Impact Of Indoor Residual Spraying Research Articles

Using routine health data to evaluate the impact of indoor residual spraying on malaria transmission in Madagascar

IntroductionIndoor residual spraying (IRS) and insecticide-treated bed nets (ITNs) are cornerstone malaria prevention methods in Madagascar. This retrospective observational study uses routine data to evaluate the impacts of IRS overall,...

SARS-CoV-2 Antibody Prevalence in a Pediatric Cohort of Unvaccinated Children in Mérida, Yucatán, México

Background: The prevalence of SARS-CoV-2 exposure in children during the global Covid-19 pandemic has been underestimated due to lack of testing and the relatively mild symptoms in adolescents. Understanding the exposure rates in the pediatric population is essential as children are the last to receive vaccines and can act as a source for SARS-CoV-2 mutants that may threaten vaccine escape. This study aims to quantify the prevalence of anti-SARS-CoV-2 serum antibodies in children in a major city in Mexico.Methods: We obtained socioeconomic information and blood samples from 1,005 children and tested the sera for anti-SARS-CoV-2 IgG and IgM antibodies using lateral flow immunochromatography.Findings: We found that 25·5% of children in our cohort were positive for anti-SARS-CoV-2 antibodies and there was no correlation between age and antibody prevalence. Children that lived with large families were statistically more likely to have antibodies against SARS-CoV-2. Spatial analyses identified two hotspots of high SARS-CoV-2 seroprevalence in the west of the city.Interpretation: These results indicate that a large urban population of children has been exposed to SARS-CoV-2 and that a correlating factor was the number of people within the child’s household. There is also a larger population of children that may be susceptible to future infection upon easing of social distancing measures. This is the first analysis of a large cohort of children in a Latin American country and the results may inform public health decisions and vaccination strategies.Funding Information: This work was supported by NIH grant U01AI148069 and received support from the Universidad Autónoma de Yucatán.Declaration of Interests: The authors declare no conflicts of interestEthics Approval Statement: This study capitalized on a pediatric cohort established to evaluate the epidemiological impact of indoor residual spraying on arbovirus transmission and utilized serum stored after either participant written consent or verbal assent was attained.(7) All participants agreed to have their specimens kept for future use. All procedures for participant assent/consent, blood acquisition, and serum storage were approved by the Institutional Review Boards of Emory University (IRB00108666) and the Universidad Autónoma de Yucatán (CEI-05-2020).

Impact of IRS: Four-years of entomological surveillance of the Indian Visceral Leishmaniases elimination programme.

In 2005, Bangladesh, India and Nepal agreed to eliminate visceral leishmaniasis (VL) as a public health problem. The approach to this was through improved case detection and treatment, and controlling transmission by the sand fly vector Phlebotomus argentipes, with indoor residual spraying (IRS) of insecticide. Initially, India applied DDT with stirrup pumps for IRS, however, this did not reduce transmission. After 2015 onwards, the pyrethroid alpha-cypermethrin was applied with compression pumps, and entomological surveillance was initiated in 2016. Eight sentinel sites were established in the Indian states of Bihar, Jharkhand and West Bengal. IRS coverage was monitored by household survey, quality of insecticide application was measured by HPLC, presence and abundance of the VL vector was monitored by CDC light traps, insecticide resistance was measured with WHO diagnostic assays and case incidence was determined from the VL case register KAMIS. Complete treatment of houses with IRS increased across all sites from 57% in 2016 to 70% of houses in 2019, rising to >80% if partial house IRS coverage is included (except West Bengal). The quality of insecticide application has improved compared to previous studies, average doses of insecticide on filters papers ranged from 1.52 times the target dose of 25mg/m2 alpha-cypermethrin in 2019 to 1.67 times in 2018. Resistance to DDT has continued to increase, but the vector was not resistant to carbamates, organophosphates or pyrethroids. The annual and seasonal abundance of P. argentipes declined between 2016 to 2019 with an overall infection rate of 0.03%. This was associated with a decline in VL incidence for the blocks represented by the sentinel sites from 1.16 per 10,000 population in 2016 to 0.51 per 10,000 in 2019. Through effective case detection and management reducing the infection reservoirs for P. argentipes in the human population combined with IRS keeping P. argentipes abundance and infectivity low has reduced VL transmission. This combination of effective case management and vector control has now brought India within reach of the VL elimination targets.

The impact of indoor residual spraying on Plasmodium falciparum microsatellite variation in an area of high seasonal malaria transmission in Ghana, West Africa.

