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Internal Parasites: Listing the Different Types of Parasites

Types of Parasites

Are you infected with internal parasites? These harmful organisms are more common than you may think. There are several types of parasites that can infect the human body. Here is a list of parasites that may be affecting your health

Protozoa internal parasite

Protozoa are very small parasites that cannot be seen with the human eye. They also include some of the most common parasitic invaders in the United States, namely,
Giardia lamblia and Cryptosporidium parvum.

  • Giardia is responsible for the common illness giardiasis. Symptoms of this condition include digestive disorders such as diarrhea, bloating, foul-smelling gas, nausea, weight loss and abdominal cramping. Giardia can be transmitted via food or water that has been contaminated by human or animal feces. Giardia can also be carried by household pets. This intestinal parasite makes its home in the small intestine and interferes with the body’s levels of immunoglobulin A, vitamin A and vitamin B12.
  • Cryptosporidium is another common protozoan parasite. It is a water-borne internal parasite but it can also be transmitted from unsanitary diaper changing conditions at day care facilities. Once inside the human body, Cryptosporidium makes its home in the intestines and is responsible for such symptoms as diarrhea, fever, nausea, abdominal cramps and migraines.

Nematode internal parasites


This category of internal parasites includes the larger species such as roundworm, hookworm, and pinworms.

  • Roundworm: (Ascaris lumbricoides) The roundworm is the most common parasite in humans throughout the world. This flat worm resembles an earthworm and can infect humans via contact with contaminated food, feces or soil. Once ingested, roundworms move through the liver and the lungs causing damage as they go.

    Symptoms of a roundworm infection include abdominal pain, swelling, allergic reactions, sleep disturbances, and significant weight changes. In children, roundworm infection may be responsible for conditions such as nervousness, colic, poor appetite, allergic reactions, and malnutrition.

  • Hookworms: (Necator americanus, Ancylostoma duodenal) Hookworms are another intestinal worm that is commonly found in warm, moist soil environments. They can enter the human body by penetrating the skin. This is why people who are frequently barefoot are often infected with hookworms. Once in the body, hookworms will travel through the blood stream into the lungs and then to the trachea. Hookworm parasites may cause symptoms such as sore throats and coughing and illnesses such as bronchitis. Hookworms can then work their way into the esophagus where the will be swallowed into the digestive system. Hookworm infection can lead to symptoms that include itchy rashes, pimples, anemia, vitamin deficiencies, and weight loss.
  • Pinworm: (Enterobius vermicularis) Pinworm is one of the most common internal worms in the United States. It is found primarily in children and it can infect the body via several pathways. Pinworms tend to lay their eggs right outside the anus. These eggs can then contaminate underwear, pajamas, sheets, toilet seats, sofas, hands, doorknobs, and anywhere that contaminated hands have touched. The eggs can also float about in the air, therefore even with careful hygiene, it is possible to become infected with pinworms simply be breathing the eggs in. The main symptom of pinworm infection is anal itching, especially at night, due to the pinworm eggs that lay outside the anus. The itchiness can then lead to insomnia and, fatigue, restlessness, and irritability as a result.

Cestodes (Tapeworms) – Internal Parasites

Tapeworms are very large worms, the largest of all of the parasitic worms. (The largest of tapeworm, the beef tapeworm can grow up to forty feet (twelve meters) long! There are several species of tapeworm: the beef tapeworm (Taenia saginata), the pork tapeworm (T. solium), the fish tapeworm (Diaphyllobothrium latum), and the dog tapeworm (Dipylidium caninum). Each tapeworm can infect the human body via consumption of contaminated fish or meat (for instance, a human can become infected with beef tapeworms by eating infected beef).

Beef tapeworm internal parasite infection is not usually life threatening, but it can result in diarrhea, abdominal cramping, nervousness, nausea, and loss of appetite. Pork tapeworm infection can be dangerous and even lethal. The larvae of these tapeworms can invade the muscles, heart, eye, and brain as they migrate through the body. Once in the brain, pork tapeworms may result in seizures and brain deterioration. This type of infection is often misdiagnosed as epilepsy.

Fish tapeworm infection is common in the Great Lakes region of the United States and Canada. Humans can become infected by eating contaminated fish that is raw or lightly cooked. Fish tapeworm infection can cause serious deficiencies in the host’s vitamin B12 levels. Symptoms of fish tapeworm infection include nausea, anorexia, and pain or fullness in the upper abdomen.

Trematodes (Flukes) – Internal Parasites

Trematodes, or flukes, can make their home in many different areas of the human body. There are blood flukes (Schistosoma spp), liver flukes (Clonorchis sinensis), oriental lung flukes (Paragoniumus westermani), sheep liver flukes (Fasciola hepatica), and intestinal flukes (Fasciolopsis buski).

Blood flukes can penetrate the human skin. Infection can occur via contact with contaminated water (such as bathing or swimming.) Liver, oriental lung, sheep liver, and intestinal flukes, on the other hand, are all transmitted via consumption of contaminated food. Fluke infections are rare in the United States; however, they are still possible. Symptoms of fluke infections include urinary disorders, liver problems, hepatitis, abdominal pain, liver abscesses, fibrosis, diarrhea, and vomiting.

by Dr. Edward F. Group III, DC, ND, DACBN, DABFM

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