scholarly journals Evaluating the efficacy, impact, and feasibility of community-based house screening as a complementary malaria control intervention in southern Africa: a study protocol for a household randomized trial

Trials ◽  
2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Onyango P. Sangoro ◽  
Ulrike Fillinger ◽  
Kochelani Saili ◽  
Theresia Estomih Nkya ◽  
Rose Marubu ◽  
...  
Keyword(s):  
Vector Control ◽  
Malaria Transmission ◽  
Malaria Control ◽  
Indoor Residual Spraying ◽  
Clinical Malaria ◽  
Sub Saharan Africa ◽  
Substantial Impact ◽  
Transmission Season ◽  
Link Type ◽  
The Impact

Abstract Background Concerted effort to control malaria has had a substantial impact on the transmission of the disease in the past two decades. In areas where reduced malaria transmission is being sustained through insecticide-based vector control interventions, primarily long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS), non-insecticidal complementary tools will likely be needed to push towards malaria elimination. Once interruption in local disease transmission is achieved, insecticide-based measures can be scaled down gradually and eventually phased out, saving on costs of sustaining control programs and mitigating any unintended negative health and environmental impacts posed by insecticides. These non-insecticidal methods could eventually replace insecticidal methods of vector control. House screening, a non-insecticidal method, has a long history in malaria control, but is still not widely adopted in sub-Saharan Africa. This study aims to add to the evidence base for this intervention in low transmission settings by assessing the efficacy, impact, and feasibility of house screening in areas where LLINs are conventionally used for malaria control. Methods A two-armed, household randomized clinical trial will be conducted in Mozambique, Zambia, and Zimbabwe to evaluate whether combined the use of house screens and LLINs affords better protection against clinical malaria in children between 6 months and 13 years compared to the sole use of LLINs. Eight hundred households will be enrolled in each study area, where 400 households will be randomly assigned the intervention, house screening, and LLINs while the control households will be provided with LLINs only. Clinical malaria incidence will be estimated by actively following up one child from each household for 6 months over the malaria transmission season. Cross-sectional parasite prevalence will be estimated by testing all participating children for malaria parasites at the beginning and end of each transmission season using rapid diagnostic tests. CDC light traps and pyrethrum spray catches (PSC) will be used to sample adult mosquitoes and evaluate the impact of house screening on indoor mosquito density, species distribution, and sporozoite rates. Discussion This study will contribute epidemiological data on the impact of house screening on malaria transmission and assess the feasibility of its implementation on a programmatic scale. Trial registration ClinicalTrials.gov PACTR202008524310568. Registered on August 11, 2020.

scholarly journals Evaluating the Efficacy, Impact and Feasibility of Community-based House Screening as a Complementary Malaria Control Intervention in Southern Africa: a Study Protocol for a Household Randomized Trial.

2021 ◽  
Author(s):  
Peter Onyango Sangoro ◽  
Ulrike Fillinger ◽  
Kochelani Saili ◽  
Theresia Estomih Nkya ◽  
Rose Marubu ◽  
...  
Keyword(s):  
Vector Control ◽  
Malaria Transmission ◽  
Malaria Control ◽  
Malaria Incidence ◽  
Indoor Residual Spraying ◽  
Clinical Malaria ◽  
Sub Saharan Africa ◽  
Substantial Impact ◽  
Transmission Season ◽  
The Impact

