Gnathostomiasis

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at September 2, 2016
StartDiseasesGnathostomiasis

Gnathostomiasis is a parasitic infection and foodborne illness caused by a certain type of parasite, a roundworm (also known as a nematode) belonging to the genus from which the disease gets its name, Gnathostoma. The worms are most readily found in regions outside the United States. Other names for gnathostomiasis include wandering swelling, Yangtze edema, or Choko-Fuschu Tua Chid

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Definition & Facts

According to the Centers for Disease Control and Prevention (CDC), Gnathostoma worms are predominantly found in Africa, Southeast Asia, South America and Central America. It can affect any vertebrate, including humans and is primarily transmitted through ingestion of contaminated food.

Currently gnathostomiasis is classified as a "relatively rare" disease outside of the United States and very rare within the United States. Gnathostomiasis is also considered to be a disease "imported" from other countries to the United States. Because of increases in global tourism and a corresponding increase in global "foodie" culture, cases of gnathostomiasis are also now on the rise around the world.

There are several species of Gnasthoma worms that can infect humans. The most common species is G. spinigerum. Other known infectious worms include G. binucleatum, G. doloresi, G. procyonis, G. hispidum, and G. nipponicum.

Symptoms & Complaints

Gnathostomiasis can cause symptoms within any organ system in the human body. Most commonly, however, gnathostomiasis causes symptoms in the surface of the skin (epidermis) and subcutaneous tissues.

These symptoms manifest as skin growths that tend to move and migrate as the disease progresses. A list of the most commonly reported patient symptoms includes the following:

It is important to note that the skin boils and elevated eosinophilia counts are the two most commonly reported symptoms, but all symptoms may be present or only certain symptoms may be present depending on which organ systems are invaded.

Causes

Gnathostomiasis is a foodborne illness caused by handling or eating raw or undercooked meat, undercooked freshwater (not salt-water) fish, or by drinking contaminated water.

When the roundworm larvae are first ingested, they lodge themselves in the stomach (gastric) wall. Once they hatch, they will move out of the stomach and into the surrounding tissue and liver before coming back into the stomach. The worms then incubate inside the stomach in a tumor-type sac for up to 8 months before mating, laying eggs and emerging through feces to infect additional hosts.

Diagnosis & Tests

Diagnosing gnathostomiasis begins with taking a complete individual medical history, with inquiries about recent travels and food as well as a full list of symptoms. Sometimes a working diagnosis can be formed simply from this initial history.

The next step in diagnosing gnathostomiasis is to do a physical examination. The physician will look for physical signs of an infestation, including skin swellings. The most common organs to be infested are the skin, the stomach, the liver and the eye, and these will be physically observed or palpated where applicable.

Sometimes the worms will also invade the ear, the lungs, the urinary bladder, and the central nervous system, so the physical exam will also look for changes to vision, hearing, urination, balance, mobility, breathing, and cognition. A number of tests can detect symptoms that may relate to gnathostomiasis:

  • Blood tests. 70 percent of blood tests will detect eosinophilia in up to half of white blood cells. White blood cell count will be high (leukocytosis).
  • Urinalysis. The urinalysis will look for red blood cells in the urine (hematuria)
  • X-ray. X-ray imaging will look for changes to pulmonary function, including lungs that are filling up with fluid.
  • Sputum. Mucus expelled from the lungs can be tested to look for worms.

Treatment & Therapy

Treating gnathostomiasis can take two forms: medication and surgery to remove the worms themselves. Medications that have been shown to be successful in treatment of gnathostomiasis are called antiparasitics. Currently, the Centers for Disease Control and Prevention (CDC) highlights two specific medications in the treatment of gnathostomiasis: ivermectin and albendazole. Surgery can only be done when the worms are able to be easily located and accessed. Gnathostomiasis is not usually fatal unless the worm infects the central nervous system.

Prevention & Prophylaxis

The best way to prevent gnathostomiasis is to practice safe hygiene and eat only cooked foods and purified water while traveling. It is always a good practice to avoid eating freshwater fish that is raw or undercooked. This includes ceviche, which is considered "cooked" via marinade.

One infected individual cannot pass it along to another uninfected individual. The exception is if the uninfected individual comes in contact with an infected individual's urine or feces.

The use of safe food preparation procedures can prevent cases of gnathostomiasis from occurring. Washing hands with warm water and plenty of soap before and after handling food and wearing disposable gloves are two preventative methods.

When cooking freshwater fish, one should be sure the temperature is at least 145° F (or 63° C) and follow all of the safe food preparation tips suggested by the U.S. Food and Drug Administration (FDA).