Here, we report the first population genetic study to examine the impact of indoor residual spraying (IRS) on Plasmodium falciparum in humans. This study was conducted in an area of high seasonal malaria transmission in Bongo District, Ghana. IRS was implemented during the dry season (November–May) in three consecutive years between 2013 and 2015 to reduce transmission and attempt to bottleneck the parasite population in humans towards lower diversity with greater linkage disequilibrium. The study was done against a background of widespread use of long‐lasting insecticidal nets, typical for contemporary malaria control in West Africa. Microsatellite genotyping with 10 loci was used to construct 392 P. falciparum multilocus infection haplotypes collected from two age‐stratified cross‐sectional surveys at the end of the wet seasons pre‐ and post‐IRS. Three‐rounds of IRS, under operational conditions, led to a >90% reduction in transmission intensity and a 35.7% reduction in the P. falciparum prevalence (p < .001). Despite these declines, population genetic analysis of the infection haplotypes revealed no dramatic changes with only a slight, but significant increase in genetic diversity (H e: pre‐IRS = 0.79 vs. post‐IRS = 0.81, p = .048). Reduced relatedness of the parasite population (p < .001) was observed post‐IRS, probably due to decreased opportunities for outcrossing. Spatiotemporal genetic differentiation between the pre‐ and post‐IRS surveys (D = 0.0329 [95% CI: 0.0209 – 0.0473], p = .034) was identified. These data provide a genetic explanation for the resilience of P. falciparum to short‐term IRS programmes in high‐transmission settings in sub‐Saharan Africa.

An entomological survey in the Sudanese Guinean environmental transition zone after indoor residual spraying, Chad.

Introductionmalaria is a major public health issue in Africa. In Chad in 2019, with 955,243 confirmed cases and 2,955 deaths, malaria is the main cause of consultations. A longitudinal entomological study was conducted in Moïssala Health District. Its objective was to assess the impact of indoor residual spraying with 80% bendiocarb wettable powder on malaria transmission.Methodstwo areas were defined for the study: Dembo, located in the sprayed area, Moïssala, in the untreated area. Two sampling methods were used: pyrethrum spray catches and human landing catches.Resultssixteen sessions of human landing catches totalling 32 man-nights were conducted and 160 rooms/site were sprayed. Two anopheles were captured in Dembo and 547 in Moïssala. In Moïssala, An coluzzii, An funestus and An rufipes were captured in the rooms and on human bait. An colluzzii and An funestus were captured in pyrethrum spray catches in Dembo. The anophelian human landing catches density was zero in Dembo while it was 8.38 bites/man/night in outdoor and 10.06 bits/man/night in indoor in Moïssala. Only An coluzziiwas found infected in human landing catches and sporozoite index of was 7.46% (10/134) in outdoor and 7.45% (12/161) in indoor in Moïssala. Malaria transmission was estimated at 0.63 infected bites/man/night in outdoor and 0.75 infected bites/man/night in indoor i.e. 229.95 infected bites/man/year in outdoor and 273.75 infected bites/man/year. In pyrethrum spray catches, An coluzzii and An rufipes were the two species found infected in Moïssala with sporozoite indices of 6.70% (23/343) and 20% (2/10) respectively. However, in Dembo, neither of the two captured mosquitoes was found infected.Conclusionthe indoor residual spraying campaign in the eastern zone of Moïssala has led to the collapse of vectors´ density and aggressiveness. However, its evaluation over a short period of time is not sufficient to assess the impact of malaria transmission in this constant and endemic malaria zone.

Malaria vector species composition and entomological indices following indoor residual spraying in regions bordering Lake Victoria, Tanzania

BackgroundVector control through long-lasting insecticidal nets (LLINs) and focal indoor residual spraying (IRS) is a major component of the Tanzania national malaria control strategy. In mainland Tanzania, IRS has been conducted annually around Lake Victoria basin since 2007. Due to pyrethroid resistance in malaria vectors, use of pyrethroids for IRS was phased out and from 2014 to 2017 pirimiphos-methyl (Actellic® 300CS) was sprayed in regions of Kagera, Geita, Mwanza, and Mara. Entomological surveillance was conducted in 10 sprayed and 4 unsprayed sites to determine the impact of IRS on entomological indices related to malaria transmission risk.MethodsWHO cone bioassays were conducted monthly on interior house walls to determine residual efficacy of pirimiphos-methyl CS. Indoor CDC light traps with or without bottle rotator were hung next to protected sleepers indoors and also set outdoors (unbaited) as a proxy measure for indoor and outdoor biting rate and time of biting. Prokopack aspirators were used indoors to capture resting malaria vectors. A sub-sample of Anopheles was tested by PCR to determine species identity and ELISA for sporozoite rate.ResultsAnnual IRS with Actellic® 300CS from 2015 to 2017 was effective on sprayed walls for a mean of 7 months in cone bioassay. PCR of 2016 and 2017 samples showed vector populations were predominantly Anopheles arabiensis (58.1%, n = 4,403 IRS sites, 58%, n = 2,441 unsprayed sites). There was a greater proportion of Anopheles funestus sensu stricto in unsprayed sites (20.4%, n = 858) than in sprayed sites (7.9%, n = 595) and fewer Anopheles parensis (2%, n = 85 unsprayed, 7.8%, n = 591 sprayed). Biting peaks of Anopheles gambiae sensu lato (s.l.) followed periods of rainfall occurring between October and April, but were generally lower in sprayed sites than unsprayed. In most sprayed sites, An. gambiae s.l. indoor densities increased between January and February, i.e., 10–12 months after IRS. The predominant species An. arabiensis had a sporozoite rate in 2017 of 2.0% (95% CI 1.4–2.9) in unsprayed sites compared to 0.8% (95% CI 0.5–1.3) in sprayed sites (p = 0.003). Sporozoite rates were also lower for An. funestus collected in sprayed sites.ConclusionThis study contributes to the understanding of malaria vector species composition, behaviour and transmission risk following IRS around Lake Victoria and can be used to guide malaria vector control strategies in Tanzania.

