Performance of pirimiphos-methyl based Indoor Residual Spraying on entomological parameters of malaria transmission in the pyrethroid resistance region of Koulikoro, Mali

Abstract Background:Vector control relies heavily on Long-lasting insecticidal nets ( (LLINs) and Indoor Residual Spraying (IRS) in selected districts in Mali including Koulikoro district. As part of strengthening vector control strategies in the district, IRS was initiated by the National Malaria Control Program (NMCP) with the support of the US President's Malaria Initiative (PMI) since 2008. LLINs coverage was 93.3% and 98.2% for IRS in Koulikoro, the only district of the region where IRS was supported by PMI. Following mosquito vector resistance to both pyrethroid and carbamates, organophosphate (pirimiphos-methyl) was used for the IRS campaigns of 2015 and 2016 in the district of Koulikoro. In this study, we assessed the effect of IRS on malaria transmission by comparing entomological indices in of the district of Koulikoro, where IRS was implemented and its neighbored district of Banamba, where IRS had never been implemented. Methods:The study was conducted in two villages of each district (Koulikoro and Banamba). Pyrethrum spray catches and entry window trapping were used to collect mosquitoes on a monthly basis. WHO tube tests were carried out to assess mosquito susceptibility to insecticides. Mosquitoes were identified to species level by PCR and their infection to P. falciparum was detected by ELISA.Results:Of the 527 specimens identified, An. coluzzii was the most frequent species (95%) followed by An. gambiae (4%) and An. arabiensis (1%). Its density was rainfall dependent in the no-IRS area, and almost independent in the IRS area. The infection rate (IR) in the no-IRS area was 0.96%, while it was null in the IRS area. In the no-IRS area, the entomological inoculation rates (EIR) was 0.21 infective bites /person month with a peak in September. High resistance to pyrethroids and carbamates and susceptibility to organophosphates was observed at all sites.Conclusion:The introduction of pirimiphos-methyl based IRS in the area resulted in a significant decrease in malaria transmission. An.gambiae s.l., the main malaria vector of the area, was resistant to pyrethroids and carbamates, and remained susceptible to the organophosphates.

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Performance of pirimiphos-methyl based Indoor Residual Spraying on entomological parameters of malaria transmission in the pyrethroid resistance region of Koulikoro, Mali.

10.21203/rs.2.21391/v2 ◽

2020 ◽

Author(s):

Moussa KEITA ◽

Nafomon SOGOBA ◽

Boïssé Traoré ◽

Fousseyni Kané ◽

Boubacar Coulibaly ◽

...

Keyword(s):

Malaria Transmission ◽

Malaria Vector ◽

High Resistance ◽

Pyrethroid Resistance ◽

Indoor Residual Spraying ◽

Species Level ◽

Mosquito Vector ◽

Monthly Basis ◽

Pirimiphos Methyl ◽

Entry Window

Abstract Background: Following mosquito vector resistance to both pyrethroid and carbamates, organophosphate (pirimiphos-methyl) was used for the Indoor Residual Spray campaigns performed in 2015 to 2016 in the district of Koulikoro. In this context, we assessed the effect of IRS on malaria transmission by comparing entomological indices in two localities: Koulikoro (LLINs+IRS), and Banamba (LLINs -only) districts. Methods: The study was conducted in two villages of each district (Koulikoro and Banamba). Pyrethrum spray catches and entry window trapping were used to collect mosquitoes on a monthly basis. WHO tube tests were carried out to assess mosquito susceptibility to insecticides. Mosquitoes were identified to species level by PCR and their infection to P. falciparum was detected by ELISA. Results: An. coluzii was the most frequent species. Its density was rainfall dependent in the no-IRS area, and almost independent in the IRS area. The infection rate (IR) in the no-IRS area was 0.96%, while it was null in the IRS area. In the no-IRS area, the entomological inoculation rates (EIR) was 0.21 infective bites /person month with a peak in September. High resistance to pyrethroids and carbamates and susceptibility to organophosphates was observed at all sites. Conclusion: The introduction of pirimiphos-methyl based IRS in the area resulted to a significant decrease in malaria transmission. An.gambiae s.l., the main malaria vector of the area, was resistant to pyrethroids and carbamates, and remained susceptible to the organophosphates.

