This Guest Editorial was written by Sir Richard Feachem. Dr. Feachem, PhD, DSc(Med) is Director of the Global Health Group at the University of California, San Francisco. From 2002 to 2007, Sir Richard served as founding Executive Director of The Global Fund to Fight AIDS, Tuberculosis and Malaria and Under Secretary General of the United Nations. Read Sir Richard’s complete bio here.
Guest Editorial: Progress toward malaria elimination: highlighting the need for new strategies
Progress toward malaria elimination: highlighting the need for new strategies
Last week, the UCSF Global Health Group, published a new review in The Lancet documenting evolving epidemiological trends in many of the 34 malaria-eliminating countries. The publication, entitled The changing epidemiology of malaria elimination: new strategies for new challenges, describes changing patterns of infection in low-transmission settings, different from those seen in highly endemic settings. Malaria cases are highly clustered within small geographic areas and clustered demographically into subpopulations with shared social, behavioral, and economic characteristics. To address effectively these new patterns of infection there is an urgent need to explore and adopt novel malaria control and elimination strategies.
The substantial progress in the malaria-eliminating countries over the last decade has helped drive epidemiological shifts in malaria infection. Malaria-eliminating countries have achieved a remarkable 85% decrease in reported cases between 2000 and 2010, from 1.5 million to 232,000 cases. Twenty-five of the 34 malaria-eliminating countries reduced their total malaria caseload by more than 70% during this period. Further, four countries have been certified malaria-free in the last five years.
In contrast to high transmission areas, where pregnant women and children are at highest risk, cases in elimination settings are more common amongst adult men, migrant workers and members of other hard-to-reach populations. This trend is associated with occupation and behavioral or social risk; workers engaged in the military, forestry, plantation, agriculture and mining industries are more likely to sleep or work outdoors during peak malaria vector feeding times. In Sri Lanka, for example, overall malaria incidence decreased by 99.9% between 1999 and 2011, and the proportion of infections in adult men increased from 54% to 93% over the same period.
In countries that have achieved or are nearing elimination, the major driver of malaria transmission is the importation of malaria from endemic areas, frequently by migrant workers. Migrants move from high-transmission areas in search of work, or to escape civil strife, and can introduce malaria parasites into local populations in low-transmission areas. Finding, treating and tracking these populations can be exceptionally challenging. They are often highly mobile or concentrated in remote locations, and may avoid contact with government health workers and face substantial barriers to accessing health care.
In addition to demographic shifts, malaria is more likely to be caused by the Plasmodium vivax parasite than Plasmodium falciparum in elimination settings outside of sub-Saharan Africa. This has repercussions for malaria control programs. Although P. vivax is less deadly than P. falciparum, infections are more challenging to detect and treat due to a prolonged dormant liver phase and greater likelihood of asymptomatic infections.
Detecting malaria infections in low-transmission settings, particularly in high-risk groups who are infectious but asymptomatic, can be extremely challenging. Population movement across political boundaries and the importation of malaria makes this challenge even greater. Without effective strategies to identify and target these individuals, malaria elimination may prove difficult in certain areas.
These epidemiologic shifts require the adaptation of current malaria control interventions to target new risk groups. Optimizing current malaria control strategies, particularly active and passive surveillance, mass drug administration, and occupation-based vector control tools such as insecticide-treated clothing or hammocks, will be vital to continued progress. Interventions that target high-risk groups must also be complemented by research and development of new technologies, such as new drugs, vaccines and more sensitive and field-friendly diagnostics.
As countries continue to work towards elimination, there is a critical need for adequate funding to support national and multi-national control efforts. Despite the growing importance of imported malaria from higher endemic settings, the largest international funder for malaria control—the Global Fund to Fight AIDS, Tuberculosis and Malaria— allocates only a very small proportion of its malaria funding to multi-country proposals. Regional and multi-country funding initiatives are a potential solution to address the collective challenges faced along shared borders and within regions. Development of sustainable regional funding sources for malaria elimination will reduce importation into malaria-free areas and accelerate progress across whole regions.