scholarly journals Reduced Efficacy of Insecticide-treated Nets and Indoor Residual Spraying for Malaria Control in Pyrethroid Resistance Area, Benin

2007 ◽  
Vol 13 (2) ◽  
pp. 199-206 ◽  
Author(s):  
Raphael N’Guessan ◽  
Vincent Corbel ◽  
Martin Akogbéto ◽  
Mark Rowland
Keyword(s):  
Malaria Control ◽  
Pyrethroid Resistance ◽  
Indoor Residual Spraying ◽  
Insecticide Treated Nets

scholarly journals Evidence of pyrethroid resistance in Anopheles amharicus and Anopheles arabiensis from Arjo-Didessa irrigation scheme, Ethiopia

PLoS ONE ◽  
2022 ◽  
Vol 17 (1) ◽  
pp. e0261713
Author(s):  
Assalif Demissew ◽  
Abebe Animut ◽  
Solomon Kibret ◽  
Arega Tsegaye ◽  
Dawit Hawaria ◽  
...  
Keyword(s):  
Malaria Control ◽  
Pyrethroid Resistance ◽  
Management Strategies ◽  
Resistance Management ◽  
Indoor Residual Spraying ◽  
Resistance Mechanisms ◽  
Malaria Vectors ◽  
Insecticide Treated Nets ◽  
Irrigation Area ◽  
Specific Pcr

Background Indoor residual spraying and insecticide-treated nets are among the key malaria control intervention tools. However, their efficacy is declining due to the development and spread of insecticide resistant vectors. In Ethiopia, several studies reported resistance of An. arabiensis to multiple insecticide classes. However, such data is scarce in irrigated areas of the country where insecticides, pesticides and herbicides are intensively used. Susceptibility of An. gambiae s.l. to existing and new insecticides and resistance mechanisms were assessed in Arjo-Didessa sugarcane plantation area, southwestern Ethiopia. Methods Adult An. gambiae s.l. reared from larval/pupal collections of Arjo-Didessa sugarcane irrigation area and its surrounding were tested for their susceptibility to selected insecticides. Randomly selected An. gambiae s.l. (dead and survived) samples were identified to species using species-specific polymerase chain reaction (PCR) and were further analyzed for the presence of knockdown resistance (kdr) alleles using allele-specific PCR. Results Among the 214 An. gambiae s.l. samples analyzed by PCR, 89% (n = 190) were An. amharicus and 9% (n = 20) were An. arabiensis. Mortality rates of the An. gambiae s.l. exposed to deltamethrin and alphacypermethrin were 85% and 86.8%, respectively. On the other hand, mortalities against pirmiphos-methyl, bendiocarb, propoxur and clothianidin were 100%, 99%, 100% and 100%, respectively. Of those sub-samples (An. amharicus and An. arabiensis) examined for presence of kdr gene, none of them were found to carry the L1014F (West African) allelic mutation. Conclusion Anopheles amharicus and An. arabiensis from Arjo-Didessa sugarcane irrigation area were resistant to pyrethroids which might be synergized by extensive use of agricultural chemicals. Occurrence of pyrethroid resistant malaria vectors could challenge the ongoing malaria control and elimination program in the area unless resistance management strategies are implemented. Given the resistance of An. amharicus to pyrethroids, its behavior and vectorial capacity should be further investigated.

