Effectiveness Of Indoor Residual Spraying Research Articles

Effectiveness of Indoor Residual Spraying as A Method of Controlling Dengue Fever in Communities: A systematic review

Background: Dengue remains a significant public health issue in the Western Pacific Region. In the absence of a vaccine, vector control is the mainstay for dengue prevention and control. This study aimed to explore the effectiveness of Indoor Residual Spraying as A Method of Controlling Dengue Fever in Communities. Subjects and Method: A systematic review was conducted by searching articles from PubMed, ResearchGate, Science Direct, Google Scholar, and EBSCO is an article published from 2013 to 2023. The keywords were “dengue hemorrhagic fever” OR “DHF” AND “community” OR “family” AND “disaster” AND “IRS” OR “indoor residual spraying”. The inclusion criteria were a Cross-sectional study. The articles were selected by PRISMA flow diagram method. Results: A total of 9 studies were included in this review. All of the studies stated that IRS can have both an immediate and sustained effect on reducing adult and immature A. aegypti populations and should be considered as an adult mosquito control strategy by dengue vector control programs also IRS led to 86-96% reduction in dengue cases in sprayed premises, compared to unsprayed controls. Conclusion: IRS significantly reduces the malaria burden in high-transmission settings. Keywords: dengue hemorrhagic fever, DHF, family, community. Correspondence: Titik Anggraeni. School of Health Sciences Estu Utomo Boyolali, Central Java, Indonesia. Jl. Tentara Pelajar 7, Mudal, Boyolali, Central Java, Indonesia. Email: titik.anggraeni146@gmail.com. Mobile: +62 858-6729-2673.

Vector control for malaria prevention during humanitarian emergencies: a systematic review and meta-analysis

Humanitarian emergencies can lead to population displacement, food insecurity, severe health system disruptions, and malaria epidemics among individuals who are immunologically naive. We aimed to assess the impact of different vector control interventions on malaria disease burden during humanitarian emergencies. In this systematic review and meta-analysis, we searched ten electronic databases and two clinical trial registries from database inception to Oct 19, 2020, with no restrictions on language or study design. We also searched grey literature from 59 stakeholders. Studies were eligible if the population was affected by a humanitarian emergency in a malaria endemic region. We included studies assessing any vector control intervention and in which the primary outcome of interest was malaria infection risk. Reviewers (LAM, JF-A, KC, BP, and LP) independently extracted information from eligible studies, without masking of author or publication, into a database. We did random-effects meta-analyses to calculate pooled risk ratios (RRs) for randomised controlled trials, odds ratios (ORs) for dichotomous outcomes, and incidence rate ratios (IRR) for clinical malaria in non-randomised studies. Certainty of evidence was evaluated using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. This study is registered with PROSPERO, CRD42020214961. Of 12 475 studies screened, 22 studies were eligible for inclusion in our meta-analysis. All studies were conducted between Sept 1, 1989, and Dec 31, 2018, in chronic emergencies, with 616 611 participants from nine countries, evaluating seven different vector control interventions. Insecticide-treated nets significantly decreased Plasmodium falciparum incidence (RR 0·55 [95% CI 0·37-0·79]; high certainty) and Plasmodium vivax incidence (RR 0·69 [0·51-0·94]; high certainty). Evidence for an effect of indoor residual spraying on P falciparum (IRR 0·57 [95% CI 0·53-0·61]) and P vivax (IRR 0·51 [0·49-0·52]) incidence was of very low certainty. Topical repellents were associated with reductions in malaria infection (RR 0·58 [0·35-0·97]; moderate certainty). Moderate-to-high certainty evidence for an effect of insecticide-treated chaddars (equivalent to shawls or blankets) and insecticide-treated cattle on malaria outcomes was evident in some emergency settings. There was very low certainty evidence for the effect of insecticide-treated clothing. Study findings strengthen and support WHO policy recommendations to deploy insecticide-treated nets during chronic humanitarian emergencies. There is an urgent need to evaluate and adopt novel interventions for malaria control in the acute phase of humanitarian emergencies. WHO Global Malaria Programme.

