Targeted Indoor Residual Spraying Against Malaria

Study Overview
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Brief Summary
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Since 2000, annual numbers of malaria cases in South Africa have sharply declined to about 5,000, with case numbers fairly stable since 2007. The principal malaria prevention strategy has consisted of generalised Indoor Residual Spraying (IRS) of all houses in malaria endemic districts. As recent case data indicate that the levels of transmission in many districts have been reduced to very low levels, the continuation of untargeted IRS in areas where there is little or no evidence of recent transmission may be unwarranted. Efforts to eliminate malaria will only be sustainable if mass prevention efforts can be scaled down in an evidence-based manner, whilst maintaining or enhancing high sensitivity of the surveillance system of the disease. This trial will provide scientific evidence for targeted malaria prevention responding to localised transmission in pre-elimination settings, compared to continuation of generalised IRS of all houses. Two methods of IRS delivery for community malaria prevention will be compared through an open-label cluster-randomised trial consisting of two study arms with 30 clusters per arm of approximately 8,000 inhabitants per cluster. Comparison is on the basis of non-inferiority by showing that malaria incidence in the targeted IRS arm is no higher than malaria incidence in the generalised IRS arm within a specified margin of difference, and on the basis of superiority showing that the proportion of houses targeted for spraying is higher in the intervention than the reference arm. Neighbourhood investigation in response to each locally acquired case in the intervention arm, and comparison neighbourhoods in the reference arm, will include testing for antibody sero-conversion to malarial antigens to assess whether cases arise in communities with long term exposure to malaria parasites. The trial will be carried out in the South African provinces of Limpopo and Mpumalanga, in localities which have average reported incidence of malaria of <5 cases per 1000 per annum over the past five years.

Detailed Description
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Two methods of IRS delivery for malaria prevention, targeted spraying versus annual generalised spraying, will be compared through an open-label cluster randomised trial consisting of two trial arms with 30 clusters per arm. Clusters will be artificial constructs made up of groups of spray localities or complete wards to comprise populations of about 5,000 to 10,000 persons. The unit of randomisation will be the cluster. The intervention arm of the trial will receive IRS delivery through targeted reactive spraying in the neighbourhood of recent local cases only; the reference (control) arm of the trial will receive IRS through generalised annual spraying of all structures as per standard current practice. Comparison will be on the basis of non-inferiority by showing that malaria incidence in the targeted IRS arm is no higher than malaria incidence in the generalised IRS arm within a specified margin of difference, and on the basis of superiority showing that the proportion of houses sprayed, of those targeted for spraying, is higher in the intervention than the reference arm. Neighbourhood investigation in response to each locally acquired case in the intervention arm, and comparison neighbourhoods in the reference arm will include testing for antibody sero-conversion to malarial antigens to assess whether cases arise in communities with long term exposure to malarial parasites.

Official Title
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From Malaria Control to Sustainable Elimination: Cluster Randomised Trial Comparing Targeted Versus Generalised Vector Control in South Africa

Conditions
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Malaria

Intervention / Treatment
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* Other: Targeted indoor residual spraying
* Other: Generalised Indoor residual spraying


Participation Criteria
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Eligibility Criteria
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Inclusion criteria Entire communities of approximately 8000 persons Residents in malaria endemic districts of Limpopo and Mpumalanga Province Areas with local malaria incidence <5 cases per 1000 per year on average over 5 years
Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Prevention
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Targeted indoor residual spraying<br>The intervention arm of the trial will receive Indoor Residual Spraying delivery through targeted spraying in the neighbourhood of recent local cases only. | Other: Targeted indoor residual spraying<br>* IRS is carried out in neighbourhoods of cases<br>|
| Active Comparator: Generalised Indoor residual spraying<br>The reference (control) arm of the trial will receive Indoor Residual Spraying through generalised annual spraying of all structures, as is the current standard practice. | Other: Generalised Indoor residual spraying<br>* IRS is carried out as normally practiced<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Malaria incidence, by routine passive case detection, of clinical malaria (fever ≥37.5°C, or history of fever (48 hours), in the presence of parasitaemia confirmed by RDT or microscopy). |  | Communities will be followed for up to 20 months | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Intervention costs per 1,000 households and cost-effectiveness of reactive, targeted indoor residual spraying (TIRS) compared to generalised IRS (GIRS) | Cost of spray operations will be determined in each study arm | Up to 20 months | 
| Proportion of structures targeted for IRS unsprayed |  | Up to 20 months whenever reactive spraying is triggered | 
| Household compliance (not painting, washing, re-plastering ) | In a representative sample household survey in all clusters, a questionnaire will be used in which householders will be asked whether they painted, re-plastered or washed walls after spraying | By cross sectional household survey after 18 months | 
| Householder acceptability of IRS | In a representative sample household survey in all clusters, a questionnaire will be used in which householders will be asked whether they want their house sprayed with insecticide in future | By cross sectional household survey after 18 months | 
| If unsprayed, proportions due to refusals, spray teams not making contact and spray teams not calling back | In a representative sample household survey in all clusters, a questionnaire will be used in which householders whose houses remained unsprayed will be asked whether this was because they refused or because spray teams did not make contact or did not call back if they were away | By cross sectional household survey after 18 months | 
| Sero-prevalence of antibodies to malaria antigens AMA-1 and MSP-1-19 | In a representative sample household survey in all clusters, a filter paper dried blood spot a will be taken from a sample of individuals of all ages, subject to informed written consent | By cross sectional household survey after 18 months | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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vector control, insecticide