Parasites Found in Drinking Water

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Parasites and Diseases

A parasite is an organism that lives on, or inside of, another organism, and it relies on its host for food and survival. Parasites that cause human disease are grouped into three main classes— protozoa, helminths and ectoparasites. Common worldwide diseases contracted from parasite-infected drinking water include amebiasis, cryptosporidiosis, or Crypto, giardiasis, Guinea worm and schistosomiasis, according to the Centers for Disease Control and Prevention, or CDC1. Most parasites found in drinking water are either protozoa, which are one-celled microscopic organisms, or helminths, which are multicellular organisms—worms, according to the CDC1. Once ingested, these parasites can cause illness and even death, in some cases. Avoiding contaminated drinking water is the only way to keep from contracting the diseases associated with parasitic infection.


Protozoa-classified cryptosporidium parasites can cause cryptosporidiosis, which is a gastrointestinal disease. Once the parasites enter the body, they burrow into the walls of the intestines and cause diarrhea and other symptoms, according to the Mayo Clinic4. With treatment, this disease usually takes one to two weeks to subside. A cryptosporidium infection can be life-threatening for those with a weakened immune system, says the Mayo Clinic4

Dracunculus Medinensis

Dracunculus medinensis parasites are classified as helminth nematodes and are also known as a type of roundworm, according to the CDC1. These parasites can lead to Guinea worm disease, or dracunculosis. When people swallow these parasites found in drinking water, larvae move from the intestines to the skin, where they cause sores. Treatment is required before worms can be removed from the skin. It just takes one infected person swimming with an open wound to contaminate water, according to the CDC1. It can take up to a year for symptoms to go away.

Entamoeba Histolytica

In the protozoa class of parasites, Entamoeba histolytica, or E. histolytica, can cause amebiasis, or amebic dysentery, according to the CDC1. These ameba parasites are usually ingested via drinking water contaminated with fecal matter. The fecal matter originally contains the ameba.

Giardia Intestinalis

It can take up to six weeks to recover from giardiasis, which is caused by a giardia parasite infection. Giardia is a protozoa class microscopic parasite that is often drug-resistant, according to the Mayo Clinic5. The intestinal infection caused by giardia bugs produce symptoms, such as cramps, bloating, nausea and episodes of watery diarrhea. The parasites are common in America, adds the Mayo Clinic5.


Schistosoma parasites are helminth-classified trematodes, or flukes, and are also a type of flatworm that can cause the disease schistosomiasis. People are usually infected with the disease when they swim in, or have some other contact with, contaminated fresh water, such as lakes, according to the CDC1. If you’re traveling abroad, keep in mind that drinking water often comes from these sources.

Contaminated Water

Contaminated drinking water is something you might have to contend with, if you travel abroad, especially if you tour or do business in developing countries. Drinking boiled or bottled water can help avoid most parasites found in drinking water—but not always. Talk with your health care provider and other experts about specific precautions you can take to avoid parasites and germs while traveling to locations with known contaminated drinking water. Keep in mind that some parasites, such as Giardia, are also found in some drinking water in America.


1. Centers for Disease Control and Prevention. “Parasites,”

2. Centers for Disease Control and Prevention. “Water,”

3. Mayo Clinic. “Infectious Diseases,”

4. Mayo Clinic. “Cryptosporidium Infection,”

5. Mayo Clinic. “Giardia Infection – Giardiasis,”

6, University of Maryland. “Roundworms,”

7. Murphy, Charlotte. “Schistosomiasis,”


Praziquantel – Oral Route.

Centers for Disease Control and Prevention: Alphabetical Index of Parasitic Diseases.

UCLA: Classification of Human Parasites.