Intensity of pyrethroid resistance in An. gambiaes.l.before and after a mass distribution of insecticide treated nets in Kinshasa and from 11 provinces of the Democratic Republic of Congo

2020 ◽  
Author(s):  
Francis Wat’senga ◽  
Fiacre Agossa ◽  
Emile Z. Manzambi ◽  
Gillon Illombe ◽  
Tania Mapangulu ◽  
...  
Keyword(s):  
Mass Distribution ◽  
Malaria Control ◽  
Democratic Republic ◽  
Democratic Republic Of Congo ◽  
Pyrethroid Resistance ◽  
Common Species ◽  
Insecticide Treated Nets ◽  
Republic Of Congo ◽  
Diagnostic Dose ◽  
Llin Distribution

Abstract BackgroundBetween 2011 and 2018, an estimated 134.8 million pyrethroid-treatedlong-lasting insecticidal nets (LLINs) were distributed nationwide in the Democratic Republic of Congo (DRC) for malaria control. Pyrethroid resistance has developed in DRC in recent years, but the intensity ofresistance and impact on LLIN efficacy was not known. Therefore, the intensity of resistance of Anopheles gambiae s.l. to permethrin and deltamethrin was monitored before and after a mass distribution of LLINs in Kinshasa in December 2016, and in 7sites across the country in 2017 and 11 sites in 2018.Materials and MethodsIn Kinshasa, CDC bottle bioassays using 1, 2, 5, and 10 times the diagnostic dose of permethrin and deltamethrin were conducted using An. gambiae s.l. collected as larvae and reared to adults. Bioassays were conducted in four sites in Kinshasa province six months before a mass distribution of deltamethrin-treated ITNs and then two, six, and ten months after the distribution. One site in neighboring Kongo Central province was used as a control (no mass campaign of ITN distribution during the study). Nationwide intensity assays were conducted in six sites in 2017 using CDC bottle bioassays and in 11 sites in 2018 using WHO intensity assays. A sub-sample of An. gambiae s.l. were tested by PCR to determine species composition and frequency of kdr-1014F and 1014S alleles. ResultsIn June 2016, before LLIN distribution, permethrin resistance intensity was high in Kinshasa; the mean mortality rate was 43% at the 5× concentration and 73% at the 10× concentration. Bioassays at 3 time points after LLIN distribution showed considerable variation by site and time and there was no consistent evidence for an increase in pyrethroid resistance intensity compared to the neighboring control site. Tests of An. gambiaes.l. in 7 sites across the country in 2017 and 11 sites in 2018 showed all populations were resistant to the diagnostic doses of 3 pyrethroids.In 2018, the intensity of resistance varied by site, but was generally moderate for all three pyrethroids, with survivors at ×5 the diagnostic dose. An. gambiae s.s. was the most common species identified across 11 sites in DRC. However in Kinshasa, An. gambiae s.s.(91%) and An. coluzzii (8%) were sympatric.ConclusionsModerate or high intensity pyrethroid resistance was detected nationwide in DRC and is a serious threat to sustained malaria control with pyrethroid LLINs. Next generation nets (PBO nets or bi-treated nets) should be considered for mass distribution.

scholarly journals PREVENTION AND TREATMENT PRACTICES AND IMPLICATIONS FOR MALARIA CONTROL IN MUKONO DISTRICT UGANDA

2008 ◽  
Vol 40 (2) ◽  
pp. 283-296 ◽  
Author(s):  
A. K. MBONYE ◽  
I. C. BYGBJERG ◽  
P. MAGNUSSEN
Keyword(s):  
Malaria Control ◽  
Indoor Residual Spraying ◽  
Scaling Up ◽  
Malaria Treatment ◽  
Current Debate ◽  
Policy Debate ◽  
Insecticide Treated Nets ◽  
Cross Sectional Survey ◽  
Cross Sectional ◽  
Mukono District

SummaryAvailable data in Uganda indicate a resurgence of malaria morbidity and mortality countrywide. This study assessed the burden of malaria, treatment and prevention practices in order initiate a policy debate on the scaling-up of current interventions. A triangulation of methods using a cross-sectional survey and key informant interviews was used to assess self-reported malaria at a household level in Mukono District, Uganda. A total of 5583 households were surveyed, and a high proportion (2897, 51·9%) reported a person with malaria two weeks prior to the survey. Only 546 households (9·8%) owned and used insecticide-treated nets (ITNs) for malaria prevention. Similarly, only a few households (86, 1·5%) used indoor residual spraying. Self-treatment with home-stocked drugs was high, yet there was low awareness of the effectiveness of expired drugs on malaria treatment. Self-reported malaria was associated with socioeconomic, behavioural and environmental factors, but more especially with household ownership of ITNs. These results will contribute to the current debate on identifying new approaches for scaling-up prevention interventions and effective case management, as well as selection of priority interventions for malaria control in Uganda.

