Progress against worms for pennies
Photo: One of the most common infections in the world, worms impede children's growth and cause anaemia. Learning and memory suffer. Here, a girl attends school in India.
Asked to name the most widespread diseases, few people would think of including worms. Yet, helminth (worm) infections are indeed one of the most common - and neglected - of diseases, affecting more than 30 per cent of the world's people. Health, productivity and physical and mental capacity may all suffer.
Children in developing countries are the most severely affected, particularly those between the ages of 5 and 14, in whom intestinal worms account for up to 12 per cent of total disease burden - the largest single contributor. While the impact of worms on health and growth is commonly believed to be most significant in children after they reach the age of five, a new study in India links worm infection with growth faltering in children between one and four years old.
As many as 150,000 children die each year from intestinal obstruction and other abdominal complications caused by large adult worms. In millions more, worms are a significant cause of malnutrition, stunting growth and causing severe anaemia, dysentery, delayed puberty and problems with learning and memory. In 1990, an estimated 44 million pregnant women were infected with hookworm; their foetuses, therefore, were at risk of retarded intrauterine growth, prematurity and low birthweight.
Transmission is insidiously easy, especially where hygiene and sanitation are inadequate. A child walking barefoot can pick up hookworm; by putting a dirty finger in her mouth, she may ingest roundworm eggs. It is not uncommon for a child to carry up to 1,000 hookworms, roundworms and whipworms that deplete blood and nutrients.
Overall, about 1.5 billion people have roundworms, making it the third most common human infection in the world. Whipworm infects 1 billion people, including nearly one third of all children in Africa. More than 1.3 billion people carry hookworm in their gut, and 265 million people are infected with schistosomes, the parasites that cause the debilitating disease of schistosomiasis.
Worms affect nutrition in several ways, ingesting blood and leading to the loss of iron and other nutrients. Worms also cause the lining of the intestines to change, which reduces the surface membrane available for digestion and absorption. As a result, fat, certain carbohydrates, proteins and several vitamins (including vitamin A) are not absorbed properly. Lactose intolerance and poor use of available iron can also result.
Treatment is simple and relatively inexpensive. A single dose of antiworm medicine such as Meben dazole costs as little as 3 cents and can eliminate or significantly reduce intestinal worm infections. The total cost of treatment programmes is typically $1 to $2 per year per person. Controlled experiments in India, Indonesia, Malaysia, Myanmar and Tanzania have proved that the therapy works for months at a time. UNICEF, WHO and the World Bank have identified pre-school and school-age children, women of childbearing age and adolescent girls as those who would benefit most from worm control programmes.
The benefits are impressive. An innovative study in Kenya in 1994, which used motion detectors on the thighs of school children, found that ridding the youngsters of high levels of hookworm improved physical activity. Dewormed children reported better appetites and an end to ab dom inal pains and headaches. Within nine weeks, the treated group showed better growth, weight gain (both in terms of fat deposits and muscle mass), physical activity and appetite than the untreated group. Numerous studies have also noted the mental and cognitive effects of anaemia in children infected with worms, with intellectual performance improving after treatment.
In a large-scale study done in India in 1996, two groups of children ages one to four years received twice-yearly vitamin A supplements; one group was also given deworming tablets. At the end of the trial, the children in the group given worm treatment were on average 1 kg heavier than the children who were not treated. The study shows not only that mass de worming can improve the weights of young children in areas where worms are common, but it also opens up the practical possibility of combining worm treatment with vitamin A supplementation in areas at risk.
Some believe that deworming is not a satisfactory solution because it must be repeated in the absence of improved sanitation, hygiene and health education, and reinfection occurs frequently. Nevertheless, periodic deworming reduces helminths' drain on children's development at critical times in their lives, at least until the causes and conditions of en vi ronmental contamination and infection are successfully addressed.
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