Relationship between malaria vector survival, infectivity and insecticide treated net use in western Kenya

Background

Much effort and resources have been invested to control malaria transmission in Sub-Saharan Africa, but it remains a major public health problem. For the disease to be transmitted from one person to another, the female Anopheles vector must survive 10-14 days following an infective bite for the Plasmodiumgametocytes to develop into infectious sporozoites which can be transmitted to the next person during a bloodmeal. The goal of this investigation was to assess factors associated with wild-caught Anopheles survival and infection following host-seeking and indoor resting.

Methods

The study was conducted in a longitudinal cohort of 75 households in 5 villages including a total of 755 household members in Bungoma County, Kenya. Monthly adult mosquito collection was conducted by attenuated aspiration in all the enrolled households, and the mosquitoes were reared in the insectary for 7 days. The daily mortality rate was determined through day 7, and all the mosquitoes were morphologically identified. Female Anopheline mosquitoes were dissected, and species-level members of the Anopheles gambiae complex were resolved by molecular methods. The abdomen for all samples were processed for P. falciparum detection by PCR.

Results

Within a period of 25 months, the total number of culex and Anopheles mosquitoes collected indoors were 12,843 and 712 respectively. Anopheles gambiaeand Anopheles funestus were the major vectors though their population varied between different villages. 61.2% (n=436/712) of the Anopheles species survived up to day 7 with the lowest mortality rate recorded on day 5 of captivity. The survival rate also varied between the different Anophelesspecies. 683 of 712 mosquito abdomens were tested for P. falciparumdetection and 7.8% (53/683) tested positive for P. falciparum with An. funestus having a higher (10%) prevalence than An. gambaie s.s.(6.0%, p=0.095, Pearson Chi square test). The proportion of household members sleeping under a bednet the night before mosquito collection varied across time and village. An. funestus survival times were refractory to household ITN coverage and An. gambaie s.s. survival was reduced only under very high (>95%) ITN coverage.

Conclusion

Despite ITN coverage, mosquitoes still acquired bloodmeals and P. falciparum infections. Survival differed across species and was inversely correlated with high ITN exposure in the household, but not oocyst development.

Detection of Anopheles stephensi Mosquitoes by Molecular Surveillance, Kenya

The Anopheles stephensi mosquito is an invasive malaria vector recently reported in Djibouti, Ethiopia, Sudan, Somalia, Nigeria, and Ghana. The World Health Organization has called on countries in Africa to increase surveillance efforts to detect and report this vector and institute appropriate and effective control mechanisms. In Kenya, the Division of National Malaria Program conducted entomological surveillance in counties at risk for An. stephensi mosquito invasion. In addition, the Kenya Medical Research Institute conducted molecular surveillance of all sampled Anopheles mosquitoes from other studies to identify An. stephensi mosquitoes. We report the detection and confirmation of An. stephensi mosquitoes in Marsabit and Turkana Counties by using endpoint PCR and morphological and sequence identification. We demonstrate the urgent need for intensified entomological surveillance in all areas at risk for An. stephensi mosquito invasion, to clarify its occurrence and distribution and develop tailored approaches to prevent further spread.

Plasmodium vivax Prevalence in Semiarid Region of Northern Kenya, 2019

In urban and rural areas of Turkana County, Kenya, we found that 2% of household members of patients with Plasmodium falciparum infections were infected with P. vivax. Enhanced surveillance of P. vivax and increased clinical resources are needed to inform control measures and identify and manage P. vivax infections.

How do malaria testing and treatment subsidies affect drug shop client expenditures? A cross-sectional analysis in Western Kenya

OBJECTIVES

To examine how drug shop clients' expenditures are affected by subsidies for malaria diagnostic testing and for malaria treatment, and also to examine how expenditures vary by clients' malaria test result and by the number of medications they purchased.

DESIGN

Secondary cross-sectional analysis of survey responses from a randomised controlled trial.

SETTING

The study was conducted in twelve private drug shops in Western Kenya.

PARTICIPANTS

We surveyed 836 clients who visited the drug shops between March 2018 and October 2019 for a malaria-like illness. This included children >1 year of age if they were physically present and accompanied by a parent or legal guardian.

INTERVENTIONS

Subsidies for malaria diagnostic testing and for malaria treatment (conditional on a positive malaria test result).

PRIMARY AND SECONDARY OUTCOME MEASURES

Expenditures at the drug shop in Kenya shillings (Ksh).

RESULTS

Clients who were randomised to a 50% subsidy for malaria rapid diagnostic tests (RDTs) spent approximately Ksh23 less than those who were randomised to no RDT subsidy (95% CI (-34.6 to -10.7), p=0.002), which corresponds approximately to the value of the subsidy (Ksh20). However, clients randomised to receive free treatment (artemisinin combination therapies (ACTs)) if they tested positive for malaria had similar spending levels as those randomised to a 67% ACT subsidy conditional on a positive test. Expenditures were also similar by test result, however, those who tested positive for malaria bought more medications than those who tested negative for malaria while spending approximately Ksh15 less per medication (95% CI (-34.7 to 3.6), p=0.102).

CONCLUSIONS

Our results suggest that subsidies for diagnostic health products may result in larger household savings than subsidies on curative health products. A better understanding of how people adjust their behaviours and expenditures in response to subsidies could improve the design and implementation of subsidies for health products.

TRIAL REGISTRATION NUMBER

NCT03810014.

Experience and confidence in health technologies: evidence from malaria testing and treatment in Western Kenya

Background

Low adoption of effective health technologies increases illness morbidity and mortality worldwide. In the case of malaria, effective tools such as malaria rapid diagnostic tests (RDTs) and artemisinin-combination therapies (ACTs) are both under-used and used inappropriately. Individuals’ confidence in RDTs and ACTs likely affects the uptake of these tools.

Methods

In a cohort of 36 households (280 individuals) in Western Kenya observed for 30 months starting in June 2017, we examined if experience with RDTs and ACTs changes people’s beliefs about these technologies and how those beliefs affect treatment behavior. Household members requested a free RDT from the study team any time they suspected a malaria illness, and positive RDT results were treated with a free ACT. We conducted annual, monthly, and sick visit surveys to elicit beliefs about the accuracy of malaria RDT results and the effectiveness of ACTs. Beliefs were elicited on a 5-point Likert scale from “very unlikely” to “very likely.”

Results

Over the study period, the percentage of survey respondents that said a hypothetical negative RDT result was “very likely” to be correct increased from approximately 55% to 75%. Controlling for initial beliefs, people who had been tested at least once with an RDT in the past year had 3.6 times higher odds (95% CI [1 1.718 7.679], P = 0.001) of saying a negative RDT was “very likely” to be correct. Confidence in testing was associated with treatment behavior: those who believed a negative RDT was “very likely” to be correct had 1.78 times higher odds (95% CI [1.079 2.934], P = 0.024) of adhering to a negative RDT result (by not taking ACTs) than those who were less certain about the accuracy of negative RDTs. Adherence to a negative test also affected subsequent beliefs: controlling for prior beliefs, those who had adhered to their previous test result had approximately twice the odds (OR = 2.19, 95% CI [1.661 2.904], P < 0.001) of saying that a hypothetical negative RDT was “very likely” to be correct compared to those who had not adhered.

