The Need for New Malaria Intervention Strategies – Residual Transmission

Unfortunately, malaria is not usually transmitted by only one species of mosquito within a given region or country, and even within mosquito species, populations may develop behavioral adaptations to avoid current vector control practices. Long-lasting nets and indoor residual spraying address the vast proportion of malaria transmission that occurs from the main malaria vectors, which bite people indoors at night during sleeping hours and then rest on indoor surfaces after taking a blood meal.

However, it is becoming increasingly recognized that malaria elimination will not be reached if we rely only on these existing ‘traditional’ intervention methods. We need new tools which can effectively reduce human-vector contact with the mosquitoes that bite people outdoors or outside of the times when people sleep under a bed net; or to target mosquitoes that bite people indoors and then rest outdoors after a bloodmeal. All of these require different approaches from what we have today.

For that reason, a suite of new tools for vector control is under evaluation. In a Guidance note of 2014, WHO recommends testing the effectiveness of the following strategies:

  • Using physical screening barriers or repellants to exclude or limit indoor entry;
  • Following entry, preventing successful indoor feeding and/ or resting using exit or other barriers, repellents or insecticides with no deterrent properties;
  • Preventing successful outdoor feeding by using insecticide-treated clothing or repellants to directly protect people;
  • Reducing adult vector densities or transmission potential by outdoor attractants to trap/kill mosquitoes by tropical or systemic insecticides for livestock by applying insecticides to natural sugar sources or introducing insecticidal sugar baits.

A joint effort of national institutions, private partners, researchers and WHO will be necessary to develop, validate and implement new approaches for targeting such residual transmission.

The Role of the Private Sector in the Future of Malaria Control

In addition, to new tools and new approaches with those tools, sustaining future funding for the fight in a pre-elimination setting will play a crucial role. As disease burden comes down, commitment and interest wanes, which can result in a resurgence of the disease. “Indeed, an arsenal of potent technologies was at the ready. Insecticide-treated bed nets had been shown to protect against malaria-carrying mosquitoes, which are active primarily at night. Indoor residual spraying with insecticides remained a safe and effective alternative. And a new generation of powerful drugs had been developed for the treatment of malaria.

Despite this arsenal, the fight against malaria had stalled,” commented Margaret Chan, former head of WHO in 2010. In this regard, the private sector can play an important role.

A good example for a successful public-private partnership model for malaria elimination is Sri Lanka, where cooperation between the government and the private sector partner considerably contributed to the elimination of the disease. In this situation, private support was temporarily provided to war-damaged areas of the nation in order to ensure the continuation of these efforts supported Sri Lanka to become one of the most recent countries to achieve malaria elimination, as it was certified as malaria-free by WHO in 2016.

There are various opportunities to engage private companies in small or large-scale projects. Targeted interventions such as immunization programs, distribution of long-lasting insecticidal nets (LLNs) and improved access to diagnostics and treatments can protect communities and part of populations that live in hard-to-reach areas. In-company campaigns can help raise awareness of malaria symptoms and of the importance of prevention efforts. The expertise and resources of the private sector offer unique opportunities to confront the challenge of drug and insecticide resistance.

 

An Optimistic Future or a Long Way to Go?

The efforts of the International community over the past 15 years have reduced malaria risk levels for many millions of people. This is suggestive that elimination targets are within our reach, with the right level of resources and commitment and with the right tools in our hands. The challenges are many, but the commitment is strong. The pipeline for new modes of action to mange resistance in malaria vectors looks promising. There is no shortage of innovative ideas for a large toolbox to address other elements of malaria transmission. An as economic development in some endemic countries advances, this creates less reliance on international funding, opportunities for different domestic funding mechanisms and different models of private sector management.

Bayer awaits the results of this years’ World Malaria Report with bated breath and remains hopeful that this year we will see positive progress towards malaria elimination goals.

Meanwhile, Sarah De Souza, Marketing Analyst with Environmental Science at Bayer in Ivory Coast, West Africa, has been dedicated to this topic for the last two years. “There was limited awareness of the relevance of crop protection usage of the ‘new’ class of repurposed chemistry in West Africa, which we are developing for Malaria Vector Control, said De Souza.

“For instance, if this insecticide class was widely used in intensive agricultural production environments, did that overlap with areas where malaria mosquitoes breed?”