Abstract Background: Concerted effort to control malaria has had a substantial impact on transmission of the disease in the past two decades. In areas where reduced malaria transmission is being sustained through insecticide-based vector control interventions, primarily long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS), non-insecticidal complementary tools will likely be needed to push towards malaria elimination. Once interruption in local disease transmission is achieved, insecticide-based measures can be scaled down gradually and eventually phased out, saving on costs of sustaining control programmes and mitigating any unintended negative health and environmental impacts posed by insecticides. These non-insecticidal methods could eventually replace insecticidal methods of vector control. House screening, a non-insecticidal method, has a long history in malaria control, but is still not widely adopted in sub-Saharan Africa. This study aims to add to the evidence-base for this intervention in low transmission settings by assessing the efficacy, impact and feasibility of house screening in areas where LLINs are conventionally used for malaria control. Methods: A two-armed, household randomized clinical trial will be conducted in Mozambique, Zambia and Zimbabwe to evaluate whether combined use of house screens and LLINs affords better protection against clinical malaria in children between 6 months and 13 years compared to the sole use of LLINs. Eight hundred households will be enrolled in each study area, where 400 households will be randomly assigned the intervention, house screening and LLINs while the control households will be provided with LLINs only. Clinical malaria incidence will be estimated by actively following up one child from each household for 6 months over the malaria transmission season. Cross-sectional parasite prevalence will be estimated by testing all participating children for malaria parasites at the beginning and end of each transmission season using rapid diagnostic tests.CDC light traps and pyrethrum spray catches (PSC) will be used to sample adult mosquitoes and evaluate the impact of house screening on indoor mosquito density, species distribution and sporozoite rates.Discussion: This study will contribute epidemiological data on the impact of house screening on malaria transmission and assess the feasibility of its implementation on a programmatic scale. Trial registration: This trial was retrospectively registered on 11th August 2020. Registration number PACTR202008524310568.

scholarly journals Design and methods for a quasi-experimental pilot study to evaluate the impact of dual active ingredient insecticide-treated nets on malaria burden in five regions in sub-Saharan Africa

2022 ◽  
Vol 21 (1) ◽  
Author(s):  
Adama Gansané ◽  
Baltazar Candrinho ◽  
Aimable Mbituyumuremyi ◽  
Perpetua Uhomoibhi ◽  
Sagnon NFalé ◽  
...  
Keyword(s):  
Cost Effectiveness ◽  
Malaria Transmission ◽  
Malaria Control ◽  
Active Ingredient ◽  
Indoor Residual Spraying ◽  
Sub Saharan Africa ◽  
Bed Nets ◽  
Pilot Studies ◽  
Malaria Burden ◽  
The Impact

Abstract Background Vector control tools have contributed significantly to a reduction in malaria burden since 2000, primarily through insecticidal-treated bed nets (ITNs) and indoor residual spraying. In the face of increasing insecticide resistance in key malaria vector species, global progress in malaria control has stalled. Innovative tools, such as dual active ingredient (dual-AI) ITNs that are effective at killing insecticide-resistant mosquitoes have recently been introduced. However, large-scale uptake has been slow for several reasons, including higher costs and limited evidence on their incremental effectiveness and cost-effectiveness. The present report describes the design of several observational studies aimed to determine the effectiveness and cost-effectiveness of dual-AI ITNs, compared to standard pyrethroid-only ITNs, at reducing malaria transmission across a variety of transmission settings. Methods Observational pilot studies are ongoing in Burkina Faso, Mozambique, Nigeria, and Rwanda, leveraging dual-AI ITN rollouts nested within the 2019 and 2020 mass distribution campaigns in each country. Enhanced surveillance occurring in select study districts include annual cross-sectional surveys during peak transmission seasons, monthly entomological surveillance, passive case detection using routine health facility surveillance systems, and studies on human behaviour and ITN use patterns. Data will compare changes in malaria transmission and disease burden in districts receiving dual-AI ITNs to similar districts receiving standard pyrethroid-only ITNs over three years. The costs of net distribution will be calculated using the provider perspective including financial and economic costs, and a cost-effectiveness analysis will assess incremental cost-effectiveness ratios for Interceptor® G2, Royal Guard®, and piperonyl butoxide ITNs in comparison to standard pyrethroid-only ITNs, based on incidence rate ratios calculated from routine data. Conclusions Evidence of the effectiveness and cost-effectiveness of the dual-AI ITNs from these pilot studies will complement evidence from two contemporary cluster randomized control trials, one in Benin and one in Tanzania, to provide key information to malaria control programmes, policymakers, and donors to help guide decision-making and planning for local malaria control and elimination strategies. Understanding the breadth of contexts where these dual-AI ITNs are most effective and collecting robust information on factors influencing comparative effectiveness could improve uptake and availability and help maximize their impact.