scholarly journals Anopheles funestus mosquitoes from rural south-eastern Tanzania may have stronger resistance to pyrethroids than the other malaria vector, Anopheles arabiensis

2020 ◽  
Author(s):  
Polius Gerazi Pinda ◽  
Claudia Eichenberger ◽  
Halfan S Ngowo ◽  
Dickson S Msaky ◽  
Said Abbasi ◽  
...  
Keyword(s):  
Malaria Transmission ◽  
Anopheles Arabiensis ◽  
Pyrethroid Resistance ◽  
Anopheles Funestus ◽  
Indoor Residual Spraying ◽  
The Other ◽  
Sub Saharan Africa ◽  
Malaria Vectors ◽  
Insecticide Treated Nets ◽  
South Eastern

Abstract Background: Long-lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS) have greatly reduced malaria transmission in sub-Saharan Africa, but are threatened by insecticide resistance. In south-eastern Tanzania, pyrethroid-resistant Anopheles funestus are now implicated in > 80% of malaria infections, even in villages where the species occurs at lower densities than the other vector species, Anopheles arabiensis. This study compared the intensities of resistance between the two malaria vectors, so as to improve options for control. Methods: The study used WHO assays with 1×, 5× and 10× insecticide doses to assess levels of resistance, followed by synergist bioassays to understand possible mechanisms of the observed resistance phenotypes. The tests involved adult mosquitoes collected from villages across two districts in south-eastern Tanzania and identified using morphological and molecular approaches.Findings: At baseline doses (1×), both species were resistant to the two pyrethroids (permethrin and deltamethrin) but susceptible to the organophosphate (pirimiphos-methyl). An. funestus, but not An. arabiensis was also resistant to the carbamate (bendiocarb) at baseline doses. Both species were generally resistant to DDT, except An.arabiensis from one village. An. funestus showed strong resistance to pyrethroids, surviving the 5× and 10× doses except in one village. Pre-exposure to the synergist, piperonyl butoxide (PBO), enhanced the potency of pyrethroid in both An. arabiensis and An. funestus achieving mortalities >98%, except for An. funestus from two villages for which permethrin-associated mortalities exceeded 90% but not 98%. Conclusions: In these communities where An. funestus dominates malaria transmission, this study may suggest that the species also have much stronger resistance to pyrethroids than its counterpart, An. arabiensis and can survive more classes of insecticides, including carbamates. The pyrethroid resistance in both species appears to be mostly metabolic and may be temporarily addressed using synergists, e.g. PBO. These findings may explain the continued persistence and dominance of An. funestus despite widespread use of pyrethroid-treated LLINs, and inform new choices of interventions to tackle malaria transmission in such settings. These may include PBO-based LLINs or improved IRS with compounds to which the vectors are susceptible. Additional field validation of these indications will be necessary using age-synchronized mosquitoes.

scholarly journals Rapid selection of a pyrethroid metabolic enzyme CYP9K1 by operational malaria control activities

2018 ◽  
Vol 115 (18) ◽  
pp. 4619-4624 ◽  
Author(s):  
John Vontas ◽  
Linda Grigoraki ◽  
John Morgan ◽  
Dimitra Tsakireli ◽  
Godwin Fuseini ◽  
...  
Keyword(s):  
Malaria Control ◽  
Pyrethroid Resistance ◽  
Resistance Mechanism ◽  
Indoor Residual Spraying ◽  
Control Program ◽  
Parasite Prevalence ◽  
Metabolic Enzyme ◽  
Anopheles Coluzzii ◽  
Bioko Island ◽  
Malaria Control Program