Combining next-generation indoor residual spraying and drug-based malaria control strategies: observational evidence of a combined effect in Mali

BackgroundSégou Region in central Mali is an area of high malaria burden with seasonal transmission. The region reports high access to and use of long-lasting insecticidal nets (LLINs), though the principal vector, Anopheles gambiae, is resistant to pyrethroids. From 2011 until 2016, several high-burden districts of Ségou also received indoor residual spraying (IRS), though in 2014 concerns about pyrethroid resistance prompted a shift in IRS products to a micro-encapsulated formulation of the organophosphate insecticide pirimiphos-methyl. Also in 2014, the region expanded a pilot programme to provide seasonal malaria chemoprevention (SMC) to children aged 3–59 months in two districts. The timing of these decisions presented an opportunity to estimate the impact of both interventions, deployed individually and in combination, using quality-assured passive surveillance data.MethodsA non-randomized, quasi-experimental time series approach was used to analyse monthly trends in malaria case incidence at the district level. Districts were stratified by intervention status: an SMC district, an IRS district, an IRS + SMC district, and control districts that received neither IRS nor SMC in 2014. The numbers of positive rapid diagnostic test (RDT +) results reported at community health facilities were aggregated and epidemiological curves showing the incidence of RDT-confirmed malaria cases per 10,000 person-months were plotted for the total all-ages and for the under 5 year old (u5) population. The cumulative incidence of RDT + malaria cases observed from September 2014 to February 2015 was calculated in each intervention district and compared to the cumulative incidence reported from the same period in the control districts.ResultsCumulative peak-transmission all-ages incidence was lower in each of the intervention districts compared to the control districts: 16% lower in the SMC district; 28% lower in the IRS district; and 39% lower in the IRS + SMC district. The same trends were observed in the u5 population: incidence was 15% lower with SMC, 48% lower with IRS, and 53% lower with IRS + SMC. The SMC-only intervention had a more moderate effect on incidence reduction initially, which increased over time. The IRS-only intervention had a rapid, comparatively large impact initially that waned over time. The impact of the combined interventions was both rapid and longer lasting.ConclusionEvaluating the impact of IRS with an organophosphate and SMC on reducing incidence rates of passive RDT-confirmed malaria cases in Ségou Region in 2014 suggests that combining the interventions had a greater effect than either intervention used individually in this high-burden region of central Mali with pyrethroid-resistant vectors and high rates of household access to LLINs.

An observational analysis of the impact of indoor residual spraying in Northern, Upper East, and Upper West Regions of Ghana: 2014 through 2017

BackgroundGhana has been implementing the indoor residual spraying (IRS) of insecticides since 2006, focusing operations in the north. Insecticide resistance concerns prompted a switch from pyrethroids to organophosphates, beginning gradually in 2011 and switching fully to the micro-encapsulated formulation of pirimiphosmethyl (PM CS), Actellic® 300CS, a third-generation indoor residual spraying (3GIRS) product, by 2014. Entomological surveillance studies have shown IRS to be a highly effective malaria control tool, but epidemiological evidence is needed as well. Countrywide prevalence surveys have shown that malaria parasite prevalence in children under 5 years of age in Northern, Upper East, and Upper West Regions had declined to less than 40% in each region by 2016. Similarly, malaria deaths in children under 5 years of age have also been declining nationally since 2009. Although IRS is suspected to have contributed to this decline, stronger evidence is needed to link the IRS interventions to the epidemiological impact.MethodsTo assess the epidemiological impact of Ghana’s IRS programmatic activities, a retrospective, observational analysis using routine epidemiological data was conducted to compare malaria incidence rates from IRS and non-IRS districts in Northern, Upper East, and Upper West Regions. Routine epidemiological data consisted of passive malaria case surveillance data reported in the District Health Information System 2 (DHIS2); with cases representing patients with suspected malaria who had sought care in the public health system and had received a confirmatory diagnosis with a positive malaria RDT result. Final routine data were extracted in September 2018. All districts that had received IRS were included in the analysis and compared to all non-IRS districts within the same region. In the Northern Region, only PMI districts were included in the analysis, as they had similar historical data.ResultsDistrict-level analysis from Northern Region from 2015 to 2017 of the aggregate malaria incidence reported from IRS districts relative to non-IRS comparator districts showed 39%, 26%, and 58% fewer confirmed malaria cases reported from IRS districts in 2015, 2016, and 2017, respectively. This translates to approximately 257,000 fewer cases than expected over the three years. In Upper East Region, the effect on reported malaria cases of withdrawing IRS from the region was striking; after spray operations were suspended in 2015, incidence increased an average of 485% per district (95% confidence interval: 330% to 640%) compared to 2014.ConclusionsThe current observational analysis results are in line with the entomological studies in demonstrating the positive contribution of IRS with a 3GIRS product to malaria control programmes in northern Ghana and the value of using routine surveillance and implementation data to rapidly assess the impact of vector control interventions in operational settings, even in complex implementation environments.