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The Impact of 3 Years of Targeted Indoor Residual Spraying With Pirimiphos-Methyl on Malaria Parasite Prevalence in a High-Transmission Area of Northern Zambia

American Journal of Epidemiology ◽

10.1093/aje/kwz107 ◽

2019 ◽

Vol 188 (12) ◽

pp. 2120-2130 ◽

Cited By ~ 3

Author(s):

Marisa A Hast ◽

Mike Chaponda ◽

Mbanga Muleba ◽

Jean-Bertin Kabuya ◽

James Lupiya ◽

...

Keyword(s):

Malaria Transmission ◽

Malaria Control ◽

Malaria Parasite ◽

Control Measure ◽

Indoor Residual Spraying ◽

Parasite Prevalence ◽

Organophosphate Insecticide ◽

Malaria Burden ◽

Pirimiphos Methyl ◽

The Impact

Abstract Malaria transmission in northern Zambia has increased in the past decade, despite malaria control activities. Evidence-based intervention strategies are needed to effectively reduce malaria transmission. Zambia’s National Malaria Control Centre conducted targeted indoor residual spraying (IRS) in Nchelenge District, Luapula Province, from 2014 to 2016 using the organophosphate insecticide pirimiphos-methyl. An evaluation of the IRS campaign was conducted by the Southern Africa International Centers of Excellence for Malaria Research using actively detected malaria cases in bimonthly household surveys carried out from April 2012 to July 2017. Changes in malaria parasite prevalence after IRS were assessed by season using Poisson regression models with robust standard errors, controlling for clustering of participants in households and demographic, geographical, and climatological covariates. In targeted areas, parasite prevalence declined approximately 25% during the rainy season following IRS with pirimiphos-methyl but did not decline during the dry season or in the overall study area. Within targeted areas, parasite prevalence declined in unsprayed households, suggesting both direct and indirect effects of IRS. The moderate decrease in parasite prevalence within sprayed areas indicates that IRS with pirimiphos-methyl is an effective malaria control measure, but a more comprehensive package of interventions is needed to effectively reduce the malaria burden in this setting.

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Incremental impact upon malaria transmission of supplementing pyrethroid-impregnated long-lasting insecticidal nets with indoor residual spraying using pyrethroids or the organophosphate, pirimiphos methyl

Malaria Journal ◽

10.1186/s12936-016-1143-7 ◽

2016 ◽

Vol 15 (1) ◽

Cited By ~ 15

Author(s):

Busiku Hamainza ◽

Chadwick H. Sikaala ◽

Hawela B. Moonga ◽

Javan Chanda ◽

Dingani Chinula ◽

...

Keyword(s):

Malaria Transmission ◽

Indoor Residual Spraying ◽

Pirimiphos Methyl ◽

Long Lasting Insecticidal Nets

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The Impact of Three Years of Targeted Indoor Residual Spraying with Pirimiphos-Methyl on Household Vector Abundance in a High Malaria Transmission Area of Northern Zambia

American Journal of Tropical Medicine and Hygiene ◽

10.4269/ajtmh.20-0537 ◽

2020 ◽

Author(s):

Marisa A. Hast ◽

Jennifer C. Stevenson ◽

Mbanga Muleba ◽

Mike Chaponda ◽

Jean-Bertin Kabuya ◽

...

Keyword(s):

Malaria Transmission ◽

Indoor Residual Spraying ◽

Vector Abundance ◽

Transmission Area ◽

Pirimiphos Methyl ◽

The Impact

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Comparative assessment of insecticide resistance phenotypes in two major malaria vectors, Anopheles funestus and Anopheles arabiensis in south-eastern Tanzania

Malaria Journal ◽

10.1186/s12936-020-03483-3 ◽

2020 ◽

Vol 19 (1) ◽

Author(s):

Polius G. Pinda ◽

Claudia Eichenberger ◽

Halfan S. Ngowo ◽

Dickson S. Msaky ◽

Said Abbasi ◽

...