scholarly journals Impact of seasonality and malaria control interventions on Anopheles density and species composition from three areas of Uganda with differing malaria endemicity

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Henry Ddumba Mawejje ◽  
Maxwell Kilama ◽  
Simon P. Kigozi ◽  
Alex K. Musiime ◽  
Moses Kamya ◽  
...  
Keyword(s):  
Species Composition ◽  
Vector Control ◽  
Malaria Control ◽  
Mosquito Species ◽  
Density Ratio ◽  
Indoor Residual Spraying ◽  
Sub Saharan Africa ◽  
Malaria Vector Control ◽  
Vector Density ◽  
Llin Distribution

Abstract Background Long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) are the malaria control interventions primarily responsible for reductions in transmission intensity across sub-Saharan Africa. These interventions, however, may have differential impact on Anopheles species composition and density. This study examined the changing pattern of Anopheles species in three areas of Uganda with markedly different transmission intensities and different levels of vector control. Methods From October 2011 to June 2016 mosquitoes were collected monthly using CDC light traps from 100 randomly selected households in three areas: Walukuba (low transmission), Kihihi (moderate transmission) and Nagongera (high transmission). LLINs were distributed in November 2013 in Walukuba and Nagongera and in June 2014 in Kihihi. IRS was implemented only in Nagongera, with three rounds of bendiocarb delivered between December 2014 and June 2015. Mosquito species were identified morphologically and by PCR (Polymerase Chain Reaction). Results In Walukuba, LLIN distribution was associated with a decline in Anopheles funestus vector density (0.07 vs 0.02 mosquitoes per house per night, density ratio [DR] 0.34, 95% CI: 0.18–0.65, p = 0.001), but not Anopheles gambiae sensu stricto (s.s.) nor Anopheles arabiensis. In Kihihi, over 98% of mosquitoes were An. gambiae s.s. and LLIN distribution was associated with a decline in An. gambiae s.s. vector density (4.00 vs 2.46, DR 0.68, 95% CI: 0.49–0.94, p = 0.02). In Nagongera, the combination of LLINs and multiple rounds of IRS was associated with almost complete elimination of An. gambiae s.s. (28.0 vs 0.17, DR 0.004, 95% CI: 0.002–0.009, p < 0.001), and An. funestus sensu lato (s.l.) (3.90 vs 0.006, DR 0.001, 95% CI: 0.0005–0.004, p < 0.001), with a less pronounced decline in An. arabiensis (9.18 vs 2.00, DR 0.15 95% CI: 0.07–0.33, p < 0.001). Conclusions LLIN distribution was associated with reductions in An. funestus s.l. in the lowest transmission site and An. gambiae s.s. in the moderate transmission site. In the highest transmission site, a combination of LLINs and multiple rounds of IRS was associated with the near collapse of An. gambiae s.s. and An. funestus s.l. Following IRS, An. arabiensis, a behaviourally resilient vector, became the predominant species, which may have implications for malaria vector control activities. Development of interventions targeted at outdoor biting remains a priority.

scholarly journals Risk of Plasmodium falciparum infection in south-west Burkina Faso - potential impact of expanding eligibility for seasonal malaria chemoprevention

2021 ◽  
Author(s):  
Anne L Wilson ◽  
Steve W Lindsay ◽  
Alfred Tiono ◽  
Jean Baptiste Yaro ◽  
Hilary Ranson ◽  
...  
Keyword(s):  
Risk Factors ◽  
Plasmodium Falciparum ◽  
Burkina Faso ◽  
Malaria Transmission ◽  
Malaria Control ◽  
Control Measures ◽  
Sub Saharan Africa ◽  
South West ◽  
Seasonal Malaria Chemoprevention ◽  
The Impact