Kala-azar elimination in a highly-endemic district of Bihar, India: Asuccess story.

BackgroundVisceral leishmaniasis (VL) or Kala-azar has been a major public health problem in Bihar, India, for several decades. A few VL infected districts including Vaishali have reported >600 cases annually. Hence, in 2015, the Government of India entrusted ICMR-Rajendra Memorial Research Institute of Medical Sciences, Patna, to implement an integrated control strategy for achieving the VL elimination target (<1 case per 10,000 people at the block level) in the Vaishali District of Bihar.MethodologyThis study was conducted between January 2015 and December 2016. An integrated control strategy including the spatio-temporal mapping of VL-case distribution, active case detection, chemical-based vector control using indoor residual spraying (IRS), community awareness campaigns, the training of IRS members, the training of medical doctors for effective treatment, daily monitoring and the supervision of IRS activities, logistic management, post-IRS quality assurance, epidemiological surveillance, and entomological monitoring was performed. An insecticide quantification test was performed for evaluating the IRS quality on sprayed walls. A modern compression pump was used to maintain spray quality on different wall surfaces. The impact of IRS was assessed through sand fly collection in human dwellings and cattle sheds in pre- and post-IRS. The insecticide susceptibility of local P. argentipes was performed before each IRS round (in February and June) during 2015–2016. Statistical analysis such as the mean, percentage, and 95% CI were used to summarize the results.FindingsAll 16 blocks of the Vaishali District achieved the VL elimination target in 2016. The integrated VL control strategy helped reduce the number of VL cases from 664 in 2014 to 163 in 2016 and the number of endemic villages from 282 in 2014 to 142 in 2016. The case reduction rate was increased from 22.6% in 2014 to 58.8% in 2016. On average, 74 VL infected villages became Kala-azar free each year from 2015 to 2016.ConclusionsThe results of this study suggest that the elimination of VL is possible from all endemic blocks of Bihar if the integrated Vaishali VL control strategy is applied under strong monitoring and supervision.

Impact of indoor residual spraying with pirimiphos-methyl (Actellic 300CS) on entomological indicators of transmission and malaria case burden in Migori County, western Kenya

Indoor residual spraying (IRS) of insecticides is a major vector control strategy for malaria prevention. We evaluated the impact of a single round of IRS with the organophosphate, pirimiphos-methyl (Actellic 300CS), on entomological and parasitological parameters of malaria in Migori County, western Kenya in 2017, in an area where primary vectors are resistant to pyrethroids but susceptible to the IRS compound. Entomological monitoring was conducted by indoor CDC light trap, pyrethrum spray catches (PSC) and human landing collection (HLC) before and after IRS. The residual effect of the insecticide was assessed monthly by exposing susceptible An. gambiae s.s. Kisumu strain to sprayed surfaces in cone assays and measuring mortality at 24 hours. Malaria case burden data were extracted from laboratory records of four health facilities within the sprayed area and two adjacent unsprayed areas. IRS was associated with reductions in An. funestus numbers in the intervention areas compared to non-intervention areas by 88% with light traps (risk ratio [RR] 0.12, 95% CI 0.07–0.21, p < 0.001) and 93% with PSC collections (RR = 0.07, 0.03–0.17, p < 0.001). The corresponding reductions in the numbers of An. arabiensis collected by PSC were 69% in the intervention compared to the non-intervention areas (RR = 0.31, 0.14–0.68, p = 0.006), but there was no significant difference with light traps (RR = 0.45, 0.21–0.96, p = 0.05). Before IRS, An. funestus accounted for over 80% of Anopheles mosquitoes collected by light trap and PSC in all sites. After IRS, An. arabiensis accounted for 86% of Anopheles collected by PSC and 66% by CDC light trap in the sprayed sites while the proportion in non-intervention sites remained unchanged. No sporozoite infections were detected in intervention areas after IRS and biting rates by An. funestus were reduced to near zero. Anopheles funestus and An. arabiensis were fully susceptible to pirimiphos-methyl and resistant to pyrethroids. The residual effect of Actellic 300CS lasted ten months on mud and concrete walls. Malaria case counts among febrile patients within IRS areas was lower post- compared to pre-IRS by 44%, 65% and 47% in Rongo, Uriri and Nyatike health facilities respectively. A single application of IRS with Actellic 300CS in Migori County provided ten months protection and resulted in the near elimination of the primary malaria vector An. funestus and a corresponding reduction of malaria case count among out-patients. The impact was less on An. arabiensis, most likely due to their exophilic nature.