Effect of indoor residual spraying on malaria in pregnancy and pregnancy outcomes: a systematic review

Malaria in pregnancy increases maternal and perinatal morbidity and mortality. Indoor residual spraying (IRS) is a core vector control strategy used to reduce transmission in endemic areas; however, its effect on pregnant people is not well known. We conducted a systematic literature review to determine what is known about the effects of IRS on parasitemia in pregnancy and on pregnancy outcomes.

In communities using insecticide-treated nets (ITNs), what are the effects of indoor residual spraying (IRS) for preventing malaria?

In communities using insecticide-treated nets (ITNs), what are the effects of indoor residual spraying (IRS) for preventing malaria?

The influence of the environment and indoor residual spraying on malaria risk in a cohort of children in Uganda

Studies have estimated the impact of the environment on malaria incidence although few have explored the differential impact due to malaria control interventions. Therefore, the objective of the study was to evaluate the effect of indoor residual spraying (IRS) on the relationship between malaria and environment (i.e. rainfall, temperatures, humidity, and vegetation) using data from a dynamic cohort of children from three sub-counties in Uganda. Environmental variables were extracted from remote sensing sources and averaged over different time periods. General linear mixed models were constructed for each sub-counties based on a log-binomial distribution. The influence of IRS was analysed by comparing marginal effects of environment in models adjusted and unadjusted for IRS. Great regional variability in the shape (linear and non-linear), direction, and magnitude of environmental associations with malaria risk were observed between sub-counties. IRS was significantly associated with malaria risk reduction (risk ratios vary from RR = 0.03, CI 95% [0.03–0.08] to RR = 0.35, CI95% [0.28–0.42]). Model adjustment for this intervention changed the magnitude and/or direction of environment-malaria associations, suggesting an interaction effect. This study evaluated the potential influence of IRS in the malaria-environment association and highlighted the necessity to control for interventions when they are performed to properly estimate the environmental influence on malaria. Local models are more informative to guide intervention program compared to national models.

Understanding Malaria Persistence: A Mixed-Methods Study on the Effectiveness of Malaria Elimination Strategies in South-Central Vietnam.

Despite the scale-up of vector control, diagnosis and treatment, and health information campaigns, malaria persists in the forested areas of South-Central Vietnam, home to ethnic minority populations. A mixed-methods study using an exploratory sequential design was conducted in 10 Ra-glai villages in Bac Ai district of Ninh Thuan province to examine which social factors limited the effectiveness of the national malaria elimination strategy in the local setting. Territorial arrangements and mobility were found to directly limit the effectiveness of indoor residual spraying and long-lasting insectidical treated nets (LLINs). Households (n=410) were resettled in the “new villages” by the government, where they received brick houses (87.1%) and sufficient LLINs (97.3%). However, 97.6% of households went back to their “old villages” to continue slash-and-burn agriculture. In the old village, 48.5% of households lived in open-structured plot huts and only 5.7% of them had sufficient LLIN coverage. Household representatives believed malaria could be cured with antimalarials (57.8%), but also perceived non-malarial medicines, rituals, and vitamin supplements to be effective against malaria. Household members (n = 1,957) used public health services for their most recent illness (62.9%), but also reported to buy low-cost medicines from the private sector to treat fevers and discomfort as these were perceived to be the most cost-effective treatment option for slash-and-burn farmers. The study shows the relevance of understanding social factors to improve the uptake of public health interventions and calls for contextually adapted strategies for malaria elimination in ethnic minority populations in Vietnam and similar settings.

A model of malaria population dynamics with migrants.

We present a compartmental model in ordinary differential equations of malaria disease transmission, accommodating the effect of indoor residual spraying on the vector population. The model allows for influx of infected migrants into the host population and for outflow of recovered migrants. The system is shown to have positive solutions. In the special case of no infected immigrants, we prove global stability of the disease-free equilibrium. Existence of a unique endemic equilibrium point is also established for the case of positive influx of infected migrants. As a case study we consider the combined South African malaria region. Using data covering 31 years, we quantify the effect of malaria infected immigrants on the South African malaria region.

What are the effects of indoor residual spraying for preventing malaria?

What are the effects of indoor residual spraying for preventing malaria?

