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Symptoms of Parasitic Infection

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Common symptoms of parasitic infection include fever, fatigue, digestive issues, skin rash, and weight loss.

Medically reviewed by

Dr. Shubadeep Debabrata Sinha

Published At May 26, 2023
Reviewed AtDecember 21, 2023


A parasitic infection is caused by a parasite, an organism that lives in or on another organism and depends on it for nourishment. In humans, parasites cause various illnesses raning from minor to life-threatening. Parasitic infections are prevalent globally with numbers over 3.5 billion people worldwide affected by them.

Parasites can be classified into two main types: protozoa and helminths. Both types of parasites can cause disease in humans.

  • Protozoa: Protozoa are single-celled organisms that can live in the body’s tissues or bloodstream.

  • Helminths: Helminths are worms, including roundworms and tapeworms, which are usually longer than protozoa.

What Causes Parasitic Infections?

Parasitic infections can be caused by three main types of parasites: protozoa, helminths, and ectoparasites.

  • Protozoa are single-celled organisms that cause a wide range of diseases including malaria, dysentery, and giardiasis.

  • Helminths are multi-celled organisms that can include worms like hookworm and roundworm.

  • Ectoparasites such as fleas and ticks, attach to the outside of the body and feed on blood.

Most parasitic infections are transmitted through contact with contaminated food or water, animal feces, or direct contact with an infected person or animal. Insects that carry parasites may also transmit them through bites. People with weakened immune systems due to HIV (human immunodeficiency virus) or AIDS (acquired immunodeficiency syndrome), organ transplantation, diabetes, cancer, and other conditions are more susceptible to parasitic infections.

What Are the Signs and Symptoms of Common Parasitic Infections In Humans?

Parasitic infections are caused by parasites, which can be microscopic organisms such as viruses, bacteria, fungi, or worms. These infections can range from mild to severe and affect a person's skin, digestive system, and other organs. Following are some common parasitic infections that include:

  1. Trichomoniasis: It is a sexually transmitted infection (STI) caused by a single-celled parasite known as Trichomonas vaginalis. This parasite is most often transmitted through sexual intercourse, although it can also be passed from mother to baby during childbirth. Symptoms of trichomoniasis include:

    1. Itching.

    2. Burning.

    3. Soreness in the genital area.

    4. Pain during urination and intercourse and an increased discharge that is often frothy, yellow-green, and foul-smelling.

  1. Giardiasis: It is an intestinal infection caused by the giardia parasite. This infection is commonly spread through contact with contaminated water, food, or feces. Symptoms of giardiasis include:

    1. Abdominal cramps.

    2. Bloating.

    3. Nausea.

    4. Fatigue.

    5. Diarrhea that is foul-smelling and sometimes bloody.

  1. Cryptosporidiosis: It is an infection caused by the parasite cryptosporidium. This parasite is often found in contaminated food or water, and can also be spread through contact with infected animals or people. Symptoms of cryptosporidiosis include:

    1. Diarrhea.

    2. Nausea.

    3. Vomiting.

    4. Abdominal cramps.

    5. Weight loss.

  1. Toxoplasmosis: It is an infection caused by the Toxoplasma gondii parasite. This parasite is most often spread through contact with cat feces or eating contaminated meat. Symptoms of toxoplasmosis include:

    1. Swollen lymph nodes.

    2. Fever.

    3. Muscle aches.

    4. Fatigue.

    5. Confusion.

In some cases, the infection can cause serious complications such as encephalitis or blindness.

Malaria: Malaria is caused by the plasmodium. It is mainly transferred by the Anopheles mosquito. Humans can easily get malaria as Anopheles mosquitoes bite them. As these mosquitoes bite they release plasmodium into the bloodstream and from there, it goes to the human liver. These plasmodia form merozoites and complete their life cycle in the human body. They caused malaria infection. symptoms associated with malaria are:

  1. Fever.
  2. Chills.
  3. Headache.
  4. Nausea and vomiting.
  5. Abdominal pain.
  6. Rapid heart rate.
  7. Rapid breathing.
  8. Cough.
  9. Malarial attack- Shivering and chills followed by high fever and sweating and later returning to normal temperature.

Trypanosomiasis: In Africa, some Trypanosomes can cause diseases like sleeping sickness in humans. the flies called tsetse bite humans and soon harm their immune systems. A similar disease called Chagas disease is seen in South America due to trypanosomes. Symptoms related to trypanosomiasis are:

  1. Severe headache.
  2. Irritability.
  3. Weight loss.
  4. Loss of concentration.
  5. Insomnia at night.
  6. Seizures,
  7. Slurred speech.
  8. Difficulty in talking and walking.
  9. Confusion.
  10. Personality change.