Lessons learned, challenges and outlooks for decision-making after a decade of experience monitoring the impact of indoor residual spraying in Benin, West Africa

BackgroundSince 2008, Indoor Residual Spraying (IRS) has been performed in Benin in 19 districts, including 4 in southern Benin, 9 in Atacora, and 8 in Atacora, Alibori and Donga in northern Benin. However, Benin still struggles with questions about IRS cost–benefit and epidemiological impact. Lessons learned and challenges from 10 years of IRS in Benin to be shared with the stakeholders involved in vector control implementation for decision-making.MethodsEntomological parameters have been assessed entomological parameters in IRS communes since 2008. In all IRS intervention communes, decreases in human biting rate (HBR) of Anopheles gambiae, blood feeding inhibition and entomological inoculation rate (EIR) as compared to control district have been measured.ResultsEIR was reduced by 80–90%, which is encouraging, but should be observed with caution because: (i) the reduction may be insufficient to decrease epidemiological indicators given that the residual EIR in IRS districts is still higher than it is in some regions of stable malaria; (ii) the reduction in EIR is based on comparisons with control communes, but it is difficult to select control areas with the same environmental characteristics as intervention areas; (iii) despite the reduction, half of all mosquitoes that entered IRS-treated houses succeeded in taking human blood meals. Further, there are behaviours among Benin’s population that limit IRS efficacy, including recent data showing that > 90% of people are not protected by IRS between 7 and 10 p.m. This is due to the fact that they remain outdoors and that most people are not protected from mosquito bites after 10 p.m. because they either sleep outdoors without IRS protection or indoors without an ITN. Moreover, people have large amounts of clothing hanging on walls where mosquitoes can rest instead of IRS-treated walls. Finally, other components are important to consider in implementing IRS among which: (i) Vector resistance management strategies are sometimes poorly understood; this is actually different from the need to replace one insecticide with another after the emergence of resistance; (ii) African countries should prepare to finance IRS themselves.ConclusionTo curtail residual malaria transmission, additional interventions able to target vectors escaping IRS should be prioritized.

Models of effectiveness of interventions against malaria transmitted by Anopheles albimanus

BackgroundMost impact prediction of malaria vector control interventions has been based on African vectors. Anopheles albimanus, the main vector in Central America and the Caribbean, has higher intrinsic mortality, is more zoophilic and less likely to rest indoors. Therefore, relative impact among interventions may be different. Prioritizing interventions, in particular for eliminating Plasmodium falciparum from Haiti, should consider local vector characteristics.MethodsField bionomics data of An. albimanus from Hispaniola and intervention effect data from southern Mexico were used to parameterize mathematical malaria models. Indoor residual spraying (IRS), insecticide-treated nets (ITNs), and house-screening were analysed by inferring their impact on the vectorial capacity in a difference-equation model. Impact of larval source management (LSM) was assumed linear with coverage. Case management, mass drug administration and vaccination were evaluated by estimating their effects on transmission in a susceptible-infected-susceptible model. Analogous analyses were done for Anopheles gambiae parameterized with data from Tanzania, Benin and Nigeria.ResultsWhile LSM was equally effective against both vectors, impact of ITNs on transmission by An. albimanus was much lower than for An. gambiae. Assuming that people are outside until bedtime, this was similar for the impact of IRS with dichlorodiphenyltrichloroethane (DDT) or bendiocarb, and impact of IRS was less than that of ITNs. However, assuming people go inside when biting starts, IRS had more impact on An. albimanus than ITNs. While house-screening had less impact than ITNs or IRS on An. gambiae, it had more impact on An. albimanus than ITNs or IRS. The impacts of chemoprevention and chemotherapy were comparable in magnitude to those of strategies against An. albimanus. Chemo-prevention impact increased steeply as coverage approached 100%, whilst clinical-case management impact saturated because of remaining asymptomatic infections.ConclusionsHouse-screening and repellent IRS are potentially highly effective against An. albimanus if people are indoors during the evening. This is consistent with historical impacts of IRS with DDT, which can be largely attributed to excito-repellency. It also supports the idea that housing improvements have played a critical role in malaria control in North America. For elimination planning, impact estimates need to be combined with feasibility and cost-analysis.