Abstract Background Burkina Faso has one of the highest malaria burdens in sub-Saharan Africa despite the mass deployment of insecticide-treated nets (ITNs) and use of seasonal malaria chemoprevention (SMC) in children aged up to 5 years. Identification of risk factors for Plasmodium falciparum infection in rural Burkina Faso could help to identify and target malaria control measures. Methods A cross-sectional survey of 1,199 children and adults was conducted during the peak malaria transmission season in south-west Burkina Faso in 2017. Logistic regression was used to identify risk factors for microscopically confirmed P. falciparum infection. A malaria transmission dynamic model was used to determine the impact on malaria cases averted of administering SMC to children aged 5–15 year old. Results P. falciparum prevalence was 32.8% in the study population. Children aged 5 to < 10 years old were at 3.74 times the odds (95% CI = 2.68–5.22, p < 0.001) and children aged 10 to 15 years old at 3.14 times the odds (95% CI = 1.20–8.21, p = 0.02) of P. falciparum infection compared to children aged less than 5 years old. Administration of SMC to children aged up to 10 years is predicted to avert an additional 57 malaria cases per 1000 population per year (9.4% reduction) and administration to children aged up to 15 years would avert an additional 89 malaria cases per 1000 population per year (14.6% reduction) in the Cascades Region, assuming coverage of pyrethroid-piperonyl butoxide ITNs. Conclusion Malaria infections were high in all age strata, although highest in children aged 5 to 15 years, despite roll out of core malaria control interventions. Given the burden of infection in school-age children, extension of the eligibility criteria for SMC could help reduce the burden of malaria in Burkina Faso and other countries in the region.

scholarly journals 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

2019 ◽  
Vol 188 (12) ◽  
pp. 2120-2130 ◽  
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.

Mosquitoes and Malaria Control – A Complex Problem for Entomologists to Unravel

2019 ◽  
Vol 30 (5) ◽  
pp. 213-216
Author(s):  
Basil Brooke
Keyword(s):  
Vector Control ◽  
Malaria Vector ◽  
Malaria Control ◽  
Life Stage ◽  
Indoor Residual Spraying ◽  
Transmission Intensity ◽  
Sub Saharan Africa ◽  
Malaria Vectors ◽  
Bed Nets ◽  
Vector Species

The control of malaria transmitting mosquitoes hinges on accurate species identification. This enables assessments of insecticide susceptibilities and important behavioural characteristics (such as feeding and resting behaviours) by species, leading to the design of coherent insecticide-based control strategies that can be enhanced by additional methodologies for malaria elimination. Malaria is a mosquito-borne parasitic disease that affects many vertebrates including humans. Prior to the 20th century the human malarias (Plasmodium falciparum, P. vivax, P. malariae, P. ovale and P. knowlesi) occurred in tropical and temperate regions but their distribution has since reduced to the tropical belt with by far the highest incidence in sub-Saharan Africa. Global incidence for 2017 was estimated by the WHO at 219 million cases corresponding to 435 000 deaths. It is also estimated that investment in malaria control and elimination amounted to $3.1 billion in 2017. The control (and elimination) of malaria largely hinges on the suppression of mosquito vectors, accurate diagnosis and case detection, and case management using appropriate antimalarial drug regimens. Controlling malaria vector mosquitoes (and of course other mosquito-borne diseases) means being able to identify that which needs to be controlled. This is not unlike the maxim of knowing one's enemy, and disease vector control is often phrased in militaristic terms. The arsenal of tools in the war against malaria vectors includes insecticides, bed nets, repellents, larvicides, endectocides, toxic baits and even modified genes. This call to arms against the transmitters of a deadly disease presupposes that the enemy can be identified, which, unfortunately, is not as easy as it sounds. Identifying malaria vectors to species has posed a significant challenge ever since Ronald Ross and Giovanni Grassi implicated dappled-winged Anopheles mosquitoes in malaria transmission. They could not have known the Pandora's Box they had opened, because several Anopheles species are cryptic. Many hide in cryptic species complexes and groups that confound straightforward morphological methods of identifying them. A species complex is a group of morphologically identical species that are very closely related, but nevertheless vary significantly in their feeding and resting behaviours, and mate assortatively (i.e. they recognise and tend only to mate with conspecific partners) enough that hybridisations between them are rare. Many member species of these complexes are sufficiently diverged that cross-mating between them yields infertile or non-viable offspring, but not in all cases. A species group is a looser assortment of related species whose morphological features match to a point where they are very nearly identical, often requiring specimens from more than one life stage to identify them. They also mate assortatively, and hybrids are rarer or simply never occur. The problem for malaria control is that several vector species, including many primary vectors, are members of cryptic complexes or groups. These invariably contain vector and non-vector species, requiring a complex and laborious system to unravel them and ascribe unambiguous genetic methods for their identification. Added to this complexity is the possibility that any Anopheles. species that takes human blood is a potential vector of the human malarias, with the added caveat that not all populations within a species are vectors. Some member species, and even populations within a species, feed either exclusively on humans (anthropophagy) and are potentially high transmission intensity vectors, or exclusively on livestock animals (zoophagy) making them non-vectors, or take blood from a range of sources including humans, becoming potential vectors of low to medium transmission intensity. An added layer of complexity is genetic heterogeneity between populations within a species. It can be argued that this complexity is not necessarily a problem for malaria control. After all, the aim of suppressing or even eliminating vector populations is the interruption of transmission, regardless of what species they are. But mosquito adaptability dictates otherwise. This is because the primary method of malaria vector control is deployment of specially formulated insecticides against adult mosquitoes, either by indoor residual spraying (IRS) or the treatment of bed nets. Mosquito adaptability has enabled a powerful response to these interventions, with resistance to insecticides becoming so widespread that fully insecticide susceptible malaria vector populations are now quite rare.

