Reduced susceptibility to DDT in field populations of <i>Anopheles quadriannulatus </i>and <i>Anopheles arabiensis </i>in Malawi: evidence for larval selection

Mzilahowa, Themba; Ball, Amanda; Bass, Chris; Morgan, John C.; Nyoni, Benjamin N; Steen, Keith; Donnelly, Martin J.; Wilding, Craig S.

doi:10.1111/j.1365-2915.2008.00736.x

Cited by 21 publications

(24 citation statements)

References 22 publications

(28 reference statements)

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“…Since travel is also associated with malaria illness in this study, it is possible that LLINs were not used during travel, hence decreasing their effectiveness in preventing malaria illness. The lack of effectiveness also raises the possibility that insecticide resistance, which has been well documented in Malawi [30–32], could be contributing. More research on the role of insecticide resistance on LLIN effectiveness in the urban and peri-urban setting will help address this issue.…”

Section: Discussionmentioning

confidence: 99%

Patterns and determinants of malaria risk in urban and peri-urban areas of Blantyre, Malawi

Mathanga

Kapito-Tembo

Mzilahowa

et al. 2016

Malar J

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BackgroundAlthough malaria disease in urban and peri-urban areas of sub-Saharan Africa is a growing concern, the epidemiologic patterns and drivers of transmission in these settings remain poorly understood. Factors associated with variation in malaria risk in urban and peri-urban areas were evaluated in this study.MethodsA health facility-based, age and location-matched, case–control study of children 6–59 months of age was conducted in four urban and two peri-urban health facilities (HF) of Blantyre city, Malawi. Children with fever who sought care from the same HF were tested for malaria parasites by microscopy and PCR. Those testing positive or negative on both were defined as malaria cases or controls, respectively.ResultsA total of 187 cases and 286 controls were studied. In univariate analyses, higher level of education, possession of TV, and electricity in the house were negatively associated with malaria illness; these associations were similar in urban and peri-urban zones. Having travelled in the month before testing was strongly associated with clinical malaria, but only for participants living in the urban zones (OR = 5.1; 95% CI = 1.62, 15.8). Use of long-lasting insecticide nets (LLINs) the previous night was not associated with protection from malaria disease in any setting. In multivariate analyses, electricity in the house, travel within the previous month, and a higher level of education were all associated with decreased odds of malaria disease. Only a limited number of Anopheles mosquitoes were found by aspiration inside the households in the peri-urban areas, and none was collected from the urban households.ConclusionTravel was the main factor influencing the incidence of malaria illness among residents of urban Blantyre compared with peri-urban areas. Identification and understanding of key mobile demographic groups, their behaviours, and the pattern of parasite dispersal is critical to the design of more targeted interventions for the urban setting.Electronic supplementary materialThe online version of this article (doi:10.1186/s12936-016-1623-9) contains supplementary material, which is available to authorized users.

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Section: Discussionmentioning

confidence: 99%

Patterns and determinants of malaria risk in urban and peri-urban areas of Blantyre, Malawi

Mathanga

Kapito-Tembo

Mzilahowa

et al. 2016

Malar J

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“…An earlier study carried out in Chikwawa district showed that An. arabiensis was completely susceptible to both pyrethroids (permethrin and deltamethrin) [30]. While insecticide resistance appears to be increasing, the overall trends are less striking compared to An.…”

Section: Discussionmentioning

confidence: 99%

“…Earlier results obtained from Chikwawa showed moderate resistance to DDT by An. arabiensis populations [30] and it was speculated that there could be selection occurring at larval stage against DDT derivatives that might still be present in the environment.…”

Section: Discussionmentioning

confidence: 99%

Increasing insecticide resistance in Anopheles funestus and Anopheles arabiensis in Malawi, 2011–2015