Conclusions

Our results suggest that greater experience with RDTs can not only increase people’s confidence in their accuracy but also improve adherence to the test result.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-022-14102-y.

The prevalence and density of asymptomatic Plasmodium falciparum infections among children and adults in three communities of western Kenya

BACKGROUND

Further reductions in malaria incidence as more countries approach malaria elimination require the identification and treatment of asymptomatic individuals who carry mosquito-infective Plasmodium gametocytes that are responsible for furthering malaria transmission. Assessing the relationship between total parasitaemia and gametocytaemia in field surveys can provide insight as to whether detection of low-density, asymptomatic Plasmodium falciparum infections with sensitive molecular methods can adequately detect the majority of infected individuals who are potentially capable of onward transmission.

METHODS

In a cross-sectional survey of 1354 healthy children and adults in three communities in western Kenya across a gradient of malaria transmission (Ajigo, Webuye, and Kapsisywa-Kipsamoite), asymptomatic P. falciparum infections were screened by rapid diagnostic tests, blood smear, and quantitative PCR of dried blood spots targeting the varATS gene in genomic DNA. A multiplex quantitative reverse-transcriptase PCR assay targeting female and male gametocyte genes (pfs25, pfs230p), a gene with a transcriptional pattern restricted to asexual blood stages (piesp2), and human GAPDH was also developed to determine total parasite and gametocyte densities among parasitaemic individuals.

RESULTS

The prevalence of varATS-detectable asymptomatic infections was greatest in Ajigo (42%), followed by Webuye (10%). Only two infections were detected in Kapsisywa. No infections were detected in Kipsamoite. Across all communities, children aged 11-15 years account for the greatest proportion total and sub-microscopic asymptomatic infections. In younger age groups, the majority of infections were detectable by microscopy, while 68% of asymptomatically infected adults (> 21 years old) had sub-microscopic parasitaemia. Piesp2-derived parasite densities correlated poorly with microscopy-determined parasite densities in patent infections relative to varATS-based detection. In general, both male and female gametocytaemia increased with increasing varATS-derived total parasitaemia. A substantial proportion (41.7%) of individuals with potential for onward transmission had qPCR-estimated parasite densities below the limit of microscopic detection, but above the detectable limit of varATS qPCR.

CONCLUSIONS

This assessment of parasitaemia and gametocytaemia in three communities with different transmission intensities revealed evidence of a substantial sub-patent infectious reservoir among asymptomatic carriers of P. falciparum. Experimental studies are needed to definitively determine whether the low-density infections in communities such as Ajigo and Webuye contribute significantly to malaria transmission.

Correction to: Incentivizing appropriate malaria case management in the private sector: a study protocol for two linked cluster randomized controlled trials to evaluate provider- and client-focused interventions in western Kenya and Lagos, Nigeria

An amendment to this paper has been published and can be accessed via the original article.

Incentivizing appropriate malaria case management in the private sector: a study protocol for two linked cluster randomized controlled trials to evaluate provider- and client-focused interventions in western Kenya and Lagos, Nigeria

Background

A large proportion of artemisinin-combination therapy (ACT) anti-malarial medicines is consumed by individuals that do not have malaria. The over-consumption of ACTs is largely driven by retail sales in high malaria-endemic countries to clients who have not received a confirmatory diagnosis. This study aims to target ACT sales to clients receiving a confirmatory diagnosis using malaria rapid diagnostic tests (mRDTs) at retail outlets in Kenya and Nigeria.

Methods

This study comprises two linked four-arm 2 × 2 factorial cluster randomized controlled trials focused on malaria diagnostic testing and conditional ACT subsidies with the goal to evaluate provider-directed and client-directed interventions. The linked trials will be conducted at two contrasting study sites: a rural region around Webuye in western Kenya and the urban center of Lagos, Nigeria. Clusters are 41 and 48 participating retail outlets in Kenya and Nigeria, respectively. Clients seeking care at participating outlets across all arms will be given the option of paying for a mRDT—at a study-recommended price—to be conducted at the outlet. In the provider-directed intervention arm, the outlet owner receives a small monetary incentive to perform the mRDT. In the client-directed intervention arm, the client receives a free ACT if they purchase an mRDT and receive a positive test result. Finally, the fourth study arm combines both the provider- and client-directed interventions. The diagnosis and treatment choices made during each transaction will be captured using a mobile phone app. Study outcomes will be collected through exit interviews with clients, who sought care for febrile illness, at each of the enrolled retail outlets.

Results

The primary outcome measure is the proportion of all ACTs that are sold to malaria test-positive clients in each study arm. For all secondary outcomes, we will evaluate the degree to which the interventions affect purchasing behavior among people seeking care for a febrile illness at the retail outlet.

Conclusions

If our study demonstrates that malaria case management can be improved in the retail sector, it could reduce overconsumption of ACTs and enhance targeting of publicly funded treatment reimbursements, lowering the economic barrier to appropriate diagnosis and treatment for patients with malaria.

Trial registration

ClinicalTrials.govNCT04428307, registered June 9, 2020, and NCT04428385, registered June 9, 2020.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13012-020-01077-w.

Mosquito Exposure and Malaria Morbidity: A Microlevel Analysis of Household Mosquito Populations and Malaria in a Population-Based Longitudinal Cohort in Western Kenya

BACKGROUND

Malaria morbidity is highly overdispersed in the population. Fine-scale differences in mosquito exposure may partially explain this heterogeneity in individual malaria outcomes.

METHODS

In 38 households we explored the effect of household-level mosquito exposure and individual insecticide-treated net (ITN) use on relative risk (RR) of confirmed malaria. We conducted monthly active surveillance (n = 254; 2624 person-months) and weekly mosquito collection (2092 household-days of collection), and used molecular techniques to confirm human blood feeding and exposure to infectious mosquitoes.

RESULTS

Of 1494 female Anopheles (89.8% Anopheles gambiae sensu lato), 88.3% were fed, 51.9% had a human blood meal, and 9.2% were sporozoite infected. In total, 168 laboratory-confirmed malaria episodes were reported (incidence rate 0.064 episodes per person-month at risk; 95% confidence interval [CI], .055-.074). Malaria risk was directly associated with exposure to sporozoite-infected mosquitoes (RR, 1.24; 95% CI, 1.11-1.38). No direct effect was measured between ITN use and malaria morbidity; however, ITN use did moderate the effect of mosquito exposure on morbidity.

CONCLUSIONS

Malaria risk increases linearly with vector density and feeding success for persons with low ITN use. In contrast, malaria risk among high ITN users is consistently low and insensitive to variation in mosquito exposure.