scholarly journals Impact of Seasonality and Malaria Control Interventions on Anopheles Density and Species Composition From Three Areas of Uganda With Differing Malaria Endemicity.

2020 ◽  
Author(s):  
Henry Mawejje ◽  
Maxwell Kilama ◽  
Simon P. Kigozi ◽  
Alex K. Musiime ◽  
Moses Kamya ◽  
...  
Keyword(s):  
Species Composition ◽  
Vector Control ◽  
Malaria Control ◽  
Mosquito Species ◽  
Density Ratio ◽  
Indoor Residual Spraying ◽  
Sub Saharan Africa ◽  
Malaria Vector Control ◽  
Vector Density ◽  
Llin Distribution

Abstract Background Long lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) are malaria control interventions primarily responsible for reductions in transmission intensity across sub-Saharan Africa. These interventions, however, may have differential impact on Anopheles species composition and density. Here, we studied the changing pattern of Anopheles species in three areas of Uganda with markedly different transmission intensities and different levels of vector control.Methods From October 2011 to June 2016 mosquitoes were collected monthly using CDC light traps from 100 randomly selected households in three areas: Walukuba (low transmission), Kihihi (moderate transmission) and Nagongera (high transmission). LLINs were distributed in November 2013 in Walukuba and Nagongera and in June 2014 in Kihihi. IRS was implemented only in Nagongera, with three rounds of bendiocarb delivered between December 2014 and June 2015. Mosquito species were identified morphologically and by PCR (Polymerase Chain Reaction). Results In Walukuba, LLIN distribution was associated with a decline in Anopheles funestus vector density (0.07 vs 0.02 mosquitoes per house per night, density ratio [DR] 0.34, 95% CI: 0.18-0.65, p=0.001), but not An. gambiae s.s. nor An. arabiensis. In Kihihi, over 98% of mosquitoes were An. gambiae s.s. and LLIN distribution was associated with a decline in An. gambiae s.s. vector density (4.00 vs 2.46, DR 0.68, 95% CI: 0.49-0.94, p=0.02). In Nagongera, the combination of LLINs and multiple rounds of IRS was associated with almost complete elimination of An. gambiae s.s. (28.0 vs 0.17, DR 0.004, 95% CI: 0.002-0.009, p<0.001), and An. funestus s.l. (3.90 vs 0.006, DR 0.001, 95% CI: 0.0005-0.004, p<0.001), with a less pronounced decline in An. arabiensis (9.18 vs 2.00, DR 0.15 95% CI: 0.07-0.33, p<0.001). Conclusions LLIN distribution was associated with reductions in An. funestus s.l. in the lowest transmission site and An. gambiae s.s. in the moderate transmission site. In the highest transmission site, a combination of LLINs and multiple rounds of IRS was associated with the near collapse of An. gambiae s.s. and An. funestus s.l. Following IRS, An. arabiensis, a behaviorally resilient vector, became the predominant species, which may have implications for malaria vector control activities.

