What is Anisakiasis?
Anisakiasis is a parasitic infection affecting the parts of the gastrointestinal tract. It occurs on ingesting raw and uncooked seafood. It is a herring worm disease, an infectious disease that can be transmitted from fish and squid to humans.(1)
Adult Anisakis worms live within the stomach of marine animals. The eggs from these worms pass out through the feces of these mammals.
The larvae from these eggs develop and hatch in water. These are ingested by small marine animals such as crabs who then become their host. These small marine animals are ingested by fish or squid and this way the larvae are transferred to them.
Marine animals that commonly carry Anisakis include:
According to a systemic review, the worldwide prevalence of anisakiasis is 0.32 per 100,000 population.(2)
Causes and Risk Factors of Anisakiasis
Anisakiasis cannot spread from one person to another.(3)
Species of Anisakis that commonly cause infection in humans include:(4)
- A. pegreffii
- A. physeteris
- A. simplex
On consuming raw and uncooked fish and squid that may contain Anisakis nematode, the larvae may invade and penetrate the gastrointestinal tract. It may be excreted normally as a part of a bowel movement. The larvae, however, may produce an inflamed mass in the esophagus, stomach, or intestine. It may lead to gastrointestinal symptoms.
Anisakiasis is considered to be an endemic disease in countries including Japan, Spain, Mexico, and the United States.(5)
Symptoms of Anisakiasis
The symptoms of Anisakiasis include:
- Abdominal pain
- Swelling of the stomach
- Mild fever
- Diarrhea and blood in stool
Some people may also have an allergic reaction to the parasite, which may result in hives, breathing problems, skin rashes, and teary eyes. The allergic reaction may be seen 1-2 hours after consumption of food products containing the parasite. There may be stomach pain within 8 hours of consumption.
Some symptoms may persist for up to 5 days.
Diagnosis of Anisakiasis
To diagnose anisakiasis, the doctor may enquire about recent food consumption.
A radiograph may be suggested to look into if larvae are present. Research shows that computed tomography may also be an important tool for diagnosing anisakiasis.(6)
An allergy test may be conducted to check if a person is allergic to Anisakis. It is a skin prick test that detects the specific IgE antibodies in the blood test.(7)
Treatment of Anisakiasis
Anisakiasis does not require any treatment as the worms eventually die. In case treatment is required, the following options can be considered:
- Endoscopic removal of the foreign body: In this, a long thin tube passes through a person’s mouth. It contains light and a medium to insert instruments that can be helpful in removing foreign bodies.
- Medications: Albendazole can be given for the treatment of worms. It works by impairing glucose utilization, decreasing the worm’s glycogen stores, and eventually causing the worms to die.
- Surgery: In case of obstruction such as appendicitis or swelling in the abdomen, surgery can be a treatment of choice
How to Prevent Anisakiasis from Occurring?
Anisakiasis can be prevented by preventing eating raw or undercooked seafood. The safety of the seafood can be detected with a food thermometer.(8) It is also suggested that the seafood should be cooked at an internal temperature of 145°F.
The following tips should be considered while buying and cooking seafood:
- Purchase fish that is refrigerated or displayed on a bed of ice
- While purchasing previously frozen fish, make sure that it is fresh and mild
- Avoid buying packaged food if the package is open
- Packages that appear frosty or contain ice crystals should be avoided
- After purchasing seafood store it in the refrigerator and use it within 2 days
The outlook for anisakiasis is positive. Most of the infections occurring due to it are self-limiting as the larvae are not able to survive for longer periods of time. Tissue damage symptoms can last a little longer. People experiencing allergic reactions can get treatment to help relieve symptoms.