Assessing the Effectiveness of Indoor Residual Spraying (IRS) in the Prevention of Malaria among Children of Under Five Years Old In Ikorodu Local Government, Lagos State, Nigeria

Assessing the Effectiveness of Indoor Residual Spraying (IRS) in the Prevention of Malaria among Children of Under Five Years Old In Ikorodu Local Government, Lagos State, Nigeria

Effects of indoor residual spraying and outdoor larval control on Anopheles coluzzii from S\xe3o Tom\xe9 and Pr\xedncipe, two islands with pre-eliminated malaria

BackgroundVector control is a key component of malaria prevention. Two major vector control strategies have been implemented in São Tomé and Príncipe (STP), indoor residual spraying (IRS) and outdoor larval control using Bacillus thuringiensis israelensis (Bti). This study evaluated post-intervention effects of control strategies on vector population density, composition, and knockdown resistance mutation, and their implications for malaria epidemiology in STP.MethodsMosquitoes were collected by indoor and outdoor human landing catches and mosquito light traps in seven districts. Mosquito density was calculated by numbers of captured adult mosquitoes/house/working hour. Mitochondrial cytochrome c oxidase subunit I (COI) was PCR amplified and sequenced to understand the spatial–temporal population composition of malaria vector in STP. Knockdown resistance L1014F mutation was detected using allele-specific PCR. To estimate the malaria transmission risks in STP, a negative binomial regression model was constructed. The response variable was monthly incidence, and the explanatory variables were area, rainfall, entomological inoculation rate (EIR), and kdr mutation frequency.ResultsMalaria vector in STP is exophilic Anopheles coluzzii with significant population differentiation between Príncipe and São Tomé (mean FST = 0.16, p < 0.001). Both vector genetic diversity and knockdown resistance mutation were relatively low in Príncipe (mean of kdr frequency = 15.82%) compared to São Tomé (mean of kdr frequency = 44.77%). Annual malaria incidence rate in STP had been rapidly controlled from 37 to 2.1% by three rounds of country-wide IRS from 2004 to 2007. Long-term application of Bti since 2007 kept the mosquito density under 10 mosquitoes/house/hr/month, and malaria incidence rate under 5% after 2008, except for a rising that occurred in 2012 (incidence rate = 6.9%). Risk factors of area (São Tomé compared to Príncipe), rainfall, outdoor EIR, and kdr mutation frequency could significantly increase malaria incidence by 9.33–11.50, 1.25, 1.07, and 1.06 fold, respectively.ConclusionsIndoor residual spraying could rapidly decrease Anopheles density and malaria incidence in STP. Outdoor larval control using Bti is a sustainable approach for controlling local vector with exophilic feature and insecticide resistance problem. Vector control interventions should be intensified especially at the north-eastern part of São Tomé to minimize impacts of outbreaks.

Forecasting the effectiveness of indoor residual spraying for reducing dengue burden.

BackgroundHistorically, mosquito control programs successfully helped contain malaria and yellow fever, but recent efforts have been unable to halt the spread of dengue, chikungunya, or Zika, all transmitted by Aedes mosquitoes. Using a dengue transmission model and results from indoor residual spraying (IRS) field experiments, we investigated how IRS-like campaign scenarios could effectively control dengue in an endemic setting.Methods and findingsIn our model, we found that high levels of household coverage (75% treated once per year), applied proactively before the typical dengue season could reduce symptomatic infections by 89.7% (median of 1000 simulations; interquartile range [IQR]:[83.0%, 94.8%]) in year one and 78.2% (IQR: [71.2%, 88.0%]) cumulatively over the first five years of an annual program. Lower coverage had correspondingly lower effectiveness, as did reactive campaigns. Though less effective than preventative campaigns, reactive and even post-epidemic interventions retain some effectiveness; these campaigns disrupt inter-seasonal transmission, highlighting an off-season control opportunity. Regardless, none of the campaign scenarios maintain their initial effectiveness beyond two seasons, instead stabilizing at much lower levels of benefit: in year 20, median effectiveness was only 27.3% (IQR: [-21.3%, 56.6%]). Furthermore, simply ceasing an initially successful program exposes a population with lowered herd immunity to the same historical threat, and we observed outbreaks more than four-fold larger than pre-intervention outbreaks. These results do not take into account evolving insecticide resistance, thus long-term effectiveness may be lower if new, efficacious insecticides are not developed.ConclusionsUsing a detailed agent-based dengue transmission model for Yucatán State, Mexico, we predict that high coverage indoor residual spraying (IRS) interventions can largely eliminate transmission for a few years, when applied a few months before the typical seasonal epidemic peak. However, vector control succeeds by preventing infections, which precludes natural immunization. Thus, as a population benefits from mosquito control, it gradually loses naturally acquired herd immunity, and the control effectiveness declines; this occurs across all of our modeled scenarios, and is consistent with other empirical work. Long term control that maintains early effectiveness would require some combination of increasing investment, complementary interventions such as vaccination, and control programs across a broad region to diminish risk of importation.