Since 2004, indoor residual spraying (IRS) and long-lasting insecticide-impregnated bednets (LLINs) have reduced the malaria parasite prevalence in children on Bioko Island, Equatorial Guinea, from 45% to 12%. After target site-based (knockdown resistance; kdr) pyrethroid resistance was detected in 2004 in Anopheles coluzzii (formerly known as the M form of the Anopheles gambiae complex), the carbamate bendiocarb was introduced. Subsequent analysis showed that kdr alone was not operationally significant, so pyrethroid-based IRS was successfully reintroduced in 2012. In 2007 and 2014–2015, mass distribution of new pyrethroid LLINs was undertaken to increase the net coverage levels. The combined selection pressure of IRS and LLINs resulted in an increase in the frequency of pyrethroid resistance in 2015. In addition to a significant increase in kdr frequency, an additional metabolic pyrethroid resistance mechanism had been selected. Increased metabolism of the pyrethroid deltamethrin was linked with up-regulation of the cytochrome P450 CYP9K1. The increase in resistance prompted a reversion to bendiocarb IRS in 2016 to avoid a resurgence of malaria, in line with the national Malaria Control Program plan.

scholarly journals A deltamethrin crystal polymorph for more effective malaria control

2020 ◽  
Vol 117 (43) ◽  
pp. 26633-26638
Author(s):  
Jingxiang Yang ◽  
Bryan Erriah ◽  
Chunhua T. Hu ◽  
Ethan Reiter ◽  
Xiaolong Zhu ◽  
...  
Keyword(s):  
Malaria Control ◽  
Low Income ◽  
Pyrethroid Resistance ◽  
Indoor Residual Spraying ◽  
Low Income Countries ◽  
Inexpensive Method ◽  
Epidemiological Modeling ◽  
Simple Preparation ◽  
The Face ◽  
Public Health Challenge

Pyrethroid contact insecticides are mainstays of malaria control, but their efficacies are declining due to widespread insecticide resistance in Anopheles mosquito populations, a major public health challenge. Several strategies have been proposed to overcome this challenge, including insecticides with new modes of action. New insecticides, however, can be expensive to implement in low-income countries. Here, we report a simple and inexpensive method to improve the efficacy of deltamethrin, the most active and most commonly used pyrethroid, by more than 10 times against Anopheles mosquitoes. Upon heating for only a few minutes, the commercially available deltamethrin crystals, form I, melt and crystallize upon cooling into a polymorph, form II, which is much faster acting against fruit flies and mosquitoes. Epidemiological modeling suggests that the use of form II in indoor residual spraying in place of form I would significantly suppress malaria transmission, even in the presence of high levels of resistance. The simple preparation of form II, coupled with its kinetic stability and markedly higher efficacy, argues that form II can provide a powerful, timely, and affordable malaria control solution for low-income countries that are losing protection in the face of worldwide pyrethroid resistance.

scholarly journals The dominant malaria vector, Anopheles funestus from rural south-eastern Tanzania, is more strongly resistant to insecticides than Anopheles arabiensis

2020 ◽  
Author(s):  
Polius Gerazi Pinda ◽  
Claudia Eichenberger ◽  
Halfan S Ngowo ◽  
Dickson S Msaky ◽  
Said Abbasi ◽  
...  
Keyword(s):  
Malaria Transmission ◽  
Pyrethroid Resistance ◽  
Mosquito Species ◽  
Anopheles Funestus ◽  
Indoor Residual Spraying ◽  
Sub Saharan Africa ◽  
Malaria Vectors ◽  
Insecticide Treated Nets ◽  
South Eastern ◽  
Sub Saharan

