The effect of indoor residual spraying on malaria and anemia in a high-transmission area of northern Uganda

Impact of population based indoor residual spraying with and without mass drug administration with dihydroartemisinin-piperaquine on malaria prevalence in a high transmission setting: a quasi-experimental controlled before-and-after trial in northeastern Uganda

BACKGROUND

Declines in malaria burden in Uganda have slowed. Modelling predicts that indoor residual spraying (IRS) and mass drug administration (MDA), when co-timed, have synergistic impact. This study investigated additional protective impact of population-based MDA on malaria prevalence, if any, when added to IRS, as compared with IRS alone and with standard of care (SOC).

METHODS

The 32-month quasi-experimental controlled before-and-after trial enrolled an open cohort of residents (46,765 individuals, 1st enumeration and 52,133, 4th enumeration) of Katakwi District in northeastern Uganda. Consented participants were assigned to three arms based on residential subcounty at study start: MDA+IRS, IRS, SOC. IRS with pirimiphos methyl and MDA with dihydroartemisinin- piperaquine were delivered in 4 co-timed campaign-style rounds 8 months apart. The primary endpoint was population prevalence of malaria, estimated by 6 cross-sectional surveys, starting at baseline and preceding each subsequent round.

RESULTS

Comparing malaria prevalence in MDA+IRS and IRS only arms over all 6 surveys (intention-to-treat analysis), roughly every 6 months post-interventions, a geostatistical model found a significant additional 15.5% (95% confidence interval (CI): [13.7%, 17.5%], Z = 9.6, p = 5e-20) decrease in the adjusted odds ratio (aOR) due to MDA for all ages, a 13.3% reduction in under 5's (95% CI: [10.5%, 16.8%], Z = 4.02, p = 5e-5), and a 10.1% reduction in children 5-15 (95% CI: [8.5%, 11.8%], Z = 4.7, p = 2e-5). All ages residents of the MDA + IRS arm enjoyed an overall 80.1% reduction (95% CI: [80.0%, 83.0%], p = 0.0001) in odds of qPCR confirmed malaria compared with SOC residents. Secondary difference-in-difference analyses comparing surveys at different timepoints to baseline showed aOR (MDA + IRS vs IRS) of qPCR positivity between 0.28 and 0.66 (p < 0.001). Of three serious adverse events, one (nonfatal) was considered related to study medications. Limitations include the initial non-random assignment of study arms, the single large cluster per arm, and the lack of an MDA-only arm, considered to violate equipoise.

CONCLUSIONS

Despite being assessed at long time points 5-7 months post-round, MDA plus IRS provided significant additional protection from malaria infection over IRS alone. Randomized trials of MDA in large areas undergoing IRS recommended as well as cohort studies of impact on incidence.

TRIAL REGISTRATION

This trial was retrospectively registered 11/07/2018 with the Pan African Clinical Trials Registry (PACTR201807166695568).

Effectiveness of indoor residual spraying on malaria control: a systematic review and meta-analysis

Background

Indoor residual spraying (IRS) is one of the key interventions recommended by World Health Organization in preventing malaria infection. We aimed to conduct a systematic review and meta-analysis of global studies about the impact of IRS on malaria control.

Method

We searched PubMed, Web of Science, Embase, and Scopus for relevant studies published from database establishment to 31 December 2021. Random-effects models were used to perform meta-analysis and subgroup analysis to pool the odds ratio (OR) and 95% confidence interval (CI). Meta-regression was used to investigate potential factors of heterogeneity across studies.

Results

Thirty-eight articles including 81 reports and 1,174,970 individuals were included in the meta-analysis. IRS was associated with lower rates of malaria infection (OR = 0.35, 95% CI: 0.27–0.44). The significantly higher effectiveness was observed in IRS coverage ≥ 80% than in IRS coverage < 80%. Pyrethroids was identified to show the greatest performance in malaria control. In addition, higher effectiveness was associated with a lower gross domestic product as well as a higher coverage of IRS and bed net utilization.

Conclusions

IRS could induce a positive effect on malaria infection globally. The high IRS coverage and the use of pyrethroids are key measures to reduce malaria infection. More efforts should focus on increasing IRS coverage, developing more effective new insecticides against malaria, and using multiple interventions comprehensively to achieve malaria control goals.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40249-022-01005-8.

Vulnerability of populations to malaria after indoor residual spraying is withdrawn from areas where its use has previously been sustained: a protocol for a systematic review

INTRODUCTION

With its proven effectiveness, indoor residual spraying (IRS) as a malaria vector control strategy forms one of the reliable vector control strategies, especially when at least 80% of the population is covered. However, to date, there is uncertainty regarding the consequences of IRS withdrawal on malaria control when there is no clear exit strategy in place. Therefore, there is a need to comprehensively update literature regarding malaria burden indicators when IRS is withdrawn following sustained use.

METHODS AND ANALYSIS

This protocol follows the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. A systematic search of studies published between 2000 and 2022 will be performed in CINAHL, Embase, MEDLINE, ProQuest, PsychInfo, Scopus and OpenGrey. Preset eligibility criteria will be used to identify studies for inclusion by two independent reviewers. Title/abstracts will first be screened and potentially eligible ones screened using their full-text publications. Any conflicts/discrepancies at the two stages will be resolved through regular discussion sessions. Included studies will be extracted to capture study and patient characteristics and relevant outcomes (malaria incidence and malaria vector abundance). Relevant tools will be used to assess the risk of bias in the studies measuring the impact of withdrawal. A meta-analysis will be performed if sufficient homogeneity exists; otherwise, data arising will be presented using tables and by employing narrative synthesis techniques. Heterogeneity will be assessed using a combination of visual inspection of the forest plot along with consideration of the χ² test and I² statistic results.

ETHICS AND DISSEMINATION

Ethics approval is not applicable for this study since no original data will be collected. The results will be disseminated through peer-reviewed publications and conference presentations. Furthermore, this systematic review will inform the design of exit strategies for IRS-based programmes in malaria-endemic areas.

PROSPERO REGISTRATION NUMBER

CRD42022310655.

Association between indoor residual spraying and pregnancy outcomes: a quasi-experimental study from Uganda

BACKGROUND

Malaria is a risk factor for adverse pregnancy outcomes. Indoor residual spraying with insecticide (IRS) reduces malaria infections, yet the effects of IRS on pregnancy outcomes are not well established. We evaluated the impact of a large-scale IRS campaign on pregnancy outcomes in Eastern Uganda.

METHODS

Birth records (n = 59 992) were obtained from routine surveillance data at 25 health facilities from five districts that were part of the IRS campaign and six neighbouring control districts ∼27 months before and ∼24 months after the start of the campaign (January 2013-May 2017). Campaign effects on low birthweight (LBW) and stillbirth incidence were estimated using the matrix completion method (MC-NNM), a machine-learning approach to estimating potential outcomes, and compared with the difference-in-differences (DiD) estimator. Subgroup analyses were conducted by HIV and gravidity.

RESULTS

MC-NNM estimates indicated that the campaign was associated with a 33% reduction in LBW incidence: incidence rate ratio (IRR) = 0.67 [95% confidence interval (CI): 0.49-0.93)]. DiD estimates were similar to MC-NNM [IRR = 0.69 (0.47-1.01)], despite a parallel trends violation during the pre-IRS period. The campaign was not associated with substantial reductions in stillbirth incidence [IRRMC-NNM = 0.94 (0.50-1.77)]. HIV status modified the effects of the IRS campaign on LBW [βIRSxHIV = 0.42 (0.05-0.78)], whereby HIV-negative women appeared to benefit from the campaign [IRR = 0.70 (0.61-0.81)], but not HIV-positive women [IRR = 1.12 (0.59-2.12)].

CONCLUSIONS

Our results support the effectiveness of the campaign in Eastern Uganda based on its benefit to LBW prevention, though HIV-positive women may require additional interventions. The IRS campaign was not associated with a substantively lower stillbirth incidence, warranting further research.

Reduction in malaria burden following the introduction of indoor residual spraying in areas protected by long-lasting insecticidal nets in Western Kenya, 2016-2018

Background

Long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) are the main malaria vector control measures deployed in Kenya. Widespread pyrethroid resistance among the primary vectors in Western Kenya has necessitated the re-introduction of IRS using an organophosphate insecticide, pirimiphos-methyl (Actellic® 300CS), as a pyrethroid resistance management strategy. Evaluation of the effectiveness of the combined use of non-pyrethroid IRS and LLINs has yielded varied results. We aimed to evaluate the effect of non-pyrethroid IRS and LLINs on malaria indicators in a high malaria transmission area.

Methods

We reviewed records and tallied monthly aggregate of outpatient department (OPD) attendance, suspected malaria cases, those tested for malaria and those testing positive for malaria at two health facilities, one from Nyatike, an intervention sub-county, and one from Suba, a comparison sub-county, both located in Western Kenya, from February 1, 2016, through March 31, 2018. The first round of IRS was conducted in February–March 2017 in Nyatike sub-county and the second round one year later in both Nyatike and Suba sub-counties. The mass distribution of LLINs has been conducted in both locations. We performed descriptive analysis and estimated the effect of the interventions and temporal changes of malaria indicators using Poisson regression for a period before and after the first round of IRS.

Results

A higher reduction in the intervention area in total OPD, the proportion of OPD visits due to suspected malaria, testing positivity rate and annual malaria incidences were observed except for the total OPD visits among the under 5 children (59% decrease observed in the comparison area vs 33% decrease in the intervention area, net change -27%, P <0.001). The percentage decline in annual malaria incidence observed in the intervention area was more than twice the observed percentage decline in the comparison area across all the age groups. A marked decline in the monthly testing positivity rate (TPR) was noticed in the intervention area, while no major changes were observed in the comparison area. The monthly TPR reduced from 46% in February 2016 to 11% in February 2018, representing a 76% absolute decrease in TPR among all ages (RR = 0.24, 95% CI 0.12–0.46). In the comparison area, TPR was 16% in both February 2016 and February 2018 (RR = 1.0, 95% CI 0.52–2.09). A month-by-month comparison revealed lower TPR in Year 2 compared to Year 1 in the intervention area for most of the one year after the introduction of the IRS.