Does improving appropriate use of malaria medicines change population beliefs in testing and treatment? Evidence from a randomized controlled trial

A major puzzle in malaria treatment remains the dual problem of underuse and overuse of malaria medications, which deplete scarce public resources used for subsidies and lead to drug resistance. One explanation is that health behaviour, especially in the context of incomplete information, could be driven by beliefs, pivotal to the success of health interventions. The objective of this study is to investigate how population beliefs change in response to an experimental intervention which was shown to improve access to rapid diagnostic testing (RDT) through community health workers (CHWs) and to increase appropriate use of anti-malaria medications. By collecting data on individuals' beliefs on malaria testing and treatment 12 and 18 months after the experimental intervention started, we find that the intervention increases the belief that a negative test result is correct, and the belief that the first-line anti-malaria drugs (artemisinin-based combination therapies or ACTs) are effective. Using mediation analysis, we also explore some possible mechanisms through which the changes happen. We find that the experience and knowledge about RDT and experience with CHWs explain 62.4% of the relationship between the intervention and the belief that a negative test result is correct. Similarly, the targeted use of ACTs and taking the correct dose-in addition to experience with RDT-explain 96.8% of the relationship between the intervention and the belief that the ACT taken is effective. As beliefs are important determinants of economic behaviour and might guide individuals' future decisions, understanding how they change after a health intervention has important implications for long-term changes in population behaviour.

Direct Estimation of Sensitivity of Plasmodium falciparum Rapid Diagnostic Test for Active Case Detection in a High-Transmission Community Setting

Community-based active case detection of malaria parasites with conventional rapid diagnostic tests (cRDTs) is a strategy used most commonly in low-transmission settings. We estimated the sensitivity of this approach in a high-transmission setting in Western Kenya. We tested 3,547 members of 912 households identified in 2013-2014 by index children with (case) and without (control) cRDT-positive malaria. All were tested for Plasmodium falciparum with both a cRDT targeting histidine-rich protein 2 and with an ultrasensitive real-time polymerase chain reaction (PCR). We computed cRDT sensitivity against PCR as the referent, compared prevalence between participant types, and estimated cRDT detectability as a function of PCR-estimated parasite density. Parasite prevalence was 22.9% by cRDTs and 61.5% by PCR. Compared with children aged < 5 years or adults aged > 15 years, geometric mean parasite densities (95% CI) were highest in school-age children aged 5-15 years (8.4 p/uL; 6.6-10.6). The overall sensitivity of cRDT was 36%; among asymptomatic household members, cRDT sensitivity was 25.5% and lowest in adults aged > 15 years (15.8%). When modeled as a function of parasite density, relative to school-age children, the probability of cRDT positivity was reduced in both children aged < 5 years (odds ratio [OR] 0.48; 95% CI: 0.34-0.69) and in adults aged > 15 years (OR: 0.35; 95% CI: 0.27-0.47). An HRP2-detecting cRDT had poor sensitivity for active P. falciparum case detection in asymptomatic community members, and sensitivity was lowest in highly prevalent low-density infections and in adults. Future studies can model the incremental effects of high-sensitivity rapid diagnostic tests and the impacts on transmission.

Household beliefs about malaria testing and treatment in Western Kenya: the role of health worker adherence to malaria test results

Background

Although use of malaria diagnostic tests has increased in recent years, health workers often prescribe anti-malarial drugs to individuals who test negative for malaria. This study investigates how health worker adherence to malaria case management guidelines influences individuals’ beliefs about whether their illness was malaria, and their confidence in the effectiveness of artemisinin-based combination therapy (ACT).

Methods

A survey was conducted with 2065 households in Western Kenya about a household member’s treatment actions for a recent febrile illness. The survey also elicited the individual’s (or their caregiver’s) beliefs about the illness and about malaria testing and treatment. Logistic regressions were used to test the association between these beliefs and whether the health worker adhered to malaria testing and treatment guidelines.

Results

Of the 1070 individuals who visited a formal health facility during their illness, 82% were tested for malaria. ACT rates for malaria-positive and negative individuals were 89 and 49%, respectively. Overall, 65% of individuals/caregivers believed that the illness was “very likely” malaria. Individuals/caregivers had higher odds of saying that the illness was “very likely” malaria when the individual was treated with ACT, and this was the case both among individuals not tested for malaria [adjusted odds ratio (AOR) 3.42, 95% confidence interval (CI) [1.65 7.10], P = 0.001] and among individuals tested for malaria, regardless of their test result. In addition, 72% of ACT-takers said the drug was “very likely” effective in treating malaria. However, malaria-negative individuals who were treated with ACT had lower odds of saying that the drugs were “very likely” effective than ACT-takers who were not tested or who tested positive for malaria (AOR 0.29, 95% CI [0.13 0.63], P = 0.002).

Conclusion

Individuals/caregivers were more likely to believe that the illness was malaria when the patient was treated with ACT, regardless of their test result. Moreover, malaria-negative individuals treated with ACT had lower confidence in the drug than other individuals who took ACT. These results suggest that ensuring health worker adherence to malaria case management guidelines will not only improve ACT targeting, but may also increase patient/caregivers’ confidence in malaria testing and treatment.

Electronic supplementary material

The online version of this article (doi:10.1186/s12936-017-1993-7) contains supplementary material, which is available to authorized users.

Innovative public-private partnership to target subsidised antimalarials: a study protocol for a cluster randomised controlled trial to evaluate a community intervention in Western Kenya

INTRODUCTION

There are concerns of inappropriate use of subsidised antimalarials due to the large number of fevers treated in the informal sector with minimal access to diagnostic testing. Targeting antimalarial subsidies to confirmed malaria cases can lead to appropriate, effective therapy. There is evidence that community health volunteers (CHVs) can be trained to safely and correctly use rapid diagnostic tests (RDTs). This study seeks to evaluate the public health impact of targeted antimalarial subsidies delivered through a partnership between CHVs and the private retail sector.

METHODS AND ANALYSIS

We are conducting a stratified cluster-randomised controlled trial in Western Kenya where 32 community units were randomly assigned to the intervention or control (usual care) arm. In the intervention arm, CHVs offer free RDT testing to febrile individuals and, conditional on a positive test result, a voucher to purchase a WHO-qualified artemisinin combination therapy (ACT) at a reduced fixed price in the retail sector.Study outcomes in individuals with a febrile illness in the previous 4 weeks will be ascertained through population-based cross-sectional household surveys at four time points: baseline, 6, 12 and 18 months postbaseline. The primary outcome is the proportion of fevers that receives a malaria test from any source (CHV or health facility). The main secondary outcome is the proportion of ACTs used by people with a malaria-positive test. Other secondary outcomes include: the proportion of ACTs used by people without a test and adherence to test results.

ETHICS AND DISSEMINATION

The protocol has been approved by the National Institutes of Health, the Moi University School of Medicine Institutional Research and Ethics Committee and the Duke University Medical Center Institutional Review Board. Findings will be reported on clinicalstrials.gov, in peer-reviewed publications and through stakeholder meetings including those with the Kenyan Ministry of Health.

TRIAL REGISTRATION NUMBER

Pre-results, NCT02461628.

A retrospective cohort study to quantify the contribution of health systems to child survival in Kenya: 1996-2014

Globally, the majority of childhood deaths in the post-neonatal period are caused by infections that can be effectively treated or prevented with inexpensive interventions delivered through even very basic health facilities. To understand the role of inadequate health systems on childhood mortality in Kenya, we assemble a large, retrospective cohort of children (born 1996–2013) and describe the health systems context of each child using health facility survey data representative of the province at the time of a child’s birth. We examine the relationship between survival beyond 59 months of age and geographic distribution of health facilities, quality of services, and cost of services. We find significant geographic heterogeneity in survival that can be partially explained by differences in distribution of health facilities and user fees. Higher per capita density of health facilities resulted in a 25% reduction in the risk of death (HRR = 0.73, 95% CI:0.58 to 0.91) and accounted for 30% of the between-province heterogeneity in survival. User fees for sick-child visits increased risk by 30% (HRR = 1.30, 95% CI:1.11 to 1.53). These results implicate health systems constraints in child mortality, quantify the contribution of specific domains of health services, and suggest priority areas for improvement to accelerate reductions in child mortality.