Impact of insecticide-treated bednets and indoor residual spraying in controlling populations of Phlebotomus duboscqi, the vector of Leishmania major in Central Mali

BackgroundCutaneous leishmaniasis (CL) is an endemic neglected tropical disease prevalent in several areas where seasonal malaria transmission is active. We assessed the effect of indoor residual spraying (IRS) and the mass distribution of long-lasting insecticide-treated bednets (LLINs) for malaria control on sand fly population diversity and abundance, and its impact on the risk of Leishmania transmission in the district of Baroueli, endemic for CL in Mali.MethodsKemena and Sougoula, two villages in the district of Baroueli, were selected for entomology surveys from March to September 2016 to evaluate sand fly species composition and density, and Leishmania infection rates in the vector Phlebotomus duboscqi. The surveys followed an annual indoor residual spraying and mass distribution of long-lasting insecticide-treated bednets (IRS/LLINs) that began in 2011 for malaria vector control. We also carried out a leishmanin skin test (LST) survey in the two villages to determine the incidence of Leishmania infection in humans living in the endemic area.ResultsA total of 2936 sand fly specimens, 1013 males and 1923 females, were collected and identified from the two villages throughout the study period. Fourteen species, 2 belonging to the genus Phlebotomus and 12 to the genus Sergentomyia, were documented. The genus Sergentomyia constituted 91% of collected sand flies versus 9% for the genus Phlebotomus (P. duboscqi and P. rodhaini). Of those, P. duboscqi was the most abundant, representing 99.6% of the collected Phlebotomus species. In both villages, P. duboscqi was most abundant during the end of dry season (June). The prevalence of Leishmania infection in individual females of P. duboscqi by PCR was 3.5%. After 5 years of the IRS/LLINs, the incidence of Leishmania infection in the human population as measured by LST was 4.2%.ConclusionsCompared to historical data collected from 2005–2008, a considerable reduction was observed in both sand fly density and prevalence of human Leishmania infection in the villages of Kemena and Sougoula, Baroueli District, following IRS/LLINs. This suggests that IRS/LLINs used for mosquito control also impacts sand fly vectors reducing the incidence of leishmaniasis.Trial registrationNCT00344084. Registered: 23 June 2006

Risk factors for the expansion of cutaneous leishmaniasis by Leishmania tropica: Possible implications for control programmes.

Cutaneous leishmaniasis (CL) caused by Leishmania tropica is emerging in new areas, initially as outbreaks and then establishing endemic foci. There is little evidence of the risk factors and effectiveness of existing control measures, what limits our ability to generalize in different epidemiological settings. The disease is described as anthroponotic; however, zoonotic outbreaks have been reported in some countries. Our aim was to identify risk factors in a recently reported endemic focus in Morocco in order to design more effective control programmes. A case-control study was conducted from September 2014 to October 2015 for epidemiological data collection from families with and without CL cases. Sandflies were captured and L.tropica infection determined. The presence of potential animal reservoirs was evaluated. 71 CL cases (44 diagnosed between 2013 and 2015) and 137 healthy people were surveyed. The average age of the new cases was 33.1±22.3years, and 69.0% were women. Phlebotomus sergenti was the most abundant species with a density of 4.27 sandflies/trap/night and differences between houses with and without CL cases were detected (p-value=0.014). Overall, 2.7% female P.sergenti and 3.0% dogs were positive for L.tropica. Human, cat, rabbit and bird blood was detected in blood-fed P.sergenti females. 45% people used preventive measures that were not translated into a reduction in the individual risk of acquiring CL. Exposure to P.sergenti was the only risk factor found, and the reduction in its density could be achieved through the improvement of water wells management, organic fertilizers' disposal and dogs control. The lack of effectiveness of indoor residual spraying and treated nets are attributable to poor compliance and misuse of them. In addition, result optimization of the awareness campaigns on the public is possible by involving patients with CL to explain their own experience.

