Paragonimiasis

Paragonimiasis is an infection with parasitic worms. It is caused by eating undercooked crab or crayfish.

Paragonimiasis can cause illness resembling pneumonia or stomach flu. The infection can last for years.

Paragonimiasis Causes

Paragonimiasis is caused by infection with a flatworm. That's a parasitic worm also called a fluke or lung fluke because it commonly infects the lungs. Usually, infection comes after eating undercooked crab or crayfish that carry immature flukes.

Once swallowed by a person, the worms mature and grow inside the body. Over months, the worms spread through the intestines and belly (abdomen). They penetrate the diaphragm muscle to enter the lungs. Once inside the lungs, the worms lay eggs and can survive for years, causing chronic (long-term) paragonimiasis.

Paragonimiasis is rare in the U.S. Most cases occur in Asia, West Africa, and South and Central America.

Paragonimiasis Symptoms

Paragonimiasis causes no symptoms during initial infection. Many people with paragonimiasis never experience any symptoms. When paragonimiasis symptoms do occur, they result from the worms’ location and activity in the body, which change over time.

In the first month or so after someone is infected, paragonimiasis worms spread through the abdomen, sometimes causing symptoms that can include:

Worms then travel from the belly into the chest. There they can cause respiratory symptoms, such as:

Without treatment, paragonimiasis becomes chronic. It can continue for decades.

The most common long-term paragonimiasis symptom is a cough with bloody sputum (hemoptysis) that comes and goes. Other chronic paragonimiasis symptoms may include:

  • Belly pain
  • Nausea
  • Vomiting
  • Bloody diarrhea
  • Lumps or bumps on the skin of the belly or legs that come and go over time

Some people with chronic paragonimiasis have no noticeable symptoms.

In less than 1% of people with paragonimiasis, the worms infect the brain. Symptoms can include:

Paragonimiasis Diagnosis

Diagnosing paragonimiasis can be difficult or delayed. That's because its symptoms are often mild and overlap with more common conditions.

Continued

Most often, a person with symptoms has multiple tests before a doctor makes the diagnosis of paragonimiasis. Exams and tests used to make a diagnosis include:

Patient History. Your doctor will get clues about possible paragonimiasis by looking at the pattern in which your symptoms appeared. Your doctor will ask about your past eating of undercooked crab or crayfish.

Physical examination. Abnormal breath sounds or belly tenderness observed with a doctor’s examination of the chest or belly can suggest a problem and direct further testing.

Blood tests. A high number of a specific type of white blood cells can suggest parasitic infection. Antibodies against flukes may be present in the blood.

Sputum microscopy. Fluke eggs can be detected during examination of coughed-up sputum under a microscope.

Chest X-ray. Nodules (spots) in the lungs, hollowed-out areas (cysts or cavities), or fluid around the lungs (pleural effusions) may be present.

CT scan. High-resolution images of the lungs may show more detailed information than a chest X-ray. Also,CT of the head or abdomen may be abnormal if paragonimiasis involves the brain or liver.

MRI. Very high-definition images of the brain can identify cysts or brain swelling caused by paragonimiasis.

Bronchoscopy . A doctor can put an endoscope (flexible tube with a camera on its tip) through the nose or mouth into the lungs. Flukes or their eggs are collected from lung fluid samples. The flukes or eggs may be seen under a microscope.

Thoracentesis. A doctor puts a needle through the chest wall to sample fluid around the lungs (pleural effusion).

Stool studies. Fluke eggs may be seen in stool samples when examined under a microscope.

A definite diagnosis of paragonimiasis is made when fluke eggs are detected in an infected person’s sputum or stool. But the flukes may not lay eggs until two months after you are infected. That makes early diagnosis difficult.

Paragonimiasis Treatment

In most people, paragonimiasis can be cured with oral anti-parasite medications. The recommended treatment is praziquantel (Biltricide). It is taken three times daily for two days.

In the rare cases of paragonimiasis with brain involvement, other treatments may be necessary, such as anti-seizure medications or surgery to reduce brain swelling.

WebMD Medical Reference Reviewed by Laura J. Martin, MD on July 11, 2018

Sources

SOURCES:

CDC. "Parasites -- Paragonimiasis (also known as Paragonimus Infection)."

Procop, G. Clinical Microbiology Reviews, 2009.

Fried, B. Parasitology Research, 2010.

Harinasuta, T. Infectious Disease Clinics of North America, 1993.

Yang, S. Diseases of the Chest, 1959.

Johnson, R. Reviews of Infectious Diseases, 1985.

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