A soil-transmitted helminth (STH) infection is a sub-group within the group of helminth infections. It is caused specifically by those helminthes (worms) which are transmitted through soil contaminated with faecal matter and are therefore called soil-transmitted helminth (Intestinal parasitic worms) infections.
Soil-transmitted helminth (STH) infections are a major public health problem in tropical and sub-tropical countries and affect the poorest and most deprived communities. More than 1.5 billion people, or 24% of the world’s population, are infected with soil-transmitted helminth infections worldwide. The World Health Organization estimates that in India around 241 million children between the ages of 1and14 are at a risk of parasitic intestinal worm infestation. STH infections are transmitted by eggs present in human faeces which in turn contaminate soil in areas where sanitation is poor.
People with light infections usually have no symptoms.
Heavier infections can cause diarrhoea and abdominal pain, general malaise and weakness, and impaired cognitive and physical development.
Hookworms cause chronic intestinal blood loss that can result in anaemia.
Soil-transmitted helminths impair the nutritional status of the people they infect in multiple ways.
The nutritional impairment caused by soil-transmitted helminths is recognized to have a significant impact on growth and physical development.
The main species that infect people are the roundworm (Ascaris lumbricoides), the whipworm (Trichuris trichiura) and hookworms (Necator americanus and Ancylostoma duodenale).
Transmission: 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.
Transmission can happen in several ways:
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, reinfection occurs only as a result of contact with infective stages in the environment.
STH can be diagnosed by examination of stool sample using Microscope for the presence of eggs.
In developing countries, groups at higher risk for soil-transmitted helminth infections are often treated without a prior stool examination. Treating in this way is called preventive treatment
Some people notice infection when a worm is passed in their stool or is coughed up. If this happens, bring in the worm specimen to health care provider for diagnosis.
Anthelminthic medications (drugs that expel parasitic worms) are used for the treatment of helminthiasis.
WHO recommends periodic treatment with anthelminthic (deworming) medicines, without previous individual diagnosis to all at-risk people living in endemic (constant presence of disease in a population) areas. Treatment should be given once a year when the prevalence of soil-transmitted helminth infections in the community is over 20%, and twice a year when the prevalence of soil-transmitted helminth infections in the community exceeds 50%.
The strategy for control of soil-transmitted helminth infections is to prevent and control morbidity through the periodic treatment of at-risk population living in endemic areas. People at risk are:
Women of childbearing age (including pregnant women in the second and third trimesters and breastfeeding women)
In addition infections can be prevented by taking precautions, including:
Education on health and hygiene reduces transmission and reinfection by encouraging healthy behaviours; such as washing of hands with soap and water before handling food, wearing of protective footwear, thorough washing of raw vegetables and fruits with safe water before eating.
Ministry of Health and Family Welfare, Government of India has launched the “National Deworming Day” (NDD) in 12 States/UT in the first phase; subsequently it will be expanded to all States/UTs of India.
The objective of NDD in India is to deworm all preschool and school-age children (enrolled and non-enrolled) between the ages of 1-19 years through the platform of Government/Government aided schools and Anganwadi Centers in order to improve their overall health, nutritional status, access to education and quality of life.