Insecticide Resistance and Its Intensity in Populations of Malaria Vectors in Colombia

Abstract

Insecticide resistance in malaria vectors threatens malaria prevention and control efforts. In Colombia the three primary vectors, Anopheles darlingi, An. nuneztovari s.l., and An. albimanus, have reported insecticide resistance to pyrethroids, organophosphates, carbamates, and DDT; however, the insecticide resistance monitoring is not continuous, and the data on the prevalence of resistance is scarce and geographically limited. We describe the resistance levels and intensity of previously detected resistant populations among primary malaria vectors from the most endemic malaria areas in Colombia. The study was carried out in 10 localities of five states in Colombia. Bioassays were carried out following the methodology of CDC Bottle Bioassay using the discriminating concentration and in order to quantify the intensity the specimens were exposed to 2, 5, and 10X discriminating concentrations. Five insecticides were tested: deltamethrin, lambda-cyhalothrin, alpha-cypermethrin, permethrin, and DDT. The results provide evidence of low resistance intensity and resistance highly localized to pyrethroids and DDT in key malaria vectors in Colombia. This may not pose a threat to malaria control yet but frequent monitoring is needed to follow the evolution of insecticide resistance.

Absence of knockdown mutations in pyrethroid and DDT resistant populations of the main malaria vectors in Colombia

“…nuneztovari s.l. from malaria-endemic areas of Colombia [21]. This suggest that metabolic resistance mechanism reported previously in these species might be responsible for the resistance observed [11, 12].…”

“…albimanus from six localities of Valle del Cauca, Chocó and Norte de Santander Departments were selected (Table 1). The study sites were chosen to encompass a range of primary malaria vector distribution, taking into account rates of malaria incidence, previous results regarding pyrethroids and DDT resistance and biochemical mechanisms, easy access by land or water, safety, and public health priority in terms of resistance monitoring given the history of insecticide use [21]. The main insecticides used in these areas for malaria control are deltamethrin, lambda-cyhalothrin, alphacypermethrin, permethrin and fenitrothion.…”

“…darlingi from Bocas de Pune (Medio Atrato—Chocó), Tagachi (Quibdó-Chocó) and Encharcazón (Rio Iró-Chocó) were resistant to deltamethrin, lambda-cyhalothrin, permethrin and DDT with mortalities ranging between 80 and 97%, and An. nuneztovari from Santa Rosa (El Zulia-Norte de Santander) and Córdoba (Buenaventura-Valle del Cauca) were resistant to deltamethrin and DDT, with mortalities ranging between 94 and 98% [21]. When quantifying the intensity of these resistance, all of these populations were found with low resistance intensity to the pyrethroid insecticides (alpha-cypermethrin, deltamethrin, lambdacyhalothrin, permethrin) and the organochlorine DDT.…”

“…When quantifying the intensity of these resistance, all of these populations were found with low resistance intensity to the pyrethroid insecticides (alpha-cypermethrin, deltamethrin, lambdacyhalothrin, permethrin) and the organochlorine DDT. A detailed description of the sampling sites and the results of the biological tests are provided in a previous paper [21]. Although identifying the presence of kdr mutations in An.…”

“…albimanus , and in the case of An. darlingi also to carbamates [8–12, 20, 21]. Insecticide resistance mechanisms described are: increased metabolism through mixed function oxidases (MFO) and non-specific esterases (NSE) involved in cross-resistance between lambda-cyhalothrin and DDT in An.…”