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

Abstract

BackgroundKnockdown resistance (kdr) is a well-characterized target-site insecticide resistance mechanism that is associated with DDT and pyrethroid resistance. Even though insecticide resistance to pyrethroids and DDT have been reported in Anopheles albimanus, Anopheles benarrochi sensu lato (s.l.), Anopheles darlingi, Anopheles nuneztovari s.l., and Anopheles pseudopunctipennis s.l. malaria vectors in Latin America, there is a knowledge gap on the role that kdr resistance mechanisms play in this resistance. The aim of this study was to establish the role that kdr mechanisms play in pyrethroid and DDT resistance in the main malaria vectors in Colombia, in addition to previously reported metabolic resistance mechanisms, such as mixed function oxidases (MFO) and nonspecific esterases (NSE) enzyme families.MethodsSurviving (n = 62) and dead (n = 67) An. nuneztovari s.l., An. darlingi and An. albimanus mosquitoes exposed to diagnostic concentrations of DDT and pyrethroid insecticides were used to amplify and sequence a ~ 225 bp fragment of the voltage-gated sodium channels (VGSC) gene. This fragment spanning codons 1010, 1013 and 1014 at the S6 segment of domain II to identify point mutations, which have been associated with insecticide resistance in different species of Anopheles malaria vectors.ResultsNo kdr mutations were detected in the coding sequence of this fragment in 129 samples, 62 surviving mosquitoes and 67 dead mosquitoes, of An. darlingi, An. nuneztovari s.l. and An. albimanus.ConclusionMutations in the VGSC gene, most frequently reported in other species of the genus Anopheles resistant to pyrethroid and DDT, are not associated with the low-intensity resistance detected to these insecticides in some populations of the main malaria vectors in Colombia. These results suggest that metabolic resistance mechanisms previously reported in these populations might be responsible for the resistance observed.

Evaluation of acaricidal resistance status of Rhipicephalus microplus ticks from the hilly state (Uttarakhand) of India and evaluation of efficacy of a natural formulation for the management of resistant ticks

“…Interestingly, in all five sequences of UTK, the C190A mutation was not detected even though the RR 50 against deltamethrin was 19.42. The results are in accordance with a similar study conducted by Orjuela et al (2019), where absence of kdr mutation was observed in pyrethroid resistant Anopheles spp. mosquitoes hypothesizing the role of another mechanism such as the involvement of detoxifying enzymes in the development of resistance.…”

Ecology, evolution, and epidemiology of zoonotic and vector-borne infectious diseases in French Guiana: Transdisciplinarity does matter to tackle new emerging threats

“…An. darlingi has rarely developed resistance across its spatial distribution and is still mostly susceptible, except in Columbia where it harbors metabolic resistance to pyrethroid and organochlorate insecticide families (Fonseca-González et al, 2009;Orjuela et al, 2018Orjuela et al, , 2019. The constant renewal of susceptible genes from sylvatic populations is suspected to prevent resistance built-up (Epelboin et al, 2018).…”

Variation in Pyrethroid Resistance Phenotypes in Anopheles darlingi in an Area with Residual Malaria Transmission: Warning of Suspected Resistance in French Guiana

“…No mutation on the vgsc fragment was detected. The sequences obtained showed 100% identity with amino acid sequences already published 15 (GenBank accession number MN053065). The observations described here, made over multiple years, raise the concern of insecticide resistance development in An.…”

“…Both strands of 170 base pairs fragment of the vgsc was sequenced as described in Orjuela (2019). 15 The codons 1010, 1013, and 1014 at the S6 segment of domain II is used to identify point mutations, which have been associated with insecticide resistance in different species of Anopheles malaria vectors. No mutation on the vgsc fragment was detected.…”