Towards elimination of visceral leishmaniasis in the Indian subcontinent-Translating research to practice to public health.

BackgroundThe decade following the Regional Strategic Framework for Visceral Leishmaniasis (VL) elimination in 2005 has shown compelling progress in the reduction of VL burden in the Indian subcontinent. The Special Programme for Research and Training in Tropical Diseases (TDR), hosted by the World Health Organization (WHO) and other stakeholders, has coordinated and financed research for the development of new innovative tools and strategies to support the regional VL elimination initiative. This paper describes the process of the TDR’s engagement and contribution to this initiative.Methodology/principal findingsMultiple databases were searched to identify 152 scientific papers and reports with WHO funding or authorship affiliation around the following 3 framework strategies: detection of new cases, morbidity reduction, and prevention of infection. TDR has played a critical role in the evaluation and subsequent use of the 39-aminoacid–recombinant kinesin antigen (rK39) rapid diagnostic test (RDT) as a confirmatory test for VL in the national program. TDR has supported the clinical research and development of miltefosine and single-dose liposomal amphotericin B as a first-line treatment against VL. TDR has engaged with in-country researchers, national programme managers, and partners to generate evidence-based interventions for early detection and treatment of VL patients. TDR evaluated the quality, community acceptance, and cost effectiveness of indoor residual spraying, insecticide-treated bed nets, insecticide-impregnated durable wall linings, insecticidal paint, and environmental management as tools for integrated vector management in reducing sandfly density.Conclusions/significanceTDR’s engagement with country policy makers, scientists, and clinicians in the development of effective diagnosis, treatment, case detection, and vector control represents an important example of TDR’s stewardship toward the elimination of VL in the Indian subcontinent.

Protective Effect of Indoor Residual Spraying of Insecticide on Preterm Birth Among Pregnant Women With HIV Infection in Uganda: A Secondary Data Analysis.

Recent evidence demonstrated improved birth outcomes among human immunodeficiency virus (HIV)-uninfected pregnant women protected by indoor residual spraying of insecticide (IRS). Evidence regarding its impact on HIV-infected pregnant women is lacking. Data were pooled from 2 studies conducted before and after an IRS campaign in Tororo, Uganda, among HIV-infected pregnant women who received bed nets, daily trimethoprim-sulfamethoxazole, and combination antiretroviral therapy at enrollment. Exposure was the proportion of pregnancy protected by IRS. Adverse birth outcomes included preterm birth, low birth weight, and fetal or neonatal death. Multivariate Poisson regression with robust standard errors was used to estimate risk ratios. Of 565 women in our analysis, 380 (67%), 88 (16%), and 97 (17%) women were protected by IRS for 0%, >0% to 90%, and >90% of their pregnancy, respectively. Any IRS protection significantly reduced malaria incidence during pregnancy and placental malaria risk. Compared with no IRS protection, >90% IRS protection reduced preterm birth risk (risk ratio, 0.35; 95% confidence interval, .15-.84), with nonsignificant decreases in the risk of low birth weight (0.68; .29-1.57) and fetal or neonatal death (0.24; .04-1.52). Our exploratory analyses support the hypothesis that IRS may significantly reduce malaria and preterm birth risk among pregnant women with HIV receiving bed nets, daily trimethoprim-sulfamethoxazole, and combination antiretroviral therapy.

Insecticide resistance patterns in Uganda and the effect of indoor residual spraying with bendiocarb on kdr L1014S frequencies in Anopheles gambiae s.s.

