As unsavory as it sounds, parasites are relatively common in the United States and other developed and developing countries. These microscopic moochers don’t usually cause serious problems, but they can make some people seriously ill. The best way to reduce the risk of a parasitic infection is to always properly clean food, practice good hygiene, and avoid walking outside barefoot or swimming in unclean bodies of water.

Tapeworm

Humans can become infected with intestinal tapeworms by ingesting eggs or larvae in foods and beverages. Tapeworms hide out in raw or undercooked meats of animals whose muscles hosted the larvae before slaughter. Prevent these parasites by always washing up well before cooking and eating and avoiding undercooked or potentially contaminated products.

Cyclospora cayetanensis

Cyclospora is a microscopic parasite that is spread through contact with an infected person’s stool or a contaminated item. Since this parasite takes a week or two to become infectious in stool, it is more likely that someone will pick up this parasite via contaminated produce. It can cause digestive problems such as diarrhea and vomiting as well as lethargy and flu-like symptoms. A Cyclospora cayetanensis infection is easily treated with antibiotics.

Giardia

Giardia is another microscopic parasite that spreads through infected feces, but in this case, contaminated water is the most common source of human illness. This parasite can live outside of the body for weeks and has a shell that protects it against the corrosive effects of chlorine, so it can also survive in chlorinated bodies of water. To prevent a giardia infection, avoid drinking pond or pool water.

Crypto

This parasite causes a diarrheal illness by the same name when ingested, usually from infected water. Like giardia, crypto has a protective shell that gives it a measure of longevity outside of the body. It usually doesn’t cause serious illness in people with healthy immune systems, although it is one of the leading water-borne contaminants in the United States. In immunocompromised people, however, crypto can cause more severe problems. Most people recover on their own the with help of fluids.

Whipworm

Whipworms live in soil containing human feces infected with the eggs or larvae of the parasite. Most people with a light load will experience no symptoms, but a heavier load can cause digestive problems and growth issues in children. It is most common in tropical climates but is also present in the southern U.S. The use of wastewater as fertilizer is one cause of this parasite’s prevalence; statistics suggest it sickens 604 to 795 million people around the world.

Pinworm

Pinworms are the most common intestinal worm infection in the United States and are primarily found in children. Pinworms are easily spread from child to child because they touch multiple surfaces, each other, and their faces often. Anal itching is the most common symptom, but some people may not have any signs of the infection. It can easily be treated with antibiotics and by washing all clothing and bedding in the household.

Hookworm

Hookworms are often grouped with whipworms and other parasites in the category of soil-transmitted helminths, or STHs. Since the larvae can penetrate the skin, one of the primary ways to pick up hookworms is by walking barefoot in areas where people defecate in the soil or where the soil may be contaminated in other ways. Wearing shoes outdoors is a good way to prevent hookworm infections, as is practicing good hygiene.

Entamoeba histolytica

Another one of the most common parasites in developing and underdeveloped countries is entamoeba histolytica. It causes amoebiasis. Although many people with this disease are asymptomatic, some experience digestive problems. Poor sanitation allows this parasite to spread easily, but scientists have undertaken efforts to develop a vaccine and make treatments more available. Hand washing is considered the best way to prevent the spread of entamoeba histolytica.

Trichinosis Roundworms

Trichinosis roundworms are found in raw or uncooked meat and infect people around the world, especially in rural areas. There are usually no complications and most people aren’t even aware they’re infected with these roundworms. Treatment isn’t usually necessary unless a person has a heavy load. Cooking meat thoroughly will help kill trichinosis roundworms, and freezing pork for at least three weeks will kill any larvae or eggs that may have lived in the animal.

Toxoplasma gondii

Excreted by cats in their feces, toxoplasma gondii is a parasite that is typically identified in both animals and humans. The most common way to come into contact with this parasite is by touching cat feces and then somehow ingesting it, although cooking utensils and foods can also be contaminated. Lamb, pork, and venison are other usual carriers of Toxoplasma gondii. In rare cases, this parasite is transmitted through a contaminated blood transfusion.