Mzilahowa

Chiumia

Mbewe

et al. 2016

Malar J

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BackgroundSusceptibility of principal Anopheles malaria vectors to common insecticides was monitored over a 5-year period across Malawi to inform and guide the national malaria control programme.MethodsAdult blood-fed Anopheles spp. and larvae were collected from multiple sites in sixteen districts across the country between 2011 and 2015. First generation (F1) progeny aged 2–5 days old were tested for susceptibility, using standard WHO procedures, against pyrethroids (permethrin and deltamethrin), carbamates (bendiocarb and propoxur), organophosphates (malathion and pirimiphos-methyl) and an organochlorine (DDT).ResultsMortality of Anopheles funestus to deltamethrin, permethrin, bendiocarb and propoxur declined significantly over the 5-year (2011–2015) monitoring period. There was wide variation in susceptibility to DDT but it was not associated with time. In contrast, An. funestus exhibited 100% mortality to the organophosphates (malathion and pirimiphos-methyl) at all sites tested. There was reduced mortality of Anopheles arabiensis to deltamethrin over time though this was not statistically significant. However, mortality of An. arabiensis exposed to permethrin declined significantly over time. Anopheles arabiensis exposed to DDT were more likely to be killed if there was high ITN coverage in the mosquito collection area the previous year. There were no other associations between mosquito mortality in a bioassay and ITN coverage or IRS implementation. Mortality of An. funestus from four sites exposed to deltamethrin alone ranged from 2 to 31% and from 41 to 94% when pre-exposed to the synergist piperonyl butoxide followed by deltamethrin. For permethrin alone, mortality ranged from 2 to 13% while mortality ranged from 63 to 100% when pre-exposed to PBO.ConclusionPyrethroid resistance was detected in An. funestus and An. arabiensis populations across Malawi and has worsened over the last 5 years. New insecticides and control strategies are urgently needed to reduce the burden of malaria in Malawi.Electronic supplementary materialThe online version of this article (doi:10.1186/s12936-016-1610-1) contains supplementary material, which is available to authorized users.

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“…Field testing of the VPMT by ourselves and others has taken place in Malawi and South Africa, and VPMT protocols are now being used routinely to support interventions in Equatorial Guinea and southern Africa and for other studies [37–40]. Feedback from end users has enabled us to develop additional guidelines and advice.…”

Section: Feedback From Field Testingmentioning

confidence: 99%

The Vector Population Monitoring Tool (VPMT): High-Throughput DNA-Based Diagnostics for the Monitoring of Mosquito Vector Populations

Bass

Nikou

Vontas

et al. 2010

Malaria Research and Treatment

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Regular monitoring of mosquito vector populations is an integral component of most vector control programmes. Contemporary data on mosquito species composition, infection status, and resistance to insecticides are a prerequisite for effective intervention. For this purpose we, with funding from the Innovative Vector Control Consortium (IVCC), have developed a suite of high-throughput assays based on a single “closed-tube” platform that collectively comprise the “Vector Population Monitoring Tool” (VPMT). The VPMT can be used to screen mosquito disease vector populations for a number of traits including Anopheles gambiae s.l. and Anopheles funestus species identification, detection of infection with Plasmodium parasites, and identification of insecticide resistance mechanisms. In this paper we focus on the Anopheles-specific assays that comprise the VPMT and include details of a new assay for resistance todieldrin Rdl detection. The application of these tools, general and specific guidelines on their use based on field testing in Africa, and plans for further development are discussed.

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Reduced susceptibility to DDT in field populations of Anopheles quadriannulatus and Anopheles arabiensis in Malawi: evidence for larval selection

Cited by 21 publications

References 22 publications

Patterns and determinants of malaria risk in urban and peri-urban areas of Blantyre, Malawi

Patterns and determinants of malaria risk in urban and peri-urban areas of Blantyre, Malawi

Increasing insecticide resistance in Anopheles funestus and Anopheles arabiensis in Malawi, 2011–2015

The Vector Population Monitoring Tool (VPMT): High-Throughput DNA-Based Diagnostics for the Monitoring of Mosquito Vector Populations

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