Parasites Symptoms and Causes


A parasitic infection is suspected if a patient has signs and symptoms of an infection and lives in or has visited an area known to have certain parasites. A diagnosis is confirmed after the parasite is identified in the body. Samples of blood, stool, urine, or phlegm may be analyzed for the presence of parasites.
A tissue biopsy may also be performed. During the procedure a small sample of tissue from the affected area, such as the lungs or intestines, may be taken. The sample is then analyzed for the presence of parasites.

signs and symptoms

General: Symptoms vary depending on the type and severity of the infection.
Ascariasis: Symptoms of ascariasis can range from mild to severe, depending on how many parasites are inside the patient's body. If only a few parasites are consumed, patients generally experience few, if any, symptoms.
When the larvae enter the lungs, patients may experience symptoms similar to pneumonia, such as persistent cough, shortness of breath, and wheezing.
When the larvae reach the intestines and develop into adults, mild or moderate symptoms may include abdominal pain, nausea, diarrhea, and sometimes bloody stools. Severe infections may cause abdominal pain, fatigue, vomiting, weight loss, worm in vomit or stools, or worm emerging from the nose or mouth.
Chiggers: After a chigger is fully fed, it will drop off the individual. Three to six hours after a bite, patients develop a red, itchy welt that has a white center. The welt may develop into dermatitis (dry, itchy, flaky skin). Some patients may also experience fever and swelling. Depending on the sensitivity of the patient, symptoms may last for weeks. Patients should not scratch the bite mark because it may break the skin and potentially lead to secondary infections.
Giardia infection (giardiasis): Giardiasis typically causes diarrhea, soft or greasy stools, nausea, fatigue, abdominal cramping and bloating, and weight loss.
Guinea worm disease: Symptoms of guinea worm disease develop after about one year, when adult guinea worm is ready to release its eggs. Symptoms develop a few days to hours before the adult worm emerges through the skin, to release its eggs. The patient may develop a fever and have pain and swelling in the area near the worm. A blister, which eventually forms an open wound, develops near the worm. When the wound is immersed in water, the tip of the worm begins to emerge from the skin to lay its eggs. Although these worms may be present in any area of the body, they are usually found on the legs or feet. After the worm emerges, it goes back inside the body, and the wound becomes painful and swollen.
Histoplasmosis: The most common form of histoplasmosis causes no symptoms. However, the parasite is present in the body for the rest of his/her life.
Patients who are symptomatic usually develop symptoms three to 17 days after exposure. Common symptoms include fever, headache, dry cough, chills, chest pain, weight loss, and sweats.
When a fungal infection enters the bloodstream and affects multiple body tissues and organs, the condition is often life threatening. Histoplasmosis may spread to virtually any part of the body, including the liver, bone marrow, eyes, skin, adrenal glands, and/or intestinal tract. When this happens, the condition is called disseminated histoplasmosis. Symptoms vary depending on which organs are infected.
Hookworm infection: Most patients with hookworm infections do not experience any symptoms. Some patients may develop an itchy skin rash where the worm entered the body. When the worm enters the lung, some patients may develop symptoms similar to asthma or pneumonia, such as persistent cough, wheezing, or difficulty breathing. When the worm enters the intestine, patients may experience abdominal pain, diarrhea, weight loss, decreased appetite, and excessive gas.
Leishmaniasis: Patients with leishmaniasis typically develop skin sores weeks to months after the parasite enters the body. The skin may become red, ulcerated, or have lesions, blisters, or pimples. Smaller lesions may be present around one larger ulcer.
Some patients may develop a stuffy or runny nose, nosebleeds, difficulty breathing, difficulty swallowing, as well as ulcers and sores in the mouth, tongue, gums, lips, nose, and the wall that separates the nostrils (called the nasal septum).
The parasite may also enter the bloodstream and burrow into internal organs. If internal organs are involved, symptoms may include persistent fever, night sweats, fatigue, weakness, appetite loss, weight loss, vomiting (most common in children), abdominal pain, scaly skin, gray or dark skin, and thinning hair.
Loiasis: Symptoms include irritated and watery itchy eyes, blurred vision, and eye discharge (called eye congestion). Patients may be able to see the thread-like worms move across their own eyeballs.
Lymphatic filariasis: Symptoms of lymphatic filariasis generally develop 5-18 months after being bitten by an infected mosquito. Lymphatic filariasis causes tissue damage that limits the normal flow of lymph fluid through the body. As a result, patients typically experience swelling, scarring, and infections, especially of the legs and groin.
Malaria: Symptoms of malaria include cycles of chills, fever, and sweating. These symptoms occur in cycles every one, two, or three days if the infection is not treated. Some individuals may also experience diarrhea, jaundice (yellowing of the skin and eyes), coughing, nausea, and vomiting.
Ringworm: Athlete's foot (tinea pedis) may cause burning or itching anywhere on the feet. Symptoms are usually most noticeable in between the toes. Patients may also develop itchy blisters, cracked or peeling skin, dry skin, or toenails that are thick, crumbly, discolored, or pulling away from the nail bed.
Jock itch (tinea cruris) typically causes the skin near the genitals, buttocks, and inner thighs to become red and itchy. The skin may also start to peel or crack.
Patients with ringworm of the scalp (tinea capitis) typically develop a circle-shaped rash on the skin that is swollen. The skin may be scaly and itchy. There may be small black dots on the scalp. Patients may lose small patches of hair. However, the hair will grow back once treatment is started.
Ringworm of the skin (tinea corporis) causes a circular red rash to form on the skin. This rash typically develops in patches and may be raised. The skin may be also be scaly and flakey.
River blindness (onchocerciasis): Symptoms usually develop one to three years after the larvae enter the body. Patients may develop an itchy skin rash, skin lesions, loss of skin pigmentation (which causes the skin to become white), enlarged lymph nodes, visual impairment, and sometimes blindness.
Scabies: Scabies causes pimple-like irritations, burrows, or a rash to develop on the skin. The skin on the wrists, elbows, knees, genitals (in men), breasts (in females), shoulder blades, and between the fingers is most likely to be affected. The affected skin is extremely itchy, especially at night. Individuals may also develop sores and small cuts from scratching the skin.
Tapeworm infection: Tapeworm infections do not always cause symptoms. The most common symptoms include weakness, nausea, decreased appetite, diarrhea, weight loss, and abdominal pain. Some patients may be able to see small white tapeworm eggs in their stools.
Threadworm infection: The signs and symptoms of threadworm infection vary, depending on the stage of the disease.
After the larvae enter the body through the skin, the area may be swollen and itchy, similar to a bug bite. Patients with long-term threadworm infections may develop an itchy skin rash near the buttocks, abdomen, and/or thighs.
Some patients may only have mild diarrhea and cramping, while others may have nausea, vomiting, fever, fatigue, and blood or mucus in the stools.
When the larvae move to the lungs and airways, the patient may develop a dry cough, fever, or difficulty breathing and may cough up blood or pus.
Trichinosis: Symptoms of trichinosis range from mild to severe, depending on the number of parasites in the body. Patients with a very mild form may experience no symptoms at all. When the parasite is in the intestine, common symptoms include diarrhea, abdominal pain, and general feeling of discomfort.
About one week after the parasite enters the body, the females produce larvae that penetrate body tissues, including muscles. Symptoms at this stage may include high fever, muscle pain and tenderness, weakness, swelling of the eyelids or face, sensitivity to light, headache, and pinkeye (called conjunctivitis).
Whipworm infection: Symptoms range from mild to severe. Common symptoms include abdominal pain and diarrhea. A severe infection may cause bloody diarrhea, iron-deficiency anemia and, sometimes, rectal prolapse, which occurs when the rectum slips down outside the anus.


