NTDs: Soil-transmitted helminthiases – almost 1/4 of the world’s population are infected

This post is the 15th in a series highlighting the WHO’s list of 17 Neglected Tropical Diseases (now technically 18 as mycetoma was added to the list at the 69th World Health Assembly in May 2016). To read the previous posts in this series click here.

Child receiving de-worming medication. Courtesy PAHO/WHO.

Child receiving de-worming medication. Courtesy PAHO/WHO.

Soil-transmitted helminth infections, caused by various species of parasitic worms, are the most common infections worldwide. Almost 25% of the population are infected, but that risk is not distributed equally around the world. The poorest people living in tropical and sub-tropical areas have the highest burden of disease. And of those infected, childrenĀ are perhaps the demographic hardest hit.

Soil-transmitted helminth infections (STH) are caused by parasitic worms. Infections are transmitted by the parasite releasing eggs into a person’s feces. The eggs from the feces contaminate the soil and, after maturing in the soil, infect a new person via the person eating unwashed/under-cooked vegetables grown in the contaminated soil, ingesting contaminated water, or touching their mouth with contaminated hands. Additionally, hookworm (one of the STH species, in addition to roundworm and whipworm) can infect people by burrowing into their bare feet when they walk on contaminated soil.

Distribution of global STH survey data. No date. Courtesy Global Atlas of Helminth Infections.

Distribution of global STH survey data. No date. Courtesy Global Atlas of Helminth Infections.

The map above shows the locations with helminth activity. Most of the transmission is occurring in sub-Saharan Africa, the Americas, China and East Asia. STH infections in children stunt their growth by inhibiting nutrient absorption, the parasites take blood from the host resulting in a loss of blood volume and protein, and some parasites cause lack of appetite and diarrhea. However, drug treatment does exist. In 2014 an estimated 45% of school-aged children who needed treatment were treated. Similar to schistosomiasis, regular de-worming of school-aged children is recommended in areas of high STH burden. The WHO is committed to reducing the prevalence of STH and increasing the number of children receiving chemo-prophylaxis.

While I think it’s a worthwhile effort to ensure children are treated for STH regularly, which gives them a better chance at a healthy life, I wonder about the other ways to prevent STH? And how much WHO is doing to implement those changes? The people most affected by STH are those in the poorest areas, so we can predict that they have poor sanitation, lack of adequate personal hygiene resources, and perhaps a lack of knowledge about how to protect themselves with the resources they have available to them. In order to truly eliminate STH, the basic health rights of the affected populations must be addressed. Continuing to provide treatment without addressing the underlying issues will only get you so far in the effort to eliminate a disease.

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