Where Can Parasites Survive in the Human Body?

Many parts of the human body provide habitats for other organisms. Parasites of humans include single-celled creatures, many kinds of worms, and some insects. In the US, these parasites are not a major issue, but they cause serious problems in developing countries with poor sanitation.

Intestines

• Single-celled parasites such as Giardia can live in the human intestine and cause diarrhea. Some kinds of worms, such as hookworms and tapeworms, also inhabit the intestines.

Bloodstream

• Some parasites live in the bloodstream, including the organisms that cause malaria. According to the Center for Disease Control, over one million people die of malaria each year. Several species from the genus Plasmodium can infect humans and cause different types of malaria.

Liver

• The liver fluke is a flatworm that infects the liver. A liver fluke can survive inside a human for as long as 40 years.

Skin and Hair

• Parasites such as lice and mites live on the surface of skin or cling to the hair. One type of lice lives on the head, and another type (commonly known as "crabs") lives in pubic hair.

Nervous System

• Toxoplasma gondii is a single-celled parasite that infects the nervous system. Humans can catch it from contact with cat litter.

Body Cavity

• The guinea worm grows within the body cavity for about a year before emerging from its host. No symptoms of infection occur until the worm begins to burrow out through the skin. This process is very painful, and the worms are typically 2 to 3 feet long.