How Do Parasites Get Into the Human Stomach?

Intestinal parasites get into your stomach when you ingest contaminated food or water, or when the larvae penetrate your skin, usually your bare feet.

Worms

• Tapeworms, roundworms and pinworms are common intestinal worms that lay eggs inside a host, which are passed in the stool. They develop into cysts or larvae that are ingested by another host. This is called fecal-oral transmission.

Common Sources

• You may become infected if your hands come in contact with stool contaminated with cysts or larvae, or if you eat unwashed raw vegetables, undercooked pork, freshwater fish or wild meat.

Other Sources

• Larval worms can also penetrate your skin when you are swimming or walking barefoot. Intestinal worms are very common in areas with poor hygiene and contaminated water sources, recreational water areas and child-care centers.

Protozoa and Amoeba

• Giardia and cryptosporidium are intestinal protozoa that are single-celled. Entamoeba histolytica is an amoeba that can infect humans. These organisms also enter a host via contaminated water or food. Infections are more common in the tropics.

Sources

• Like intestinal worms, protozoa and amoeba can more readily enter a new host when sanitation is poor, and when there is close contact with other humans or animal hosts. Pigs and fish are common hosts.