Conclusions

Our findings demonstrated a reduced malaria burden among populations protected by both non-pyrethroid IRS and LLINs implying a possible additional benefit afforded by the combined intervention in the malaria-endemic zone.

Asymptomatic malaria and nurturing factors in lowlands of Ethiopia: A community based cross-sectional study

Although asymptomatic malaria cases are reservoirs of malaria parasites, there is limited evidence on the burden and nurturing factors in malaria endemic areas during dry season. Thus, this study aims to determine the prevalence of asymptomatic malaria infection and nurturing factors in endemic areas of Ethiopia during dry season.A community based cross-sectional study was conducted in malaria endemic areas in Ethiopia. Six villages with a total of 1,366 households from three malaria endemic regions of Ethiopia were selected by stratified random sampling method. One asymptomatic member of the household was randomly selected from each household. A structured questionnaire was used to collect data on socio-demographic and other factors. Finger prick blood samples for malaria rapid diagnostic test (RDT) and blood film were collected and examined. Multivariable logistic regression model was used to determine the nurturing factors with asymptomatic malaria infection. The prevalence of asymptomatic malaria infection was 7.7% with both blood film microscopic examination and malaria RDT. Plasmodium falciparum was the predominantly observed type of malaria species (48.0%). The presence of bodies of water around the households (adjusted odds ratio (AOR = 5.4; 95% CI (2.7 ─ 9.7); p < 0.000), infrequent indoor residual spray (IRS) applied four to six months ago (AOR = 3.5; 95% CI (1.0─11.6); p = 0.045) and more than six months (AOR = 5.2; 95% CI (1.3─20.5); p = 0.019) and personal protection measure for malaria prevention (LLIN, repellent and clothing) (AOR = 0.41; 95% CI (0.2 ─ 0.9); p = 0.028) were associated significantly with asymptomatic malaria infection. The prevalence of asymptomatic malaria infection during dry season was considerable. Strong interventions that target stagnant bodies of water, infrequent household IRS spray and personal protection measure for malaria prevention is required to decrease asymptomatic malaria infection during dry season.

Integrated malaria prevention in rural communities in Uganda: a qualitative feasibility study for a randomised controlled trial

Background

A randomised controlled trial (RCT) on integrated malaria prevention, which advocates the use of several malaria prevention methods holistically, has been proposed. However, before conducting an RCT, it is recommended that a feasibility study is carried out to provide information to support the main study, particularly for such a complex intervention. Therefore, a feasibility study for an RCT on integrated malaria prevention in Uganda was conducted.

Methods

The qualitative study carried out in Wakiso District employed focus group discussions (FGDs) and key informant interviews (KIIs) to explore community willingness to participate in the RCT as well as assess stakeholder perspectives on the future study. The participants of the FGDs were community members, while the key informants were selected from malaria stakeholders including Ministry of Health officials, health practitioners, local leaders, district health team members, and community health workers (CHWs). Thematic analysis was employed with the support of NVivo.

Results

A total of 12 FGDs and 19 KIIs were conducted. Five main themes emerged from the study: malaria prevention practices related to integrated malaria prevention; preferred malaria prevention methods in the integrated approach; potential challenges of integrated malaria prevention; perspectives on the proposed RCT; and sustainability of integrated malaria prevention. Despite a few methods being employed holistically in the community, insecticide-treated nets were the most widely used and preferred method for malaria prevention mainly because they were provided free by the government. The main challenges in the integrated approach were the high cost of some methods such as house screening, and concerns about the potential side effects of insecticide-based methods such as indoor residual spraying. Participants expressed high willingness to participate in the RCT to promote the use of multiple methods in their households and community. Involvement of CHWs during implementation was proposed as a sustainability strategy for the RCT interventions.

Conclusion

There was high willingness to participate in the proposed RCT on integrated malaria prevention. However, high cost and perceived negative health effects from some methods were identified as potential challenges. The type of methods to be included as well as sustainability mechanisms needs to be considered during the design of the RCT.

The impact of stopping and starting indoor residual spraying on malaria burden in Uganda

The scale-up of malaria control efforts has led to marked reductions in malaria burden over the past twenty years, but progress has slowed. Implementation of indoor residual spraying (IRS) of insecticide, a proven vector control intervention, has been limited and difficult to sustain partly because questions remain on its added impact over widely accepted interventions such as bed nets. Using data from 14 enhanced surveillance health facilities in Uganda, a country with high bed net coverage yet high malaria burden, we estimate the impact of starting and stopping IRS on changes in malaria incidence. We show that stopping IRS was associated with a 5-fold increase in malaria incidence within 10 months, but reinstating IRS was associated with an over 5-fold decrease within 8 months. In areas where IRS was initiated and sustained, malaria incidence dropped by 85% after year 4. IRS could play a critical role in achieving global malaria targets, particularly in areas where progress has stalled.

Spatial-temporal patterns of malaria incidence in Uganda using HMIS data from 2015 to 2019

BACKGROUND

As global progress to reduce malaria transmission continues, it is increasingly important to track changes in malaria incidence rather than prevalence. Risk estimates for Africa have largely underutilized available health management information systems (HMIS) data to monitor trends. This study uses national HMIS data, together with environmental and geographical data, to assess spatial-temporal patterns of malaria incidence at facility catchment level in Uganda, over a recent 5-year period.

METHODS

Data reported by 3446 health facilities in Uganda, between July 2015 and September 2019, was analysed. To assess the geographic accessibility of the health facilities network, AccessMod was employed to determine a three-hour cost-distance catchment around each facility. Using confirmed malaria cases and total catchment population by facility, an ecological Bayesian conditional autoregressive spatial-temporal Poisson model was fitted to generate monthly posterior incidence rate estimates, adjusted for caregiver education, rainfall, land surface temperature, night-time light (an indicator of urbanicity), and vegetation index.

RESULTS

An estimated 38.8 million (95% Credible Interval [CI]: 37.9-40.9) confirmed cases of malaria occurred over the period, with a national mean monthly incidence rate of 20.4 (95% CI: 19.9-21.5) cases per 1000, ranging from 8.9 (95% CI: 8.7-9.4) to 36.6 (95% CI: 35.7-38.5) across the study period. Strong seasonality was observed, with June-July experiencing highest peaks and February-March the lowest peaks. There was also considerable geographic heterogeneity in incidence, with health facility catchment relative risk during peak transmission months ranging from 0 to 50.5 (95% CI: 49.0-50.8) times higher than national average. Both districts and health facility catchments showed significant positive spatial autocorrelation; health facility catchments had global Moran's I = 0.3 (p < 0.001) and districts Moran's I = 0.4 (p < 0.001). Notably, significant clusters of high-risk health facility catchments were concentrated in Acholi, West Nile, Karamoja, and East Central - Busoga regions.

CONCLUSION

Findings showed clear countrywide spatial-temporal patterns with clustering of malaria risk across districts and health facility catchments within high risk regions, which can facilitate targeting of interventions to those areas at highest risk. Moreover, despite high and perennial transmission, seasonality for malaria incidence highlights the potential for optimal and timely implementation of targeted interventions.

Malaria Diagnosed in an Urban Setting Strongly Associated with Recent Overnight Travel: A Case-Control Study from Kampala, Uganda

Malaria is frequently diagnosed in urban Kampala, despite low transmission intensity. To evaluate the association between recent travel out of Kampala and malaria, we conducted a matched case-control study. Cases were febrile outpatients with a positive malaria test; controls were febrile outpatients with a negative test. For every two cases, five controls were selected, matching on age. Data were collected on recent overnight travel out of Kampala (past 60 days), destination and duration of travel, and behavioral factors, including sleeping under an insecticide-treated net (ITN) during travel. From July to August 2019, 162 cases and 405 controls were enrolled. The locations of residence of cases and controls were similar. More controls were female (62.7% versus 46.3%, P < 0.001). Overall, 158 (27.9%) participants reported recent overnight travel. Travelers were far more likely to be diagnosed with malaria than those who did not travel (80.4% versus 8.6%, OR 58.9, 95% CI: 23.1-150.1, P < 0.001). Among travelers, traveling to a district not receiving indoor residual spraying of insecticide (OR 35.0, 95% CI: 4.80-254.9, P < 0.001), no ITN use (OR 30.1, 95% CI: 6.37-142.7, P < 0.001), engaging in outdoor activities (OR 22.0, 95% CI: 3.42-141.8, P = 0.001), and age < 16 years (OR 8.36, 95% CI: 2.22-56.2, P = 0.03) were associated with increased odds of malaria. Kampala residents who traveled overnight out of the city were at substantially higher risk of malaria than those who did not travel. For these travelers, personal protection measures, including sleeping under an ITN when traveling, should be advocated.

Changing malaria fever test positivity among paediatric admissions to Tororo district hospital, Uganda 2012-2019

BACKGROUND

The World Health Organization (WHO) promotes long-lasting insecticidal nets (LLIN) and indoor residual house-spraying (IRS) for malaria control in endemic countries. However, long-term impact data of vector control interventions is rarely measured empirically.

METHODS

Surveillance data was collected from paediatric admissions at Tororo district hospital for the period January 2012 to December 2019, during which LLIN and IRS campaigns were implemented in the district. Malaria test positivity rate (TPR) among febrile admissions aged 1 month to 14 years was aggregated at baseline and three intervention periods (first LLIN campaign; Bendiocarb IRS; and Actellic IRS + second LLIN campaign) and compared using before-and-after analysis. Interrupted time-series analysis (ITSA) was used to determine the effect of IRS (Bendiocarb + Actellic) with the second LLIN campaign on monthly TPR compared to the combined baseline and first LLIN campaign periods controlling for age, rainfall, type of malaria test performed. The mean and median ages were examined between intervention intervals and as trend since January 2012.