scholarly journals Indoor residual spraying for malaria control in Sub-Saharan Africa 1997 to 2017; an adjusted retrospective analysis

2020 ◽  
Author(s):  
Julie-Anne Tangena ◽  
Chantal M.J. Hendriks ◽  
Maria Devine ◽  
Meghan Tammaro ◽  
Anna E. Trett ◽  
...  
Keyword(s):  
Malaria Control ◽  
Malaria Incidence ◽  
Resistance Management ◽  
Indoor Residual Spraying ◽  
Control Program ◽  
Sub Saharan Africa ◽  
World Health ◽  
Policy And Practice ◽  
Sub Saharan ◽  
The Impact

Abstract Background: Indoor residual spraying (IRS) is a key tool for controlling and eliminating malaria by targeting vectors. To support the development of effective intervention strategies it is important to understand the impact of vector control tools on malaria incidence and on the spread of insecticide resistance. In 2006, the World Health Organization (WHO) stated that countries should report on coverage and impact of IRS, yet IRS coverage data are still sparse and unspecific. Here we estimated the subnational coverage of IRS across sub-Saharan Africa for the four main insecticide classes from 1997 to 2017. Methods: Data on IRS deployment were collated from a variety of sources, including the President’s Malaria Initiative spray reports and National Malaria Control program reports, for all 46 malaria-endemic countries in Sub-Saharan Africa from 1997 to 2017. The data were mapped to the applicable administrative divisions and the proportion of households sprayed for each of the four main insecticide classes; carbamates, organochlorines, organophosphates and pyrethroids was calculated. Results: We found that the number of countries implementing IRS increased considerably over time, although the focal nature of deployment means the number of people protected remains low. From 1997 to 2010, DDT and pyrethroids were commonly used, then partly replaced by carbamates from 2011 and by organophosphates from 2013. IRS deployment since the publication of resistance management guidelines has typically avoided overlap between pyrethroid IRS and ITN use. However, annual rotations of insecticide classes with differing modes of action are not routinely used. Conclusion: This study highlights the gaps between policy and practice, emphasizing the continuing potential of IRS to drive resistance. The data presented here can improve studies on the impact of IRS on malaria incidence and help to guide future malaria control efforts.

scholarly journals Impact of seasonality and malaria control interventions on Anopheles density and species composition from three areas of Uganda with differing malaria endemicity.

2021 ◽  
Author(s):  
Henry Mawejje ◽  
Maxwell Kilama ◽  
Simon P. Kigozi ◽  
Alex K. Musiime ◽  
Moses Kamya ◽  
...  
Keyword(s):  
Species Composition ◽  
Vector Control ◽  
Malaria Control ◽  
Mosquito Species ◽  
Density Ratio ◽  
Indoor Residual Spraying ◽  
Sub Saharan Africa ◽  
Malaria Vector Control ◽  
Vector Density ◽  
Llin Distribution