BackgroundResistance of malaria vectors to pyrethroid insecticides has been attributed to selection pressure from long-lasting insecticidal nets (LLINs), indoor residual spraying (IRS), and the use of chemicals in agriculture. The use of different classes of insecticides in combination or by rotation has been recommended for resistance management. The aim of this study was to understand the role of IRS with a carbamate insecticide in management of pyrethroid resistance.MethodsAnopheles mosquitoes were collected from multiple sites in nine districts of Uganda (up to five sites per district). Three districts had been sprayed with bendiocarb. Phenotypic resistance was determined using standard susceptibility tests. Molecular assays were used to determine the frequency of resistance mutations. The kdr L1014S homozygote frequency in Anopheles gambiae s.s. was used as the outcome measure to test the effects of various factors using a logistic regression model. Bendiocarb coverage, annual rainfall, altitude, mosquito collection method, LLIN use, LLINs distributed in the previous 5 years, household use of agricultural pesticides, and malaria prevalence in children 2–9 years old were entered as explanatory variables.ResultsTests with pyrethroid insecticides showed resistance and suspected resistance levels in all districts except Apac (a sprayed district). Bendiocarb resistance was not detected in sprayed sites, but was confirmed in one unsprayed site (Soroti). Anopheles gambiae s.s. collected from areas sprayed with bendiocarb had significantly less kdr homozygosity than those collected from unsprayed areas. Mosquitoes collected indoors as adults had significantly higher frequency of kdr homozygotes than mosquitoes collected as larvae, possibly indicating selective sampling of resistant adults, presumably due to exposure to insecticides inside houses that would disproportionately affect susceptible mosquitoes. The effect of LLIN use on kdr homozygosity was significantly modified by annual rainfall. In areas receiving high rainfall, LLIN use was associated with increased kdr homozygosity and this association weakened as rainfall decreased, indicating more frequency of exposure to pyrethroids in relatively wet areas with high vector density.ConclusionThis study suggests that using a carbamate insecticide for IRS in areas with high levels of pyrethroid resistance may reduce kdr frequencies in An. gambiae s.s.

Net Loss? Agrochemicals and Insecticide Resistance in the Fight against Malaria.

Net Loss? Agrochemicals and Insecticide Resistance in the Fight against Malaria.

Assessing the effect of indoor residual spraying (IRS) on malaria morbidity in Northern Uganda: a before and after study

BackgroundIndoor residual spraying (IRS) is known to reduce malaria transmission. In northern Uganda, a high endemic area, IRS has been implemented since 2006. Limited data however, exists on the effect of IRS on the malaria burden. This study sought to assess the effect of IRS on malaria morbidity in the high intensity area of northern Uganda. Retrospective routine data from ten health facilities in three districts which had received at least five rounds of IRS in northern Uganda was analysed. The primary outcome of interest was malaria morbidity, measured by the slide positivity rate (SPR). Descriptive statistics were used to describe the malaria morbidity stratified by age and sex. The average change in the malaria morbidity, measured by the SPR was assessed according to time, measured as calendar months. A fixed-effects linear regression model was used which included a polynomial function of time and controlled for malaria seasonality and variations between districts/facilities.ResultsThe total out-patient department attendance in the ten health facilities for the study period was 2,779,246, of which 736,034 (26.5%) malaria cases were diagnosed with 374,826 (50.9%) cases of under 5 years and an overall SPR of 37.5%. The percentage point (p.p.) changes in SPR according to time measured as calendar months following IRS, revealed a decreasing trend in malaria morbidity in the first 3 months following each round of IRS. The highest percentage point decrease in the SPR was observed in the second month following IRS (9.5 p.p., CI −17.85 to −1.16, p = 0.026), among patients above 5 years. The SPR decline however waned by the fourth month following IRS, with an increase in the SPR of 8.4 p.p. at district level by the sixth month, p = 0.510.ConclusionThe study results show that IRS was associated with a significant reduction in malaria morbidity in northern Uganda in the first 3 months following IRS. The malaria reduction however waned by the fourth month following IRS.

Spatio-temporal analysis of malaria vector density from baseline through intervention in a high transmission setting.

