribution of mono-oxygenases, suggest an independent evolution of resistance in the studied populations of T.  infestans.