RESULTS

Among 28,049 febrile admissions between January 2012 and December 2019, TPR decreased from 60% at baseline (January 2012-October 2013) to 31% during the final period of Actellic IRS and LLIN (June 2016-December 2019). Comparing intervention intervals to the baseline TPR (60.3%), TPR was higher during the first LLIN period (67.3%, difference 7.0%; 95% CI 5.2%, 8.8%, p < 0.001), and lower during the Bendiocarb IRS (43.5%, difference - 16.8%; 95% CI - 18.7%, - 14.9%) and Actellic IRS (31.3%, difference - 29.0%; 95% CI - 30.3%, - 27.6%, p < 0.001) periods. ITSA confirmed a significant decrease in the level and trend of TPR during the IRS (Bendicarb + Actellic) with the second LLIN period compared to the pre-IRS (baseline + first LLIN) period. The age of children with positive test results significantly increased with time from a mean of 24 months at baseline to 39 months during the final IRS and LLIN period.

CONCLUSION

IRS can have a dramatic impact on hospital paediatric admissions harbouring malaria infection. The sustained expansion of effective vector control leads to an increase in the age of malaria positive febrile paediatric admissions. However, despite large reductions, malaria test-positive admissions continued to be concentrated in children aged under five years. Despite high coverage of IRS and LLIN, these vector control measures failed to interrupt transmission in Tororo district. Using simple, cost-effective hospital surveillance, it is possible to monitor the public health impacts of IRS in combination with LLIN.

Estimating the optimal interval between rounds of indoor residual spraying of insecticide using malaria incidence data from cohort studies

Background

Indoor residual spraying (IRS) reduces vector densities and malaria transmission, however, the most effective spraying intervals for IRS have not been well established. We estimated the optimal timing interval for IRS using a statistical approach.

Methods

Six rounds of IRS were implemented in Tororo District, a historically high malaria transmission setting in Uganda, during the study period (3 rounds with bendiocarb active ingredient (Ficam®): December 2014 to December 2015, and 3 rounds with pirimiphos methyl active ingredient (Actellic 300®CS): June 2016 to July 2018). A generalized additive model was used to estimate the optimal timing interval for IRS based on the predicted malaria incidence. The model was fitted to clinical incidence data from a cohort of children aged 0.5–10 years from selected households observed throughout the study period.

Results

494 children, 67% aged less than 5 years at enrolment were analysed. Six-months period incidence of malaria decreased from 2.96 per person-years at the baseline to 1.74 following the first round of IRS and then to 0.02 after 6 rounds of IRS. The optimal time interval for IRS differed between bendiocarb and pirimiphos methyl and by IRS round. To retain an optimum impact, bendiocarb would require respraying 17 (95% CI: 14.2–21.0) weeks after application whereas pirimiphos methyl could remain impactful for 40 (95% CI: 37.0–42.8) weeks, although in the final year this estimates 36 (95% CI: 32.7–37.7) weeks. However, we could not estimate from the data the optimal time after the second and third rounds of bendiocarb and after the second round of pirimiphos methyl. Neither the amount of rainfall nor the EIR nor the distribution of nets were found to be statistically significant for determining the time period between spray rounds.

Conclusion

In our setting, the effect of the two IRS products was distinct. Statistically, pirimiphos methyl provided a longer window of protection than bendiocarb, although impact varied between different spray rounds and years which was not explained by rainfall or EIR or distribution of nets in our statistical approach. Understanding the effectiveness of IRS and how long it lasts can help for planning campaigns, but one should consider the financial cost and insecticide resistance. Monitoring the timing of spray campaigns using clinical incidence could be repeated in future programs to help determine the average period of protectivity of these products.

The Impact of Multiple Rounds of Indoor Residual Spraying on Malaria Incidence and Hemoglobin Levels in a High-Transmission Setting

BACKGROUND

Indoor residual spraying (IRS) is widely used as a vector control measure, although there are conflicting findings of its effectiveness in reducing malaria incidence. The objective of this study was to estimate the effect of multiple IRS rounds on malaria incidence and hemoglobin levels in a cohort of children in rural southeastern Uganda.

METHODS

The study was based upon a dynamic cohort of children aged 0.5-10 years enrolled from August 2011 to June 2017 in Nagongera Subcounty. Confirmed malaria infections and hemoglobin levels were recorded over time for each participant. After each of 4 rounds of IRS, malaria incidence, hemoglobin levels, and parasite density were evaluated and compared with pre-IRS levels. Analyses were carried out at the participant level while accounting for repeated measures and clustering by household.

RESULTS

Incidence rate ratios comparing post-IRS to pre-IRS incidence rates for age groups 0-3, 3-5, and 5-11 were 0.108 (95% confidence interval [CI], .078-.149), 0.173 (95% CI, .136-.222), and 0.226 (95% CI, .187-.274), respectively. The mean hemoglobin levels significantly increased from 11.01 (pre-IRS) to 12.18 g/dL (post-IRS).

CONCLUSIONS

Our study supports the policy recommendation of IRS usage in a stable and perennial transmission area to rapidly reduce malaria transmission.

Antenatal visits are positively associated with uptake of tetanus toxoid and intermittent preventive treatment in pregnancy in Ivory Coast

Background

Malaria and tetanus infections among pregnant women represent two major public health problems in sub-Saharan Africa. Optimum use of Intermittent preventive treatment in pregnancy (IPTp) with sulfadoxine-pyrimethamine (IPTp-SP) and immunization against tetanus among pregnant women during antenatal care (ANC) visits are recommended strategies to prevent these issues. Despite these recommendations, many women in Africa remain deprived of these cost-effective and life-saving interventions. In this study, we aimed to examine the prevalence of women using these two services, and the association between women’s uptake of IPTp-SP and tetanus toxoid (TT) with antenatal care use in Ivory Coast.

Methods

This study was based on the fifth round of Multiple Indicator Cluster Survey (MICS 5) conducted in Ivory Coast in 2016. Participants were 9583 women aged between 15 and 49 years. Outcomes were TT and Intermittent preventive treatment with sulfadoxine-pyrimethamine (IPTp-SP). Data analysis was conducted using bivariate and multiple logistic regression.

Results

In this study, the prevalence of taking TT immunization and IPTp-SP drugs was 81.97 and 17.83% respectively. Of the participants who took these drugs at all, the prevalence of taking adequate doses of TT immunization was 78.75% and that of IPTp-SP was 35.46%. In the multivariable analysis model, higher age groups, 25–29 years (OR = 2.028, 95%CI = 1.120–3.669) were found to be positively associated with uptake of adequate doses of IPTp-SP drugs. Women who attended at least four ANC visits had higher odds of taking IPTp-SP drugs (OR = 1.656, 95%CI = 1.194–2.299) and TT immunization (OR = 2.347, 95%CI = 1.384–3.981), and also had higher odds of receiving adequate doses of IPTp-SP drugs (OR = 3.291, 95%CI = 2.157–5.020) and that of TT immunization (OR = 1.968, 95%CI = 1.398–2.771). The odds of taking IPTp-SP drugs were significantly higher among women with primary (OR = 2.504, 95%CI = 1.020–6.146) and secondary/higher education (OR = 3.298, 95%CI = 1.343–8.097) compared to those with no education. Also, women with higher parity had lower odds of taking TT immunization (OR = 0.218, 95%CI = 0.055–0.858) compared to those with lower parity. Findings from this study also revealed that the odds of taking adequate doses of IPTp-SP drugs were significantly lower among participants from Mandé du Nord ethnicity (OR = 0.378,95%CI = 0.145–0.983) compared to those from other ethnicities.

Conclusion

In this study, uptake of IPTp-SP drugs was much lower than TT immunization. High number of ANC visits were found to be significantly associated with taking IPTp-SP drugs and TT immunization and also with that of taking them in adequate doses. Vaccination promotion is necessary to protect pregnant women and reduce adverse health outcomes among the newborn in Ivory Coast.

A Cross-Sectional Population Study of Geographic, Age-Specific, and Household Risk Factors for Asymptomatic Plasmodium falciparum Malaria Infection in Western Kenya

The burden of Plasmodium falciparum (Pf) malaria in Kenya is decreasing; however, it is still one of the top 10 causes of morbidity, particularly in regions of western Kenya. Between April 2015 and June 2016, we enrolled 965 apparently healthy children aged 0-15 years in former Nyanza and Western Provinces in Kenya to characterize the demographic, geographic, and household risk factors of asymptomatic malaria as part of an epidemiologic study to investigate the risk factors for endemic Burkitt lymphoma. The children were sampled using a stratified, multistage cluster sampling survey design. Malaria was assessed by rapid diagnostic test (RDT) and thick-film microscopy (TFM). Primary analyses of Pf malaria prevalence (pfPR) are based on RDT. Associations between weighted pfPR and potential risk factors were evaluated using logistic regression, accounting for the survey design. Plasmodium falciparum malaria prevalence was 36.0% (27.5%, 44.5%) by RDT and 22.3% (16.0%, 28.6%) by TFM. Plasmodium falciparum malaria prevalence was positively associated with living in the lake-endemic area (adjusted odds ratio [aOR] 3.46; 95% confidence interval [95% CI] 1.63, 7.37), paternal occupation as peasant farmer (aOR 1.87; 1.08, 3.26) or manual laborer (aOR 1.83; 1.00, 3.37), and keeping dogs (aOR 1.62; 0.98-2.69) or cows (aOR 1.52; 0.96-2.40) inside or near the household. Plasmodium falciparum malaria prevalence was inversely associated with indoor residual insecticide spraying (IRS) (aOR 0.44; 0.19, 1.01), having a household connected to electricity (aOR 0.47; 0.22, 0.98), and a household with two (aOR 0.45; 0.22, 0.93) or ≥ three rooms (aOR 0.41; 0.18, 0.93). We report high but geographically heterogeneous pfPR in children in western Kenya and significant associations with IRS and household-level socioeconomic factors.

