Stomach parasites, which are often called intestinal parasites, are organisms that live in the digestive tract of humans, feeding off human tissue. Most of the human stomach parasites are either single celled organisms called protozoa or multi-cellular worms known as helminths, explains the United States Department of Agriculture. These organisms often reproduce inside humans or other animals, and their offspring are commonly passed out of the body through feces. The offspring infect other humans when the feces contaminates food or drinking water. Many of the human stomach parasites cause similar symptoms.
Upset Stomach
A frequent symptom of human stomach parasites is an upset stomach and nausea, which may be accompanied by vomiting, reports the University of Maryland Medical Center. In addition, a stomach parasite will often cause pain and cramping, either in the area of the stomach or lower in the abdomen. Alternatively, tenderness around the stomach or abdomen may also result. Excess gas may also develop, leading to bloating and flatulence.
Diarrhea
Diarrhea is another symptom frequently caused by stomach parasites. Some parasites, particularly the protozoa Giardia, may cause the stools to become very greasy, the U.S. Centers for Disease Control and Prevention explains. In other cases, the stools may contain blood or mucus, which is sometimes referred to as dysentery. Alternatively, certain hookworms such as Strongyloides stercoralis may cause the opposite symptom of constipation. The combined effects of nausea and diarrhea may result in an infected person unintentionally losing weight. Some parasites, such as the pinworm Enterobius vermicularis, may cause an intense itching sensation or rash around the area of the rectum, or around the area of the vulva in women.
Fatigue
A person infected with a stomach parasite often feels unexplained tiredness or fatigue. Infected individuals may also experience muscle weakness. Some parasites, such as the roundworm Trichinella spiralis, also tend to cause aching muscles and joints, reports the website GI Tract.info.
Aditional Symptoms
Certain stomach parasites, including the hookworm Necator americanus, tend to also cause anemia in infected people, GI Tract.info explains. Hookworms may also cause irritation of the skin at the site where they penetrated the skin and entered the blood stream. Some roundworm parasites, for example Ascaris, may cause the intestines to become completely blocked in cases of severe infestation. Several species of parasitic worm may reproduce inside the digestive tract, which may result in an infected person passing a worm in the stool.