Synergy and timing: a concurrent mass medical campaign predicted to augment indoor residual spraying for malaria

BackgroundControl programmes for high burden countries are tasked with charting effective multi-year strategies for malaria control within significant resource constraints. Synergies between different control tools, in which more than additive benefit accrues from interventions used together, are of interest because they may be used to obtain savings or to maximize health impact per expenditure. One commonly used intervention in sub-Saharan Africa is indoor residual spraying (IRS), typically deployed through a mass campaign. While possible synergies between IRS and long-lasting insecticide-treated nets (LLINs) have been investigated in multiple transmission settings, coordinated synergy between IRS and other mass medical distribution campaigns have not attracted much attention. Recently, a strong timing-dependent synergy between an IRS campaign and a mass drug administration (MDA) was theoretically quantified. These synergistic benefits likely differ across settings depending on transmission intensity and its overall seasonal pattern.MethodsHigh coverage interventions are modelled in different transmission environments using two methods: a Ross–Macdonald model variant and openmalaria simulations. The impact of each intervention strategy was measured through its ability to prevent host infections over time, and the effects were compared to the baseline case of deploying interventions in isolation.ResultsBy modelling IRS and MDA together and varying their deployment times, a strong synergy was found when the administered interventions overlapped. The added benefit of co-timed interventions was robust to differences in the models. In the Ross–Macdonald model, the impact compared was roughly double the sequential interventions in most transmission settings. Openmalaria simulations of this medical control augmentation of an IRS campaign show an even stronger response with the same timing relationship.ConclusionsThe strong synergies found for these control tools between the complementary interventions demonstrate a general feature of effective concurrent campaign-style vector and medical interventions. A mass treatment campaign is normally short-lived, especially in higher transmission settings. When co-timed, the rapid clearing of the host parasite reservoir via chemotherapy is protected from resurgence by the longer duration of the vector control. An effective synchronous treatment campaign has the potential to greatly augment the impact of indoor residual spraying. Mass screening and treatment (MSAT) with highly sensitive rapid diagnostic tests may demonstrate a comparable trend while mass LLIN campaigns may similarly coordinate with MDA/MSAT.

Indoor Residual Spraying for Malaria Control in Sub-Saharan Africa 1997 to 2017: An Adjusted Retrospective Analysis

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. 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. Findings: The number of countries implementing IRS has increased considerably although coverage in-country is often low, particularly in West Africa. From 1997 to 2010 there was an expansion of IRS using organochlorines (DDT) and pyrethroids. From 2011, carbamates partly replaced these insecticides and organophosphate use increased from 2013 onwards, however, policy recommendations to rotate between insecticide classes were rarely followed. Interpretation: Our results highlight trends in IRS coverage and insecticide choice in sub Saharan Africa. The data presented here can improve studies on the impact of IRS on malaria incidence and on insecticide resistance development and help to guide future malaria control efforts. Funding Statement: Wellcome Trust grant 108440/Z/15/Z. Declaration of Interests: The authors declare no conflict of interest. Ethics Approval Statement: Not Required.

Impact of indoor residual spraying on malaria parasitaemia in the Bunkpurugu-Yunyoo District in northern Ghana

BackgroundSince 2008 indoor residual spraying (IRS) has become one of the interventions for malaria control in Ghana. Key partners in the scale-up of IRS have been the US President’s Malaria Initiative (PMI) and AngloGold Ashanti (AGA). This study was designed to assess the impact of IRS on malaria parasitaemia among children less than 5 years-old in Bunkpurugu-Yunyoo, one of PMI-sponsored districts in northern Ghana, where rates of parasitaemia significantly exceeded the national average.MethodsTwo pre-IRS cross-sectional surveys using microscopy were conducted in November 2010 and April 2011 to provide baseline estimates of malaria parasitaemia for the high and low transmission seasons, respectively. IRS for the entire district was conducted in May/June to coincide with the beginning of the rains. Alpha-cypermethrin was used in 2011 and 2012, and changed to pirimiphos-methyl in 2013 and 2014 following declining susceptibility of local vectors to pyrethroids. Post-IRS cross-sectional surveys were conducted between 2011 and 2014 to provide estimates for the end of high (2011–2014) and the end of low (2012–2013) transmission seasons.ResultsThe end of high transmission season prevalence of asexual parasitaemia declined marginally from 52.4% (95% CI: 50.0–54.7%) to 47.7% (95% CI: 45.5–49.9%) following 2 years of IRS with alpha-cypermethrin. Prevalence declined substantially to 20.6% (95% CI: 18.4–22.9%) following one year of IRS with pirimiphos-methyl.ConclusionsThe use of a more efficacious insecticide for IRS can reduce malaria parasitaemia among children less than 5 years-old in northern Ghana.

