By SuJin Kang, Ashish Damania, M. Farhan Majid and Peter J. Hotez
Introduction
In 2015, we reported on a new national “worm index” for human development using data released by the World Health Organization (WHO) for the total number of school-aged children requiring mass drug administration (MDA) to treat their intestinal helminth infections and schistosomiasis, together with the population requiring MDA for lymphatic filariasis (LF). The worm index was calculated by adding these 3 populations at risk and then dividing it by the total population. We found that for the 25 most populated nations, there was a strong inverse association between the national worm index and its human development index (HDI), a summary metric that incorporates living standards, educational attainment, and health. We subsequently found a similar inverse relationship for the world’s Muslim-majority countries belonging to the Organization of Islamic Cooperation (OIC).
Our finding that high national worm indices link to low human development generates a number of hypotheses regarding how human helminth infections adversely affect child development, overall health, and even economic development. Including all intestinal helminth infections, schistosomiasis, and LF also helps to evaluate global effects. For example, many Asian nations might have high worm indices due to widespread intestinal helminth infections and LF, whereas in many African countries, schistosomiasis also contributes greatly to calculating national worm indices. Employing the worm index also presents an opportunity to evaluate how integrated MDA for intestinal helminth infections, schistosomiasis, and LF could both reduce worm indices and translate into health and economic gains as an approach towards sustainable development.
Here, we extend our earlier findings by calculating worm indices for all 191 countries for which there are available data. We also calculate the worm index in 2 different ways, using both the methods described earlier that rely on WHO data (now with the most recently reported data in 2016), as well as newly released data from the Institute for Health Metrics and Evaluation (IHME) for the Global Burden of Disease Study (GBD) 2016. It should be noted that WHO data provides the estimated number of school-aged children (intestinal helminth infections and schistosomiasis) or adults (LF) requiring preventive chemotherapy (PC) for endemic countries, whereas GBD data provides the prevalence of each of the intestinal helminth infections (e.g., ascariasis, trichuriasis, hookworm disease, schistosomiasis, and LF) in every country.
Using either approach, we confirm a strong inverse association between worm indices and HDIs. In addition, we observed especially strong associations between worm indices and low educational attainment, years of schooling, and school completion. Our findings suggest that helminth control and elimination might comprise an essential element of global efforts to improve childhood education.
