The WHO global malaria strategy for malaria urges all malaria-endemic countries to accelerate progress towards the goal of elimination. In settings approaching elimination, interventions will be most effective at reducing transmission if they are tailored to the distribution of the reservoir of malaria infection.

The new recommendations for the final phase of elimination now available in the WHO Guidelines for malaria. Some of these recommendations are also relevant to areas that have achieved elimination and are working to prevent re-establishment of transmission. The recommendations are divided into 3 categories of possible interventions: “mass” strategies, “targeted” strategies and “reactive” strategies.

What are “mass” strategies, and which of these strategies does WHO recommend for reducing malaria transmission in countries with a low burden of malaria?

In areas where malaria transmission is generalized across the population of a defined geographical area (for example, in a district or village), strategies that cover the whole population may be needed to reduce transmission. These strategies could include mass drug administration, mass testing and treatment or mass relapse prevention. Mass strategies are generally not recommended for post-elimination settings unless there is a resumption of local transmission of malaria.

Conditional recommendation for mass drug administration (MDA). Through MDA, all individuals in a defined geographical area are given a treatment course of antimalarial drugs. The medicine treats any existing malaria infections while also acting as a prophylactic, preventing new infections for some period of time, depending on the medicine. WHO has issued a new conditional recommendation for the use of MDA to reduce transmission of P. falciparum in very low to low transmission settings and P. vivax in all settings. The recommendation notes, however, that MDA programmes ask many asymptomatic, healthy people to take a medicine when they do not feel ill, with the potential for adverse reactions. Community engagement is a key factor in determining the success of MDA to improve participation rates and adherence to the full treatment course of the medicine. Although MDA may rapidly reduce malaria transmission in low transmission settings, the effect wanes within 1–3 months. As such, an MDA intervention, if implemented, should be one component of a broader malaria elimination programme that includes, at a minimum, good coverage of case-based surveillance and malaria diagnosis, effective antimalarial treatment, and appropriate prevention tools and strategies.

Conditional recommendation against mass testing and treatment (MTaT). MTaT involves testing the entire population for malaria in a defined geographical area and treating all positive cases with an effective antimalarial medicine at approximately the same time. Based on available evidence, MTaT has a very limited beneficial impact on malaria prevalence and incidence, and the resources required to implement this strategy are considered large. However, WHO’s conditional recommendation against MTaT notes that there may be exceptional circumstances under which MTaT might be appropriate, such as in very low transmission or post-elimination settings where MDA is not an acceptable or feasible strategy.

Conditional recommendation against mass relapse prevention (MRP) to reduce transmission of P. vivax. WHO has issued a conditional recommendation against the use of mass treatment with an 8-aminoquinoline medicine alone to reduce the transmission of P. vivax malaria. The recommendation notes the potential for severe harm from the use of this medicine without prior testing for G6PD deficiency, and that conducting such tests for a large population would significantly add to the complexity and cost of the intervention. The WHO recommendation also takes into account the very low quality of available evidence to assess the beneficial impact of MRP on P. vivax transmission.

What are “targeted” strategies, and in which settings would they apply? Which groups stand to benefit most from these strategies?

At very low and low levels of transmission, malaria cases are often concentrated among people with shared risk factors. The premise behind targeted strategies is that interventions applied to a small subset of the population that is believed to encompass the reservoir of infection could reduce transmission overall. In many low-transmission settings, populations at higher risk of malaria infection are engaged in outdoor activities such as mining, rubber tapping, forestry and cattle herding. People who participate in night-time sports, socialize outdoors or sleep outside are also at higher risk of contracting the disease. Targeted strategies for reaching such populations could include targeted drug administration and targeted testing and treatment.

Conditional recommendation for targeted drug administration (TDA). TDA is a form of chemoprevention involving the provision of a full course of an antimalarial medicine to individuals who are at increased risk of malaria infection compared to the general population. The medicine treats all existing infections and prevents new infections over the duration of the drug’s post-treatment prophylaxis period. Community engagement is a key factor in determining the success of TDA, to improve participation rates and adherence to treatment. The recommendation also notes that care should be taken to avoid stigmatizing groups at increased risk of infection, and that additional complementary strategies to eliminate or prevent re-establishment of malaria transmission should be in place.