Entomological impact of indoor residual spraying with pirimiphos-methyl: a pilot study in an area of low malaria transmission in Senegal

BackgroundScaling-up of effective anti-malarial control strategies in Central-West region of Senegal has resulted in the sharp decline in malaria prevalence in this area. However, despite these strategies, residual malaria transmission has been observed in some villages (hot spots). The objective of this study was to assess the impact of indoor residual spraying (IRS) with pirimiphos-methyl on malaria transmission in hot spot areas.MethodsThe malaria vector population dynamics were monitored in each of the six selected villages (4 of which used IRS, 2 were unsprayed control areas) using overnight human landing catches (HLC) and pyrethrum spray catches (PSC). The host source of blood meals from freshly fed females collected using PSC was identified using the direct ELISA method. Females caught through HLC were tested by ELISA for the detection of Plasmodium falciparum circumsporozoite protein and Anopheles gambiae complex was identified using PCR.ResultsPreliminary data shown that the densities of Anopheles populations were significantly lower in the sprayed areas (179/702) compared to the control. Overall, malaria transmission risk was 14 times lower in the intervention zone (0.94) compared to the control zone (12.7). In the control areas, three Anopheles species belonging to the Gambiae complex (Anopheles arabiensis, Anopheles coluzzii and Anopheles melas) maintained the transmission, while only An. coluzzii was infective in the sprayed areas.ConclusionThe preliminary data from this pilot study showed that IRS with the CS formulation of pirimiphos-methyl is likely very effective in reducing malaria transmission risk. However, additional studies including further longitudinal entomological surveys as well as ecological and ethological and genetical characterization of vectors species and their populations are needed to better characterize the entomological impact of indoor residual spraying with pirimiphos-methyl in the residual transmission areas of Senegal.

An observational analysis of the impact of indoor residual spraying with non-pyrethroid insecticides on the incidence of malaria in S\xe9gou Region, Mali: 2012\u20132015

BackgroundSégou Region in Central Mali is an area of high malaria burden with seasonal transmission, high access to and use of long-lasting insecticidal nets (LLINs), and resistance to pyrethroids and DDT well documented in Anopheles gambiae s.l. (the principal vector of malaria in Mali). Ségou has recently received indoor residual spraying (IRS) supported by Mali’s collaboration with the US President’s Malaria Initiative/Africa Indoor Residual Spraying programme. From 2012 to 2015, two different non-pyrethroid insecticides: bendiocarb in 2012 and 2013 and pirimiphos-methyl in 2014 and 2015, were used for IRS in two districts. This report summarizes the results of observational analyses carried out to assess the impact of these IRS campaigns on malaria incidence rates reported through local and district health systems before and after spraying.MethodsA series of retrospective time series analyses were performed on 1,382,202 rapid diagnostic test-confirmed cases of malaria reported by district routine health systems in Ségou Region from January 2012 to January 2016. Malaria testing, treatment, surveillance and reporting activities remained consistent across districts and years during the study period, as did LLIN access and use estimates as well as An. gambiae s.l. insecticide resistance patterns. Districts were stratified by IRS implementation status and all-age monthly incidence rates were calculated and compared across strata from 2012 to 2014. In 2015 a regional but variable scale-up of seasonal malaria chemoprevention complicated the region-wide analysis; however IRS operations were suspended in Bla District that year so a difference in differences approach was used to compare 2014 to 2015 changes in malaria incidence at the health facility level in children under 5-years-old from Bla relative to changes observed in Barouéli, where IRS operations were consistent.ResultsDuring 2012–2014, rapid reductions in malaria incidence were observed during the 6 months following each IRS campaign, though most of the reduction in cases (70% of the total) was concentrated in the first 2 months after each campaign was completed. Compared to non-IRS districts, in which normal seasonal patterns of malaria incidence were observed, an estimated 286,745 total fewer cases of all-age malaria were observed in IRS districts. The total cost of IRS in Ségou was around 9.68 million USD, or roughly 33.75 USD per case averted. Further analysis suggests that the timing of the 2012–2014 IRS campaigns (spraying in July and August) was well positioned to maximize public health impact. Suspension of IRS in Bla District after the 2014 campaign resulted in a 70% increase in under-5-years-old malaria incidence rates from 2014 to 2015, significantly greater (p = 0.0003) than the change reported from Barouéli District, where incidence rates remained the same.ConclusionsFrom 2012 to 2015, the annual IRS campaigns in Ségou are associated with several hundred thousand fewer cases of malaria. This work supports the growing evidence that shows that IRS with non-pyrethroid insecticides is a wise public health investment in areas with documented pyrethroid resistance, high rates of LLIN coverage, and where house structures and population densities are appropriate. Additionally, this work highlights the utility of quality-assured and validated routine surveillance and well defined observational analyses to rapidly assess the impact of malaria control interventions in operational settings, helping to empower evidence-based decision making and to further grow the evidence base needed to better understand when and where to utilize new vector control tools as they become available.

