SCIENCE / MEDICINE : Intestinal Parasites Plague Third World : Health: A little-recognized problem is considered a roadblock to progress in developing nations.

Nelson, retired Times medical writer, now free-lances from Woodland Hills

The Third World is faced with numerous health and economic problems, but there is one little-recognized scourge that represents a significant roadblock to future prosperity in Third World countries: intestinal worms.

Diseases caused by parasites are a diverse group ranging from malaria to a number of illnesses that are largely unknown in developed countries and which require a variety of methods to control. A special category are the intestinal parasites, which until recently have received less attention because they have been considered to be relatively innocuous. The most common examples are hookworm, roundworm and whipworm.

Recent studies indicate that infections by these worms play a much larger role in sapping energy and well-being than previously believed. And the studies have spurred an increase in drug treatment of the afflictions, an approach that has proved highly controversial.

Perhaps only famine and malaria exceed intestinal worm infections as the leading producers of misery and economic loss in the developing world. International health experts estimate that the number of individuals infected today worldwide probably equals, or may even exceed, the number infected 50 years ago.

They say at least one-fourth of the 5 billion people living today have worms, often more than one kind. The vast majority are the same individuals in the developing world for whom malnutrition is also a primary cause of illness and lethargy.

"Perhaps as many as half of all cases of severe child malnutrition . . . are precipitated not primarily by the lack of food but by intestinal parasites, fever and infection--especially diarrheal infection--which depresses the appetite, burns the energy and drains away the body weight of the child," declares James P. Grant, executive director of the United Nations Children's Fund.

Experts warn that the problem of parasitic diseases in developing countries is so serious that neither economic development, population control nor foreign aid will suffice to foster prosperity in those countries until the diseases are controlled.

Dr. Andrew Davis, director of parasitic diseases for the World Health Organization, says: "It is unrealistic to expect rapid advancement in Third World countries, which, in addition to their economic misfortunes, are totally overburdened with crushing disease problems that diminish output of both individuals and communities."

It has been known since the last century that sanitary facilities, clean water and personal hygiene are the ways to control intestinal worms. Except for pockets of infection due largely to refugee populations, that is why intestinal worms are not a major problem in the United States. International aid agencies have striven most of this century to improve sanitation and public awareness of sanitation's essential role in the Third World by funding water purification and latrine-building projects and health education programs.

The World Health Organization currently is winding up a decade-long thrust to extend drinking water and sanitation services to hundreds of millions of people living in rural and urban slums. While gains have been made and the push will continue, UNICEF estimates that 800 million people still will be without access to safe water supplies and 1.3 billion will lack adequate sanitation services.

Another problem is the difficulty of persuading the people to change eons of habit by using latrines, which they view as confining and a nuisance to maintain. In one Mexican village where health workers finally managed to get the residents to use newly installed pit latrines, the cooperation ended abruptly when a child fell through the seat opening.

Although a wide selection of anti-worm drugs have been available for some time, physicians working in the developing world have been reluctant to use them on a wide scale. They believe that the absence of adequate sanitation facilities and good hygiene make widespread drug treatment economically useless because individuals soon become reinfected.

Recently, however, there have been signs that the traditional attitude toward drug treatment may be changing--but not without opposition from those who fear that treatment may lead to diminished attention to prevention through sanitation. In the last several years new studies have indicated that treating heavily infected children within a community has health benefits to the whole community that may justify the cost--even though the youngsters subsequently do become reinfected.

According to Dr. Michael C. Latham, director of the international nutrition program at Cornell University, studies over the last five years are revealing that the health consequences of infection in children--the most vulnerable age group--are far more serious than previously believed. For example, of the 1 billion people infected with roundworm, about a million acquire intestinal obstructions that result in between 50,000 and 100,000 deaths a year, according to Latham.

Roundworms, hookworms and whipworms also enhance the debilitating effects of malnutrition by causing anemia or decreasing absorption of nutrients or sapping the energy that comes from the protein in food, resulting in stunted growth and increased vulnerability to other infections.

In a recent study conducted in Kenya, Latham and other researchers from the Kenya Medical Research Institute and McMaster University in Canada showed that treating children with a single dose of an anti-worm drug, albendazole, brought highly significant improvements in growth rates over untreated children. The drug is seen as valuable because it is effective against each of the life-cycle stages of all three kinds of worms.

Treating a few thousand children in a study and getting good results is one thing, said Dr. Clive Shiff of the Johns Hopkins School of Public Health, but even for international agencies it's another thing to do it on a global scale. "It's ethically needed," he said, "but not affordable." Nevertheless, according to Dr. Peter Schantz of the U.S. Centers for Disease Control, interest in the drug approach is sufficient for CDC to be planning its own field trials to verify the positive findings of the Kenya and Montserrat studies.

INTESTINAL PARASITES PLAGUE THIRD WORLD HOOKWORM Larvae penetrate human skin (1), enter blood stream and are carried to heart (2), reach lung via pulmonary artery, penetrate alveoli and enter bronchi (3), ascend trachea to pharynx and are swallowed (4). Mature worms develop in duodenum and jejunum, bite into mucosa and suck blood (5). Fertilized ova discharged in feces (6). WHIPWORM Eggs are ingested with contaminated food (1), larvae leave egg and develop into adult forms (2), adult worms migrate to cecum and appendix where they live and reproduce (3). Fertilized eggs expelled in feces (4). ROUNDWORM Eggs ingested with food (1), larvae emerge in small intestine (2), penetrate gut wall and pass to heart (3), reach lung by pulmonary artery, penetrate alveoli and enter bronchi (4), ascend trachea to larynx and are swallowed (5). Larvae develop into adult worms in small intestine (6) and may pass to other organs. Eggs expelled in feces (7).

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