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Feature

Malaria: The Neglected Disease

Posted on: 30 Apr 03

Summary

Malaria kills more people in the world than any other communicable disease except tuberculosis, yet in terms of new drug development the disease is widely seen as a neglected one.
The world’s best known parasitic disease One of the biggest challenges for governments and industry in the future is to decrease the health disparities between poor and affluent populations and to improve drug access across the world. The pharmaceutical industry has come in for strong criticism for not focusing more on tropical diseases such as malaria. In a recent study by Medecins Sans Frontiers (MSF), an international medical aid agency, it was reported that despite tropical diseases accounting for 10 percent of the global health burden few new medicines were being developed in this area. The World Health Organization (WHO) has described malaria as the "Number One Priority Tropical Disease". It kills more people in the world than any other communicable disease except tuberculosis. Malaria is endemic in 91 countries, affecting 40 percent of the world’s population. According to recent WHO estimates the disease is responsible for up to 2.5 million deaths a year, many of these among those aged 5 years or younger, yet in terms of new drug development the disease is widely seen as a neglected one. Clinical aspects of the disease Malaria is a protozoal disease transmitted by the Anopheles mosquito, and is caused by minute parasitic protozoa of the genus Plasmodium, which infect humans and insects alternatively. There are four kinds of malaria that can infect humans: Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale and Plasmodium malariae. Plasmodium falciparum is the most widespread and dangerous of the four: untreated it can lead to fatal cerebral malaria. Humans contract malaria from the bite of a malaria-infected mosquito. The Plasmodium parasite develops in the gut of the mosquito and is passed on in the saliva of an infected insect each time it takes a new “blood meal”. The parasites are carried by the blood in the victim's liver where they invade the cells and multiply. After about two weeks the Plasmodium parasites return to the blood and penetrate the red blood cells, where they multiply again, progressively breaking down the red cells. This induces bouts of fever and anaemia in the infected person. In cerebral malaria, the infected red cells obstruct the blood vessels in the brain. Malaria can also damage other vital organs, which can lead to death. A heavy health and economic burden One of the problems in tackling malaria is that the countries most severely affected are among the poorest in the world. Many have inadequate healthcare systems and insufficient finances to adequately tackle the disease. On a rather depressing note, the disease weakens the economies of these countries even further. For example, it has been estimated that malaria has slowed economic growth in African countries by 1.3 percent per year. The economic losses in Africa due to malaria have been put at US$12 billion per year (1). The disability-adjusted life-year (DALY) system has been used to evaluate the effect of malaria on populations across the world. DALYs for a disease are calculated as the total of the years of life lost due to premature mortality in the population and the years of life lost because of disability. In effect the DALY system measures the actual health of a population versus the hypothetical norm. In 1999, nearly 50,000 DALYs were lost as a result of malaria reflecting its enormous impact on the lives of those in developing countries (2). Progress through Partnerships Although the affected population for malaria is large, in general their purchasing power is low. This has discouraged companies from investing in this area, as they may not gain a return on their investment. Pharmaceutical companies also want reassurances regarding their intellectual property rights over any new drugs produced. Furthermore, companies are unsure how they would interact with local governments whose role it would also be to promote health education and to help distribute the drugs. In many developing countries, the focus of governments on healthcare has also come in for criticism. Observers believe that none of this should be standing in the way of progress in tackling malaria and that both sets of parties can work together. One of the agreed ways that progress could be made is through Public-Private Partnerships (PPP) and a number of these have now been set up worldwide. The Medicines for Malaria Venture (MMV) is one such example (3). The MMV initiative is a result of discussions between the World Health Organization (WHO) and the representative body of the pharmaceutical industry, the International Federation of Pharmaceutical Manufacturers