Keyword(s):

Insecticide Resistance ◽

Malaria Transmission ◽

Anopheles Arabiensis ◽

Pyrethroid Resistance ◽

Anopheles Funestus ◽

Indoor Residual Spraying ◽

Sub Saharan Africa ◽

World Health ◽

Malaria Vectors ◽

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, Anopheles arabiensis. This study compared the insecticide resistance phenotypes between the two malaria vectors in an area where pyrethroid-LLINs are widely used. Methods The study used the World Health Organization (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 three villages across two districts in south-eastern Tanzania and included four insecticide classes. Findings At baseline doses (1×), both species were resistant to the two candidate pyrethroids (permethrin and deltamethrin), but susceptible to the organophosphate (pirimiphos-methyl). Anopheles funestus, but not An. arabiensis was also resistant to the carbamate (bendiocarb). Both species were resistant to DDT in all villages except in one village where An. arabiensis was susceptible. Anopheles funestus showed strong resistance to pyrethroids, surviving the 5× and 10× doses, while An. arabiensis reverted to susceptibility at the 5× dose. Pre-exposure to the synergist, piperonyl butoxide (PBO), enhanced the potency of the pyrethroids against both species and resulted in full susceptibility of An. arabiensis (> 98% mortality). However, for An. funestus from two villages, permethrin-associated mortalities after pre-exposure to PBO only exceeded 90% but not 98%. Conclusions In south-eastern Tanzania, where An. funestus dominates malaria transmission, the species also has much stronger resistance to pyrethroids than its counterpart, An. arabiensis, and can survive more classes of insecticides. The pyrethroid resistance in both species appears to be mostly metabolic and may be partially 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 intervention choices for such settings. In short and medium-term, these may include PBO-based LLINs or improved IRS with compounds to which the vectors are still susceptible.

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Comparative assessment of insecticide resistance phenotypes in two major malaria vectors, Anopheles funestus and Anopheles arabiensis in south-eastern Tanzania

10.21203/rs.3.rs-19762/v3 ◽

2020 ◽

Author(s):

Polius Gerazi Pinda ◽

Claudia Eichenberger ◽

Halfan S Ngowo ◽

Dickson S Msaky ◽

Said Abbasi ◽

...

Keyword(s):

Insecticide Resistance ◽

Malaria Transmission ◽

Anopheles Arabiensis ◽

Pyrethroid Resistance ◽

Anopheles Funestus ◽

Indoor Residual Spraying ◽

Sub Saharan Africa ◽

World Health ◽

Malaria Vectors ◽

South Eastern

Abstract BackgroundLong-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, Anopheles arabiensis. This study compared the insecticide resistance phenotypes between the two malaria vectors in an area where pyrethroid-LLINs are widely used.MethodsThe study used the World Health Organization (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 three villages across two districts in south-eastern Tanzania and included four insecticide classes.FindingsAt baseline doses (1×), both species were resistant to the two candidate pyrethroids (permethrin and deltamethrin), but susceptible to the organophosphate (pirimiphos-methyl). Anopheles funestus, but not An. arabiensis was also resistant to the carbamate (bendiocarb). Both species were resistant to DDT in all villages except in one village where An. arabiensis was susceptible. Anopheles funestus showed strong resistance to pyrethroids, surviving the 5× and 10× doses, while An. arabiensis reverted to susceptibility at the 5× dose. Pre-exposure to the synergist, piperonyl butoxide (PBO), enhanced the potency of the pyrethroids against both species and resulted in full susceptibility of An. arabiensis (>98% mortality). However, for An. funestus from two villages, permethrin-associated mortalities after pre-exposure to PBO only exceeded 90% but not 98%.ConclusionsIn south-eastern Tanzania, where An. funestus dominates malaria transmission, the species also has much stronger resistance to pyrethroids than its counterpart, An. arabiensis, and can survive more classes of insecticides. The pyrethroid resistance in both species appears to be mostly metabolic and may be partially 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 intervention choices for such settings. In short and medium-term, these may include PBO-based LLINs or improved IRS with compounds to which the vectors are still susceptible.

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Variation in pyrethroid resistance phenotypes in Anopheles darlingi from residual malaria transmission area: warning on suspected resistance built-up in French Guiana

10.1101/2020.12.21.423491 ◽

2020 ◽

Author(s):

Samuel Vezenegho ◽

Romuald Carinci ◽

Jean Issaly ◽

Christophe Nguyen ◽

Pascal Gaborit ◽

...