Chiggers: If patients scratch chigger bites, the skin may break. This increases the risk of developing secondary infections.
Giardia infection (giardiasis): Giardiasis typically causes diarrhea, which causes the body to lose water and salts. As a result, patients may become dehydrated.
Patients with giardiasis may become lactose intolerant. Individuals may continue to be lactose intolerant for several weeks after the infection is treated.
Guinea worm disease: Guinea worm disease often causes severe pain that may be crippling.
Histoplasmosis: Disseminated histoplasmosis may lead to severe and fatal complications, including pneumonia, pericarditis, meningitis, and/or adrenal insufficiency.
Hookworm infection: Long-term hookworm infections may cause the patient to become anemic because the worms feed on the patient's blood. Symptoms of anemia may include difficulty breathing, pale complexion, fatigue, weakness, fast heartbeat, generalized swelling, or bloating. Once the parasite is killed, symptoms of anemia will resolve.
Leishmaniasis: Patients with leishmaniasis may develop allergic reactions when the larvae enter the muscle tissue. This typically happens when the dead or dying larvae release chemicals into the tissues. The body's immune system overreacts to these chemicals, and allergic symptoms, such as hives and itchy eyes, develop.
Loaisis: If left untreated, the Loa loa worm may sometimes enter the brain, causing brain swelling (called encephalitis) and possibly brain damage.
River blindness (onchocerciasis): If left untreated, river blindness may cause permanent blindness.
Scabies: Individuals with scabies often develop sores and small cuts from scratching affected areas of skin. If bacteria enter the skin through these sores or cuts, an infection may develop.
Tapeworm infection: Tapeworm infections may lead to malnutrition. The parasites absorb many of the nutrients from the food its host eats before the patient is able to do so. As a result, the patient may not get the necessary vitamins and minerals to stay healthy. This may also lead to weight loss. Once the parasite is killed, the patient will be able to absorb nutrients and will gain back lost weight.
Threadworm infection: If the larvae spread to other organs in the body, the condition is called hyperinfection syndrome. Symptoms of this condition may include inflammation of the heart tissue, stomach ulcers, perforations of the intestines, blood poisoning, meningitis (which often causes fever, headache, vomiting, nausea, confusion, and fatigue), sudden and life-threatening drop in blood flow throughout the body (called shock), and possible death.