LLIN Evaluation in Uganda Project (LLINEUP): factors associated with childhood parasitaemia and anaemia 3 years after a national long-lasting insecticidal net distribution campaign: a cross-sectional survey

Background

Recent reductions in malaria burden have been attributed largely to long-lasting insecticidal nets (LLINs). In March–June 2017, approximately 3 years after a national LLIN distribution campaign, a cross-sectional community survey was conducted to investigate factors associated with malaria parasitaemia and anaemia, in advance of Uganda’s 2017–2018 LLIN campaign.

Methods

Households from 104 clusters in 48 districts were randomly selected using two-staged cluster sampling; 50 households were enrolled per cluster. Eligible children aged 2–10 years had blood obtained for a thick blood smear and those aged 2–4 years had haemoglobin measured. Associations between outcomes and variables of interest were assessed using log-binomial regression with generalized estimating equations to adjust for household clustering.

Results

In total, 5196 households, 8834 children with blood smear results, and 3753 with haemoglobin results were included. Only 16% of children lived in households with adequate LLIN coverage. Overall, parasite prevalence was 26.0%, ranging from 8.0% in the South West to 53.1% in East Central. Limiting data to children 2–4 years of age, parasite prevalence was 21.4%, up from 16.9% in 2014–2015 following the national LLIN campaign. In a multivariate analysis, factors associated with parasitaemia included region (East-Central vs South-Western; adjusted prevalence ratio [aPR] 6.45, 95% CI 5.55–7.50; p < 0.001), older age (8–10 vs 2–3 years; aPR 1.57, 95% CI 1.43–1.72; p < 0.001), living in a poorer household (poorest vs least poor tercile; aPR 2.32, 95% CI 2.05–2.63; p < 0.001), one constructed of traditional materials (aPR 1.13, 95% CI 1.03–1.24; p = 0.008), or without adequate LLIN coverage (aPR 1.30, 95% CI 1.14–1.48; p < 0.001). Overall, the prevalence of anaemia (haemoglobin < 10 g/dL) was 15.1% and varied geographically. In a multivariate analysis, factors associated with anaemia included region, younger age, living in a traditional house, and parasitaemia, which was the strongest predictor (aPR 2.50, 95% CI 2.12–2.95; p < 0.001).

Conclusions

Three years after a national LLIN campaign, LLIN coverage was low and parasite prevalence had increased. Parasite prevalence varied widely across Uganda; older children, those living in poorer households, and those with inadequate LLIN coverage, were at highest risk of parasitaemia. LLINs may need to be distributed more frequently through mass campaigns or continuously through sustainable mechanisms. Targeting interventions to geographic areas and populations at highest risk should also be considered.

LLIN Evaluation in Uganda Project (LLINEUP) - Impact of long-lasting insecticidal nets with, and without, piperonyl butoxide on malaria indicators in Uganda: study protocol for a cluster-randomised trial

BACKGROUND

Long-lasting insecticidal nets (LLINs) are a key malaria control intervention, but their effectiveness is threatened by resistance to pyrethroid insecticides. Some new LLINs combine pyrethroids with piperonyl butoxide (PBO), a synergist that can overcome P450-based metabolic resistance to pyrethroids in mosquitoes. In 2017-2018, the Ugandan Ministry of Health distributed LLINs with and without PBO through a national mass-distribution campaign, providing a unique opportunity to rigorously evaluate PBO LLINs across different epidemiological settings.

METHODS/DESIGN

Together with the Ministry of Health, we embedded a cluster-randomised trial to evaluate the impact of LLINs delivered in the 2017-2018 national campaign. A total of 104 clusters (health sub-districts) in Eastern and Western Uganda were involved, covering 48 of 121 (40%) districts. Using adaptive randomisation driven by the number of LLINs available, clusters were assigned to receive one of four types of LLINs, including two brands with PBO: 1) PermaNet 3.0 (n = 32) and 2) Olyset Plus (n = 20); and two without PBO: 3) PermaNet 2.0 (n = 37) and 4) Olyset Net (n = 15). We are conducting cross-sectional community surveys in 50 randomly selected households per cluster (5200 households per survey) and entomological surveillance for insecticide resistance in up to 10 randomly selected households enrolled in the community surveys per cluster (1040 households per survey) at baseline and 6, 12, and 18 months after LLIN distribution. Net durability and bio-efficacy will be assessed in 400 nets withdrawn from households with replacement at 12 months. The primary trial outcome is parasite prevalence as measured by microscopy in children aged 2-10 years in the follow-up surveys.

DISCUSSION

PBO LLINs are a promising new tool to reduce the impact of pyrethroid resistance on malaria control. The World Health Organization has issued a preliminary endorsement of PBO LLINs, but additional epidemiological evidence of the effect of PBO LLINs is urgently needed. The results of this innovative, large-scale trial embedded within a routine national distribution campaign will make an important contribution to the malaria control policy in Uganda and throughout Africa, where pyrethroid resistance in malaria vectors has increased dramatically. This model of evaluation could be a paradigm for future assessment of malaria control interventions.

TRIAL REGISTRATION

ISRCTN, ISRCTN17516395 . Registered on 14 February 2017.

WORLD HEALTH ORGANIZATION TRIAL REGISTRATION DATA SET

See Additional file 1.

LLIN Evaluation in Uganda Project (LLINEUP): a cross-sectional survey of species diversity and insecticide resistance in 48 districts of Uganda

BACKGROUND

Long-lasting insecticidal nets (LLINs) are the principal tool for malaria control in Africa and are presently treated with a single class of insecticide; however, increasing levels of insecticide resistance threaten their success. In response to this threat nets have been developed that incorporate the synergist, piperonyl butoxide (PBO), which inhibits the activity of cytochrome P450s which is one main mechanisms of insecticide resistance, allowing resistance to pyrethroids to be reversed. However, data on the value and cost effectiveness of these nets is lacking. A large-scale cluster randomised trial of conventional LLINs and PBO-LLINs was conducted in Uganda in 104 health sub-districts (HSDs) in 2017-2019. Prior to the mass distribution of LLINs, a baseline entomological survey was carried out, the results of which are reported herein. Ten households from each HSD were randomly selected for entomological surveillance at baseline which included household mosquito collections.

RESULTS

Prior to LLIN distribution entomological collections were carried out in 1029 houses across the 104 HSDs. Anopheles gambiae (s.l.) was the principal vector in all but 9 of the 71 HSDs that yielded vector species. Molecular analysis found An. gambiae (s.s.) to be the predominant vector collected. Plasmodium falciparum was detected in 5.5% of An. gambiae (s.s.) and in 4.0% of An. funestus (s.s.) examined. Infection rates of other plasmodium species (P. vivax, P. ovale and P. malariae) were lower with infection rates of 1.2% and 1.7% for An. gambiae (s.s.) and An. funestus (s.s.), respectively. The knockdown resistance (kdr) mutation Vgsc-L1014S was found at very high frequency in An. gambiae (s.s.) with the Vgsc-L1014F mutation at low frequency and the wild-type allele virtually absent. In An. arabiensis the wild-type allele was predominant. The resistance-associated alleles, Cyp4j5-L43F and Coeae1d were found at moderate frequencies which varied across the study site. Vgsc-N1575Y mutation was not found in any samples examined.

CONCLUSIONS

No significant differences between planned intervention arms was observed in vector densities, sporozoite infection rate or insecticide resistance marker frequency across the study site prior to the distribution of LLINs. Very high levels of kdr resistance were observed in all areas; however, the resistance-associated markers Cyp4j5-L43F and Coeae1d were found at varying frequencies across the study site which may have implications for the effectiveness of standard LLINs. Trial registration This study is registered with ISRCTN, ISRCTN17516395. Registered 14 February 2017, http://www.isrctn.com/ISRCTN17516395.

Effects and factors associated with indoor residual spraying with Actellic 300 CS on malaria morbidity in Lira District, Northern Uganda

BACKGROUND

Indoor residual spraying (IRS) with Actellic 300 CS was conducted in Lira District between July and August 2016. No formal assessment has been conducted to estimate the effect of spraying with Actellic 300 CS on malaria morbidity in the Ugandan settings. This study assessed malaria morbidity trends before and after IRS with Actellic 300 CS in Lira District in Northern Uganda.

METHODS

The study employed a mixed methods design. Malaria morbidity records from four health facilities were reviewed, focusing on 6 months before and after the IRS intervention. The outcome of interest was malaria morbidity defined as; proportion of outpatient attendance due to total malaria, proportion of outpatient attendance due to confirmed malaria and proportion of malaria case numbers confirmed by microscopy or rapid diagnostic test. Since malaria morbidity was based on count data, an ordinary Poisson regression model was used to obtain percentage point change (pp) in monthly malaria cases before and after IRS. A household survey was also conducted in 159 households to determine IRS coverage and factors associated with spraying. A modified Poisson regression model was fitted to determine factors associated with household spray status.

RESULTS

The proportion of outpatient attendance due to malaria dropped from 18.7% before spraying to 15.1% after IRS. The proportion of outpatient attendance due to confirmed malaria also dropped from 5.1% before spraying to 4.0% after the IRS intervention. There was a decreasing trend in malaria test positivity rate (TPR) for every unit increase in month after spraying. The decreasing trend in TPR was more prominent 5-6 months after the IRS intervention (Adj. pp = - 0.60, P-value = 0.015; Adj. pp = - 1.19, P-value < 0.001). The IRS coverage was estimated at 89.3%. Households of respondents who were formally employed or owned any form of business were more likely to be unsprayed; (APR = 5.81, CI 2.72-12.68); (APR = 3.84, CI 1.20-12.31), respectively.

CONCLUSION

Coverage of IRS with Actellic 300 CS was high and was associated with a significant decline in malaria related morbidity 6 months after spraying.

Improving socioeconomic status may reduce the burden of malaria in sub Saharan Africa: A systematic review and meta-analysis

Background

A clear understanding of the effects of housing structure, education, occupation, income, and wealth on malaria can help to better design socioeconomic interventions to control the disease. This literature review summarizes the relationship of housing structure, educational level, occupation, income, and wealth with the epidemiology of malaria in sub-Saharan Africa (SSA).