BackgroundAn increase in effective malaria control since 2000 has contributed to a decline in global malaria morbidity and mortality. Knowing when and how existing interventions could be combined to maximise their impact on malaria vectors can provide valuable information for national malaria control programs in different malaria endemic settings. Here, we assess the effect of indoor residual spraying on malaria vector densities in a high malaria endemic setting in eastern Uganda as part of a cohort study where the use of long-lasting insecticidal nets (LLINs) was high.Methods Anopheles mosquitoes were sampled monthly using CDC light traps in 107 households selected randomly. Information on the use of malaria interventions in households was also gathered and recorded via a questionnaire. A Bayesian spatio-temporal model was then used to estimate mosquito densities adjusting for climatic and ecological variables and interventions.Results Anopheles gambiae (sensu lato) were most abundant (89.1%; n = 119,008) compared to An. funestus (sensu lato) (10.1%, n = 13,529). Modelling results suggest that the addition of indoor residual spraying (bendiocarb) in an area with high coverage of permethrin-impregnated LLINs (99%) was associated with a major decrease in mosquito vector densities. The impact on An. funestus (s.l.) (Rate Ratio 0.1508; 97.5% CI: 0.0144–0.8495) was twice as great as for An. gambiae (s.l.) (RR 0.5941; 97.5% CI: 0.1432–0.8577).ConclusionsHigh coverage of active ingredients on walls depressed vector populations in intense malaria transmission settings. Sustained use of combined interventions would have a long-term impact on mosquito densities, limiting infectious biting.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1917-3) contains supplementary material, which is available to authorized users.

The Effect of Indoor Residual Spraying on the Prevalence of Malaria Parasite Infection, Clinical Malaria and Anemia in an Area of Perennial Transmission and Moderate Coverage of Insecticide Treated Nets in Western Kenya.

BackgroundInsecticide treated nets (ITNs) and indoor residual spraying (IRS) have been scaled up for malaria prevention in sub-Saharan Africa. However, there are few studies on the benefit of implementing IRS in areas with moderate to high coverage of ITNs. We evaluated the impact of an IRS program on malaria related outcomes in western Kenya, an area of intense perennial malaria transmission and moderate ITN coverage (55–65% use of any net the previous night).MethodsThe Kenya Division of Malaria Control, with support from the US President’s Malaria Initiative, conducted IRS in one lowland endemic district with moderate coverage of ITNs. Surveys were conducted in the IRS district and a neighboring district before IRS, after one round of IRS in July-Sept 2008 and after a second round of IRS in April-May 2009. IRS was conducted with pyrethroid insecticides. At each survey, 30 clusters were selected for sampling and within each cluster, 12 compounds were randomly selected. The primary outcomes measured in all residents of selected compounds included malaria parasitemia, clinical malaria (P. falciparum infection plus history of fever) and anemia (Hb<8) of all residents in randomly selected compounds. At each survey round, individuals from the IRS district were matched to those from the non-IRS district using propensity scores and multivariate logistic regression models were constructed based on the matched dataset.ResultsAt baseline and after one round of IRS, there were no differences between the two districts in the prevalence of malaria parasitemia, clinical malaria or anemia. After two rounds of IRS, the prevalence of malaria parasitemia was 6.4% in the IRS district compared to 16.7% in the comparison district (OR = 0.36, 95% CI = 0.22–0.59, p<0.001). The prevalence of clinical malaria was also lower in the IRS district (1.8% vs. 4.9%, OR = 0.37, 95% CI = 0.20–0.68, p = 0.001). The prevalence of anemia was lower in the IRS district but only in children under 5 years of age (2.8% vs. 9.3%, OR = 0.30, 95% CI = 0.13–0.71, p = 0.006). Multivariate models incorporating both IRS and ITNs indicated that both had an impact on malaria parasitemia and clinical malaria but the independent effect of ITNs was reduced in the district that had received two rounds of IRS. There was no statistically significant independent effect of ITNs on the prevalence of anemia in any age group.ConclusionsBoth IRS and ITNs are effective tools for reducing malaria burden and when implemented in an area of moderate to high transmission with moderate ITN coverage, there may be an added benefit of IRS. The value of adding ITNs to IRS is less clear as their benefits may be masked by IRS. Additional monitoring of malaria control programs that implement ITNs and IRS concurrently is encouraged to better understand how to maximize the benefits of both interventions, particularly in the context of increasing pyrethroid resistance.