Associations (IFPMA). In another venture called the Challenge Grant Programme (4), the National Institute of Allergy and Infectious Diseases (NIAID) in the US provides matching funds to pharmaceutical companies who will commit their resources to R&D for neglected diseases such as malaria. A similar initiative has been set up in Japan (5). In October 1999, an alliance called the JPMW was set up between a number of pharmaceutical companies, the Japanese Ministry of Health and Welfare and The Special Programme for Research and Training in Tropical Diseases (TDR), a WHO body. The name JPMW is taken from the initials of each of the participants. The aim of the JPMW was to focus on 12,000 different chemical entities from the chemical libraries of the participants. From the programme around 48 candidates have shown promise and are being further investigated. These PPPs are a welcome step towards producing the next generation of anti-malarial drugs. However, with the average development time for a new drug predicted to be around 10 years, it will be some time before new drugs emerge. In addition, the development of new drugs must go hand in hand with improving the healthcare infrastructure in affected countries. No room for complacency Malaria is mainly associated with Africa, Asia and Latin America, but cases have been reported in industrialised countries for a number of years. For example, the so-called "airport malaria", representing the inadvertent transport of live mosquitoes aboard aircraft arriving from tropical regions, has become a worrying problem in recent years. Since 1969, thirteen countries reported a total of 89 cases of malaria in people living near an airport (6-8). In one case in the UK, a person working close to London's Heathrow Airport became acutely ill and was found to be suffering from falciparum malaria, although he had never been out of the country. Four workers unloading a cargo plane at Amsterdam airport also became infected with malaria. Public health officials concluded that infected mosquitoes were carried on planes from Africa and released at the destination airport (8). Airport malaria is particularly dangerous because physicians generally have little reason to suspect it, as the sufferers may never have travelled to a region where the disease is endemic (7). In European cases of airport malaria the delays in correctly diagnosing the disease has led to the patients developing complications. In one Swiss case of airport malaria, 31 days elapsed before a correct diagnosis was made (6, 7). A serious consequence of the importation of mosquito species is that they may establish themselves in the country into which they have been introduced. For example, in the 1930s, mosquitoes that arrived aboard a ship in Brazil led to an epidemic of malaria, which caused 16,000 deaths (6, 7). Given the growing volume of international air traffic, the WHO is determined to tackle the problem of airport malaria. The WHO has conducted field trials on various materials and methods for the effective “disinsection” of any aircraft coming from regions where vector-borne diseases are endemic (7). The dangers of the mosquito as a disease vector have been highlighted by the recent outbreak of West Nile virus disease in the USA. A Centers for Disease Control and Prevention (CDC) report released in August reported that there had been at least 112 human cases of the mosquito-borne virus in 2002. The number of human cases in the USA during 2002 surpassed all previous years (9). The west Nile virus outbreak also serves as a grim reminder that diseases that typically affect developing countries can equally strike in affluent nations and must not be ignored. References
  1. Roll back malaria. http://www.rbm.who.int/
  2. Michaud C.M. et al. (2001). Journal of the American Medical Association 285 (5): 535-537
  3. Medicines for Malaria Venture. http://www.mmv.org
  4. Interest in malaria research reignited. IMS Health. http://www.ims-global.com/insight/news_story/0102/news_story_010209.htm
  5. JPMW and the Search for New Antimalarials. Japan Pharmaceutical Manufacturers Association. http://www.jpma.or.jp/12english/publications/pub021f_international/
  6. “Airport Malaria” – Experts warn of deadly risk ready to land in many countries. http://www.who.int/inf-pr-2000/en/pr2000-52.html
  7. Gratz NG et al. (2000). Why aircraft disinsection? Bulletin of the World Health Organization, 2000, 78
  8. Malaria: An On-line Resource (2002). Division of Laboratory Medicine at Royal Perth Hospital, Australia. http://www.rph.wa.gov.au/labs/haem/malaria/index.html
  9. West Nile Virus Update. Centers for Disease Control and Prevention. http://www.cdc.gov/od/oc/media/pressrel/r020816.htm

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Dr Faiz Kermani

Last updated on: 27/08/2010 11:40:18

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