Methods

A systematic review and meta-analysis was conducted following the preferred reporting items for systematic reviews and meta-analyses guidelines. The protocol for this study is registered in PROSPERO (ID=CRD42017056070), an international database of prospectively registered systematic reviews. On January 16, 2016, available literature was searched in PubMed, Embase, CINAHL, and Cochrane Library. All but case studies, which reported prevalence or incidence of Plasmodium infection stratified by socioeconomic status among individuals living in SSA, were included without any limits. Odds Ratio (OR) and Relative Risk (RR), together with 95% CI and p-values were used as effect measures. Heterogeneity was assessed using chi-square, Moran’s I², and tau² tests. Fixed (I²<30%), random (I²≥30%) or log-linear dose-response model was used to estimate the summary OR or RR.

Results

After removing duplicates and screening of titles, abstracts, and full text, 84 articles were found eligible for systematic review, and 75 of them were included in the meta-analyses. Fifty-seven studies were cross-sectional, 12 were prospective cohort, 10 were case-control, and five were randomized control trials. The odds of Plasmodium infection increased among individuals who were living in poor quality houses (OR 2.13, 95% CI 1.56–3.23, I² = 27.7), were uneducated (OR 1.36, 95% CI 1.19–1.54, I² = 72.4.0%), and were farmers by occupation (OR 1.48, 95% CI 1.11–1.85, I² = 0.0%) [p<0.01 for all]. The odds of Plasmodium infection also increased with a decrease in the income (OR 1.02, 95% CI 1.01–1.03, tau²<0.001), and wealth index of individuals (OR 1.25, 95% CI 1.18–1.35, tau² = 0.028) [p<0.001 for both]. Longitudinal studies also showed an increased risk of Plasmodium infection among individuals who were living in poor quality houses (RR 1.86, 95% CI 1.47–2.25, I² = 0.0%), were uneducated (OR 1.27, 1.03–1.50, I² = 0.0%), and were farmers (OR 1.36, 1.18–1.58) [p<0.01 for all].

Conclusions

Lack of education, low income, low wealth, living in poorly constructed houses, and having an occupation in farming may increase risk of Plasmodium infection among people in SSA. Public policy measures that can reduce inequity in health coverage, as well as improve economic and educational opportunities for the poor, will help in reducing the burden of malaria in SSA.

The 2015-2016 malaria epidemic in Northern Uganda; What are the implications for malaria control interventions?

Vector control and effective case management are currently the backbone strategies of malaria control. Kitgum district, an area of perennial holoendemic malaria transmission intensity in Northern Uganda, appears to have experienced a malaria epidemic in 2015. This study aimed to describe the malaria trends in Kitgum General Hospital from 2011 to 2017 in relation to climatic factors and the application of population-based malaria control interventions. Hospital records were examined retrospectively to calculate malaria normal channels, malaria cases per 1000 population, test positivity rates (TPR) and to enumerate pregnancy malaria, hospitalizations and deaths. Climatic factors (humidity, temperature and rainfall) and population-based malaria control interventions that had been applied during this period were described. Kitgum district experienced an epidemic between the years 2015 and 2016; the malaria burden rose above the established normal channels. At its peak the number of malaria cases attending KGH was over 20 times above the normal channels. The total number of cases per 1000 population increased from 7 in 2014 to 113 in 2015 and 114 in 2016 (p value for trend <0.0001). Similarly, TPR increased from 10.5% to 54.6% between 2014 and 2016 (p value for trend <0.0001). This trend was also observed for malaria attributable hospitalizations, and malaria in pregnancy. There were no significant changes in any of the climatic factors assessed (p value = 0.92, 0.99, 0.52 for relative humidity, max temperature, and rainfall, respectively). The malaria upsurge occurred in conjunction with a general decline in the use and application of malaria control interventions. Specifically, indoor residual spraying was interrupted in 2014. In response to the epidemic, IRS was reapplied together with mass distribution of long-lasting insecticide treated nets (LLINs) in 2017. Subsequently, there was a decline in all malaria indicators. The epidemic in Kitgum occurred in association with the interruption of IRS and appears to have abated following its re-introduction alongside LLINs. The study suggests that to enable malaria elimination in areas of high malaria transmission intensity, effective control measures may need to be sustained for the long-term.

LLIN Evaluation in Uganda Project (LLINEUP): factors associated with ownership and use of long-lasting insecticidal nets in Uganda: a cross-sectional survey of 48 districts

BACKGROUND

Long-lasting insecticidal nets (LLINs) are a key malaria control intervention. To investigate factors associated with ownership and use of LLINs in Uganda, a cross-sectional community survey was conducted in March-June 2017, approximately 3 years after a national Universal Coverage Campaign (UCC).

METHODS

Households from 104 clusters (health sub-districts) in 48 districts were randomly selected using two-staged cluster sampling; 50 households were enrolled per cluster. Outcomes were household ownership of LLINs (at least one LLIN), adequate LLIN coverage (at least one LLIN per 2 residents), and use of LLINs (resident slept under a LLIN the previous night). Associations between variables of interest and outcomes were made using multivariate logistic regression.

RESULTS

In total, 5196 households, with 29,627 residents and 6980 bed-nets, were included in the analysis. Overall, 65.0% of households owned at least one LLIN (down from 94% in 2014). In the adjusted analysis, factors most strongly associated with LLIN ownership were living in a wealthier household (highest tercile vs lowest; adjusted odds ratio [aOR] 1.94, 95% CI 1.66-2.28, p < 0.001) and time since the last UCC (29-37 vs 42-53 months; aOR 1.91, 95% CI 1.60-2.28, p < 0.001). Only 17.9% of households had adequate LLIN coverage (down from 65% in 2014). Factors most strongly associated with adequate coverage were fewer residents (2-4 vs ≥ 7; aOR 6.52, 95% CI 5.13-8.29, p < 0.001), living in a wealthier household (highest tercile vs lowest; aOR: 2,32, 95% CI 1.88-2.85, p < 0.001) and time since the last UCC (29-37 vs 42-53 months; aOR 2.13, 95% CI 1.61-2.81, p < 0.001). Only 39.5% of residents used a LLIN the previous night. Age was strongly associated with LLIN use, as were household wealth and time since the last UCC. Children < 5 years (44.7%) and residents > 15 years (44.1%) were more likely to use nets than children aged 5-15 years (30.7%; < 5 years: aOR 1.71, 95% CI 1.62-1.81, p < 0.001; > 15 years: aOR 1.37, 95% CI 1.29-1.45, p < 0.001).

CONCLUSIONS

Long-lasting insecticidal net ownership and coverage have reduced markedly in Uganda since the last net distribution campaign in 2013/14. Houses with many residents, poorer households, and school-aged children should be targeted to improve LLIN coverage and use. Trial registration This study is registered with ISRCTN (17516395).

Influence of Climatic Factors on Malaria Epidemic in Gulu District, Northern Uganda: A 10-Year Retrospective Study

Background

Globally, 15 countries, mainly in Sub-Saharan Africa, account for 80% of malaria cases and 78% of malaria related deaths. In Uganda, malaria is endemic and the mortality and morbidity due to malaria cause significant negative impact on the economy. In Gulu district, malaria is the leading killer disease among children <5 years. In 2015, the high intensity of malaria infection in Northern Uganda revealed a possible link between malaria and rainfall. However, available information on the influence of climatic factors on malaria are scarce, conflicting, and highly contextualized and therefore one cannot reference such information to malaria control policy in Northern Uganda, thus the need for this study.

Methods and Results

During the 10 year's retrospective study period a total of 2,304,537 people suffered from malaria in Gulu district. Malaria infection was generally stable with biannual peaks during the months of June-July and September-October but showed a declining trend after introduction of indoor residual spraying. Analysis of the departure of mean monthly malaria cases from the long-term mean monthly malaria cases revealed biannual seasonal outbreaks before and during the first year of introduction of indoor residual spraying. However, there were two major malaria epidemics in 2015 following discontinuation of indoor residual spraying in the late 2014. Children <5 years of age were disproportionally affected by malaria and accounted for 47.6% of the total malaria cases. Both rainfall (P=0.04) and relative humidity (P=0.003) had significant positive correlations with malaria. Meanwhile, maximum temperature had significant negative correlation with malaria (P=0.02) but minimum temperature had no correlation with malaria (P=0.29).

Conclusion

Malaria in Gulu disproportionately affects children under 5 years and shows seasonality with a generally stable trend influenced by rainfall and relative humidity. However, indoor residual spraying is a very promising method to achieve a sustained malaria control in this population.

A cross-sectional study of asymptomatic Plasmodium falciparum infection burden and risk factors in general population children in 12 villages in northern Uganda

BACKGROUND

Plasmodium falciparum malaria is an important cause of morbidity in northern Uganda. This study was undertaken to assess village-, household-, and individual-level risk factors of asymptomatic falciparum malaria in children in 12 villages in northern Uganda.

METHODS

Between 10/2011 and 02/2014, 1006 apparently healthy children under 16 years old were enrolled in 12 villages using a stratified, multi-stage, cluster survey design and assessed for P. falciparum malaria infection using the rapid diagnostic test (RDT) and thick film microscopy (TFM), and structured interviewer-administered questionnaires. Associations between weighted P. falciparum malaria prevalence (pfPR), based on RDT, and covariates were estimated as odds ratios and 95% confidence intervals (ORs, 95% CIs) using logistic models accounting for the survey design.

RESULTS

Among 942 (93.5%) children successfully tested, pfPR was 52.4% by RDT and 32.7% by TFM. Overall pfPR was lower in villages where indoor residual insecticide spray (IRS) was, versus not, implemented (18.4% versus 75.2%, P < 0.0001). However, pfPR was heterogeneous both within IRS (10.6-34.8%) and non-IRS villages (63.6-86.2%). Elevated pfPR was associated with having a sibling who was RDT positive (OR 5.39, 95% CI 2.94-9.90, P = 0.0006) and reporting a fever at enrollment (aOR 4.80, 95% CI 1.94-11.9, P = 0.0094). Decreased pfPR was associated with living in an IRS village (adjusted OR 0.06, 95% CI 0.04-0.07, P < 0.0001), in a household with one (aOR 0.48, 95% CI 0.30-0.76) or more than one child below 5 years (aOR 0.23, 95% CI 0.12-0.44, Ptrend = 0.014), and reporting keeping a goat inside or near the house (aOR 0.42, 95% CI 0.29-0.62, P = 0.0021).

