Effectiveness and cost-effectiveness of reactive, targeted indoor residual spraying for malaria control in low-transmission settings: a cluster-randomised, non-inferiority trial in South Africa.

BACKGROUND: Increasing insecticide costs and constrained malaria budgets could make universal vector control strategies, such as indoor residual spraying (IRS), unsustainable in low-transmission settings. We investigated the effectiveness and cost-effectiveness of a reactive, targeted IRS strategy. METHODS: This cluster-randomised, open-label, non-inferiority trial compared reactive, targeted IRS with standard IRS practice in northeastern South Africa over two malaria seasons (2015-17). In standard IRS clusters, programme managers conducted annual mass spray campaigns prioritising areas using historical data, expert opinion, and other factors. In targeted IRS clusters, only houses of index cases (identified through passive surveillance) and their immediate neighbours were sprayed. The non-inferiority margin was 1 case per 1000 person-years. Health service costs of real-world implementation were modelled from primary and secondary data. Incremental costs per disability-adjusted life-year (DALY) were estimated and deterministic and probabilistic sensitivity analyses conducted. This study is registered with ClinicalTrials.gov, NCT02556242. FINDINGS: Malaria incidence was 0·95 per 1000 person-years (95% CI 0·58 to 1·32) in the standard IRS group and 1·05 per 1000 person-years (0·72 to 1·38) in the targeted IRS group, corresponding to a rate difference of 0·10 per 1000 person-years (-0·38 to 0·59), demonstrating non-inferiority for targeted IRS (p<0·0001). Per additional DALY incurred, targeted IRS saved US$7845 (2902 to 64 907), giving a 94-98% probability that switching to targeted IRS would be cost-effective relative to plausible cost-effectiveness thresholds for South Africa ($2637 to $3557 per DALY averted). Depending on the threshold used, targeted IRS would remain cost-effective at incidences of less than 2·0-2·7 per 1000 person-years. Findings were robust to plausible variation in other parameters. INTERPRETATION: Targeted IRS was non-inferior, safe, less costly, and cost-effective compared with standard IRS in this very-low-transmission setting. Saved resources could be reallocated to other malaria control and elimination activities. FUNDING: Joint Global Health Trials.

Serology reveals heterogeneity of Plasmodium falciparum transmission in northeastern South Africa: implications for malaria elimination.

BACKGROUND: It is widely acknowledged that modifications to existing control interventions are required if South Africa is to achieve malaria elimination. Targeting indoor residual spraying (IRS) to areas where cases have been detected is one strategy currently under investigation in northeastern South Africa. This seroprevalence baseline study, nested within a targeted IRS trial, was undertaken to provide insights into malaria transmission dynamics in South Africa and evaluate whether sero-epidemiological practices have the potential to be routinely incorporated into elimination programmes. METHODS: Filter-paper blood spots, demographic and household survey data were collected from 2710 randomly selected households in 56 study wards located in the municipalities of Ba-Phalaborwa and Bushbuckridge. Blood spots were assayed for Plasmodium falciparum apical membrane antigen-1 and merozoite surface protein-119 blood-stage antigens using an enzyme linked immunosorbent assay. Seroprevalence data were analysed using a reverse catalytic model to determine malaria seroconversion rates (SCR). Geospatial cluster analysis was used to investigate transmission heterogeneity while random effects logistic regression identified risk factors associated with malaria exposure. RESULTS: The overall SCR across the entire study site was 0.012 (95% CI 0.008-0.017) per year. Contrasting SCRs, corresponding to distinct geographical regions across the study site, ranging from <0.001 (95% CI <0.001-0.005) to 0.022 (95% CI 0.008-0.062) per annum revealed prominent transmission heterogeneity. Geospatial cluster analysis of household seroprevalence and age-adjusted antibody responses detected statistically significant (p < 0.05) spatial clusters of P. falciparum exposure. Formal secondary education was associated with lower malaria exposure in the sampled population (AOR 0.72, 95% CI 0.56-0.95, p = 0.018). CONCLUSIONS: Although overall transmission intensity and exposure to malaria was low across both study sites, malaria transmission intensity was highly heterogeneous and associated with low socio-economic status in the region. Findings suggest focal targeting of interventions has the potential to be an appropriate strategy to deploy in South Africa. Furthermore, routinely incorporating sero-epidemiological practices into elimination programmes may prove useful in monitoring malaria transmission intensity in South Africa, and other countries striving for malaria elimination.

Knowledge and practices towards malaria amongst residents of Bushbuckridge, Mpumalanga, South Africa

Background: Malaria remains one of the greatest public health challenges worldwide and it is amongst the top killers in sub-Saharan Africa. There is however, a general scepticism about the accuracy of Health Management Information Systems (HMIS) in recording all the episodes of malaria in Africa. Given the importance of community knowledge of malaria, its signs and symptoms, as well as prompt treatment-seeking behaviour, the study assessing adult residents' knowledge and practices in Bushbuckridge provided much needed insights into the Malaria Control Programme (MCP). Objectives: The objectives of this study were to determine the adult residents' knowledge and practices towards malaria in Bushbuckridge, Mpumalanga Province, South Africa. Method: The study was undertaken as a descriptive cross-sectional survey in Bushbuckridge in August 2008. Six hundred and two (602) household heads or their proxies from the randomly selected households in 20 localities were interviewed (one household member per household), using a structured field-piloted questionnaire. Results: Approximately 93% of the respondents had heard about malaria, 84.6% of whom correctly associated it with mosquito bites. The health facility (29.1%) and radio (19.8%) were the main sources of malaria information. Knowledge of signs and symptoms was low, whilst treatment-seeking intention at the health facility was high (99%) with 82% of which would be carried out promptly. Survey data showed an indoor residual spraying (IRS) coverage of approximately 70% and a good understanding of the reasons for spraying. Walls were re-plastered infrequently and no evidence was established linking it to the removal of insecticide marks on the wall. Conclusion: The study revealed not only that householders possessed an adequate knowledge of malaria, but also that they had positive malaria treatment-seeking intentions. Their knowledge of malaria signs and symptoms was inadequate and required attention. Whilst IRS coverage needed some improvements, the reasons for IRS were well known