The symptoms of parasitic infections vary widely, depending on the type of parasitic organism and the underlying health of the person. The most common parasites infect the intestinal tract, but some parasites infect the brain, eye, skin or sexual organs. Symptoms range from merely annoying to life threatening, and all parasitic infections should be treated by a doctor as soon as possible.
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Giardia duodenalis is one of the most frequent causes of disease contracted from water. This single-celled organism can colonize the intestines of people and animals, causing a range of symptoms, including diarrhea, gas, abdominal pain and nausea. If left untreated, a chronic infection may result in severe weight loss and dehydration.
Another leading cause of disease contracted from water and food is Cryptosporidium parvum. This one-celled parasite commonly infects intestines of herd animals, such as cows and sheep, but can also infect humans. Symptoms include watery diarrhea, nausea, stomach cramps and a slight fever, although some cases of infection do not cause symptoms.
Toxoplasma gondii is the third-leading cause of death resulting from disease contracted from food. When this single-celled parasite infects healthy adults, it often causes no symptoms. In some cases, flu-like symptoms, including muscle aches, fatigue, fever, swollen lymph nodes and difficulty breathing occur. People with compromised immune systems may develop severe swelling of the brain, causing damage to the eyes or brain.
Trichinella spiralis is a multicellular roundworm that infects the intestinal tract. Initial symptoms of infection include diarrhea, nausea, vomiting, fever and abdominal pain. Left untreated, the additional symptoms of headache, aching muscles and joints, itchy skin, eye swelling and weakness develop. Severe infections may progress to breathing and heart difficulties, problems in muscle coordination and death.
Chagas disease is the common name for the illness caused by the parasite Trypanosoma cruzi. Symptoms occur in three stages. In the acute stage, swollen eye, fever, swollen lymph glands, fatigue and enlarged liver or spleen may occur. However, only 1 percent of cases show acute symptoms. In the indeterminate state, occurring eight to 10 weeks after infection, no symptoms occur. Ten to 40 years after infection, the chronic stage may develop, leading to severe cardiac problems and enlargement of the throat or intestines.
Taenia solium is a parasitic worm that can infect the brain, causing neurocysticercosis. Infection may cause no symptoms or may cause nausea, headaches or seizures. Severe chronic infection may cause life-threatening symptoms such as increased pressure on the brain.
Trichomoniasis is a sexually transmitted disease caused by the parasite trichomonas vaginalis. Infected women may have no symptoms or may have vaginal itching or redness, foul smelling or frothy green discharge from the vagina, painful sexual intercourse, abdominal discomfort or the urge to urinate. Infected men usually do not exhibit symptoms but may occasionally experience the urge to urinate, discharge from the urethra and a burning sensation with urination.