CONCLUSIONS

The results show high but heterogeneous pfPR in villages in northern Uganda, confirm significantly decreased pfPR associated with IRS implementation, and suggest significant associations with some household characteristics. Further research is needed to elucidate the factors influencing malaria heterogeneity in villages in Uganda.

Evaluation of the long-term efficacy of K-Othrine® PolyZone on three surfaces against laboratory reared Anopheles gambiae in semi-field conditions

Background

In this semi-field study, a new polymer-enhanced deltamethrin formulation, K-Othrine^® PolyZone, was compared to a standard deltamethrin product for residual activity against a susceptible strain of laboratory-reared Anopheles gambiae using standard WHO cone bioassays.

Methods

Residual insecticide efficacy was recorded after exposure to metal, cement and wood panels maintained in experimental huts in sub-tropical environmental conditions in north central Florida, USA, and panels stored in a climate controlled chamber located at the Centers for Disease Control and Prevention, Georgia, USA.

Conclusions

K-Othrine^® PolyZone demonstrated 100% control on metal and cement panels 1 year post application and > 80% control on wood panels up to 6 mo. The new formulation should be considered for use in indoor residual spray programmes requiring long-term control of malaria vectors.

Electronic supplementary material

The online version of this article (10.1186/s12936-018-2239-z) contains supplementary material, which is available to authorized users.

An observational analysis of the impact of indoor residual spraying with non-pyrethroid insecticides on the incidence of malaria in Ségou Region, Mali: 2012-2015

Background

Ségou 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.

Methods

A 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.

Results

During 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.

Conclusions

From 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.

Electronic supplementary material

The online version of this article (10.1186/s12936-017-2168-2) contains supplementary material, which is available to authorized users.

Performance of Loop-Mediated Isothermal Amplification for the Identification of Submicroscopic Plasmodium falciparum Infection in Uganda

Accurately identifying and targeting the human reservoir of malaria parasitemia is critical for malaria control, and requires a reliable and sensitive diagnostic method. Loop-mediated isothermal amplification (LAMP) is increasingly used to diagnose submicroscopic parasitemia. Although most published studies report the sensitivity of LAMP compared with nested polymerase chain reaction (PCR) as ≥ 80%, they have failed to use a consistent, sensitive diagnostic as a comparator. We used cross-sectional samples from children and adults in Tororo, Uganda, a region with high but declining transmission due to indoor residual spraying, to characterize the sensitivity and specificity of pan-Plasmodium LAMP for detecting submicroscopic infections. We compared LAMP results targeting a mitochondrial DNA sequence conserved in all Plasmodium species, performed on DNA extracted from dried blood spots, to those of a gold standard quantitative PCR assay targeting the var gene acidic terminal sequence of Plasmodium falciparum (varATS qPCR), performed on DNA extracted from 200 µL of whole blood. Using LAMP and varATS qPCR increased the detection of parasitemia 2- to 5-fold, compared with microscopy. Among microscopy-negative samples, the sensitivity of LAMP was 81.5% for detecting infection ≥ 1 parasites/µL. However, low density infections were common, and LAMP failed to identify more than half of all infections diagnosed by varATS qPCR, performing with an overall sensitivity of 44.7% for detecting submicroscopic infections ≥ 0.01 parasites/µL. Thus, although the LAMP assay is more sensitive than microscopy, it missed a significant portion of the submicroscopic reservoir. These findings have important implications for malaria control, particularly in settings where low-density infections predominate.

The protective effectiveness of control interventions for malaria prevention: a systematic review of the literature

Background: Thanks to a considerable increase in funding, malaria control interventions (MCI) whose efficacy had been demonstrated by controlled trials have been largely scaled up during the last decade. Nevertheless, it was not systematically investigated whether this efficacy had been preserved once deployed on the field. Therefore, we sought the literature to assess the disparities between efficacy and effectiveness and the effort to measure the protective effectiveness (PE) of MCI.

Methods: The PubMed database was searched for references with keywords related to malaria, to control interventions for prevention and to study designs that allow for the measure of the PE against parasitemia or against clinical outcomes.

Results: Our search retrieved 1423 references, and 162 articles were included in the review. Publications were scarce before the year 2000 but dramatically increased afterwards. Bed nets was the MCI most studied (82.1%). The study design most used was a cross-sectional study (65.4%). Two thirds (67.3%) were conducted at the district level or below, and the majority (56.8%) included only children even if the MCI didn’t target only children. Not all studies demonstrated a significant PE from exposure to MCI: 60.6% of studies evaluating bed nets, 50.0% of those evaluating indoor residual spraying, and 4/8 showed an added PE of using both interventions as compared with one only; this proportion was 62.5% for intermittent preventive treatment of pregnant women, and 20.0% for domestic use of insecticides.

Conclusions: This review identified numerous local findings of low, non-significant PE –or even the absence of a protective effect provided by these MCIs. The identification of such failures in the effectiveness of MCIs advocates for the investigation of the causes of the problem found. Ideal evaluations of the PE of MCIs should incorporate both a large representativeness and an evaluation of the PE stratified by subpopulations.

Resurgence of Malaria Following Discontinuation of Indoor Residual Spraying of Insecticide in an Area of Uganda With Previously High-Transmission Intensity

BACKGROUND

Indoor residual spraying (IRS) and long-lasting insecticidal nets (LLINs) are the primary tools for malaria prevention in Africa. It is not known whether reductions in malaria can be sustained after IRS is discontinued. Our aim in this study was to assess changes in malaria morbidity in an area of Uganda with historically high transmission where IRS was discontinued after a 4-year period followed by universal LLIN distribution.

METHODS

Individual-level malaria surveillance data were collected from 1 outpatient department and 1 inpatient setting in Apac District, Uganda, from July 2009 through November 2015. Rounds of IRS were delivered approximately every 6 months from February 2010 through May 2014 followed by universal LLIN distribution in June 2014. Temporal changes in the malaria test positivity rate (TPR) were estimated during and after IRS using interrupted time series analyses, controlling for age, rainfall, and autocorrelation.

RESULTS

Data include 65 421 outpatient visits and 13 955 pediatric inpatient admissions for which a diagnostic test for malaria was performed. In outpatients aged <5 years, baseline TPR was 60%-80% followed by a rapid and then sustained decrease to 15%-30%. During the 4-18 months following discontinuation of IRS, absolute TPR values increased by an average of 3.29% per month (95% confidence interval, 2.01%-4.57%), returning to baseline levels. Similar trends were seen in outpatients aged ≥5 years and pediatric admissions.

CONCLUSIONS

Discontinuation of IRS in an area with historically high transmission intensity was associated with a rapid increase in malaria morbidity to pre-IRS levels.

Assessment of Ficam VC (Bendiocarb) Residual Activity on Different Wall Surfaces for Control of Anopheles gambiae s.s. (Diptera: Culicidae) in Northern Uganda

Insecticide decay rate on different wall surfaces is of importance to indoor residual spray (IRS) programs used as a malaria control intervention. Past IRS operations showed increasing populations of endophilic malaria vectors resting on indoor surfaces from various sites in Uganda following use of Ficam VC (bendiocarb) insecticide; variability of insecticide life was believed to be primarily due to wall surface type. Bendiocarb longevity was tested in the northern Uganda districts of Amuru, Apac, and Pader to assess its residual efficacy on three commonly encountered wall surfaces. Wall types included mud and wattle, plain brick, and painted plaster. A susceptible mosquito strain (Anopheles gambiae Kisumu) was used in all trials. Nine houses in each of the three districts were set with three test cones and one control cone per house, divided evenly among the three wall surfaces. Bioassays were run monthly through 6 mo. Painted plastered surfaces produced 100% mortality (at 24 h) through 6 mo. Plain brick surfaces killed 100% of test mosquitoes through 4 mo, while mud and wattle wall surfaces produced a 98% mortality rate at 3 mo post spray. The KD60 (knockdown at 60 min) for painted plastered surfaces was 100% for 6 mo, plain brick surface KD60 was 80% at 6 mo, and the mud and wattle surface KD60 was >80% at 3 mo. There was a significant effect on Ficam VC longevity by wall type and evidence of a relationship between test period and wall type on the KD60.

Environmental contaminants of honeybee products in Uganda detected using LC-MS/MS and GC-ECD

Pollinator services and the development of beekeeping as a poverty alleviating tool have gained considerable focus in recent years in sub-Saharan Africa. An improved understanding of the pervasive environmental extent of agro-chemical contaminants is critical to the success of beekeeping development and the production of clean hive products. This study developed and validated a multi-residue method for screening 36 pesticides in honeybees, honey and beeswax using LC-MS/MS and GC-ECD. Of the 36 screened pesticides, 20 were detected. The highest frequencies occurred in beeswax and in samples from apiaries located in the proximity of citrus and tobacco farms. Fungicides were the most prevalent chemical class. Detected insecticides included neonicotinoids, organophosphates, carbamates, organophosphorus, tetrazines and diacylhydrazines. All detected pesticide levels were below maximum residue limits (according to EU regulations) and the lethal doses known for honeybees. However, future risk assessment is needed to determine the health effects on the African genotype of honeybees by these pesticide classes and combinations of these. In conclusion, our data present a significant challenge to the burgeoning organic honey sector in Uganda, but to achieve this, there is an urgent need to regulate the contact routes of pesticides into the beehive products. Interestingly, the "zero" detection rate of pesticides in the Mid-Northern zone is a significant indicator of the large potential to promote Ugandan organic honey for the export market.