Malaria Prevalence: Influence of Communal Knowledge and Practices Post IRS Intervention in Epe, Southwest, Nigeria

Malaria still remains a major public health in Nigeria despite interventions that are in place. This study aims to evaluate the impact of the local community’s Knowledge Attitudes and Practices (KAP) and the impact of Indoor Residual Spraying (IRS) exercise in Epe community.Malaria rapid testing was used to determine the prevalence of malaria from a total of 252 participants. Structured questionnaires were administered to 252 randomly selected households to obtain information on malaria related KAP. Hospital data relating to malaria outpatient/inpatient visits were perused from the community health facilities.The overall prevalence of malaria was 36.11%. There was a significant difference in the prevalence of malaria between participants with appropriate information about malaria and participants without appropriate information (p&lt;0.05). The frequency of hospital visits due to malaria between the pre-IRS and post IRS periods was insignificant (p&gt;0.05). The proportion (53.98%) of the households whom their houses were not sprayed may contribute to the mild impact of IRS observed.The persistence of malaria among participants with low KAP and the households who are not beneficiary of the concluded IRS exercise cannot be over-emphasized. The need for intensification of malaria awareness programmes, surveillance and proper allocation of interventions are advocated.

Insecticide resistance in phlebotomine sandflies in Southeast Asia with emphasis on the Indian subcontinent.

BackgroundVisceral leishmaniasis, commonly known as kala-azar in India, is a global public health problem. In Southeast Asia, Bangladesh, Bhutan, India, Nepal, Sri Lanka and Thailand are endemic for visceral leishmaniasis. The role of sandflies as the vector of kala-azar was first confirmed in 1942 in India. Insecticide resistance in Phlebotomus argentipes Annandale and Brunetti, the vector of kala-azar in the Indian subcontinent, was first reported in 1987 in Bihar, India. This article provides a scoping review of the studies undertaken from 1959 to 2015 on insecticide resistance in P. argentipes and P. papatasi (Scopoli), the vectors of visceral and cutaneous leishmaniasis respectively, in Southeast Asia, mainly in Bangladesh, India, Nepal and Sri Lanka.ResultsStudies undertaken in areas of Bihar and West Bengal in India where kala-azar is endemic have reported resistance of P. argentipes to DDT, while in non-endemic areas it has been reported to be susceptible. In areas of Nepal bordering India, there are indications of resistance to DDT; biochemical resistance has been reported in Sri Lanka. No laboratory studies have been undertaken in Bangladesh; however, the sandfly vector is reported to be still susceptible to pyrethroids in all kala-azar endemic areas in the aforementioned countries.ConclusionsStudies are needed to determine the resistance of sandfly vectors to all available classes of potential insecticides in kala-azar endemic areas. There is a need to assess the impact of indoor residual spraying with DDT and pyrethroids on the incidence of kala-azar in India where 54 districts remain endemic for the disease, strengthen entomological surveillance capacity, and develop and implement an insecticide management plan. Alpha-cypermethrin indoor residual spraying has been introduced in 33 kala-azar endemic districts in Bihar State of India in a pilot trial; the outcomes should be used to inform decisions on expanding coverage with alpha-cypermethrin in all remaining endemic districts to achieve the revised goal of elimination of visceral leishmaniasis by 2020.Electronic supplementary materialThe online version of this article (doi:10.1186/s40249-016-0200-3) contains supplementary material, which is available to authorized users.

Indoor Residual Spraying (IRS) and Its Impact on Malaria Prevalence in West Africa Using the Panel Data Regression Model

Malaria remains one of the most important public health concerns across the globe. In 2012 alone, the World Health Organization reported an estimated 207 million cases and associated death of about 670,000 with majority of cases coming from Africa. There have been tremendous efforts at controlling malaria and its related mortality. The two main interventions recommended by the World Health Organization for malaria control and prevention are, Indoor Residual Spraying (IRS) and the use of Insecticides Treated Nets (ITNs). On a limited scope, studies conducted within some communities and limited geographical areas have shown the effectiveness of IRS in reducing the prevalence of the disease. However, not many such studies have looked at the impact of IRS on the prevalence of malaria at the universal level. This paper seeks to evaluate the impact of Indoor Residual Spraying on the prevalence of malaria in West Africa by accounting for the effects of alternative malaria prevention strategies, economic, demographic and funding availability for malaria prevention and control. A panel data for fifteen West African countries from 2008 to 2012 was analyzed. The results showed that for years in which Indoor Residual Spraying was implemented, prevalence of malaria reduced by 71% compared to periods preceding the implementation of Indoor Residual Spraying. This paper further established that ITN coverage, funding availability for Malaria intervention and gross domestic product have a significant negative impact on the prevalence of Malaria while population and the combination of Indoor Residual Spraying and ITN have a significant positive impact on the prevalence of the disease. Indoor Residual Spraying and its impact on the prevalence of Malaria were observed to be higher than the impact of ITN coverage on the prevalence of the disease. These findings are relevant for policy direction regarding the continuance of Indoor Residual Spraying implementation especially in the post 2015 agenda for malaria control and prevention.