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Parasites: Types, Symptoms, Tests, and Treatment

How much do you know about parasites? The average person doesn’t know a whole lot about these critters. But if you have a complex chronic illness, you need to learn about these pathogens. 

Most U.S. physicians aren’t aware of how widespread parasitic infections are. They might even tell you that your idea of being infected with parasites is “all in your head.” (1, 2)

Dont let a well-meaning but poorly-informed doctor lead you astray. You arent suffering from a parasitic delusion disorder.” Quite possibly, parasites are contributing to your health problems. 

Parasites are much more common in developed countries than most people realize. For example, it’s estimated that more than 12% of Americans carry Toxoplasma gondii. That’s a microscopic parasite you might get from your cat. (2)

Ignoring parasites won’t make them go away. And the increasingly toxic environment — including from pollution — could worsen the parasite problem. Toxins can weaken your body’s defenses and alter parasite activity. (3)

Parasites can trigger a wide range of health issues. In some cases, they may be the real culprit behind chronic issues like irritable bowel syndrome and some autoimmune diseases. (4, 5)

Consider this your primer on all things parasites. Find out exactly what they are, different types, and common symptoms. Plus, learn how they’re diagnosed and how to get rid of them naturally.

What Is a Parasite?

Parasites are pathogens that live on or inside other organisms. Their livelihood is generally at the expense of their host and can cause harm. They depend on their host for nourishment. (6)

These critters can range in size. Some are microscopic, such as Toxoplasma gondii and Giardia. Other parasites can easily be seen by the naked eye. An adult tapeworm, for example, can reach a length of more than 49 feet (15 meters). (7)

Some microscopic parasites live inside your cells, such as red blood cells or fat cells. Larger critters — like parasitic worms — are more likely to live in the spaces between your cells. Parasites can invade your muscles, lymph, brain, gut, lungs, liver, and other organs and tissues. (8, 9, 10)

Also, parasites can obstruct parts of your organs and disrupt their function. For example, some worms can block the valves between your intestines or clog your bile ducts. No wonder they commonly mess up your digestive system, as you’ll see in the next section. (11, 12, 13)

How do parasites get away with all this?

The critters use various tactics to evade and manipulate your immune system. For example, single-celled parasites can change the proteins on their surface, so your immune cells don’t recognize them. (13, 14, 15)

And some parasites alter their form — such as changing into a protective cyst — to evade your immune system. (16, 17, 18)

You need to be smarter than the parasites if you want to kick them out and reclaim your health. Gaining the upper hand starts with knowing the symptoms of parasitic infections. 

What Are the Symptoms of Having a Parasite?

What Are the Symptoms of Having a Parasite?

The symptoms of parasitic infections vary with specific critters. But many symptoms are vague and can happen for several reasons. So, they may be incorrectly attributed to other diseases.

For example, many parasites infect your gut, leading to a range of digestive symptoms. But you may be misdiagnosed as having irritable bowel syndrome or inflammatory bowel disease. In reality, parasites could be at the root of your gut distress. (19)

So, keep an open mind about your symptoms. Consider, could they be due to parasites that conventional doctors have overlooked?

Some of the signs and symptoms linked with parasite infections are: (5, 10, 20, 21, 22, 23)

  • Abdominal pain or discomfort
  • Air hunger 
  • Allergies 
  • Anemia 
  • Anxiety
  • Arthritis
  • Autoimmune disease
  • Bed-wetting (kids)
  • Bladder inflammation
  • Bloating
  • Chronic fatigue
  • Constipation 
  • Diarrhea
  • Eye inflammation 
  • Fever
  • Flu-like symptoms
  • Food sensitivities
  • Gallbladder and bile duct disease
  • Gassiness
  • Hashimoto’s thyroiditis 
  • Headaches
  • Insomnia
  • Itching around your anus
  • Leaky gut
  • Low blood sugar
  • Muscle and joint pain 
  • Nausea 
  • Nutritional deficiencies 
  • Seizures
  • Skin rashes and sores
  • Teeth grinding 
  • Vomiting
  • Weak immunity
  • Weight loss

Parasites tend to be more active at night. That can cause a spike in some symptoms when you’re trying to sleep. Still, symptoms may strike at any time of day, and some are ongoing. (24

Also, realize that symptoms of parasite infections aren’t necessarily immediate. Some new infections may cause digestive upset within a day. But others may not produce noticeable symptoms for longer periods, like a few weeks. Some parasitic infections drag on for years. (25)

In addition, keep in mind that parasites are like a Trojan horse. They may harbor other pathogens, such as the Lyme bacteria, viruses, and mold spores. Those can contribute to your symptoms as well. That can make getting to the root of the problem tricky. (26, 27, 28, 29)

What Are the Different Types of Parasites?

What Are the Different Types of Parasites?

Parasites that infect people fall into one of three broad categories: protozoa, helminths, and ectoparasites. 

It’s helpful to understand each type when you embark on a parasite cleanse. That way, you know what you might see coming out in your stools. You can see some parasites with the naked eye. But many others are microscopic, like the protozoan Giardia, shown greatly magnified above.

Also, it’s good to be familiar with the scientific names of common parasites. That’s useful if you do any testing or want to look up the symptoms of specific critters. You’ll find many examples below. 