Development and validation of a rapid assessment tool for malaria prevention

BACKGROUND

Insecticide-treated bed nets (ITN) have been shown to be efficacious in reducing malaria morbidity and mortality in many regions. Unfortunately in some areas, malaria has persisted despite the scale up of ITNs. Recent reports indicate that human behaviour and mosquito behaviour are potential threats to the efficacy of ITNs. However, these concerns are likely highly heterogeneous even at very small scales. This study aimed at developing, testing and validating a rapid assessment tool to collect actionable information at local levels for a quick evaluation of potential barriers to malaria prevention.

METHODS

The study was conducted at the Webuye Health and Demographic Surveillance Site in Bungoma East Sub-County, Kenya. Based on the findings from the case-control study, 12 primary surveillance components that encompass the major impediments to successful prevention were identified and used to develop a rapid assessment tool. Twenty community health volunteers were trained to identify patients with laboratory-confirmed malaria in six peripheral health facilities located within six sub locations and subsequently followed them up to their homes to conduct a rapid assessment. Sampling and analysis of the results of the survey are based on Lot Quality Assurance.

RESULTS

The tool was able to detect local heterogeneity in bed net coverage, bed net use and larval site abundance in the six health facility catchment areas. Nearly all the catchment areas met the action threshold for incomplete household coverage (i.e. not all household members not using a net the previous night) except the peri-urban area. Although the threshold for nets not in good condition was set very high (≥50%), only two catchment areas failed to meet the action threshold. On the indicator for "Net not used every day last week", half of the areas failed, while for net ownership, only two areas met the action threshold.

CONCLUSION

The rapid assessment tool was able to detect marked heterogeneity in key indicators for malaria prevention between patients attending health facilities, and can distinguish between priority areas for intervention. There is need to validate it for use in other contexts.

Assessing the independent and combined effects of subsidies for antimalarials and rapid diagnostic testing on fever management decisions in the retail sector: results from a factorial randomised trial in western Kenya

Objectives

There is an urgent need to understand how to improve targeting of artemisinin combination therapy (ACT) to patients with confirmed malaria infection, including subsidised ACTs sold over-the-counter. We hypothesised that offering an antimalarial subsidy conditional on a positive malaria rapid diagnostic test (RDT) would increase uptake of testing and improve rational use of ACTs.

Methods

We designed a 2×2 factorial randomised experiment evaluating 2 levels of subsidy for RDTs and ACTs. Between July 2014 and June 2015, 444 individuals with a malaria-like illness who had not sought treatment were recruited from their homes. We used scratch cards to allocate participants into 4 groups in a ratio of 1:1:1:1. Participants were eligible for an unsubsidised or fully subsidised RDT and 1 of 2 levels of ACT subsidy (current retail price or an additional subsidy conditional on a positive RDT). Treatment decisions were documented 1 week later. Our primary outcome was uptake of malaria testing. Secondary outcomes evaluated ACT consumption among those with a negative test, a positive test or no test.

Results

Offering a free RDT increased the probability of testing by 18.6 percentage points (adjusted probability difference (APD), 95% CI 5.9 to 31.3). An offer of a conditional ACT subsidy did not have an additional effect on the probability of malaria testing when the RDT was free (APD=2.7; 95% CI −8.6 to 14.1). However, receiving the conditional ACT subsidy increased the probability of taking an ACT following a positive RDT by 19.5 percentage points (APD, 95% CI 2.2 to 36.8). Overall, the proportion who took ACT following a negative test was lower than those who took ACT without being tested, indicated improved targeting among those who were tested.

Conclusions

Both subsidies improved appropriate fever management, demonstrating the impact of these costs on decision making. However, the conditional ACT subsidy did not increase testing. We conclude that each of the subsidies primarily impacts the most immediate decision.

Trial registration number

NCT02199977.

What Is Threatening the Effectiveness of Insecticide-Treated Bednets? A Case-Control Study of Environmental, Behavioral, and Physical Factors Associated with Prevention Failure

Background

Insecticide-treated nets are the cornerstone of global malaria control and have been shown to reduce malaria morbidity by 50–60%. However, some areas are experiencing a resurgence in malaria following successful control. We describe an efficacy decay framework to understand why high malaria burden persists even under high ITN coverage in a community in western Kenya.

Methods

We enrolled 442 children hospitalized with malaria and paired them with age, time, village and gender-matched controls. We completed comprehensive household and neighborhood assessments including entomological surveillance. The indicators are grouped into five domains in an efficacy decay framework: ITN ownership, compliance, physical integrity, vector susceptibility and facilitating factors. After variable selection, case-control data were analyzed using conditional logistic regression models and mosquito data were analyzed using negative binomial regression. Predictive margins were calculated from logistic regression models.

Results

Measures of ITN coverage and physical integrity were not correlated with hospitalized malaria in our study. However, consistent ITN use (Adjusted Odds Ratio (AOR) = 0.23, 95%CI: 0.12–0.43), presence of nearby larval sites (AOR = 1.137, 95%CI: 1.02–1.27), and specific types of crops (AOR (grains) = 0.446, 95%CI: 0.24–0.82) were significantly correlated with malaria amongst children who owned an ITN. The odds of hospitalization for febrile malaria nearly tripled when one other household member had symptomatic malaria infection (AOR–2.76, 95%CI:1.83–4.18). Overall, perfect household adherence could reduce the probability of hospitalization for malaria to less than 30% (95%CI:0.12–0.46) and adjusting environmental factors such as elimination of larval sites and growing grains nearby could reduce the probability of hospitalization for malaria to less than 20% (95%CI:0.04–0.31).

Conclusion

Availability of ITNs is not the bottleneck for malaria prevention in this community. Behavior change interventions to improve compliance and environmental management of mosquito breeding habitats may greatly enhance ITN efficacy. A better understanding of the relationship between agriculture and mosquito survival and feeding success is needed.

High sensitivity and specificity of clinical microscopy in rural health facilities in western Kenya under an external quality assurance program

Microscopic diagnosis of malaria is a well-established and inexpensive technique that has the potential to provide accurate diagnosis of malaria infection. However, it requires both training and experience. Although it is considered the gold standard in research settings, the sensitivity and specificity of routine microscopy for clinical care in the primary care setting has been reported to be unacceptably low. We established a monthly external quality assurance program to monitor the performance of clinical microscopy in 17 rural health centers in western Kenya. The average sensitivity over the 12-month period was 96% and the average specificity was 88%. We identified specific contextual factors that contributed to inadequate performance. Maintaining high-quality malaria diagnosis in high-volume, resource-constrained health facilities is possible.

Spatial autocorrelation in uptake of antenatal care and relationship to individual, household and village-level factors: results from a community-based survey of pregnant women in six districts in western Kenya

Background

The majority of maternal deaths, stillbirths, and neonatal deaths are concentrated in a few countries, many of which have weak health systems, poor access to health services, and low coverage of key health interventions. Early and consistent antenatal care (ANC) attendance could significantly reduce maternal and neonatal morbidity and mortality. Despite this, most Kenyan mothers initiate ANC care late in pregnancy and attend fewer than the recommended visits.