Abstract Background Long lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) are malaria control interventions primarily responsible for reductions in transmission intensity across sub-Saharan Africa. These interventions, however, may have differential impact on Anopheles species composition and density. Here, we studied the changing pattern of Anopheles species in three areas of Uganda with markedly different transmission intensities and different levels of vector control. Methods From October 2011 to June 2016 mosquitoes were collected monthly using CDC light traps from 100 randomly selected households in three areas: Walukuba (low transmission), Kihihi (moderate transmission) and Nagongera (high transmission). LLINs were distributed in November 2013 in Walukuba and Nagongera and in June 2014 in Kihihi. IRS was implemented only in Nagongera, with three rounds of bendiocarb delivered between December 2014 and June 2015. Mosquito species were identified morphologically and by PCR (Polymerase Chain Reaction). Results In Walukuba, LLIN distribution was associated with a decline in Anopheles funestus vector density (0.07 vs 0.02 mosquitoes per house per night, density ratio [DR] 0.34, 95% CI: 0.18-0.65, p=0.001), but not An. gambiae s.s. nor An. arabiensis. In Kihihi, over 98% of mosquitoes were An. gambiae s.s. and LLIN distribution was associated with a decline in An. gambiae s.s. vector density (4.00 vs 2.46, DR 0.68, 95% CI: 0.49-0.94, p=0.02). In Nagongera, the combination of LLINs and multiple rounds of IRS was associated with almost complete elimination of An. gambiae s.s. (28.0 vs 0.17, DR 0.004, 95% CI: 0.002-0.009, p<0.001), and An. funestus s.l. (3.90 vs 0.006, DR 0.001, 95% CI: 0.0005-0.004, p<0.001), with a less pronounced decline in An. arabiensis (9.18 vs 2.00, DR 0.15 95% CI: 0.07-0.33, p<0.001). Conclusions LLIN distribution was associated with reductions in An. funestus s.l. in the lowest transmission site and An. gambiae s.s. in the moderate transmission site. In the highest transmission site, a combination of LLINs and multiple rounds of IRS was associated with the near collapse of An. gambiae s.s. and An. funestus s.l. Following IRS, An. arabiensis, a behaviorally resilient vector, became the predominant species, which may have implications for malaria vector control activities. Development of interventions targeted at outdoor biting remains a priority.

scholarly journals Impact of vector control interventions on malaria transmission intensity, outdoor vector biting rates and Anopheles mosquito species composition in Tororo, Uganda

2019 ◽  
Vol 18 (1) ◽  
Author(s):  
Alex K. Musiime ◽  
David L. Smith ◽  
Maxwell Kilama ◽  
John Rek ◽  
Emmanuel Arinaitwe ◽  
...  
Keyword(s):  
Vector Control ◽  
Malaria Transmission ◽  
Indoor Residual Spraying ◽  
Transmission Intensity ◽  
Intervention Period ◽  
Malaria Transmission Intensity ◽  
Predominant Species ◽  
High Transmission ◽  
Human Landing ◽  
The Impact

Abstract Background Long-lasting insecticidal nets (LLINs) and indoor residual spraying of insecticide (IRS) are widely recommended for the prevention of malaria in endemic regions. Data from human landing catches provide information on the impact of vector control on vector populations. Here, malaria transmission indoors and outdoors, before and after mass deployment of LLINs and IRS in Uganda was compared. Methods The study took place in Tororo district, a historically high transmission area where universal LLIN distribution was conducted in November 2013 and May 2017 and 6 rounds of IRS implemented from December 2014 to July 2018. Human landing catches were performed in 8 houses monthly from October 2011 to September 2012 (pre-intervention period) and every 4 weeks from November 2017 to October 2018 (post-intervention period). Mosquitoes were collected outdoors from 18:00 to 22:00 h and indoors from 18:00 to 06:00 h. Female Anopheles were tested for the presence of Plasmodium falciparum sporozoites and species identification performed using gross dissection and polymerase chain reaction (PCR). Results The interventions were associated with a decline in human biting rate from 19.6 to 2.3 female Anopheles mosquitoes per house per night (p < 0.001) and annual entomological inoculation rate from 129 to 0 infective bites per person per year (p < 0.001). The proportion of mosquitoes collected outdoors increased from 11.6 to 49.4% (p < 0.001). Prior to the interventions the predominant species was Anopheles gambiae sensu stricto (s.s.), which comprised an estimated 76.7% of mosquitoes. Following the interventions, the predominant species was Anopheles arabiensis, which comprised 99.5% of mosquitoes, with almost complete elimination of An. gambiae s.s. (0.5%). Conclusions Mass distribution of LLINs and 6 rounds of IRS dramatically decreased vector density and sporozoite rate resulting in a marked reduction in malaria transmission intensity in a historically high transmission site in Uganda. These changes were accompanied by a shift in vector species from An. gambiae s.s. to An. arabiensis and a relative increase in outdoor biting.

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