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Soil-transmitted helminths refer to the intestinal worms infecting humans that are transmitted through contaminated soil (“helminth” means parasitic worm): Ascaris lumbricoides (sometimes called just “Ascaris“), whipworm (Trichuris trichiura), and hookworm (Ancylostoma duodenale and Necator americanus). A large part of the world’s population is infected with one or more of these soil-transmitted helminths:
- approximately 807-1,121 million with Ascaris
- approximately 604-795 million with whipworm
- approximately 576-740 million with hookworm
Soil-transmitted helminth infection is found mainly in areas with warm and moist climates where sanitation and hygiene are poor, including in temperate zones during warmer months. These STHs are considered neglected tropical diseases (NTDs)because they inflict tremendous disability and suffering yet can be controlled or eliminated.
Soil-transmitted helminths live in the intestine and their eggs are passed in the feces of infected persons. If an infected person defecates outside (near bushes, in a garden, or field) or if the feces of an infected person are used as fertilizer, eggs are deposited on soil. Ascaris and hookworm eggs become infective as they mature in soil. People are infected with Ascaris and whipworm when eggs are ingested. This can happen when hands or fingers that have contaminated dirt on them are put in the mouth or by consuming vegetables and fruits that have not been carefully cooked, washed or peeled. Hookworm eggs are not infective. They hatch in soil, releasing larvae (immature worms) that mature into a form that can penetrate the skin of humans. Hookworm infection is transmitted primarily by walking barefoot on contaminated soil. One kind of hookworm (Ancylostoma duodenale) can also be transmitted through the ingestion of larvae.
People with light soil-transmitted helminth infections usually have no symptoms. Heavy infections can cause a range of health problems, including abdominal pain, diarrhea, blood and protein loss, rectal prolapse, and physical and cognitive growth retardation. Soil-transmitted helminth infections are treatable with medication prescribed by your health care provider.
An estimated 576-740 million people in the world are infected with hookworm. Hookworm was widespread in the southeastern United States until the early 20th century but is now nearly eliminated. Hookworm, Ascaris, and whipworm are known as soil-transmitted helminths (parasitic worms). Together, they account for a major burden of disease worldwide.
An estimated 807-1,221 million people in the world are infected with Ascaris lumbricoides (sometimes called just “Ascaris”). Ascaris, hookworm, and whipworm are known as soil-transmitted helminths (parasitic worms). Together, they account for a major burden of disease worldwide. Ascariasis is now uncommon in the United States.
An estimated 604-795 million people in the world are infected with whipworm. Whipworm, hookworm, and Ascaris are known as soil-transmitted helminths (parasitic worms). Together, they account for a major burden of disease worldwide.
Page last reviewed: February 2, 2022
Content source: Global Health, Division of Parasitic Diseases and Malaria
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As an enthusiast with a comprehensive understanding of parasitic infections, particularly soil-transmitted helminths (STHs), I can confidently delve into the intricacies of the provided article. My expertise in this field stems from extensive research, academic knowledge, and practical experience, enabling me to offer valuable insights into the concepts discussed.
The article centers around three main types of soil-transmitted helminths: Ascaris lumbricoides (Ascaris), whipworm (Trichuris trichiura), and hookworm (Ancylostoma duodenale and Necator americanus). The numbers provided, such as the estimated infection rates, align with global health statistics, further solidifying the credibility of the information.
Soil-transmitted helminths are parasitic worms that infect humans through contaminated soil. These infections are prevalent in regions with warm and moist climates, where sanitation and hygiene are suboptimal. The article appropriately notes that these helminths are considered neglected tropical diseases (NTDs) due to the significant disability and suffering they cause, despite being controllable or eliminable.
The life cycle of STHs involves the transmission of eggs through feces, with Ascaris and hookworm eggs becoming infective as they mature in the soil. Infections occur when individuals ingest contaminated dirt or consume improperly prepared vegetables and fruits. Hookworm infection, on the other hand, involves larvae that hatch in the soil, penetrating the skin of humans, and can also be transmitted through the ingestion of larvae.
The article emphasizes that people with light STH infections may be asymptomatic, while heavy infections can lead to various health issues, including abdominal pain, diarrhea, blood and protein loss, rectal prolapse, and growth retardation. Fortunately, the infections are treatable with medication prescribed by healthcare providers.
The specifics provided for each helminth—Ascaris, hookworm, and whipworm—further enrich the understanding of their prevalence and impact. Notably, hookworm infection was widespread in the southeastern United States until the early 20th century but has now been nearly eliminated.
In conclusion, my expertise in parasitology allows me to affirm the accuracy and importance of the information presented in the article. The inclusion of infection estimates, detailed life cycles, and the impact of these soil-transmitted helminths on human health contributes to a comprehensive overview of this critical public health issue.
