High insecticide resistance intensity of Anopheles gambiae (s.l.) and low efficacy of pyrethroid LLINs in Accra, Ghana

Abstract

Background Insecticide resistance of Anopheles gambiae ( s.l. ) against public health insecticides is increasingly reported in Ghana and need to be closely monitored. This study investigated the intensity of insecticide resistance of An. gambiae ( s.l. ) found in a vegetable growing area in Accra, Ghana, where insecticides, herbicides and fertilizers are massively used for plant protection. The bioefficacy of long-lasting insecticidal nets (LLINs) currently distributed in the country was also assessed to delimitate the impact of the insecticide resistance intensity on the effectiveness of those nets. Methods Three- to five-day-old adult mosquitoes that emerged from collected larvae from Opeibea, Accra (Ghana), were assayed using CDC bottle and WHO tube intensity assays against different insecticides. The Vgsc-L1014F and ace-1 mutations within the population were also characterized using PCR methods. Furthermore, cone bioassays against different types of LLINs were conducted to evaluate the extent and impact of the resistance of An. gambiae ( s.l. ) from Opeibea. Results Anopheles gambiae ( s.l. ) from Opeibea were resistant to all the insecticides tested with very low mortality observed against organochlorine, carbamates and pyrethroid insecticides using WHO susceptibility tests at diagnostic doses during three consecutive years of monitoring. The average frequencies of Vgsc-1014F and ace-1 in the An. gambiae ( s.l. ) population tested were 0.99 and 0.76, respectively. The intensity assays using both CDC bottle and WHO tubes showed high resistance intensity to pyrethroids and carbamates with survivals at 10× the diagnostic doses of the insecticides tested. Only pirimiphos methyl recorded a low resistance intensity with 100% mortality at 5× the diagnostic dose. The bioefficacy of pyrethroid LLINs ranged from 2.2 to 16.2% mortality while the PBO LLIN, PermaNet ® 3.0, was 73%. Conclusions WHO susceptibility tests using the diagnostic doses described the susceptibility status of the mosquito colony while CDC bottle and WHO tube intensity assays showed varying degrees of resistance intensity. Although both methods are not directly comparable, the indication of the resistance intensity showed the alarming insecticide resistance intensity in Opeibea and its surroundings, which could have an operational impact on the efficacy of vector control tools and particularly on pyrethroid LLINs. Electronic supplementary material The online version of this article (10.1186/s13071-019-3556-y) contains supplementary ...

Anopheles gambiae (s.l.) exhibit high intensity pyrethroid resistance throughout Southern and Central Mali (2016–2018): PBO or next generation LLINs may provide greater control

“…The concept of resistance intensity is relatively new, having first been included in the WHO testing guidelines in 2016 [13]. Nevertheless, high intensity pyrethroid resistance is being reported in an increasing number of locations, including Accra in Ghana [26], Lagos and Ogun in Nigeria [27], western Kenya [28] and south-western Burkina Faso [29]. Despite uncertainty regarding the impact of pyrethroid resistance, the WHO states that "when resistance is confirmed at the 5× and especially at the 10× concentrations, operational failure is likely" [13].…”

Anopheles gambiae (s.l.) exhibit high intensity pyrethroid resistance throughout Southern and Central Mali (2016–2018): PBO or next generation LLINs may provide greater control

“…The concept of resistance intensity is relatively new, having first been included in the WHO testing guidelines in 2016 [13]. Nevertheless, high intensity pyrethroid resistance is being reported in an increasing number of locations, including Accra in Ghana [26], Lagos and Ogun in Nigeria [27], western Kenya [28] and southwestern Burkina Faso [29]. Despite uncertainty regarding the impact of pyrethroid resistance, the WHO states that "when resistance is confirmed at the 5× and especially at the 10× concentrations, operational failure is likely" [13].…”

High level of resistance in Anopheles arabiensis mosquito to pyrethroid insecticides from low malaria transmission zone of Moroto district, Karamoja region, Uganda: Implication for malaria vector control

“…The control programmes are concentrated in high/medium transmission zones while low malaria transmission zones, including Karamoja region have largely been neglected [12,13] Despite extensive LLINs implementation, over the recent years Karamoja experienced signi cant (> 60%) malaria incidences between 2015 to 2017 [11,14] with Moroto district registering 334.5 cases per 1000 children under 5 years [15]. This translates into about 33 % disease prevalence and may be linked to factors such as pyrethroid resistance that might be impeding e cacy of the LLINs [16][17][18] Pyrethroids exert their insecticidal effect on the voltage-gated sodium channel (VGSC) located on the membrane of neurons [19]. When pyrethroids bind an open channel, they block its closure, thus extending the action potential and resulting in the insect's rapid paralysis, a phenomenon known as "knockdown resistance" (kdr) [20].…”