Rapid reduction of malaria following introduction of vector control interventions in Tororo District, Uganda: a descriptive study

BACKGROUND

In 2012, Tororo District had the highest malaria burden in Uganda with community Plasmodium prevalence of 48%. To control malaria in the district, the Ministry of Health introduced universal distribution of long lasting insecticide-treated nets (LLINs) in 2013 and added indoor residual spraying (IRS) in 2014. This study assessed malaria incidence, test positivity rates and outpatient (OPD) attendance due to malaria before and after vector control interventions.

METHODS

This study was based on analysis of Health Management Information System (HMIS) secondary malaria surveillance data of 2,727,850 patient records in OPD registers of 61 health facilities from 2012 to 2015. The analysis estimated monthly malaria incidence for the entire population and also separately for <5- and ≥5-year-olds before and after introduction of vector control interventions; determined laboratory test positivity rates and annual percentage of malaria cases in OPD. Chi square for trends was used to analyse annual change in malaria incidence and logistic regression for monthly reduction.

RESULTS

Following universal LLINs coverage, the annual mean monthly malaria incidence fell from 95 cases in 2013 to 76 cases per 1000 in 2014 with no significant monthly reduction (OR = 0.99, 95% CI 0.96-1.01, P = 0.37). Among children <5 years, the malaria incidence reduced from 130 to 100 cases per 1000 (OR = 0.98, 95% CI 0.97-1.00, P = 0.08) when LLINs were used alone in 2014, but declined to 45 per 1000 in 2015 when IRS was combined with LLINs (OR = 0.94, 95% CI 0.91-0.996, P < 0.0001). Among individuals aged ≥5 years, mean monthly malaria incidence reduced from 59 to 52 cases per 1000 (OR = 0.99, 95% CI 0.97-1.02, P = 0.8) when LLINs were used alone in 2014, but reduced significantly to 25 per 1000 in 2015 (OR = 0.91, 95% CI 0.88-0.94, P < 0.0001). Malaria test positivity rate reduced from 57% in 2013 to 30% (Chi = 15, P < 0.0001) in 2015. Slide positivity rate reduced from 45% in 2013 to 21% in 2015 (P = 0.004) while RDT positivity declined from 69 to 40%.

CONCLUSIONS

A rapid reduction in malaria incidence was observed in Tororo District following the introduction of IRS in addition to LLINs. There was no significant reduction in malaria incidence following universal distribution of LLINs to communities before introduction of IRS.

Factors associated with malaria parasitaemia among children under 5 years in Uganda: a secondary data analysis of the 2014 Malaria Indicator Survey dataset

BACKGROUND

In the midst of success with malaria reduction in Uganda, there are areas that still have high prevalence of malaria parasitaemia. This project aimed at investigating factors associated with this prevalence and its relationship with anaemia.

METHODS

This is a secondary data analysis of the 2014 Malaria Indicator Survey dataset of children under 5 years. All had a blood sample taken by finger or heel prick for determination of malaria parasitaemia and estimation of haemoglobin level for anaemia status. The main outcome was the presence of malaria parasitaemia by microscopy and independent variables included: age, gender, residence (urban vs rural), use of a long-lasting, insecticidal-treated net, indoor residual spraying (IRS) of household in the past 6 months, mother's highest education level, mother heard malaria prevention message in the past 6 months, and household wealth status.

RESULTS

The analysis included 4930 children and of these, 938 (19.04%: 95% CI 16.63-21.71) tested positive for malaria parasites. Malaria parasite prevalence significantly increased from 11.08 (95% CI 9.12-13.40) among children with no anaemia to 50.99% (95% CI 39.13-62.74) with severe anaemia (Chi-square p-value = 0.001). Additionally, prevalence significantly rose from the youngest age group (under 6 months) by 1.62 times (95% CI 1.04-2.52, p = 0.033) among the age group of 7-12 months and to four times (95% CI 2.57-6.45, p = 0.001) among those who were between 49 and 59 months. The following were associated with reduced parasitaemia: IRS use (AOR 0.23 [0.08-0.61], p = 0.004), educated mothers (primary AOR 0.75 [0.59-0.96], p = 0.023 to tertiary AOR 0.11 [0.02-0.53], 0.006), mother heard malaria message (AOR 0.78 [0.62-0.99], p = 0.037), and wealthier households (richest AOR 0.17 [0.08-0.36], p = 0.001).

CONCLUSIONS

Increasing malaria parasite prevalence among children under 5 years is still related to increasing age and severity of anaemia even in the context of decreasing malaria prevalence. Designing interventions that include the use of IRS and behaviour change communication tailored to include older children, especially in areas with high malaria prevalence, could be of added value. All this should be done in an environment that improves the socio-economic status and equity of such populations.

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

BACKGROUND

Resistance 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.

METHODS

Anopheles 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.

RESULTS

Tests 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.

CONCLUSION

This 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.

Age and geographic patterns of Plasmodium falciparum malaria infection in a representative sample of children living in Burkitt lymphoma-endemic areas of northern Uganda

BACKGROUND

Falciparum malaria is an important risk factor for African Burkitt lymphoma (BL), but few studies have evaluated malaria patterns in healthy BL-age children in populations where both diseases are endemic. To obtain accurate current data, patterns of asymptomatic malaria were investigated in northern Uganda, where BL is endemic.

METHODS

Between 2011 and 2015, 1150 apparently healthy children under 15 years old were sampled from 100 villages in northern Uganda using a stratified, multi-stage, cluster survey design. Falciparum malaria prevalence (pfPR) was assessed by questionnaire, rapid diagnostic test (RDT) and thick film microscopy (TFM). Weighted pfPR and unadjusted and adjusted associations of prevalence with covariates were calculated using logistic models and survey methods.

RESULTS

Based on 1143 children successfully tested, weighted pfPR was 54.8% by RDT and 43.4% by TFM. RDT sensitivity and specificity were 97.5 and 77.8%, respectively, as compared to TFM, because RDT detect malaria antigens, which persist in peripheral blood after clinical malaria, thus results based on RDT are reported. Weighted pfPR increased from 40% in children aged under 2 years to 61.8% in children aged 6-8 years (odds ratio 2.42, 95% confidence interval (CI) 1.26-4.65), then fell slightly to 49% in those aged 12-15 years. Geometric mean parasite density was 1805.5 parasites/µL (95% CI 1344.6-2424.3) among TFM-positive participants, and it was higher in children aged <5 years at 5092.9/µL (95% CI 2892.7-8966.8) and lower in those aged ≥10 years at 983.8/µL (95% CI 472.7-2047.4; P = 0.001). Weighted pfPR was lower in children residing in sub-regions employing indoor residual spraying (IRS) than in those residing in non-IRS sub-regions (32.8 versus 65.7%; OR 0.26, 95% CI 0.14, 0.46). However, pfPR varied both within IRS (3.2-55.3%) and non-IRS sub-regions (29.8-75.8%; Pheterogeneity <0.001). pfPR was inversely correlated with a child's mother's income (P = 0.011) and positively correlated with being enrolled in the wet season (P = 0.076), but sex was irrelevant.

CONCLUSIONS

The study observed high but geographically and demographically heterogenous patterns of asymptomatic malaria prevalence among children living in northern Uganda. These results provide important baseline data that will enable precise evaluation of associations between malaria and BL.

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

Background

Indoor 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.

Results

The 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.

Conclusion

The 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.

Electronic supplementary material

The online version of this article (doi:10.1186/s12936-016-1652-4) contains supplementary material, which is available to authorized users.

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

Background

An 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).

Conclusions

High 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 material

The online version of this article (doi:10.1186/s13071-016-1917-3) contains supplementary material, which is available to authorized users.

A malariometric survey of under-fives residing in indoor residual spraying-implementing and non-implementing communities of Lagos, Nigeria

Background

Indoor residual spraying (IRS) is used as part of the integrated vector management strategy for the control of malaria in Lagos, Nigeria. The purpose of this study was to compare the malariometric indices of children under 5 years old living in IRS-implementing and non-IRS-implementing communities of Lagos, Nigeria.

Methods

The study was a community-based, comparative, cross-sectional study of 480 children under five recruited using a multi-stage sampling method. Data on each child were collected using a household questionnaire administered to the consenting care-giver of each selected child. Each child underwent a comprehensive physical examination. On-the-spot malaria rapid diagnostic testing and haemoglobin estimation to assess parasitaemia and anaemia, respectively, were also carried out. Risk factors for parasitaemia and anaemia were identified using multivariate logistic regression.

Results

A total of 238 children were studied in the IRS-implementing group while 242 children were studied in the non-IRS-implementing group. The IRS -implementing community had a lower level of parasitaemia (1.3 %) compared to the non-IRS-implementing community (5.8 %) (p < 0.001). There was no significant difference in anaemia, spleen rate and fever in the IRS-implementing group (10.9, 9.7 and 5 %) and the non-IRS-implementing group (9.9, 8.8 and 8.7 %), respectively. Residing in an IRS-implementing community was associated with lower odds of parasitaemia (OR 0.17, p < 0.01). Sleeping under a bed net was the only factor associated with anaemia (p < 0.01).

Conclusion

IRS has led to a reduction in the level of parasitaemia in the under-fives in the study areas.

Experiences of households using integrated malaria prevention in two rural communities in Wakiso district, Uganda: a qualitative study

Background

The integrated approach to malaria prevention which advocates use of several methods in a holistic manner is being explored to complement existing strategies. A pilot project that promoted integrated malaria prevention established 40 demonstration households using the approach. As part of impact evaluation of the project 2 years after implementation, the experiences of these households using integrated malaria prevention were assessed.

Methods

A qualitative cross-sectional survey was carried out in Wakiso district, Uganda which involved 40 in-depth interviews among households implementing integrated malaria prevention. The study assessed practices on malaria prevention, benefits and challenges of using integrated malaria prevention, preference of malaria prevention methods, and impact of the demonstration households on the community. Thematic analysis was employed using Atlas ti software.

