Transmission: Soil Transmitted Helminths (STH) is a  term that encompasses parasitic worms such as Roundworms (Ascaris Lumbricoides) Whipworms (Trichuris trichiura) and Hookworms (Necator Americanus or Ancylostoma Duodenale). Each female species produces thousands of eggs in a day. The three species of worms are grouped together due incidence of children in underdeveloped countries having chronic infections of the three worms simultaneously. The worms are found within the environment and have multiple modes of transmission via from animal products or from the natural environment. 

Adult Hookworms:  affect the upper part of the human small intestine

Ascaris Roundworms: affect the entire small intestine

Adult Trichuris Whipworms: affect the large intestine (caceum)
Symptoms: An infection may result in a painful abdomen, diarrhea, blood and protein loss. More severe infections may include rectal prolapse, physical and cognitive growth retardation. 

Hosts: Depending on how matured the worm is, multiple species may act as hosts. STH develop within the soil, dogs, cats, humans and domestic livestock. 

Risk Factors: Climate is an important determinant of  larval survival especially due to hydration needs. Poverty and lack of access to clean water and sanitation systems increases the risk of infection. Walking barefoot on infected soil, along with eating or consuming the eggs of the worms. 

Treatment: Anthelmintic drugs exists, however over time resistance against the drugs have been reported. 

Prevention: Practice safe and hygienic food handling along with thorough hand washing. Have adequate water and sanitation systems to avoid infection. Also, be aware of the incidence within your area so preventative measures can be taken.