Helminths, transmitted by contact with soil and known as Soil Transmitted Helminths (STH) or intestinal parasites, are the most common infections worldwide and affect the poorest and most vulnerable populations. The causative agents are Ascaris lumbricoidesTrichuris trichiura, and hookworms.

In the Americas, soil-transmitted helminths are present throughout the Region. It is estimated that one out of every three people is infected with geohelminths. Close to 46 million children between the ages of 1 and 14 are at risk of infection by these parasites [approximately 13 million pre-school age children (1 to 4 years) and 33.3 million school-age children (5 to 14 years)] due to lack of basic sanitation and access to clean water. Infection is most common in women and children. Lack of access to water and sanitation causes the persistence of these infections. Mass deworming once or twice a year in communities and countries with high prevalence, practicing personal hygiene measures, and increasing access to water and sanitation are interventions to reduce the burden of disease.

Key facts
  • Approximately 1.5 billion people are infected with soil-transmitted helminths worldwide, making this the most common infection in the world.
  • In the Americas, STH infections are present Region-wide, affecting an estimated one-third of the population. Nearly 46 million children between the ages of 1 and 14 are at risk of infection by these parasites. The countries with the greatest presence of helminthiasis are Brazil, Colombia, Mexico, Bolivia, Guatemala, Haiti, Honduras, Nicaragua, Peru, and the Dominican Republic.
  • It is essential to improve and increase access to basic sanitation facilities, such as ventilated pit latrines and septic tanks in order to ensure proper disposal of human feces. One gram of feces from an infected individual can contain up to 100 parasite eggs.
  • PAHO/WHO recommends mass administration of the antiparasitic drugs- albendazole (400mg) or mebendazole (500mg)- to the following population groups in areas at risk for STH infection: pre-school age children (ages 1 to 4) and school-age children (ages 5 to 14), women of childbearing age (including pregnant women in the second and third trimesters and breastfeeding women). Treatment should be given once a year when the baseline 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 is over 50%. This intervention reduces morbidity by reducing the worm burden. In addition: health and hygiene education reduces transmission and reinfection by encouraging healthy behaviours; and provision of adequate sanitation is also important but not always possible in resource-poor settings.

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