Helminths (Soil-transmitted)

Soil-transmitted helminths is a term applied to parasites whose life-cycle usually depends on a period of development outside the human host – usually in moist and warm soil. Globally, roundworms and hookworms are the most important.


Incredibly, over 800m people worldwide are affected by Ascaris lumbricoides with peak infection intensity and prevalence among 3 to 8 year old children. Places of poor environmental hygiene are where infection occurs.

The Ascaris eggs are swallowed, and then liberate larvae as they pass through the stomach and large intenstine. Ascaris pneumonitis my result, and if this is accompanied by eosinophilia (increase in blood eosinophils).



Widely distributed throughout the tropics and sub-tropics, Hookworm infections commonly cause significant anaemia in all age groups – especially if dietary iron intake is limited. Most infections however are asymptomatic, although Eosinphilia is common.



The ‘whipworm’, called Trichuris triciura has a global distribution but is mostly prevalent in warm humid climates. Infection occurs when eggs contaminating soil, food or fomites are swallowed. Most infections are asymptomatic although IBS can result in severe cases. Trichruasis may again cause a significant eoisinphilia.



Infection occurs following ingestion of eggs in soil contaminated by dog or cat faeces. Young children are at the greatest risk of infection with parasitic roundworms of dogs and cats. Eggs are not excreted in human faeces as they seldom reach maturity in the intestine. Visceral and Ocular clinical syndromes may result, but clinical disease is relatively uncommon.

Children are most commonly affected by soil-transmitted helminths, and mass treatment programmes have been introduced in some areas.


Hookworm – approximately 600 million people worldwide are affected.




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