Zinc and vitamin A: Taking the sting out of malaria
Photo: Women and their children wait outside a UNICEF-assisted health centre in the Peruvian Amazon, where malaria is a major health concern.
Early evidence from a study in Papua New Guinea suggests that zinc and vitamin A sup plements may boost children's resistance to one of the world's most insidious infectious diseases: malaria.
Two fifths of the world's population, in 90 countries across sub-Saharan Africa, Asia and Central and South America, is at risk of contracting malaria. At least 300 million people worldwide endure its recurrent fevers, malaise, anaemia and risk of seizures or coma. Malaria kills from 1.5 million to 2.7 million people annually. It is the sixth leading cause of disability among children under four years of age in the developing world. Some 600,000 young children die of malaria alone each year; over 1 million die of malaria in conjunction with other illnesses - a rate of one child every 30 seconds.
Many approaches have already been tried to combat the disease. However, the parasite that causes malaria is no longer vulnerable to some of the most powerful antimalarial compounds available. For a time, the widespread use of pesticides in the 1950s managed to suppress the Anopheles mosquito that transmits the parasite, but it, too, has developed resistance.
Arming the body to defend itself through immunization is one approach to preventing the disease. But vaccines are difficult to develop since the parasite moves between organs, changing its appearance from stage to stage and hiding from the immune system in a place that the immune system doesn't check: inside red blood cells. Consequently, the best vaccines to date have managed to protect only around 30 per cent of test populations from infection.
However, naturally acquired resistance does develop over time as people are repeatedly exposed to the parasite. A recent study by the Johns Hopkins School of Public Health and the Papua New Guinea Institute of Medical Research investigated the ability of vitamin A and zinc to help boost such natural resistance.
Nearly 800 children under the age of five were enrolled in the study. All of the children lived in an area of north-western Papua New Guinea where malarial infection is common. The parasite that is responsible for the disease can be found in the blood of over 40 per cent of under-fives in the region, and it is the major cause of death among children from the age of six months to four years.
In controlled trials, regular vitamin A and zinc supplementation appeared to be complementary in decreasing the burden of malaria in children. According to Dr. Anuraj Shankar of Johns Hopkins Uni ver sity, chief researcher of the study, vitamin A reduced by more than a third the febrile illnesses due to mild to moderately high levels of malaria parasites in children and significantly reduced spleen swelling, an indicator of chronic malaria. However, it had little influence on the worst cases, where children had a very high number of parasites in their blood.
Zinc, on the other hand, helped blunt the severity of the worst cases. As a result, there were over a third fewer malaria cases seen at health centres among those given zinc than among those given a placebo. In addi tion, overall clinic visits by those children who had received zinc decreased by a third, and signs of other infections (cough and diarrhoea, for ex am ple) were reduced by 20-50 per cent.
The Papua New Guinea experience shows that vitamin A and zinc status in children may be as im portant in reducing malaria as other com monly used malaria-control tech niques, such as insecticide spray ing and the use of insecticide-treated bed nets. And the cost is minimal: A year's supply of zinc supplements costs $1 per child, with an additional 10 cents for vitamin A capsules.
A second study is under way in the Peruvian Amazon to measure the effectiveness of vitamin A and zinc in boosting the efficacy of anti malarial drugs. Peruvian scientists at the Loreto Department of Health and colleagues from Johns Hopkins are studying more than 1,000 children who are suffering from malaria to see if a short, five-day course of zinc or vitamin A in conjunction with anti malarial drugs improves their health. Some children are receiving both the micronutrients, in the hope that the zinc-vitamin A combination will be more effective, as zinc is known to promote vitamin A metabolism in the body.
Despite the surge of international interest in malaria from both the public sector and private industry and the promise that vitamin A and zinc may hold, funding for research into disease prevention and treatment unfortunately remains meagre. Cur rently, funding levels run at roughly $42 per malaria death, compared with $3,274 for each AIDS fatality.
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