(PRWEB) September 22, 2003
The World Health Organization [WHO], founded in 1948, targeted for eradication one of the worldÂs oldest diseases, Malaria, which dates back to the fifth century BC.
A potential consequence of global warming, foreseen for the coming century, is a change in the distribution and incidence of malaria. This may directly affect the behavior and geographical distribution and life cycle of malaria mosquitoes. This could also have an indirect effect by influencing environmental factors such as vegetation and available breeding sites.
Malaria is back in full force; killing more than three million people a year, making it humanity's deadliest infection. This includes an estimated 700,000 children. This death toll is comparable to the AIDS death toll. More than 90 per cent of these deaths are in sub-Saharan Africa. This deadly re-emergence can have numerous causes: the malaria parasite developing a resistant to vaccines; ever-increasing international travel; climate change due to global warming; mass refugee migration; increased logging, irrigation, road building, and mining, all creating a favorable climate for increased mosquito breeding.
The parasites that cause malaria infect 300 to 500 million people annually. Nearly half the world's population lives in countries where malaria epidemics occur, and as the parasites' resistance to drugs grows, the toll is expected to steadily worsen.
Deaths due to Malaria affect more than the direct victims; countries with a high incidences of malaria have one-third the income levels of nations that are unaffected by malaria. Malaria increases the incidences of poverty by interfering with school attendance by sick children and by disabling agricultural workers during peak harvests. WHO claims that the estimated costs of malaria, directly and indirectly, in sub-Saharan Africa are over $2 billion each year.
What puzzles the researchers is how malaria continues to outsmart both the human immune system and modern science, causing researchers to struggle to understand the history of malaria and how it arose. There is new evidence that malariaÂs devastation is a relatively recent phenomenon and that it is more deadly now that it was just a few thousand years ago.
The mosquito needs sunshine and shallow pools of water to lay their eggs in. The dense forest that covered most of Africa wouldn't have provided such pools. Coluzzi's research suggests A. gambiae [malaria-carrying mosquito] is highly adaptable, and he argues the mosquito could have fed on other mammals when forest-dwelling people were less accessible. Agriculture is considered to be another factor in malaria's spread. In 1958, anthropologist Frank Livingstone, then a professor at the University of Michigan in Ann Arbor, suggested that ecological changes accompanying the human transition to farming fostered the spread of malaria. This change also placed a concentrated population of people on which they could feed. This theory would place Africa's first farmers and the land changes they wrought as causing the malaria to become so widespread.
According to Livingstone's scenario: early West African cultivators about 3,000 years ago began clearing forest to grow crops. As cultivators slashed, burned, and planted swathes through the forest, A. gambiae mosquitoes could have adapted to feed on people, states Coluzzi. The agricultural scenario is appealing, but the archeological evidence to back it up isn't strong. Slash-and-burn cultivation has been common throughout much of sub-Saharan Africa for at least 500 years, but there is "very scant evidence [of it] in tropical forest zones in the archeological record," says Robert Dewar, an African archeologist at the University of Connecticut in Storrs.
Zimbabwe is in the grip of a malaria epidemic, infecting 13,000 people and killing 18 people in the past week alone, a senior official of the Health Ministry disclosed Sunday.
Dr Jokonya Chirenda feared a further dramatic increase in infection and fatalities, as conditions are ideal for breeding of mosquitoes that carry the malaria blood parasite. Two deaths were recorded over the past week in the traditionally malaria-free municipal area of the capital, now troubled by deteriorating infrastructure and massive overcrowding. However, said Chirenda, the two victims may have picked up the infection in rural areas.
Manicaland province, next to Mozambique, was worst affected, with 5,028 cases and seven deaths over the past week.
Africa nearly reached its goal of eradicating malaria in the 1960s, but new, resistant strains have evolved that are resistant to the usual methods of medication as well as to normal insecticides.
Some authorities have called for reintroduction of the insecticide DDT, dropped in the 1970s because of damaging environmental effects. Zimbabwe's under-funded hospitals are already unable to cope with an AIDS epidemic claiming up to 1,000 lives a day and infecting at least one adult in five.
If temperate climates see a small increase in temperature this can result in a malaria epidemic. This would not have such a dramatic effect in most developed countries because they would be in a position to take mitigating measures; the numbers of life lost due to malaria infection would remain negligible compared with the endemic areas in the world.
The main changes would be in temperate climates where mosquitoes already occur but where development of the parasite is limited by temperature. By the year 2100 the potential for malaria transmission would exist in large parts of North America, Europe, and Asia even with a mosquito density a hundred or more times smaller than in 1990. Because of their high potential receptivity, the highest risks for the introduction of malaria transmission remain in the non-endemic regions bordering on malarial areas.
Epidemic potential at higher altitudes within malarial areas such as the eastern highlands of Africa or the Andes region in South America is of particular importance. An increase of several degrees in temperature may raise the epidemic potential sufficiently to change normally non-malarial areas to areas with seasonal epidemics.
In areas that have a lower incidence of malaria, a relatively small increase in malaria transmission could lead to a large increase in people suffering from malaria. Where malaria is common, the population develops, over time, high levels of immunity so that the change is far less pronounced. However, the major part of the malaria fatalities will remain in the highly endemic countries of tropical Africa.
A global increase of several degrees in the year 2100, doubles the malaria epidemic potential in tropical regions and more than 100-fold in temperate climates. There is a risk of reintroducing malaria into non-malarial areas, including parts of Australia, the United States, and Southern Europe, by importing cases of malaria, since the former breeding sites of several Anopheles species still exist.
The developed countries would be less affected, having the economic advantage to enact control measures.
A recent U.N. treaty aimed at eliminating toxic chemicals allows an exception for some developing countries to continue using the pesticide DDT. Five African nations have lowered or abolished taxes on mosquito nets, which can reduce the risk of contracting the disease by as much as 63 percent. The Roll Back Malaria initiative, launched jointly by the World Bank, WHO, UNICEF, and the United Nations Development Programme, hopes to halve the burden of malaria by 2010 by promoting public-private partnerships. And the cost should such efforts prove insufficient? *
ÂForeign PolicyÂ, July 01 2001
Issue: Nov 10, 2001
January 27, 2002
British Medical Journal, April 29 2000
*Environmental Health Perspectives
Volume 103, Number 5, May 1995
By Margot B