As you look at parasite names, you’ll see words like Giardia lamblia. The genus (Giardia) is the first word in the parasite name. The second word (lamblia) is the species. 

Sometimes people refer to parasites by only part of their scientific name. And sometimes the genus is abbreviated with the first initial, such as T. gondii. That’s the same thing as Toxoplasma gondii.

Don’t worry. There won’t be a quiz at the end of this blog. But it could be a helpful reference for you in the future. Bookmark it.

Protozoan parasites

You’d need a microscope to see these single-celled parasites. But don’t dismiss protozoan parasites due to their small size. They can wreak havoc in your body and create serious health issues. (6

Examples of protozoan parasites that infect people and some symptoms are: (9, 22, 25)

  • Babesia microti: Is a Lyme coinfection that can cause flu-like symptoms and anemia
  • Blastocystis hominis: Is one cause of leaky gut, which can lead to food sensitivities 
  • Cyclospora cayetanensis: Can result in explosive bowel movements and diarrhea
  • Cryptosporidium parvum: Causes watery diarrhea and other digestive upset 
  • Dientamoeba fragilis: Causes diarrhea, abdominal pain, and appetite loss
  • Entamoeba histolytica: Triggers stomach pain and loose stools, which may be bloody
  • Giardia lamblia: Causes diarrhea, greasy stools that float, and upset stomach 
  • Leishmania tropica: Leads to skin sores, which may start as bumps 
  • Plasmodium falciparum: Causes malaria, characterized by flu-like symptoms 
  • Toxoplasma gondii: Sparks mild flu-like symptoms and enlarged lymph nodes
  • Trichomonas vaginalis: Triggers burning and itching of your reproductive organs  
  • Trypanosoma cruzi: May lead to enlarged spleen and liver, plus abnormal heart rhythms   

    Specific parasites tend to infect certain types of cells. For example, Plasmodium infects your red blood cells, and Blastocystis infects your intestinal cells. But Toxoplasma infects a wide range of different cells. Your symptoms could vary based on what cells the parasites infect. (30, 31, 32)


    Helminth is the general term for a parasitic worm. Unlike protozoan parasites, you can see many helminths with the naked eye. (6)

    For example, some Ascaris lumbricoides worms are up to 12 inches (35 centimeters) in length. But pinworms are just the size of a staple and white, so you might miss them if you’re not looking closely. (6)

    Similar to protozoans, different helminths gravitate toward specific areas of your body. That’s why they affect the functioning of specific organs and systems. (9)

    The two main groups of helminths that infect people are roundworms and flatworms. Up next is a closer look at those.


    These parasitic worms are also known as nematodes. They could infect various areas of your body, including your skin, lungs, liver, intestines, and tissues — such as your muscles. (6, 33)

    Some subtypes within the roundworm category are hookworms and pinworms. Hookworms get their name from the hook-like bend of their head. Pinworms are so-named due to the females’ pin-like tail. (25, 34, 35)

    Examples of common nematodes and some of their effects include: (9, 25

    • Ancylostoma duodenale: Hookworm that infects your gut and causes anemia
    • Ascaris lumbricoides: Common intestinal roundworm that causes abdominal discomfort
    • Enterobius vermicularis: Pinworm that infects your colon and makes your anus itch
    • Necator americanus: Hookworm that infects your gut and causes anemia
    • Strongyloides stercoralis: Infects your gut, and each new batch of larvae can reinfect you
    • Trichinella spiralis: Can cause stomach upset and infect your muscles, causing pain 
    • Trichuris trichiura: Also called a whipworm and causes painful, bloody diarrhea 


    Within the flatworm category, two common subtypes are flukes and tapeworms. As you might guess from the name, both have flattened bodies. But their shapes are pretty different from each other. (6)

    Flukes have a leaf-like shape. These critters may invade your blood, intestines, lungs, and liver. Flukes that infect your liver can damage your bile ducts. (36, 37)

    Tapeworms have ribbonlike bodies that are segmented. They most commonly infect your small intestine and can cause nausea and weight loss. They may also migrate to your gallbladder and block the common bile duct. (7)

    Examples of flukes and tapeworms are: (9, 25, 38)

    • Schistosoma mansoni: Blood fluke that hides in your intestines and steals your nutrients
      • Clonorchis sinensis: Liver fluke that you may get from eating raw fish 
      • Taenia solium: Long tapeworm that you may get from eating undercooked pork 
      • Taeniarhynchus saginatus: Long tapeworm that you may get from undercooked beef


      Ectoparasites are bugs that attach to your skin to feed on your blood or skin tissue. A few kinds even burrow under your skin. They may trigger itching. Ectoparasites are very common. (6, 39)

      Some familiar examples of ectoparasites are: (39, 40)

      • Bed bugs
      • Fleas
      • Flies 
      • Lice
      • Mites (including chiggers and scabies)
      • Mosquitoes
      • Ticks

      Some ectoparasites (such as bed bugs) only visit you temporarily to get their blood meal. Others (like lice) don’t leave until you take efforts to get rid of them.

      More significant than what these bugs take from you is what they give in return. Some ectoparasites not only feed on you, but many are also vectors that carry other pathogens. They can transmit these to you as they feast. (6, 39)

      For example, ectoparasites can give you pathogens like West Nile virus, Borrelia burgdorferi bacteria (which cause Lyme disease), and Plas

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