Methods

We used survey data from 6,200 pregnant women across six districts in western Kenya to understand demand-side factors related to use of ANC. Bayesian multi-level models were developed to explore the relative importance of individual, household and village-level factors in relation to ANC use.

Results

There is significant spatial autocorrelation of ANC attendance in three of the six districts and considerable heterogeneity in factors related to ANC use between districts. Working outside the home limited ANC attendance. Maternal age, the number of small children in the household, and ownership of livestock were important in some districts, but not all. Village proportions of pregnancy in women of child-bearing age was significantly correlated to ANC use in three of the six districts. Geographic distance to health facilities and the type of nearest facility was not correlated with ANC use. After incorporating individual, household and village-level covariates, no residual spatial autocorrelation remained in the outcome.

Conclusions

ANC attendance was consistently low across all the districts, but factors related to poor attendance varied. This heterogeneity is expected for an outcome that is highly influenced by socio-cultural values and local context. Interventions to improve use of ANC must be tailored to local context and should include explicit approaches to reach women who work outside the home.

The association between price, competition, and demand factors on private sector anti-malarial stocking and sales in western Kenya: considerations for the AMFm subsidy

Background

Households in sub-Saharan Africa are highly reliant on the retail sector for obtaining treatment for malaria fevers and other illnesses. As donors and governments seek to promote the use of artemisinin combination therapy in malaria-endemic areas through subsidized anti-malarials offered in the retail sector, understanding the stocking and pricing decisions of retail outlets is vital.

Methods

A survey of all medicine retailers serving Bungoma East District in western Kenya was conducted three months after the launch of the AMFm subsidy in Kenya. The survey obtained information on each anti-malarial in stock: brand name, price, sales volume, outlet characteristics and GPS co-ordinates. These data were matched to household-level data from the Webuye Health and Demographic Surveillance System, from which population density and fever prevalence near each shop were determined. Regression analysis was used to identify the factors associated with retailers’ likelihood of stocking subsidized artemether lumefantrine (AL) and the association between price and sales for AL, quinine and sulphadoxine-pyrimethamine (SP).

Results

Ninety-seven retail outlets in the study area were surveyed; 11% of outlets stocked subsidized AL. Size of the outlet and having a pharmacist on staff were associated with greater likelihood of stocking subsidized AL. In the multivariable model, total volume of anti-malarial sales was associated with greater likelihood of stocking subsidized AL and competition was important; likelihood of stocking subsidized AL was considerably higher if the nearest neighbour stocked subsidized AL. Price was a significant predictor of sales volume for all three types of anti-malarials but the relationship varied, with the largest price sensitivity found for SP drugs.

Conclusion

The results suggest that helping small outlets overcome the constraints to stocking subsidized AL should be a priority. Competition between retailers and prices can play an important role in greater adoption of AL.

An innovative pay-for-performance (P4P) strategy for improving malaria management in rural Kenya: protocol for a cluster randomized controlled trial

Background

In high-resource settings, ‘pay-for-performance’ (P4P) programs have generated interest as a potential mechanism to improve health service delivery and accountability. However, there has been little or no experimental evidence to guide the development or assess the effectiveness of P4P incentive programs in developing countries. In the developing world, P4P programs are likely to rely, at least initially, on external funding from donors. Under these circumstances, the sustainability of such programs is in doubt and needs assessment.

Methods/design

We describe a cluster-randomized controlled trial underway in 18 health centers in western Kenya that is testing an innovative incentive strategy to improve management of an epidemiologically and economically important problem—diagnosis and treatment of malaria. The incentive scheme in this trial promotes adherence to Ministry of Health guidelines for laboratory confirmation of malaria before treatment, a priority area for the Ministry of Health. There are three important innovations that are unique to this study among those from other resource-constrained settings: the behavior being incentivized is quality of care rather than volume of service delivery; the incentives are applied at the facility-level rather than the individual level, thus benefiting facility infrastructure and performance overall; and the incentives are designed to be budget-neutral if effective.

Discussion

Linking appropriate case management for malaria to financial incentives has the potential to improve patient care and reduce wastage of expensive antimalarials. In our study facilities, on average only 25% of reported malaria cases were confirmed by laboratory diagnosis prior to the intervention, and the total treatment courses of antimalarials dispensed did not correspond to the number of cases reported. This study will demonstrate whether facility rather than individual incentives are compelling enough to improve case management, and whether these incentives lead to offsetting cost-savings as a result of reduced drug consumption.

Trial registration

ClinicalTrials.gov Registration Number NCT01809873

Abstract P2-11-13: The Effect of Positive Axillary Lymph Nodes on Symptoms, Physical Impairments, and Function

Purpose/Objective(s): The role of axillary lymph node (ALN) sampling in breast cancer (BC) treatment continues to evolve, and BC patients are recommended for post-operative regional nodal radiation therapy (RNRT) based on the number of positive ALN. RNRT is recommended for patients with 4 or more positive ALN, but it remains controversial in patients with 1–3 positive ALN and is rarely recommended for patients without positive ALN. Consideration of anticipated functional impairments often guides decision making. The purpose of this analysis is to investigate functional impairments in BC patients with varying numbers of positive ALN.

Materials/Methods: 166 women were diagnosed with BC between 2001–05 and enrolled and treated in a prospective surveillance physical therapy program. 110 had zero positive ALN, 37 had 1–3 positive ALN, and 19 had 4 or more positive ALN on either sentinel LN biopsy or ALN dissection. Participants' upper extremity (UE) range of motion, strength, and limb volume were assessed pre-operatively and at 1, 3, 6, 9, and 12+ months post-operatively by a physical therapist. Limb volume was assessed using infrared optoelectronic perometry. At 12+ months, overall health status, UE symptoms and function, and physical activity levels were reported using standardized questionnaires. Chi-square tests and one-way ANOVA analyses were used to determine significance between groups (p ≤ 0.05).

Results: Of these 166 patients, 94 received mastectomy and 72 received lumpectomy, while 41 received RNRT and 58 received whole breast tangent RT. No significant differences were found between groups with regard to age or race. The number of dissected LN was not significantly different between those patients with 1–3 positive ALN and 4 or more positive ALN. Rates of lymphedema and seroma were not significantly different between those patients with zero positive ALN and 1–3 positive ALN, and rates of cording were not significantly different between any of the groups. Increased lymphedema (p = 0.03) and seroma (p = 0.005) were seen in those patients with 4 or more positive ALN compared to those patients with zero positive ALN, but this may also be related to a significantly greater number of dissected LN in the former group. By 12+ months post-operatively, there were no differences in shoulder abduction, shoulder flexion, internal rotation, or external rotation between groups. No differences were seen between groups in self-reported fatigue, UE swelling or weakness, arm stiffness, or ability to climb stairs.

Conclusions: Functional impairments represent an important category of morbidity for BC survivors and should be considered in pre-treatment decision making. The number of positive ALN may not correlate with increased impairment over the first year of treatment when a prospective surveillance physical therapy program is part of the plan of care. Additional research is needed to assess longer-term changes and the impact of axillary surgery and/or radiation in the context of aggregate effects of other BC treatment modalities.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P2-11-13.

