that infect people are the roundworm (Ascaris lumbricoides), the whipworm (Trichuris trichiura) and hookworms (Necator americanus and Ancylostoma duodenale).
More than 1.5 billion people, or 24 per cent of the world’s population, are infected with soil-transmitted helminth infections worldwide. Infections are widely distributed in tropical and subtropical areas, with the greatest numbers occurring in sub-Saharan Africa, the Americas, China and East Asia.
Over 267 million preschool-age children and over 568 million school-age children live in areas where these parasites are intensively transmitted, and are in need of treatment and preventive interventions.Soil-transmitted helminths are transmitted by eggs that are passed in the faeces of infected people. Adult worms live in the intestine where they produce thousands of eggs each day.
In areas that lack adequate sanitation, these eggs contaminate the soil. This can happen in several ways: eggs that are attached to vegetables are ingested when the vegetables are not carefully cooked, washed or peeled; eggs are ingested from contaminated water sources; eggs are ingested by children who play in the contaminated soil and then put their hands in their mouths without washing them.
In addition, hookworm eggs hatch in the soil, releasing larvae that mature into a form that can actively penetrate the skin. People become infected with hookworm primarily by walking barefoot on the contaminated soil.
There is no direct person-to-person transmission, or infection from fresh faeces, because eggs passed in faeces need about three weeks to mature in the soil before they become infective. Since these worms do not multiply in the human host, re-infection occurs only as a result of contact with infective stages in the environment.
Soil-transmitted helminths impair the nutritional status of the people they infect in multiple ways.The worms feed on host tissues, including blood, which leads to a loss of iron and protein.(UNI)