Leishmaniasis: Many Leishmania species cause many human infections. some of the common infections by leishmania are visceral leishmaniasis, cutaneous leishmaniasis, and mucocutaneous leishmaniasis. symptoms related to leishmaniasis are:

  1. Fever.
  2. Chills.
  3. Cold sweats.
  4. Swollen lymph nodes and spleen.
  5. Weight loss.
  6. Fatigue.
  7. Weakness.
  8. Dark patches over the skin.

Schistosomiasis: There is some schistosomiasis that can cause acute and chronic infections. usually, people get affected through their larva forms or eggs. These are helminthis. Symptoms related to schistosomiasis are:

  1. Blood in stools.
  2. Enlarged liver and spleen.
  3. Diarrhea.
  4. Abdominal pains.
  5. Blood in the urine.
  6. Kidney damage in severe cases.

Amebiasis: There is Entamoeba histolytica which causes amebiasis and a severe form of it is amebic dysentery. Symptoms associated with amebiasis are:

  1. Loose stool.
  2. Bloody stools.
  3. Stomach pains.
  4. Stomach cramps.
  5. Abscess invading the liver.
  6. Fever.

How Are Parasitic Infections Diagnosed?

A parasitic infection can be hard to diagnose as many of the symptoms can mimic other illnesses. To help make a diagnosis, the doctor will take a detailed medical history and perform a physical exam. Depending on the type of parasite that may be causing the infection, the doctor may also order several tests to confirm the diagnosis, including:

  • Blood Test: This is the most common test used to detect parasites. A blood sample is taken and then examined under a microscope to look for signs of parasites or their eggs.

  • Fecal Examination: This is done to look for parasites or their eggs in the stool. It involves taking a sample of stool and looking for evidence of parasites.

  • Endoscopy or Colonoscopy: In some cases, the doctor may order an endoscopy or colonoscopy to get a better view of the intestines. During these procedures, a thin tube with a camera attached is inserted into the intestine. This allows the doctor to look for signs of parasites.

  • X-ray: An X-ray can help the look for signs of parasites in the body. They can detect changes in the organs that could indicate a parasitic infection.

  • MRI: MRI (magnetic resonance imaging) scans use magnetic fields to create detailed images of the body. This allows the doctor to look for signs of parasitic infections, such as cysts or tumors.

  • CAT Scan: A CAT (computerized axial tomography) scan uses X-rays to produce cross-sectional images of the body. This can help the doctor identify any abnormal masses or cysts caused by parasites.

How Are Parasitic Infections Treated?

When it comes to treating parasitic infections, there are several options available. Depending on the type of infection, treatment may include medications such as antiparasitic, antifungal, antibiotics, or anthelmintics drugs. The doctor may also suggest lifestyle changes, including good hygiene practices, avoiding contact with others who may be infected, and using insect repellents when necessary.

The type of medication the doctor prescribes will depend on the specific parasite involved.

  1. Antiparasitic drugs kill the parasites.

  2. Antifungal drugs kill the fungi that may cause the infection.

  3. Antibiotics fight bacteria.

  4. Anthelmintics are used to treat worm infections.

The doctor may also prescribe lifestyle changes to reduce the risk of re-infection or spread of the parasite. These include proper hygiene practices, avoiding contact with anyone else who may have an infection, and using insect repellents when necessary.

In addition to the treatment prescribed by the doctor, a person can also take steps to reduce their risk of contracting a parasitic infection in the first place. This includes:

  1. Washing hands regularly and thoroughly.

  2. Cooking meat and fish thoroughly before eating them.

  3. Avoiding contact with soil or sand in areas where parasites may live.

  4. Wearing protective clothing in areas where insects can transmit parasites, and using insect repellent when necessary.

What Are the Complications Associated With Parasitic Infections?

Parasitic infections can cause various complications. People with weakened immune systems may be more vulnerable to severe symptoms and long-term complications from the infection. Common complications from a parasitic infection include:

  • Malnutrition: Parasites can prevent the body from absorbing nutrients, leading to weight loss and malnutrition.

  • Organ Damage: If a parasite infects a specific organ, such as the brain or liver, it can lead to permanent organ damage.

  • Dehydration: Symptoms of a parasitic infection such as diarrhea and vomiting, can cause dehydration. Severe dehydration can lead to further complications.

  • Anemia: Some parasites are known to cause anemia by destroying red blood cells. This can lead to fatigue, shortness of breath, and an increased risk of infection.

  • Infertility: Certain parasites may spread to the reproductive organs and cause infertility in both men and women.

  • Neurological Problems: Some parasites can invade the nervous system and cause neurological problems, such as seizures or memory problems.


Parasitic infections can cause a range of uncomfortable symptoms and if left untreated, can lead to serious health complications. If a person suspects of having a parasitic infection, it is important to see the doctor for proper diagnosis and treatment. Early diagnosis and treatment can help ensure a quick and successful recovery. Treatment will vary depending on the type of parasitic infection they have but may include a combination of medications and lifestyle changes.

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Dr. Shubadeep Debabrata Sinha
Dr. Shubadeep Debabrata Sinha

Infectious Diseases


parasitic infection
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