Conditional recommendation against targeted testing and treatment (TTaT). Through TTaT, individuals at increased risk of malaria infection are tested for the disease, and only those who test positive are treated with an antimalarial medicine. WHO has issued a conditional recommendation against TTaT noting that the likely impact of this intervention on malaria transmission in very low to low or post-elimination settings would be limited. The recommendation considers that that there may be limited circumstances under which TTaT could be beneficial; for example, the intervention could be used when chemoprevention is not acceptable to people at a higher risk of infection.

Conditional recommendation against routine testing and treatment at points of entry. Testing and treatment at points of entry (sometimes referred to as “border screening”) involves testing individuals crossing a border – whether by land, sea or air – and treating all positive cases with an appropriate antimalarial medicine. This intervention is often implemented at the borders between countries approaching elimination and their neighbours with higher levels of malaria transmission. WHO’s conditional recommendation against this intervention considers that it is unlikely to be an acceptable or feasible strategy to implement; many borders are highly porous, with numerous unofficial border crossings, making it difficult to achieve a high coverage of testing and treatment.

Conditional recommendation for malaria testing and treatment of organized or identifiable groups arriving or returning from malaria-endemic areas. The WHO recommendation notes that testing these groups (e.g. military, migrant workers or religious pilgrims) for malaria, and treating those who test positive with an antimalarial medicine, could help countries nearing elimination or preventing re-establishment of transmission by reducing imported cases of the disease. The acceptability and feasibility of this strategy was considered higher than routine testing and treatment at points of entry but would depend upon local circumstances.

What are WHO’s new recommendations relating to “reactive” strategies in elimination settings?

As malaria transmission declines and approaches zero, cases tend to cluster geographically (in small areas such as households and neighbourhoods) or socially, among people exposed to the disease at the same time and place (such as through a common occupation or shared travel to endemic areas). If clusters can be identified and targeted with effective interventions, malaria transmission at the community level may be reduced.

“Reactive” strategies are triggered “in reaction” to the identification of a confirmed case of malaria. They include: reactive drug administration, reactive case detection and treatment, and reactive indoor residual spraying. The success of these 3 interventions depends on a strong surveillance system that is capable of detecting suspected malaria cases and investigating all confirmed cases at their place of origin.

When used, these interventions should be one of several components of a programme to eliminate or prevent re-establishment of malaria, including intensive surveillance, as described in the Framework for malaria elimination. As cases of malaria may be identified in post-elimination settings, reactive strategies are also relevant to areas working to prevent re-establishment of malaria.

Conditional recommendation for reactive drug administration (RDA). RDA is the provision of antimalarial medicine to every individual living with or near a person with a confirmed malaria infection, or to every person who was likely exposed to infection at the same time and place. The aim of this strategy is to treat all existing infections and prevent new infections over a period of time. In view of available evidence, WHO has issued a conditional recommendation in favor of RDA. The recommendation notes, however, that RDA programmes ask many asymptomatic, healthy people to take a medicine when they do not feel ill, with the potential for adverse reactions. Community engagement is a key factor in determining the success of RDA, to improve participation rates and adherence to the full treatment course of the medicine.

Conditional recommendation for reactive case detection and treatment to reduce transmission of malaria (RACDT). This strategy involves testing every individual living with or near a person with a confirmed malaria case, or every person who was likely exposed to infection at the same time and place. Only those who test positive for malaria receive a full course of antimalarial medicine. Providing the medicine only to those who are known to be infected may improve adherence to treatment and population acceptance of the intervention, while decreasing the risk of adverse reactions and depleting stocks of medicines. The WHO conditional recommendation in favor of this intervention notes it is unlikely that RACDT will have any effect on malaria transmission until an area is nearing elimination. However, when a country approaches interruption of transmission, RACDT becomes an essential component of its malaria surveillance effort by improving the sensitivity of surveillance through active case detection in the areas most likely to have additional cases, and by monitoring progress towards elimination.

Conditional recommendation for reactive indoor residual spraying (IRS). Indoor residual spraying (IRS) is the application of an insecticide to the interior surfaces of homes or dwellings to kill mosquitoes that rest on those surfaces and reduce malaria transmission. Reactive IRS is the use of this intervention in the homes of an individual with a confirmed case of malaria as well as in neighboring houses at approximately the same time. WHO has issued a conditional recommendation in favor of this intervention to prevent or reduce transmission of malaria in areas approaching elimination, or in post-elimination settings.