Abstract P2-11-14: Symptoms, Physical Impairments, and Function in Breast Cancer Patients with Negative Axillary Lymph Nodes

Purpose/Objective(s): Breast cancer (BC) patients are recommended for post-operative regional nodal radiation therapy (RNRT) based on the number of positive axillary lymph nodes (LN). While RNRT is recommended for patients with 4 or more positive LN, it remains controversial in patients with 1–3 positive LN. For these patients, consideration of anticipated functional impairments often guides decision making, but these considerations are confounded by the inseparable effects of disease in and treatment of the axilla. The purpose of this analysis is to investigate the effect of various therapies on functional impairments in BC patients without axillary disease.

Materials/Methods: 166 women were diagnosed with BC between 2001–05 and enrolled and treated in a prospective surveillance physical therapy program. 110 had zero positive axillary LN on either sentinel LN biopsy or axillary LN dissection and were analyzed for this report. Participants' upper extremity (UE) range of motion, strength, and limb volume were assessed pre-operatively and at 1, 3, 6, 9, and 12+ months post-operatively by a physical therapist. Limb volume was assessed using infrared optoelectronic perometry. At 12+ months, overall health status, UE symptoms and function, and physical activity levels were reported using standardized questionnaires. Chi-square tests and one-way ANOVA analyses were used to determine significance between groups (p ≤ 0.05).

Results: Of these 110 patients, 34 received mastectomy without RT, 21 received mastectomy with RNRT, 10 received lumpectomy alone, and 45 received lumpectomy with whole breast tangent RT. No significant differences were found between groups with regard to stage, ER/PR status, and number of dissected LN. Rates of lymphedema, cording, and seroma were not significantly different between groups. By 12+ months post-operatively, there were no differences in shoulder abduction, shoulder flexion, internal rotation, or external rotation between groups. No differences were seen between groups in self-reported fatigue, UE swelling or weakness, arm stiffness, or ability to climb stairs.

Conclusions: Functional impairments represent an important category of morbidity for BC survivors and should be considered in pre-treatment decision making. In patients without axillary disease, post-operative RNRT or whole breast tangent RT may not contribute significantly to impairment over the first year of treatment when a prospective surveillance physical therapy program is part of the plan of care. Additional research is needed to assess longer-term changes and the impact of radiation in the context of the aggregate effect of disease burden combined with other BC treatment modalities.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P2-11-14.

PD02-03: The Effect of Breast Conservation Therapy vs Mastectomy on Symptoms, Physical Impairments, and Function

Background: Early-stage breast cancer (BC) patients choose between breast conservation therapy (BCT) and mastectomy based on comparable recurrence rates and overall survival. In the absence of mortality benefit, consideration of anticipated functional impairments could guide decision making. Although BCT offers less extensive surgery, the administration of radiation therapy (RT) may adversely impact upper extremity (UE) function. The purpose of this analysis is to investigate the effect of BCT vs modified radical mastectomy (MRM) without RT on functional impairments among BC survivors.

Materials and Methods: 196 women diagnosed with BC between 200105 were enrolled and treated in a prospective surveillance physical therapy program. 115 received either BCT, including lumpectomy and whole breast RT, or MRM without RT and were analyzed for this report. Participants’ UE range of motion (ROM), strength, and limb volume were assessed pre-operatively and at 1, 3, 6, 9, and 12+ months post-operatively by a physical therapist. Limb volume was assessed using infrared optoelectronic perometry. At 12+ months, overall health status, UE symptoms and function, and physical activity levels were reported using standardized questionnaires. Analysis of variance estimated differences in impairments and self-reported symptoms and function. One-way ANOVA analysis was used to determine significance between groups (p ≤ 0.05).

Results: 65 women (57.5%) received BCT and 50 women (42.5%) received MRM. No significant differences in age, BMI, stage, ER/PR status, and number of dissected lymph nodes were found between groups. At 1 month post-operatively, shoulder internal rotation (p=0.03), abduction (p=0.01), and flexion (p=0.004) were worse in post-MRM patients, with a trend towards worse external rotation (p=0.06). A higher rate of axillary cording was seen in patients post-MRM (p=0.02). By 12+ months post-operatively, there were no differences in any of the shoulder ROM variables. BCT patients reported, however, greater weakness (p=0.03) and diminished ability to perform heavy household tasks (p=0.03). There was no significant difference between BCT vs. MRM in rates of early lymphedema (40% vs 38%) or seroma (14% vs 22%).

Conclusion: Functional impairments represent an important category of morbidity for BC survivors and should be considered in pre-treatment decision making. Post-operative RT as part of BCT may not contribute significantly to impairment over the first year of treatment. The presence of self-reported weakness and difficulty performing heavy household tasks at 12+ months suggest possible future functional deficits, especially considering the potentially progressive nature of RT-associated tissue changes. Additional research is needed to assess longer-term changes and the impact of RT in the context of aggregate effects of other BC treatment modalities.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr PD02-03.

Accessibility, availability and affordability of anti-malarials in a rural district in Kenya after implementation of a national subsidy scheme

Background

Poor access to prompt and effective treatment for malaria contributes to high mortality and severe morbidity. In Kenya, it is estimated that only 12% of children receive anti-malarials for their fever within 24 hours. The first point of care for many fevers is a local medicine retailer, such as a pharmacy or chemist. The role of the medicine retailer as an important distribution point for malaria medicines has been recognized and several different strategies have been used to improve the services that these retailers provide. Despite these efforts, many mothers still purchase ineffective drugs because they are less expensive than effective artemisinin combination therapy (ACT). One strategy that is being piloted in several countries is an international subsidy targeted at anti-malarials supplied through the retail sector. The goal of this strategy is to make ACT as affordable as ineffective alternatives. The programme, called the Affordable Medicines Facility - malaria was rolled out in Kenya in August 2010.

Methods

In December 2010, the affordability and accessibility of malaria medicines in a rural district in Kenya were evaluated using a complete census of all public and private facilities, chemists, pharmacists, and other malaria medicine retailers within the Webuye Demographic Surveillance Area. Availability, types, and prices of anti-malarials were assessed. There are 13 public or mission facilities and 97 medicine retailers (registered and unregistered).

Results

The average distance from a home to the nearest public health facility is 2 km, but the average distance to the nearest medicine retailer is half that. Quinine is the most frequently stocked anti-malarial (61% of retailers). More medicine retailers stocked sulphadoxine-pyramethamine (SP; 57%) than ACT (44%). Eleven percent of retailers stocked AMFm subsidized artemether-lumefantrine (AL). No retailers had chloroquine in stock and only five were selling artemisinin monotherapy. The mean price of any brand of AL, the recommended first-line drug in Kenya, was $2.7 USD. Brands purchased under the AMFm programme cost 40% less than non-AMFm brands. Artemisinin monotherapies cost on average more than twice as much as AMFm-brand AL. SP cost only $0.5, a fraction of the price of ACT.

Conclusions

AMFm-subsidized anti-malarials are considerably less expensive than unsubsidized AL, but the price difference between effective and ineffective therapies is still large.

