Angiostrongyliasis is infection caused by Angiostrongylus cantonensis or by Angiostrongylus costaricensis, which are roundworms (nematodes).
People become infected by eating raw or undercooked land snails, slugs, and certain other animals that are infected with the roundworm larvae or sometimes by eating raw produce that contains a small, infected snail or slug or a part of one.
Infection with Angiostrongylus cantonensis causes eosinophilic meningitis, and people have symptoms such as headache, double vision, neck stiffness, and sometimes fever and other symptoms.
Infection with Angiostrongylus costaricensis causes eosinophilic enteritis, and people have symptoms such as abdominal pain, nausea, vomiting, and sometimes fever and other symptoms.
Doctors usually diagnose the infection by doing a procedure to remove a sample of cerebrospinal fluid or abdominal tissue and then analyze it to look for evidence of the parasites.
People are given medications to relieve symptoms such as pain, but the infection typically goes away on its own.
Helminths are parasitic worms that can infect humans and animals. There are 3 types of helminths: flukes (trematodes), tapeworms (cestodes), and roundworms (nematodes). Angiostrongylus cantonensis and Angiostrongylus costaricensis are roundworms.
Angiostrongyliasis caused by Angiostrongylus cantonensis mostly occurs in Southeast Asia and the Pacific Basin but has occurred elsewhere, including the Caribbean, Hawaii, and parts of the southern United States. Angiostrongylus cantonensis typically affects the brain in people and is one of the most common causes of eosinophilic meningitis worldwide. Eosinophilic meningitis is a brain infection caused by parasites.
Angiostrongyliasis caused by Angiostrongylus costaricensis occurs in the Americas, mostly in Latin America and the Caribbean. Angiostrongylus costaricensis typically affects the intestines and abdomen in people.
(See also Overview of Parasitic Infections.)
Transmission of Angiostrongyliasis
Angiostrongylus cantonensis and Angiostrongylus costaricensis are parasites that live in the lungs of rats (also called rat lungworms).
Adult worms that live in the rats produce eggs. The eggs hatch into larvae. Rats pass the larvae in their feces. The larvae then are ingested by land snails and slugs. Certain land crabs, freshwater shrimp and prawns, frogs, and toads can also come in contact with the larvae and are known as transport hosts.
People become infected by eating raw or undercooked hosts that are infected with the larvae or by eating raw produce that contains a small, infected snail or slug or a part of one. Mucus trails from slugs and snails may contain small numbers of larvae, but these are not considered major sources of infection.
Angiostrongylus cantonensis
In people, Angiostrongylus cantonensis larvae do not mature to adult worms and do not produce eggs.
Once the larvae are in a person's body, they travel from the digestive tract to the meninges in the brain. The presence of the larvae causes eosinophilia and meningitis (eosinophilic meningitis). Eosinophilia is a higher than normal number of eosinophils in the blood. Eosinophils are a type of disease-fighting white blood cell that play an important role in the body's response to allergic reactions, asthma, and infection with parasitic worms. Meningitis is inflammation of the layers of tissue that cover the brain and spinal cord (meninges) and of the fluid-filled space between the meninges (subarachnoid space).
Sometimes Angiostrongylus cantonensis affects the eyes.
Image from the Centers for Disease Control and Prevention, Global Health, Division of Parasitic Diseases and Malaria.
Angiostrongylus costaricensis
In people, Angiostrongylus costaricensis larvae can mature to adult worms that produce eggs.
Once the larvae are in a person's body, they travel to the wall of the intestines and may mature to adult worms. Adult worms live in the intestinal wall and may produce eggs that may be released into the intestinal tissues causing inflammation. The presence of larvae, adult worms, and eggs causes eosinophilia and enteritis. Eosinophilia is a higher than normal number of eosinophils in the blood. Enteritis is inflammation of the intestines. This infection can mimic symptoms that result from appendicitis.
Symptoms of Angiostrongyliasis
Eosinophilic meningitis caused by Angiostrongylus cantonensis causes symptoms such as severe headache, double vision, pins-and-needles sensations, and seizures. People typically have neck stiffness and may develop a low fever, body aches, fatigue, or gastrointestinal symptoms such as nausea, vomiting, and abdominal pain. In severe cases, blindness, paralysis, or death can occur.
Eosinophilic enteritis caused by Angiostrongylus costaricensis causes abdominal pain, nausea, vomiting, and diarrhea. Sometimes people develop a very painful and serious complication called peritonitis, or they may develop a mass in their abdomen that can be felt by a health care professional. People may have other symptoms such as fever and fatigue. In severe cases, a tear may occur in the digestive tract.
Diagnosis of Angiostrongyliasis
For meningitis, spinal tap
For enteritis, biopsy of the intestine
Blood tests
Doctors suspect angiostrongyliasis in people who have eaten a possibly infected host or who live in or have traveled to an area where this infection is known to occur.
Doctors do a spinal tap (lumbar puncture) in people who have symptoms of meningitis. A spinal tap allows doctors to remove cerebrospinal fluid, which they can test for signs of infection, a high level of white blood cells (eosinophilia), and for the parasite's DNA. Angiostrongylus cantonensis larvae and eggs are not passed in stool.
Because larvae and eggs of Angiostrongylus costaricensis also are not passed in stool, doctors base the diagnosis of enteritis on other findings. If a person has a surgical procedure because doctors suspect another medical condition, for example, appendicitis, doctors examine any abdominal tissues that were removed to look for eggs, larvae, or adult worms.
Blood tests also are done to look for eosinophilia caused by either parasite.
Treatment of Angiostrongyliasis
For meningitis, corticosteroids and sometimes spinal tap
To treat meningitis caused by Angiostrongylus cantonensis, doctors give people pain relievers and may do spinal taps to remove cerebrospinal fluid and reduce pressure within the skull (intracranial pressure). Doctors also give corticosteroids to control swelling in the brain.
Most people with Angiostrongylus cantonensis recover completely.
Most infections caused by Angiostrongylus costaricensis go away on their own.
People are not given medications that typically are used to treat worm infections because these medications may make angiostrongyliasis and the symptoms it causes worse.
Prevention of Angiostrongyliasis
People who live in or travel to areas where angiostrongyliasis is common should avoid eating raw or undercooked snails, slugs, freshwater shrimp, land crabs, and frogs as well as potentially contaminated vegetables and vegetable juices.