Results

The households continued to use many of the malaria prevention methods in the integrated approach including sleeping under long-lasting insecticidal nets, screening in windows and ventilators, removing mosquito breeding sites, and closing of doors early in the evenings. The major benefits reported from using integrated malaria prevention were reduction in mosquito populations in their houses and less occurrence of malaria particularly among children. Although several community members learnt about and admired various malaria prevention methods from the demonstration households especially screening in windows and ventilators, the majority could not afford to implement some of them due to lack of resources. The main challenge established in using integrated malaria prevention was the much time required to implement the several methods some of which had to be done regularly such as early closing of windows. In addition, complacency had led to some households not utilizing a number of methods in the integrated approach because of using others.

Conclusion

Use of the integrated approach to malaria prevention benefited the demonstration households mainly through observed reduction in mosquitoes indoors and malaria occurrence hence could be promoted in other areas. Other studies to quantify the protective effect of integrated malaria prevention particularly regarding malaria prevalence and contribution of each of the methods are required.

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

Background

Insecticide 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).

Methods

The 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.

Results

At 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.

Conclusions

Both 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.

Comparison of Indoor Residual Spray Equipment for Malaria Control in Liberia

We describe and compare a new innovative backpack compressed-air sprayer (JQSX-12) to a Stihl® 450 backpack mist blower and a manually operated compression sprayer for its effectiveness as an alternative operational tool for indoor residual insecticide application to control malaria in Liberia. Advantages and physical characteristics of each sprayer and their spray atomization parameters are discussed.

Monitoring changes in malaria epidemiology and effectiveness of interventions in Ethiopia and Uganda: Beyond Garki Project baseline survey

Background

Scale-up of malaria interventions seems to have contributed to a decline in the disease but other factors may also have had some role. Understanding changes in transmission and determinant factors will help to adapt control strategies accordingly.

Methods

Four sites in Ethiopia and Uganda were set up to monitor epidemiological changes and effectiveness of interventions over time. Here, results of a survey during the peak transmission season of 2012 are reported, which will be used as baseline for subsequent surveys and may support adaptation of control strategies. Data on malariometric and entomological variables, socio-economic status (SES) and control coverage were collected.

Results

Malaria prevalence varied from 1.4 % in Guba (Ethiopia) to 9.9 % in Butemba (Uganda). The most dominant species was Plasmodium vivax in Ethiopia and Plasmodium falciparum in Uganda. The majority of human-vector contact occurred indoors in Uganda, ranging from 83 % (Anopheles funestus sensu lato) to 93 % (Anopheles gambiae s.l.), which is an important factor for the effectiveness of insecticide-treated nets (ITNs) or indoor residual spraying (IRS). High kdr-L1014S (resistance genotype) frequency was observed in A. gambiae sensu stricto in Uganda. Too few mosquitoes were collected in Ethiopia, so it was not possible to assess vector habits and insecticide resistance levels. ITN ownership did not vary by SES and 56–98 % and 68–78 % of households owned at least one ITN in Ethiopia and Uganda, respectively. In Uganda, 7 % of nets were purchased by households, but the nets were untreated. In three of the four sites, 69–76 % of people with access to ITNs used them. IRS coverage ranged from 84 to 96 % in the three sprayed sites. Half of febrile children in Uganda and three-quarters in Ethiopia for whom treatment was sought received diagnostic tests. High levels of child undernutrition were detected in both countries carrying important implications on child development. In Uganda, 7–8 % of pregnant women took the recommended minimum three doses of intermittent preventive treatment.

Conclusion

Malaria epidemiology seems to be changing compared to earlier published data, and it is essential to have more data to understand how much of the changes are attributable to interventions and other factors. Regular monitoring will help to better interpret changes, identify determinants, modify strategies and improve targeting to address transmission heterogeneity.

The past, present and future use of epidemiological intelligence to plan malaria vector control and parasite prevention in Uganda

Background

An important prelude to developing strategies to control infectious diseases is a detailed epidemiological evidence platform to target cost-effective interventions and define resource needs.

Methods

A review of published and un-published reports of malaria vector control and parasite prevention in Uganda was conducted for the period 1900–2013. The objective was to provide a perspective as to how epidemiological intelligence was used to design malaria control before and during the global malaria eradication programme (GMEP) and to contrast this with the evidence generated in support of the Roll Back Malaria (RBM) initiative from 1998 to date.

Results

During the GMEP era, comprehensive investigations were undertaken on the effectiveness of vector and parasite control such as indoor residual house-spraying (IRS) and mass drug administration (MDA) at different sites in Uganda. Nationwide malariometric surveys were undertaken between 1964 and 1967 to provide a profile of risk, epidemiology and seasonality leading to an evidence-based national cartography of risk to characterize the diversity of malaria transmission in Uganda. At the launch of the RBM initiative in the late 1990s, an equivalent level of evidence was lacking. There was no contemporary national evidence-base for the likely impact of insecticide-treated nets (ITN), no new malariometric data, no new national cartography of malaria risk or any evidence of tailored intervention delivery based on variations in the ecology of malaria risk in Uganda.

Discussion

Despite millions of dollars of overseas development assistance over the last ten years in ITN, and more recently the resurrection of the use of IRS, the epidemiological impact of vector control remains uncertain due to an absence of nationwide basic parasite and vector-based field studies.

Conclusion

Readily available epidemiological data should become the future business model to maximize malaria funding from 2015. Over the next five to ten years, accountability, impact analysis, financial business cases supported by a culture of data use should become the new paradigm by which malaria programmes, governments and their development partners operate.

Decline in childhood iron deficiency after interruption of malaria transmission in highland Kenya

BACKGROUND

Achieving optimal iron status in children in malaria-endemic areas may increase the risk of malaria. Malaria itself may contribute to iron deficiency, but the impact of an interruption in malaria transmission on the prevalence of iron deficiency is unknown.

OBJECTIVES

We aimed to determine whether 1) iron status improved in children living in 2 Kenyan villages with a documented cessation in malaria transmission and 2) changes in iron status correlated with changes in hemoglobin.

DESIGN

We measured iron [hemoglobin, ferritin, soluble transferrin receptor (sTfR)] and inflammatory [C-reactive protein (CRP)] markers in paired plasma samples from 190 children aged 4-59 mo at the beginning (May 2007) and end (July 2008) of a documented 12-mo period of interruption in malaria transmission in 2 highland areas in Kenya with unstable malaria transmission and ongoing malaria surveillance.

RESULTS

Between May 2007 and July 2008, mean (±SD) hemoglobin increased from 10.8 ± 1.6 to 11.6 ± 1.6 g/dL. Median (25th, 75th percentile) ferritin increased from 17.0 (9.7, 25.6) to 22.6 (13.4, 34.7) μg/L (P < 0.001), whereas median sTfR decreased from 32.4 (26.3, 43.2) to 27.7 (22.1, 36.0) nmol/L (P < 0.001). Median CRP was low (<1 mg/L in both years) and did not change significantly. Iron deficiency prevalence (ferritin <12 μg/L, or <30 μg/L if CRP ≥10 mg/L) decreased from 35.9% (95% CI: 28.9%, 43.0%) to 24.9% (18.5%, 31.2%) (P = 0.005). The prevalence of iron deficiency with anemia (hemoglobin <11.0 g/dL) declined from 27.2% (20.7%, 33.8%) to 12.2% (7.4%, 17.1%) (P < 0.001). Improvement in iron status correlated with an increase in hemoglobin and was greater than explained by physiologic changes expected with age.

CONCLUSIONS

In this area of unstable malaria transmission, the prevalence of iron deficiency in children decreased significantly after the interruption of malaria transmission and was correlated with an increase in hemoglobin. These findings suggest that malaria elimination strategies themselves may be an effective way to address iron deficiency in malaria-endemic areas.

Bioefficacy of long-lasting insecticidal nets against pyrethroid-resistant populations of Anopheles gambiae s.s. from different malaria transmission zones in Uganda

BACKGROUND

There are major concerns over sustaining the efficacy of current malaria vector control interventions given the rapid spread of resistance, particularly to pyrethroids. This study assessed the bioefficacy of five WHO-recommended long-lasting insecticidal nets (LLINs) against pyrethroid-resistant Anopheles gambiae field populations from Uganda.

METHODS

Adult An. gambiae from Lira, Tororo, Wakiso and Kanungu districts were exposed to permethrin (0.75%) or deltamethrin (0.05%) in standard WHO susceptibility tests. Cone bioassays were used to measure the bioefficacy of four mono-treated LLINs (Olyset®, Interceptor®, Netprotect® and PermaNet® 2.0) and one combination LLIN (PermaNet® 3.0) against the four mosquito populations. Wireball assays were similarly conducted to determine knockdown rates. Species composition and kdr mutation frequency were determined for a sample of mosquitoes from each population. Chemical assays confirmed that test nets fell within target dose ranges.

RESULTS

Anopheles gambiae s.s. predominated at all four sites (86-99% of Anopheles spp.) with moderate kdr L1014S allelic frequency (0.34-0.37). Confirmed or possible resistance to both permethrin and deltamethrin was identified for all four test populations. Reduced susceptibility to standard LLINs was observed for all four populations, with mortality rates as low as 45.8% even though the nets were unused. The combination LLIN PermaNet®3.0 showed the highest overall bioefficacy against all four An. gambiae s.l. populations (98.5-100% mortality). Wireball assays provided a more sensitive indicator of comparative bioefficacy, and PermaNet 3.0 was again associated with the highest bioefficacy against all four populations (76.5-91.7% mortality after 30 mins).

CONCLUSIONS

The bioefficacy of mono-treated LLINs against pyrethroid-resistant field populations of An. gambiae varied by LLIN type and mosquito population, indicating that certain LLINs may be more suitable than others at particular sites. In contrast, the combination LLIN PermaNet 3.0 performed optimally against the four An. gambiae populations tested. The observed reduced susceptibility of malaria vectors to mono-treated LLINs is of particular concern, especially considering all nets were unused. With ongoing scale-up of insecticidal tools in the advent of increasing resistance, it is essential that those interventions with proven enhanced efficacy are given preference particularly in areas with high resistance.