Community and facility-level engagement in planning and budgeting for the government health sector--a district perspective from Kenya

Health systems reform processes have increasingly recognized the essential contribution of communities to the success of health programs and development activities in general. Here we examine the experience from Kilifi district in Kenya of implementing annual health sector planning guidelines that included community participation in problem identification, priority setting, and planning. We describe challenges in the implementation of national planning guidelines, how these were met, and how they influenced final plans and budgets.

The broad-based community engagement envisaged in the guidelines did not take place due to the delay in roll out of the Ministry of Health-trained community health workers. Instead, community engagement was conducted through facility management committees, though in a minority of facilities, even such committees were not involved. Some overlap was found in the priorities highlighted by facility staff, committee members and national indicators, but there were also many additional issues raised by committee members and not by other groups. The engagement of the community through committees influenced target and priority setting, but the emphasis on national health indicators left many local priorities unaddressed by the final work plans. Moreover, it appears that the final impact on budgets allocated at district and facility level was limited. The experience in Kilifi highlights the feasibility of engaging the community in the health planning process, and the challenges of ensuring that this engagement feeds into consolidated plans and future implementation.

Changes in the burden of malaria in sub-Saharan Africa

The burden of malaria in countries in sub-Saharan Africa has declined with scaling up of prevention, diagnosis, and treatment. To assess the contribution of specific malaria interventions and other general factors in bringing about these changes, we reviewed studies that have reported recent changes in the incidence or prevalence of malaria in sub-Saharan Africa. Malaria control in southern Africa (South Africa, Mozambique, and Swaziland) began in the 1980s and has shown substantial, lasting declines linked to scale-up of specific interventions. In The Horn of Africa, Ethiopia and Eritrea have also experienced substantial decreases in the burden of malaria linked to the introduction of malaria control measures. Substantial increases in funding for malaria control and the procurement and distribution of effective means for prevention and treatment are associated with falls in malaria burden. In central Africa, little progress has been documented, possibly because of publication bias. In some countries a decline in malaria incidence began several years before scale-up of malaria control. In other countries, the change from a failing drug (chloroquine) to a more effective drug (sulphadoxine plus pyrimethamine or an artemisinin combination) led to immediate improvements; in others malaria reduction seemed to be associated with the scale-up of insecticide-treated bednets and indoor residual spraying.

Malaria vaccine trial endpoints - bridging the gaps between trial design, public health and the next generation of vaccines

A recent working group convened by the World Health Organization recommended that time to first or only episode of clinical malaria should be used to evaluate vaccine efficacy in phase III trials. However, calculating vaccine efficacy based on this endpoint misses important aspects of malaria disease and transmission. Here, we discuss the gaps that this approach leaves in predicting the potential public health impact of a vaccine and the challenges faced by vaccine trial designers. We examine the implications of current vaccine trial design on effectiveness studies and the next generation of malaria vaccines.

The impact of primary health care on malaria morbidity--defining access by disease burden

OBJECTIVES

Primary care facilities are increasingly becoming the focal point for distribution of malaria intervention strategies, but physical access to these facilities may limit the extent to which communities can be reached. To investigate the impact of travel time to primary care on the incidence of hospitalized malaria episodes in a rural district in Kenya.

METHODS

The incidence of hospitalized malaria in a population under continuous demographic surveillance was recorded over 3 years. The time to travel to the nearest primary health care facility was calculated for every child between birth and 5 years of age and trends in incidence of hospitalized malaria as a function of travel time were evaluated.

RESULTS

The incidence of hospitalized malaria more than doubled as travel time to the nearest primary care facility increased from 10 min to 2 h. Good access to primary health facilities may reduce the burden of disease by as much as 66%.

CONCLUSIONS

Our results highlight both the potential of the primary health care system in reaching those most at risk and reducing the disease burden. Insufficient access is an important risk factor, one that may be inequitably distributed to the poorest households.

Pilot assessment of the sensitivity of the malaria thin film

Background

Malaria microscopy remains the reference standard for malaria diagnosis in clinical trials (drug and vaccine), new diagnostic evaluation, as well as in clinical care in much of the world today. It is known that microscopy is an imperfect gold standard, and that very low false positive rates can dramatically lower protective efficacy estimates in malaria prevention trials. Although new methods are now available, including malaria rapid diagnostic tests and PCR, neither is as yet validated in the clinical trial setting and both have limitations. Surprisingly, the sensitivity of thin smears is not well established and thin smears are not commonly used in the developing world.

Methods

Malaria thick and thin films were collected in the lowlands of Western Kenya. All had density determined by four readings with two methods, as well as species identified. Thirty-six with low density parasitaemia had the thin smear read by five independent microscopists, two were expert and three were qualified. Microscopists read the entire thin film. For the first 10 parasites seen, they reported the species, appearance, time, field number, and red blood cells in the field. Total parasites, total fields, and total time to examine the smear were also recorded.

Results

Median parasitaemia was 201 parasites/μl, mean 1,090 ± 2,195, range 6–11,124 parasites/μl for the 36 smears evaluated. The data revealed a density dependent increase in sensitivity, with 100% sensitivity achieved at >200 parasites/μl for experts and >500 parasites/μl for qualified readers. Thin film readings confirmed parasitaemia 74% of the time by experts, and 65% of the time for qualified microscopists. The 95^th percentile for time to detect parasitaemia was 15 minutes for experts, 17 minutes for qualified microscopists. This decreased to 4–10 minutes for experts at densities of > 200 parasites/μl. Additionally, substantial discordance for species identification was observed.

Conclusion

The thin film is sensitive enough to be a useful tool to confirm malaria diagnosis in study subjects in some settings. Specificity of the thin film and its utility for confirming thick film or other diagnostic test results should be assessed further.

Parasite prevalence: a static measure of dynamic infections

The intensity of malaria transmission is often measured by looking at the fraction of individuals infected at a given point in time. However, malaria infections in individuals are dynamic, leading to uncertainty about whether a cross-sectional survey that represents a single snapshot in time is a useful representation of a temporally complex process. In this analysis, we examine the impact of parasite density fluctuations on the measurement of parasite prevalence. Our results show that parasite prevalence may be underestimated by 20% or more, depending on the sensitivity of parasite detection.

Establishing a malaria diagnostics centre of excellence in Kisumu, Kenya

Background

Malaria microscopy, while the gold standard for malaria diagnosis, has limitations. Efficacy estimates in drug and vaccine malaria trials are very sensitive to small errors in microscopy endpoints. This fact led to the establishment of a Malaria Diagnostics Centre of Excellence in Kisumu, Kenya. The primary objective was to ensure valid clinical trial and diagnostic test evaluations. Key secondary objectives were technology transfer to host countries, establishment of partnerships, and training of clinical microscopists.

Case description

A twelve-day "long" and a four-day "short" training course consisting of supervised laboratory practicals, lectures, group discussions, demonstrations, and take home assignments were developed. Well characterized slides were developed and training materials iteratively improved. Objective pre- and post-course evaluations consisted of 30 slides (19 negative, 11 positive) with a density range of 50–660 parasites/μl, a written examination (65 questions), a photographic image examination (30 images of artifacts and species specific characteristics), and a parasite counting examination.

