Analysing deltamethrin susceptibility and pyrethroid esterase activity variations in sylvatic and domestic Triatoma infestans at the embryonic stage

Abstract

The aim of the present work was to study the deltamethrin susceptibility of eggs from Triatoma infestans populations and the contribution of pyrethroid esterases to deltamethrin degradation. Insects were collected from sylvatic areas, including Veinte de Octubre and Kirus-Mayu (Bolivia) and from domiciliary areas, including El Palmar (Bolivia) and La Pista (Argentina). Deltamethrin susceptibility was determined by dose-response bioassays. Serial dilutions of deltamethrin (0.0005-1 mg/mL) were topically applied to 12-day-old eggs. Samples from El Palmar had the highest lethal dose ratio (LDR) value (44.90) compared to the susceptible reference strain (NFS), whereas the Veinte de Octubre samples had the lowest value (0.50). Pyrethroid esterases were evaluated using 7-coumaryl permethrate (7-CP) on individually homogenised eggs from each population and from NFS. The El Palmar and La Pista samples contained 40.11 and 36.64 pmol/min/mg protein, respectively, and these values were statistically similar to NFS (34.92 pmol/min/mg protein) and different from Kirus-Mayu and Veinte de Octubre (27.49 and 22.69 pmol/min/mg protein, respectively). The toxicological data indicate that the domestic populations were resistant to deltamethrin, but no statistical contribution of 7-CP esterases was observed. The sylvatic populations had similar LDR values to NFS, but lower 7-CP esterase activities. Moreover, this is the first study of the pyrethroid esterases on T. infestans eggs employing a specific substrate (7-CP).

Integument CYP genes of the largest genome-wide cytochrome P450 expansions in triatomines participate in detoxification in deltamethrin-resistant Triatoma infestans

“…Regarding the metabolic resistance, the published biochemical studies were not able to explain the high resistance ratio values (100 < RR < 1000) observed in T . infestans populations from the Gran Chaco region, with no relevant differences detected in cytochrome P450, esterase (EST) and glutathione-S-transferase (GST) activities between R and S populations 6 , 25 . We have recently shown that expression induction of some CYP3 -clan genes encoding for such detoxification enzymes was evident in the integument of R nymphs (RR = 100) although appeared to be not enough to support a significant participation in the resistance mechanism 21 .…”

Novel Kdr mutations (K964R and A943V) in pyrethroid‐resistant populations of Triatoma mazzottii and Triatoma longipennis from Mexico and detoxifying enzymes

“…In the case of enzymatic activity, the percentage of individuals from the field populations that exceeded the 99th percentile of the reference strains was determined. Although in triatomines the determination of enzymatic activity and its relation to insecticide resistance has been performed, the studies did not show an established criterion for the determination of a tolerance threshold (Santo‐Orihuela et al ., , ; Santo‐Orihuela & Picollo, ; Germano et al ., ; Klotz et al ., ; Ramsey et al ., ). It was decided to follow the classification based on the criteria of Montella et al .…”

“…The average weight for T. mazzottii was 1.62 ± 0.30 mg and 1.8 ± 0.21 mg for T. longipennis. Although the weight of the individuals was not taken into account to establish the conditions for the bioassays, an adaptation of the technique by Silveira and Pinto (2011), Reyes et al (2007), Roca-Acevedo et al (2015), and Santo-Orihuela et al (2013) was used as a reference. The insecticides deltamethrin and permethrin were used (both with 99.5% purity, ChemService, West Chester, PA, USA).…”

Comparative transcriptome analyses of deltamethrin-susceptible and -resistant Culex pipiens pallens by RNA-seq

“…Metabolic resistance occurs via alterations in either the protein levels or the activity of detoxification enzyme that resist insecticides. For example, cytochrome P450s (CYP or P450) (Edi et al 2014), esterases (EST) (Santo-Orihuela et al 2013) and glutathione S-transferases (GST) (Koou et al 2014) have all been considered to be involved in metabolic resistance. Moreover, pyrethroid insecticides cause the physiological changes of mosquitoes, such as the epidermal thickening, which subsequently reduces the absorption or penetration of insecticides (Wood et al 2010).…”