Indoor Residual Spraying and Malaria Control in Africa

Indoor residual spraying (IRS) is a crucial tool in the fight against malaria in Africa. This method involves spraying insecticides on the walls and ceilings of homes to kill mosquitoes that carry the disease.

In Africa, IRS has been shown to reduce malaria cases by up to 90% in some areas. This is a significant reduction that can have a major impact on public health.

The World Health Organization (WHO) recommends IRS as a key strategy for malaria control in Africa. This is because it is a cost-effective and easy-to-implement method that can be used in conjunction with other malaria prevention measures.

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Two independent review authors assessed studies for eligibility, analyzed risk of bias, and extracted data. They used risk ratio (RR) and 95% confidence intervals (CI) to analyze the data.

The review authors stratified the data by type of insecticide, 'pyrethroid-like' and 'non-pyrethroid-like', to explore how different types of insecticides might affect malaria control.

Indoor Residual Spraying (IRS) is a malaria prevention method that targets indoor resting mosquitoes. IRS involves coating interior walls and other sprayable surfaces in a house with a residual (long-lasting) insecticide.

This method takes advantage of the indoor resting behavior of many malaria mosquitoes that rest on these surfaces inside houses after taking a blood meal.

To be effective, a very high proportion of households in an area, ideally over 80%, must be treated to protect a community.

Newer non-pyrethroid insecticides such as pirimiphos-methyl, clothianidin, and broflanilide may be contributing to the management of insecticide resistance.

Between 2000 and 2015, IRS campaigns are estimated to have contributed to approximately 10% of the 633 million malaria cases averted in Africa.

Approved insecticides are a crucial part of Indoor Residual Spraying (IRS) programs. There are 13 different insecticides approved by the WHO for IRS.

DDT is one of the approved insecticides, but it's only suitable for traditional dwellings with unpainted walls made of mud, sticks, dung, thatch, clay, or cement. Its recommended dosage is 1-2 g/m².

Fenitrothion is another approved insecticide, with a recommended dosage of 2 g/m². It has a duration of effective action of 3-6 months.

Malathion and Pirimiphos-methyl are also approved, with recommended dosages of 2 g/m². They have durations of effective action of 2-3 months.

Propoxur, Bendiocarb, and Alpha-cypermethrin are other approved insecticides, with recommended dosages ranging from 0.1-2 g/m². They have durations of effective action ranging from 2-6 months.

Here's a list of approved insecticides, their classes, recommended dosages, and durations of effective action:

Two review authors independently assessed studies for eligibility, analyzed risk of bias, and extracted data. They used risk ratio (RR) and 95% confidence intervals (CI) to evaluate the data.

We stratified the data by type of insecticide, which helped us understand how different types of insecticides performed. This included "pyrethroid-like" and "non-pyrethroid-like" insecticides.

We used subgroup analysis of ITN usage in the studies to explore heterogeneity and gain a deeper understanding of the data. This approach allowed us to identify patterns and trends in the data.

Risk ratios and 95% confidence intervals were used to analyze the data, providing a clear and concise way to present the results. This statistical approach helped us to make informed conclusions about the data.

Experimental hut trials were used to assess IRS efficacy, providing a relatively standardized method to evaluate the effectiveness of IRS. These trials are considered the entomological equivalent of a Phase II trial.

Pyrethroid resistance is a major concern in many parts of the world. It's a result of overuse and misuse of these pesticides, which has led to the development of resistant pest populations.

In the United States, pyrethroid resistance has been detected in over 100 species of insects, including mosquitoes and ticks. This is a significant problem, especially in areas where these pests can spread diseases.

The use of pyrethroids in agriculture has increased dramatically over the past few decades. This has put pressure on pest populations to develop resistance, making them less effective as a control method.

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In some cases, pyrethroid resistance can be reversed by rotating to other types of pesticides. However, this can be expensive and may not always be effective.

The development of pyrethroid resistance is often linked to the presence of other pests in the same area. For example, in the southern United States, the presence of the pyrethroid-resistant fire ant has been linked to the spread of other invasive species.

Indoor residual spraying (IRS) is a proven method for reducing malaria parasite prevalence. The addition of IRS reduced malaria parasite prevalence by 39% (RR 0.61, 95% CI 0.42 to 0.88) in four cRCTs involving 16,394 participants.

Six studies were included in the analysis of IRS using 'non-pyrethroid-like' insecticides. This type of IRS was found to reduce malaria incidence on average, but the effect was absent in two studies.

The addition of IRS may also reduce anaemia prevalence by 29% (RR 0.71, 95% CI 0.38 to 1.31) in three cRCTs involving 4288 participants. However, the effect was not significant in all studies.

