Monitoring of insecticide resistance in Aedes aegypti populations in Argentina

GOMEZ ANDREA; ZERBA, EDUARDO; LICASTRO, SUSANA; SECCACINI, EMILIA; ABRI, MARCELO

Panamá

Encuentro; 5th Panam-American Dengue Research Network Meeting; 2016

Aedes aegypti is the principal vector of dengue, chikungunya and zika viruses that are currently circulating simultaneously in different countries of Latin America and the Caribbean. One of the most important aspects in the management of the diseases they cause is the control of its vectors, and within this, chemical control. Due to the chemical pressure exerted by the use of insecticides, some populations of Ae. aegypti have registered resistance to these products, reason why monitoring of this phenomena is a crucial part of an effective entomological control.With the aim of monitoring the appearance of resistance in natural populations of Ae. aegypti in Argentina, Mundo Sano implemented a program in 2014 to evaluate the effect of the larvicide temephos on thepopulation of Ae. aegypti from two argentine cities that have reported cases of dengue in the past and border with the neighboring countries of Bolivia and Paraguay.The evaluation wasperformed through the use of bioassays following the methodology proposed bythe Latin American Network on Vector Control (RELCOV, by its acronym inSpanish) titled ?Protocol for the determination of susceptibility or resistanceto insecticides of mosquitoes of the species Aedes aegypti?.The larvicide evaluated was the organophosphate temephos, active ingredient of the brandAbate® which is used for the public health control of immaturestages of the mosquito in Argentina. The biological material used in the assays were IIIrd  and IVth stage larvae of Ae. aegypti from the two cities, Clorinda(Formosa Province) and Tartagal (Salta Province), and the Rockefeller strain asthe susceptible reference strain. Concentrations of 12, 8 and 4 ppb (2014) and12, 8, 4 and 2 ppb (2015) were evaluated in triplicate alongside a control(ethanol), using a total of 60 larvae per concentration and strain. Themortality was measured 24 hours post exposure. The effective concentrations obtained with temephos for Ae. aegypti Clorinda and Ae. aegypti Tartagal were:LC50 = 22.382ppb and 13.923 ppb, respectively for the year 2014, and LC50 = 36.418 ppb and 7.907 ppb for the year 2015.The evaluated strains presented susceptibility levels below that of the reference strain(Rochefeller); therefore, it is important to continue periodic monitoring of the grade of susceptibility/resistance of these populations to temephos given their importance as vectors of different arboviruses such as dengue, chikungunya and zika. Research funded byMundo Sano.