Discussion and Evaluation

To date, 209 microscopists have participated from 11 countries. Seventy-seven experienced microscopists participated in the "long" courses, including 47 research microscopists. Sensitivity improved by a mean of 14% (CI 9–19%) from 77% baseline (CI 73–81 %), while specificity improved by a mean of 17% (CI 11–23%) from 76% (CI 70–82%) baseline. Twenty-three microscopists who had been selected for a four-day refresher course showed continued improvement with a mean final sensitivity of 95% (CI 91–98%) and specificity of 97% (CI 95–100%). Only 9% of those taking the pre-test in the "long" course achieved a 90% sensitivity and 95% specificity, which increased to 61% of those completing the "short" course. All measures of performance improved substantially across each of the five organization types and in each course offered.

Conclusion

The data clearly illustrated that false positive and negative malaria smears are a serious problem, even with research microscopists. Training dramatically improved performance. Quality microscopy can be provided by the Centre of Excellence concept. This concept can be extended to other diagnostics of public health importance, and comprehensive disease control strategies.

Malaria vaccine efficacy: the difficulty of detecting and diagnosing malaria

New sources of funding have revitalized efforts to control malaria. An effective vaccine would be a tremendous asset in the fight against this devastating disease and increasing financial and scientific resources are being invested to develop one. A few candidates have been tested in Phase I and II clinical trials, and several others are poised to begin trials soon. Some studies have been promising, and others disappointing.

It is difficult to compare the results of these clinical trials; even independent trials of the same vaccine give highly discrepant results. One major obstacle in evaluating malaria vaccines is the difficulty of diagnosing clinical malaria. This analysis evaluates the impact of diagnostic error, particularly that introduced by microscopy, on the outcome of efficacy trials of malaria vaccines and make recommendations for improving future trials.

Reader technique as a source of variability in determining malaria parasite density by microscopy

Background

Accurate identification and quantification of malaria parasites are critical for measuring clinical trial outcomes. Positive and negative diagnosis is usually sufficient for the assessment of therapeutic outcome, but vaccine or prophylactic drug trials require measuring density of infection as a primary endpoint. Microscopy is the most established and widely-used technique for quantifying parasite densities in the blood.

Methods

Results obtained by 24–27 expert malaria microscopists, who had independently read 895 slides from 35 donors, were analysed to understand how reader technique contributes to discrepancy in measurements of parasite density over a wide range of densities.

Results

Among these 35 donations, standard deviations ranged from 30% to 250% of the mean parasite density and the percent discrepancy was inversely correlated with the mean parasite density. The number of white blood cells indexed and whether parasites were counted in the thick film or thin film were shown to significantly contribute to discrepancy amongst microscopists.

Conclusion

Errors in microscopy measurements are not widely appreciated or addressed but have serious consequences for efficacy trials, including possibly abandoning promising vaccine candidates.

Potential impact of intermittent preventive treatment (IPT) on spread of drug-resistant malaria

BACKGROUND

Treatment of asymptomatic individuals, regardless of their malaria infection status, with regularly spaced therapeutic doses of antimalarial drugs has been proposed as a method for reducing malaria morbidity and mortality. This strategy, called intermittent preventive treatment (IPT), is currently employed for pregnant women and is being studied for infants (IPTi) as well. As with any drug-based intervention strategy, it is important to understand how implementation may affect the spread of drug-resistant parasites. This is a difficult issue to address experimentally because of the limited size and duration of IPTi trials as well as the intractability of distinguishing the spread of resistance due to conventional treatment of malaria episodes versus that due to IPTi when the same drug is used in both contexts.

METHODS AND FINDINGS

Using a mathematical model, we evaluated the possible impact of treating individuals with antimalarial drugs at regular intervals regardless of their infection status. We translated individual treatment strategies and drug pharmacokinetics into parasite population dynamic effects and show that immunity, treatment rate, drug decay kinetics, and presumptive treatment rate are important factors in the spread of drug-resistant parasites. Our model predicts that partially resistant parasites are more likely to spread in low-transmission areas, but fully resistant parasites are more likely to spread under conditions of high transmission, which is consistent with some epidemiological observations. We were also able to distinguish between spread of resistance due to treatment of symptomatic infections and that due to IPTi. We showed that IPTi could accelerate the spread of resistant parasites, but this effect was only likely to be significant in areas of low or unstable transmission.

CONCLUSIONS

The results presented here demonstrate the importance of considering both the half-life of a drug and the existing level of resistance when choosing a drug for IPTi. Drugs to which little or no resistance exists are not advisable for IPT in high-transmission areas, but IPTi is not likely to significantly impact the spread of highly resistant parasites in areas where partial resistance is already established. IPTi is more likely to accelerate the spread of resistance in high-transmission areas than is IPT in adults (i.e., pregnant women).

Systematic comparison of two methods to measure parasite density from malaria blood smears

This study was designed to directly compare the accuracy, reproducibility, and efficiency of three methods commonly used to measure blood-stage malaria parasite density from Giemsa-stained blood films. Parasites and white blood cells (WBCs) were counted in 154 thick films by two independent microscopists. Forty-six slides were read by counting parasitized red blood cells (RBCs) in the thin film. Using these same slides, parasites were again counted by two independent microscopists using an ocular grid. Overall, parasite densities were significantly lower and discrepancy between readers was higher when using the grid method compared to the WBC method, but there was no difference when compared to the RBC method. When one reader who had difficulty with the grid method was excluded, the discrepancy between readers was equivalent for the three methods. Densities and discrepancy between readers were indistinguishable when parasites were counted until 200 or 500 WBCs. Counting beyond 200 WBCs may not significantly improve parasite density measurements. Using an ocular grid directly measures parasites per volume rather than using a WBC per microliter conversion factor and eliminates the need to switch from the thick film to the thin film for high parasitemias. However, significant differences in densities measured by the grid method and the WBC method need to be evaluated.

Sources of variability in determining malaria parasite density by microscopy

Enumeration of parasites by microscopic examination of blood smears is the only method available for quantifying parasitemia in infected blood. However, the sources and scale of error inherent in this technique have not been systematically investigated. Here we use data collected in outpatient clinics in Peru and Thailand to elucidate important sources of variation in parasite density measurements. We show that discrepancies between readings from two independent microscopists and multiple readings from a single microscopist are inversely related to the density of the infection. We present an example of how differences in reader technique, specifically the number of white blood cells counted, can contribute to the differences between readings. We discuss the implications of this analysis for field studies and clinical trials.

The promise and potential challenges of intermittent preventive treatment for malaria in infants (IPTi)

Intermittent preventive treatment (IPT) administers a full therapeutic course of an anti-malarial drug at predetermined intervals, regardless of infection or disease status. It is recommended by the World Health Organization (WHO) for protecting pregnant women from the adverse effects of malaria (IPTp) and shows great potential as a strategy for reducing illness from malaria during infancy (IPTi). Administered concurrently with standard immunizations, IPTi is expected to reduce the frequency of clinical disease, but to allow blood-stage infections to occur between treatments, thus allowing parasite-specific immunity to develop. While wide deployment of IPTi is being considered, it is important to assess other potential effects. Transmission conditions, drug choice and administration schedule will likely affect the possibility of post-treatment rebound in child morbidity and mortality and the increased spread of parasite drug resistance and should be considered when implementing IPTi.