Studies using 'pyrethroid-like' insecticides for IRS did not show a significant reduction in malaria incidence, parasite prevalence, or anaemia prevalence. The data on entomological inoculation rate (EIR) were limited, making it difficult to draw conclusions.

Three studies measured the prevalence of pyrethroid resistance before and after IRS being introduced, but no difference was detected.

IRS is an effective strategy for reducing malaria incidence, with a 2010 Cochrane review showing it's about as effective as using insecticide treated nets.

The cost effectiveness of IRS has been compared to other methods of malaria control, with a 2008 study finding that on a cost-per-child-death-averted basis, IRS and insecticide treated bednet distribution campaigns were about the same.

Historically, DDT has been considered the most cost effective pesticide for IRS, mainly because it lasts longer than alternatives.

However, the United Nations Environment Programme concluded in 2008 that the relative advantage of DDT vis-à-vis alternative insecticides seems to be diminishing.

Actual studies on cost effectiveness are lacking, and none have taken into account the adverse health and environmental effects of DDT or its alternatives.

The contextual evidence base on cost-effectiveness needs strengthening, and the external costs of DDT use vis-à-vis alternative insecticides require a careful assessment.

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Sylando is a product used for Indoor Residual Spraying (IRS).

Its active ingredients are specifically designed for IRS.

Sylando is used to control mosquitoes and other insects that can spread diseases.

According to the World Health Organization, national governments should introduce and/or scale up coverage of targeted IRS as a primary malaria control intervention in countries where available data indicates it can be effective towards achieving malaria targets.

The WHO recommends taking all necessary steps to ensure effective implementation of IRS interventions, including selecting the appropriate insecticide, spraying where and when necessary, and sustaining a high level of coverage, and to prevent unauthorized or un-recommended use of public health insecticides.

To be effective, there must be a high percentage of sprayable surfaces within each dwelling, the vector (mosquitoes) must feed or rest indoors, and the targeted vectors must be susceptible to the insecticide being sprayed.

The WHO emphasizes that insecticide susceptibility and vector behavior, safety for humans and the environment, and efficacy and cost-effectiveness are factors to consider when selecting an insecticide for IRS.

Here are the key factors to consider when selecting an insecticide for IRS:

The addition of indoor residual spraying (IRS) with non-pyrethroid-like insecticides to communities using insecticide-treated bednets (ITNs) has been associated with reduced malaria prevalence.

Studies have shown that this combination can lead to a decrease in malaria incidence, but the effect may not be observed in all settings due to unexplained qualitative heterogeneity.

In communities using ITNs, the use of IRS with non-pyrethroid-like insecticides can be a valuable tool in reducing malaria cases.

However, if pyrethroid-like insecticides are used, there is no detectable additional benefit of IRS in communities using ITNs.

This suggests that the type of insecticide used for IRS may play a crucial role in its effectiveness.

Transmission dynamics models can accurately predict the outcome of Indoor Residual Spraying (IRS) Randomized Control Trials (RCTs). This is shown by the fact that model predictions for a single round of Actellic 300CS or bendiocarb broadly match observed data.

The uncertainty in Actellic 300CS efficacy has a relatively minor impact on the uncertainty of public health predictions for the first 10 months after application. However, it can lead to substantial variation after this point.

A similar pattern is seen in the bendiocarb data, with uncertainty manifesting itself earlier due to its shorter residual activity. This is a crucial consideration when evaluating the effectiveness of IRS.

Interestingly, the Actellic 300CS data on A. gambiae s.l. more closely predict the observed change in prevalence during the trial. This suggests that the model is accurately capturing the impact of IRS on this particular mosquito species.

The predicted impact of IRS on malaria prevalence is also closely matched by the measured impact in RCTs. This is evident in the comparison of model predictions and observed data for a single round of Actellic 300CS or two rounds of bendiocarb.

Data from experimental hut trials provides a relatively standardized method to assess IRS efficacy, considered the entomological equivalent of a Phase II trial.

Review authors independently assessed studies for eligibility, analyzed risk of bias, and extracted data, using risk ratio (RR) and 95% confidence intervals (CI).

They stratified by type of insecticide, 'pyrethroid-like' and 'non-pyrethroid-like', to explore heterogeneity in ITN usage.

The GRADE approach is used to assess the certainty of evidence in the studies.

Subgroup analysis of ITN usage in the studies helps to explore heterogeneity and understand the effectiveness of different insecticides.

Experimental hut trials are a pivotal part of testing new products and are required by WHO Prequalification, enabling products to be bought by international procurers for low-income countries.