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Soil-Transmitted Helminths

Soil-transmitted helminths affect the poorest and most deprived communities and are among the most common infections worldwide with an estimated 2 billion people infected. The main species with this group of intestinal parasitic worms are the roundworm (Ascaris lumbricoides), the whipworm (Trichuris trichiura) and hookworms (Necator americanus and Ancylostoma duodenale).  The infections, commonly seen in children, can result in physical, nutritional and cognitive impairment.

 

Life Cycle

Soil-transmitted helminths are transmitted by the eggs produced by the adult worms which reside in the intestines of people. These eggs are passed in the faeces of infected individuals which, in areas which have poor levels of sanitation, can contaminate food, water, hands and cooking utensils which result in the ingestion of the eggs and subsequent infection.

In addition to this transmission route, hookworm eggs can develop in the soil and release the infective larvae form of the parasite which can penetrate the skin. This means that people can become infected simply by walking through an infected area if they are not wearing the correct footwear.

It is important to note that there is no direct person-to-person transmission and re-infection can only occur through contact with the infective stage of the eggs or larvae.

Symptoms

The morbidity and the symptoms presented by these diseases is directly tied to the number of worms an individual harbours. Heavy infections cause diarrhoea, abdominal pain, general malaise and weakness, though infections with hookworms can result in anaemia. 

Soil-transmitted helminths are treated with albendazole or mebendazole.