SOIL TRANSMITTED HELMINTHIASIS: A GLOBAL HEALTH CHALLENGE

Soil-Transmitted Helminthiasis: A Global Health Challenge

Introduction

Soil-transmitted helminthiasis (STH) is a type of infection caused by different species of parasitic worms¹. These worms live inside the intestines of infected people, where they lay thousands of eggs each day. These eggs are passed in the feces and can contaminate the soil in areas with poor sanitation. Once in the soil, the eggs mature and become infective, meaning they can cause new infections. This cycle continues when people come into contact with contaminated soil, either through poor hygiene practices or by consuming unwashed fruits and vegetables. It is among the most common infections worldwide, affecting the poorest and most deprived communities². The disease is transmitted by eggs present in human feces, which contaminate the soil in areas where sanitation is poor².

The Parasites

The main species that infect people are the roundworm (Ascaris lumbricoides), the whipworm (Trichuris trichiura), and the hookworms (Necator americanus and Ancylostoma duodenale)². These main culprits include the roundworm (Ascaris lumbricoides), known for its large size and resemblance to earthworms. We also have the whipworm (Trichuris trichiura), named for its whip-like shape, and the hookworms (Necator americanus and Ancylostoma duodenale), notorious for their hook-like mouthparts that attach to the intestinal wall. These parasites are essentially intestinal and their eggs are liberated along with the feces of infected persons into the soil¹.

Transmission

Infection occurs when vegetables and fruits, contaminated with soil infested eggs, are consumed; or when hands or fingers have been contaminated with dirt carrying the eggs are put in the mouth¹.

Soil-transmitted helminthiasis (STH) primarily spreads through fecal-oral transmission in areas with poor sanitation. Eggs from infected individuals contaminate the environment, particularly soil. This contamination can lead to infection in several ways.

People can become infected by:

Consuming contaminated food and water: Eggs can stick to unwashed fruits and vegetables or be present in contaminated water sources. When people ingest these, they unknowingly swallow the eggs, leading to infection.
Skin penetration: Specific hookworm species can burrow through the skin, usually the feet, if people walk barefoot on contaminated soil.
Poor hygiene: Not washing hands properly after using the toilet or before eating can transfer eggs from contaminated fingers to the mouth, introducing them into the body.

Eggs that are attached to vegetables are ingested when the vegetables are not carefully cooked, washed, or peeled². Eggs are also ingested from contaminated water sources².

Symptoms and Impact

Intestinal worms produce a wide range of symptoms including intestinal manifestations (diarrhea, abdominal pain), general malaise, and weakness². Hookworms cause chronic intestinal blood loss that results in anemia². Infected children are nutritionally and physically impaired³.

Global Impact

Approximately two billion people (about a third of the global population) are infected, and four billion are at risk¹. The largest numbers of cases occur in impoverished rural areas of Sub-Saharan Africa, Latin America, Southeast Asia, and China¹.

Prevention and Control

Simple prevention and control strategies are access to improved sanitation, public awareness on personal hygiene, and health education¹. The World Health Organization (WHO) is working towards the elimination of STH as a public health problem by donating high-quality medicines and diagnostics for the control of STH in children, building capacity of national control programs, and providing evidence-based guidance².

Conclusion

Soil-transmitted helminthiasis is a significant global health challenge. However, with concerted efforts in improving sanitation, public awareness, and access to medical care, it is hoped that the burden of this disease can be significantly reduced.

References

²: World Health Organization (WHO) ¹: Wikipedia ³: WHO Fact Sheets