Abstract Background: Long-lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS) have greatly reduced malaria transmission in sub-Saharan Africa, but are threatened by insecticide resistance in dominant malaria vectors. In south-eastern Tanzania, pyrethroid-resistant Anopheles funestus now transmit more than 80% of malaria infections even in villages where the species occurs at far lower densities than other vectors such as Anopheles arabiensis.Methods: To better understand the dominance of An. funestus in these settings and improve options for its control, this study compared intensities of resistance between females of this species and those of An. arabiensis , using WHO assays with 1×, 5× and 10× insecticide doses. Additional tests were done to assess the reversibility of such resistance using synergists. The mosquitoes were collected from villages across two districts in south-eastern Tanzania.Findings: Both species were resistant to the two pyrethroids (permethrin and deltamethrin) and the organochloride (DDT) but susceptible to the organophosphate (pirimiphos-methyl) at standard baseline doses (1×). However, An. funestus as opposed to An. arabiensis was also resistant to the carbamate (bendiocarb) at standard doses (1×). An. funestus showed strong resistance to pyrethroids, surviving the 5× doses and 10× doses except in one village. Pre-exposure to the synergist, piperonyl butoxide (PBO), reversed the pyrethroid-resistance in both An. arabiensis and An. funestus achieving mortalities >98%, except for An. funestus from two villages for which permethrin-associated mortalities exceeded 90% but not 98%.Conclusions : In these communities where An. funestus now dominates malaria transmission, the species also displays much stronger resistance to pyrethroids than its counterpart, An. arabiensis, and can readily survive more classes of insecticides, including carbamates. The resistance to pyrethroids in both mosquito species appears to be mostly metabolic and can be reversed significantly using synergists such as PBO. These findings may explain the continued persistence and dominance of An. funestus despite widespread use of pyrethroid-treated LLINs, and will also inform future choices of interventions to tackle malaria transmission in this area and other similar settings. Such interventions may include PBO-based LLINs or improved IRS with compounds such as organophosphates against which the vectors are still susceptible.

scholarly journals The role of vector control in stopping the transmission of malaria: threats and opportunities

2014 ◽  
Vol 369 (1645) ◽  
pp. 20130431 ◽  
Author(s):  
Janet Hemingway
Keyword(s):  
Public Health ◽  
Vector Control ◽  
Malaria Control ◽  
Pyrethroid Resistance ◽  
Indoor Residual Spraying ◽  
Resistance Mechanisms ◽  
New Public Health ◽  
New Public ◽  
Product Profile

Malaria control, and that of other insect borne diseases such as dengue, is heavily dependent on our ability to control the mosquito populations that transmit these diseases. The major push over the last decade to reduce the global burden of malaria has been driven by the distribution of pyrethroid insecticide-treated bednets and an increase in coverage of indoor residual spraying (IRS). This has reduced malaria deaths by a third. Progress towards the goal of reducing this further is threatened by lack of funding and the selection of drug and insecticide resistance. When malaria control was initially scaled up, there was little pyrethroid resistance in the major vectors, today there is no country in Africa where the vectors remain fully susceptible to pyrethroids. The first pyrethroid resistance mechanisms to be selected produced low-level resistance which had little or no operational significance. More recently, metabolically based resistance has been selected, primarily in West Africa, which in some mosquito populations produces more than 1000-fold resistance. As this spreads the effectiveness of pyrethroid-based bednets and IRS will be compromised. New public health insecticides are not readily available. The pipeline of agrochemical insecticides that can be re-purposed for public health dried up 30 years ago when the target product profile for agricultural insecticides shifted from broad spectrum, stable, contact-acting insecticides to narrow spectrum stomach poisons that could be delivered through the plant. A public–private partnership, the Innovative Vector Control Consortium, was established in 2005 to stimulate the development of new public health pesticides. Nine potential new classes of chemistry are in the pipeline, with the intention of developing three into new insecticides. While this has been successfully achieved, it will still take 6–9 years for new insecticides to reach the market. Careful management of the resistance situation in the interim will be needed if current gains in malaria control are not to be reversed.

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