Three key takeaways from APMEN TechTalk ‘Forest-goers and residual malaria: Addressing the challenge’

19 July 2020 Posted by APMEN

As Asia Pacific countries are progressing towards regional malaria elimination, the last remaining critical transmission foci are believed to be in the forest and border areas. Core malaria interventions have limited effectiveness in these areas. Populations residing in these areas tend to spend more time outdoors in and around the forests, exposed to outdoor biting Anopheles vectors (a particular challenge in the Asia Pacific region). Primary vector control tools such as LLINs and IRS, which are primarily designed for indoor protection, have limited use among the forest-goers. There are several viable solutions to close this protection gap, but they haven’t been brought to scale.

APMEN TechTalks are technical deep-dives design to improve information sharing and co-learning for common challenges in the region. This TechTalk was attended by a global audience; over 250 people from more than 40 different countries.

1. Do the basics right. Do them quickly. 

Dr Bill Hawley categorized the residual transmission types into 4; among migratory forest-goers of various types, among indigenous people who live in the forest, among village based people who perform seasonal work in ‘farm huts’, among people living in lowlands where Anopheles farauti spp. are prevalent. The reason for having difficulty in accessing these populations is not always geographical,  but sometimes social sensitivity especially when these populations are engaged in activities in the forest that run counter to local laws and regulations. Therefore, approaches for service delivery need to be customized based on local socio-economic and political contexts. Despite these challenges, simple solutions exist.

An example seen in the GMS region is the use of village malaria workers (VMW’s) to make malaria diagnosis, treatment, and prevention services available in their villages; this reduces the formation of gametocytes, and therefore reduces human to mosquito transmission. Dr Hawley said: “Communities are great biologists. They know how to find larval habitat and can get rid of them if they know what to do”, suggesting using community-based larval source management (LSM) which can be useful in some contexts. Experience in the Mekong region in successfully pressuring gametocytes through the VMW approaches could be an alternative to other countries in the Asia Pacific. And similarly, Mekong countries should learn from the countries that are taking LSM more seriously — suggesting why the program learning activities done by APMEN is so important. Dr Hawley simplified what seems to be a complex problem — vector control tools needed to target specific populations should be deployed so long as costs are not too high. Evidence requirements for these tools should not be as stringent as for broadly applicable tools. While doing the basics right is important, the speed of doing them will also matter.

Dr Rupam presented prophylactic strategies targeted for forest-goers using conventional ACTs. A trial was conducted by Dr Rupam and his team in Siem Peng, Cambodia, using Artemether-Lumefantrine and compared against a control using multivitamins. The weekly Artemether-based prophylaxis was found to be safe although there were some challenges worth noting such as adherence to trial and community acceptance. The finding from this trial will be important to re-define the prophylactic strategies that countries like Cambodia and other counterparts in the GMS are forced to drop due to concerns over drug pressure on ACTs, which remain the only effective arsenal amidst growing multi-ACT resistance in that regi

2. Target appropriate vector control  interventions – at the right place and at the right time

Dr Jeffery Hii presented the underlying reasons why current core vector control tools will have limited effect addressing residual transmission. GMS countries are reporting vectors and non-vectors belonging to five complexes of morphologically indistinguishable species, thus reflecting the tremendous spatial heterogeneity in distribution patterns. The consequence of this factor is making vector control stratifying problematic with the potential to be either cost-ineffective (deploying control in non-receptive areas) or by not providing vector control to the vulnerable population in receptive areas. High ownership access and use of bed nets cannot be taken for granted. For Forest-goers, unlike village residents, tools like LLINs are not practical, hence low utilization. They prefer carrying minimal gear with them and it suggests forest-packs that include low-cost and user-friendly accessories such as hammock nets, repellent, and even mosquito coils would be more appropriate. Despite the needs, the tools are not readily available for the forest-goers.

Moreover, in the Asia Pacific, the private sector partners who have the facilities to manufacture WHO pre-qualified products in the Asia Pacific are not currently selling their products in retail outlets accessible for forest-goers who need them most. Also, several commercial protection products that are available in Mekong countries do not meet the technical standards required for effective prevention. To improve access to vector control products for forest-goers, we need to explore opportunities for public-private partnership. These partnerships need to be guided by data such as individual & supply chain, implementation quality, product field durability, and medical anthropology.

3. Man, monkey, and mosquito - future threats of Plasmodium knowlesi 

Dr Indra shared her experiences in Malaysia, building a case the future threats of P.knowlesi in malaria elimination. Dr Indra suggested that with approaching elimination, humans may become less immune to malaria and started to become susceptible to P.knowlesi and other simian malaria. From her studies, it was clear that these infections are by early and outdoor biters making IRS and LLINs ineffective. Dr Hawley gave a similar message in his presentation about malaria outbreaks in Ache Province, Indonesia. In this area, the local authorities believe that they eliminated malaria. An outbreak occurred in that area, and using molecular analysis, it showed that they are P.knowlesi infections. The lesson drawn from this incidence is that even after successfully eliminating human malaria arising from P. falciparum and P. vivax, residual malaria could remain a problem, this time for a different reason, due to P. knowlesi.

While the threats from P.knowlesi may sound new, the solutions are not. Artemisinin-based combination therapy (ACTs) is effective for P. knowlesi. Coupling with more appropriate vector control tools, this last-mile challenge, too, can be eliminated.

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