Keyword(s):

Malaria Transmission ◽

French Guiana ◽

Target Genes ◽

Pyrethroid Resistance ◽

Indoor Residual Spraying ◽

Anopheles Darlingi ◽

Malaria Endemic Area ◽

Metabolic Resistance ◽

Transmission Area ◽

Residual Malaria Transmission

ABSTRACTAnopheles darlingi is the major vector of malaria in South America. In French Guiana, malaria transmission occurs inland and along the rivers with a particular reemergence in the lower Oyapock area. Control against malaria vector is performed using deltamethrin indoor residual spraying and long lasting impregnated bednets. For four years, the level of resistance to pyrethroids was monitored using CDC bottle tests in An. darlingi populations. Resistance built-up was suspected in a mosquito population in malaria endemic area but did not sustained, supposably due to the reintroduction of susceptible alleles. No mutation on the insecticide target genes was found, metabolic resistance is then suspected.

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Rapid reduction of malaria transmission following the introduction of indoor residual spraying in previously unsprayed districts: an observational analysis of Mopti Region, Mali, in 2017

Malaria Journal ◽

10.1186/s12936-020-03414-2 ◽

2020 ◽

Vol 19 (1) ◽

Author(s):

Joseph Wagman ◽

Idrissa Cissé ◽

Diakalkia Kone ◽

Seydou Fomba ◽

Erin Eckert ◽

...

Keyword(s):

Malaria Transmission ◽

Pyrethroid Resistance ◽

Indoor Residual Spraying ◽

Incidence Rates ◽

Malaria Vectors ◽

Malaria Control Programme ◽

Difference In Differences ◽

Peak Incidence ◽

Significant Difference ◽

The Impact

Abstract Background The National Malaria Control Programme (NMCP) of Mali has had recent success decreasing malaria transmission using 3rd generation indoor residual spraying (IRS) products in areas with pyrethroid resistance, primarily in Ségou and Koulikoro Regions. In 2015, national survey data showed that Mopti Region had the highest under 5-year-old (u5) malaria prevalence at 54%—nearly twice the national average—despite having high access to long-lasting insecticidal nets (LLINs) and seasonal malaria chemoprevention (SMC). Accordingly, in 2016 the NMCP and other stakeholders shifted IRS activities from Ségou to Mopti. Here, the results of a series of observational analyses utilizing routine malaria indicators to evaluate the impact of this switch are presented. Methods A set of retrospective, eco-observational time-series analyses were performed using monthly incidence rates of rapid diagnostic test (RDT)-confirmed malaria cases reported in the District Health Information System 2 (DHIS2) from January 2016 until February 2018. Comparisons of case incidence rates were made between health facility catchments from the same region that differed in IRS status (IRS vs. no-IRS) to describe the general impact of the 2016 and 2017 IRS campaigns, and a difference-in-differences approach comparing changes in incidence from year-to-year was used to describe the effect of suspending IRS operations in Ségou and introducing IRS operations in Mopti in 2017. Results Compared to communities with no IRS, cumulative case incidence rates in IRS communities were reduced 16% in Ségou Region during the 6 months following the 2016 campaign and 31% in Mopti Region during the 6 months following the 2017 campaign, likely averting a total of more than 22,000 cases of malaria that otherwise would have been expected during peak transmission months. Across all comparator health facilities (HFs) where there was no IRS in either year, peak malaria case incidence rates fell by an average of 22% (CI95 18–30%) from 2016 to 2017. At HFs in communities of Mopti where IRS was introduced in 2017, peak incidence fell by an average of 42% (CI95 31–63%) between these years, a significantly greater decrease (p = 0.040) almost double what was seen in the comparator HFCAs. The opposite effect was observed in Ségou Region, where peak incidence at those HFs where IRS was withdrawn after the 2016 campaign increased by an average of 106% (CI95 63–150%) from year to year, also a significant difference-in-differences compared to the comparator no-IRS HFs (p < 0.0001). Conclusion Annual IRS campaigns continue to make dramatic contributions to the seasonal reduction of malaria transmission in communities across central Mali, where IRS campaigns were timed in advance of peak seasonal transmission and utilized a micro-encapsulated product with an active ingredient that was of a different class than the one found on the LLINs used throughout the region and to which local malaria vectors were shown to be susceptible. Strategies to help mitigate the resurgence of malaria cases that can be expected should be prioritized whenever the suspension of IRS activities in a particular region is considered.

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