Parasitic infection or infestation can occur in children of all ages. Infants, toddlers, and very young children in day care settings are at risk for the parasitic disease called giardiasis that causes diarrhea and is spread through contaminated feces. Pinworm infection (enterobiasis) also occurs among preschool and young school-age children. Both preschool and school-age children can become infested with head lice (pediculosis) or scabies, both of which are spread by close person-to-person contact as is common during childhood play.
Children of all ages can develop parasitic diseases such as giardiasis and cryptosporidiosis from swallowing contaminated water during swimming, playing, and other activities in contaminated recreational water (e.g. pools, fountains, lakes, rivers and streams, etc.). Pets and other animals can be a potential source of parasites that can affect children. Toxoplasmosis is spread by ingesting soil or litter-box contents with infectious cat feces. Children can also be born with this infection if their mother was infected during pregnancy.
Several parasitic diseases occur occasionally in the United States and more frequently in developing countries, but their prevalence has not been well studied. They include strongyloidiasis, caused by a worm infection that is of particular danger for children with an impaired immune system. It is acquired when larvae (immature worms) in soil contaminated with infected human feces come into contact with and penetrate the skin. They also include visceral toxocariasis, spread when children ingest soil contaminated with dog or cat feces containing the eggs of cat or dog roundworms, and cutaneous larva migrans, transmitted when children walk barefoot on soil contaminated with cat or dog hookworm larvae that penetrate their skin.
Other parasitic diseases are rare among children in the United States, but are widespread and account for a major disease burden among children in developing countries. The most important of these is malaria. Children in malaria-endemic countries are at high risk of the ill effects of malaria infection. The majority of the world's malaria deaths are in African children under 5 years of age.
Children in the United States are also at high risk for malaria infection when traveling to a malaria-endemic country. Children should be sure to take antimalarial drugs before, during, and after the trip, use repellant, sleep under an insecticide-treated bed net or in an air-conditioned room, and wear protective clothing.
Soil-transmitted helminth (STH) diseases ("helminth" means parasitic worm) are of major importance in developing countries. They are caused by infection with roundworm, hookworm or whipworm, and can include diarrhea, abdominal pain, intestinal obstruction, anemia, and retarded growth and cognitive development. Children become infected by ingesting roundworm and whipworm eggs that have matured in soil contaminated by human feces, or by walking barefoot in contaminated soil where human hookworm eggs have hatched, producing larvae that penetrate the skin. Schistosomiasis, another major parasitic disease among children in some developing countries, can also cause impaired growth and development and can lead to severe health problems later in life. It is caused by a helminth that spends part of its life cycle in certain types of snail and penetrates the skin of people when they stand or swim in water where the snails live. The helminth causing onchocerciasis ("river blindness") is transmitted by the bite of a type of blackfly that breeds near flowing water. It can cause itching and impaired vision in children, and lead to blindness in adulthood. Children are infected with the helminth causing lymphatic filariasis though mosquito bites. Damage to the lymphatic system in children is mostly asymptomatic, but can become symptomatic by puberty and lead to swollen arms and legs and an enlarged, fluid-filled scrotum in adulthood.
The above diseases (STHs, onchocerciasis, schistosomiasis, and lymphatic filariasis) are considered Neglected Tropical Diseases (NTDs) because they disproportionately affect impoverished people.
More on: Neglected Tropical Diseases
One of the most important ways to help prevent these parasitic diseases is to teach children the importance of washing hands correctly with soap and running warm water, particularly after using the toilet and before eating. In many developing countries, it is also important to ensure feces are disposed of properly, to avoid walking barefoot outdoors, to sleep under an insecticide-treated bednet, and to avoid exposure to water that may be infected with the parasite that causes schistosomiasis. Periodic mass drug administrations for soil-transmitted helminth infections, schistosomiasis, onchocerciasis, and lymphatic filariasis can also greatly reduce these infection and the diseases they cause and can even lead to elimination of onchocerciasis and lymphatic filariasis. In mass drug administrations, all members of selected age groups at risk are treated.