Ascaris lumbricoides (roundworm), Ancylostoma duodenale (hookworm), Necator americanus (hookworm), and Trichuris trichiura (whipworm) are helminths (parasitic worms) that infect the intestine and are transmitted via contaminated soil.
Infection with roundworm and whipworm occurs when eggs in soil have become infective and are ingested. Hookworm infection usually occurs when larvae, hatched from eggs in the soil, penetrate the skin (for example, when people walk barefoot on contaminated soil) but can also occur when larvae are ingested.
Widespread, but the prevalence is highest in tropical, developing countries. Travelers to these countries should be at low risk of infection if prevention measures are taken.
Most infections are asymptomatic, especially when few worms are present. Pulmonary symptoms occur in a small percentage of patients when roundworm larvae pass through the lungs. Roundworm can also cause intestinal discomfort, obstruction, and impaired nutritional status. Hookworm infection can lead to anemia and protein deficiency due to blood loss. Whipworm infection can cause blood loss, as well as dysentery and rectal prolapse. However, travelers are rarely at risk for these more severe manifestations because they are generally associated with high worm burdens seen in indigenous populations.
By identifying eggs in a stool specimen. Adult roundworms may occasionally be coughed up or found in stool or vomit.
Albendazole or mebendazole.
Food and water precautions (see Chapter 2, Food & Water Precautions) and by avoiding walking barefoot on soil that may be contaminated with sewage, where human feces may have been used as fertilizer, or where people may have defecated.