Behind the Numbers: The PRB blog on population, health, and the environment

by Eric Zuehlke, editor

Also posted on End the Neglect, the Global Network for Neglected Tropical Disease blog

The damaging effects of HIV/AIDS and malaria on individuals, families, and communities in developing countries are well-documented. Public advocacy campaigns highlight the millions of deaths each year that can be prevented through basic immunizations that are taken for granted in developed countries. But did you know that 13 parasitic and bacterial infections, mostly worms and trachoma known as the “neglected tropical diseases,” are the most common afflictions of the world’s poorest people? “Neglected” tropical diseases affect about 1.4 billion people worldwide, mostly in rural areas of developing countries. Unlike AIDS and malaria, they aren’t fatal, but they are disabling, leading to lost income from missed work and lower IQs. A recent post on the Discovery magazine blog highlights recent research from the University of New Mexico that hypothesizes that the prevalence of these parasitic infections is the “most powerful predictor of average national IQ” – more than GDP, literacy rates, and school enrollment. The post questions whether correlation is causation and is skeptical about these diseases having effects on the IQ of entire countries: 

“…a link between infections and IQ tells us nothing about whether infected people grow up to be less intelligent, or whether intelligent people are less likely to become infected. Intelligence, after all, could affect one’s understanding of what a disease is, how to avoid it, and how to seek help for an infection.”

I think the author misses the point here. The issue isn’t that intelligence may lead to greater knowledge and prevent infection. How does intelligence help in seeking treatment in the poorest rural areas in the world, with little or no medical care or resources to treat these diseases? In addition, lower IQs can have huge lifelong ramifications in terms of educational attainment and employment. Young children are often afflicted by these conditions, delaying mental and cognitive development. A wide body of research has shown that deficiencies in the first years of life have lifelong effects. Nutrition shortfalls have also proven to detrimentally affect IQ. For example, deficiency in iodine, an element that we take for granted in the United States, can lead to impaired cognitive development and is the leading cause of mental retardation worldwide. Given the sheer prevalence and disabling nature of these diseases, you would think there would be more discussion of their effects on productivity, economic development, and social stability. They are a major hidden root cause of poverty. Of course, lack of education and employment opportunities, weak markets for goods and foods for poor farmers, trade imbalances, and conflict over scarce resources are all major contributors to poverty, but without a foundation of good health, how can the other issues be overcome?

I recently interviewed Dr. Peter Hotez, research professor and the chair of the Department of Microbiology, Immunology, and Tropical Medicine at George Washington University about the effects of these diseases on economic development and the interesting potential for “vaccine diplomacy.” He’s also the president of the Sabin Vaccine Institute, an organization working to reach the millions of people affected by neglected tropical diseases. A “rapid impact package” of drugs that eliminate the seven most common tropical diseases can be administered for just 50 cents a person per year. Whether or not the neglected tropical diseases are the single “most powerful predictor of national IQ,” they are a major contributor to poverty.

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