What Types of Parasites Can Humans Contract?

Human beings are infected by two different types of parasitic organisms. Protozoans, which are single-celled organisms, cause a number of different diseases -- while helminths or parasitic worms live in the intestines or other organs. The symptoms of infection and the method of treatment vary depending on the type of organism, according to Des Moines Area Community College.

Giardia

• Giardia intestinalis is also known as giardia lamblia and giardia duodenalis. Giardia parasites live in the intestines of infected people or animals. The parasite exists in every region of the United States and around the world. It is found in food, water or soil that has been contaminated with infected fecal remains. According to the Centers for Disease Control and Prevention, Giardia spreads through contaminated drinking water or by swallowing infected recreational water. It also spreads through uncooked food tainted with Giardia, among other methods. People with Giardia experience stomach upset, diarrhea, gas and greasy stools. The symptoms usually persist between two and six weeks.

Amebiasis

• The Entamoeba histolytica parasite causes amebiasis. The disease can affect anyone, according to the CDC, but it is most common in tropical countries with poor sanitation. You can become infected by accidentally ingesting contaminated food or liquid or by placing infected objects in their mouths. The symptoms are usually fairly mild and involve stomach cramps and loose bowels, but sometimes a more serious form of the disease called amebic dysentery develops. If you have amebic dysentery you can suffer from bloody bowel movements, fever and stomach pain. Rarely, the parasite may also colonize the lungs, brain or liver.

Roundworm

• Roundworms are helminths, or parasitic worms that live in the intestine. They infect people who live in warm and tropical climates. Ascariasis is the most common type of roundworm infection, according to the University of Maryland Medical Center, this disease affects approximately 1 billion people. People become infected with ascariasis by eating or drinking contaminated food. The symptoms include the presence of worms in the stool or in vomit -- as well as nausea, diarrhea, weight loss and fatigue. Hookworms are another common type of roundworm infection. Hookworm larvae penetrate the soles of bare feet and work their way through the lungs and into the small intestine. If you are infected with hookworms you may be asymptomatic and show no symptoms at all -- others experience abdominal pain, loss of appetite, rash, wheezing, cough and breathing difficulties.

Tapeworm

• Humans are susceptible to several different types of parasitic tapeworms. The Mayo Clinic indicates that the pork tapeworm or Taenia solium is the most dangerous. The adult worm, which grows to be around 20 feet long, produces eggs that hatch into larvae. The larvae form cysts in the liver, brain or muscle tissue. According to Parasitesinhumans.org, the cysts age and their shell structures deteriorate -- this creates an inflammatory bodily response that involves dizziness, headaches, seizures, organ failure and even sudden death. People become infected with pork tapeworm by eating undercooked meat, through poor hygiene and by exposure to livestock.