Intestinal worms, or soil-transmitted helminths (STH), are the most common NTDs worldwide. STHs are caused by a group of parasitic worms, most commonly hookworm, roundworm (ascariasis) and whipworm (trichuriasis) that are either transmitted through contaminated soil or by ingesting parasite eggs.
The World Health Organization (WHO) estimates that over 1.5 billion people are infected with one or more STHs. Globally, there are 700 million people infected with hookworm (including 44 million pregnant women), 807 million people infected with ascariasis, and 604 million people infected with trichuriasis. Transmission mainly occurs in tropical climates and where sanitation and hygiene are poor.
Did you know?
Hookworm was once a significant public health problem in the South of the United States and the parasite was so widespread that the economy of the South was affected. In 1909 John D. Rockefeller provided $1M for the creation of the Rockefeller Sanitation Commission for the Eradication of Hookworm Disease.
Through widespread testing and door-to-door treatment and education, the Commission was able to reduce the disease burden so that hookworm was no longer considered a public health issue by 1914
Transmission cycle and symptoms:
There is no direct person-to-person transmission as STH eggs need to mature in soil, and STH are therefore transmitted by parasite eggs that are passed in the feces of infected individuals.
Once inside the body, adult worms live in the intestines and produce thousands of eggs a day. Though symptoms vary, they include: anemia, malnutrition, vitamin A deficiency, swelling of the abdomen, weight loss, diarrhea, and inflammation of the intestines.
While hookworm infection is primarily caused by walking barefoot on contaminated soil, both roundworm and whipworm infections are caused by ingesting infective parasitic eggs. Once inside the body, adult worms live in the intestines and produce thousands of eggs a day. Though symptoms vary, they include: anemia, malnutrition, vitamin A deficiency, swelling of the abdomen, weight loss, diarrhea, and inflammation of the intestines. Studies have shown that children infected with hookworm have a 23% drop in school attendance.
Diagnosis and treatment:
Though the standard method of diagnosing STH infection is by identifying the parasite eggs in feces under a microscope, the WHO recommends periodic deworming of all at-risk individuals without previous individual diagnosis in endemic areas. Treatment is either once or twice a year depending on the prevalence of infection.
The aim of the WHO’s STH control strategy is to reduce morbidity caused by the disease and by periodically treating all at-risk populations until the intensity of the infection is reduced. At-risk populations include pre-school children; school-age children; women of childbearing age including pregnant women in their second and third trimesters, and breastfeeding women; and adults in certain high-risk occupations.
There are two fast-acting, safe, effective, and inexpensive drugs available to treat STH: albendazole and mebendazole. Both drugs are easy to administer by non-medical personnel and are donated through the WHO (GlaxoSmithKline provides albendazole and Johnson & Johnson donates mebendazole) to Ministries of Health for STH control programs.
To break the cycle of transmission, it is essential that STH treatment efforts be accompanied by health and hygiene education that encourage healthy behaviors and by the provision of adequate sanitation in resource-poor settings.