Angiostrongylus is a parasitic nematode that can cause severe gastrointestinal or central nervous system disease in humans, depending on the species. Angiostrongylus cantonensis, which is also known as the rat lungworm, causes eosinophilic meningitis and is prevalent in Southeast Asia and tropical Pacific islands. The recognized distribution of the parasite has been increasing over time and infections have been identified in other areas, including Africa, the Caribbean, and the United States.

Angiostrongylus costaricensis causes eosinophilic gastroenteritis and is found in Latin America and the Caribbean.

Causal Agent

The nematode (roundworm) Angiostrongylus (=Parastrongylus) costaricensis is the causal agent of abdominal angiostrongyliasis (intestinal angiostrongyliasis). The related species A. cantonensis (rat lungworm), which causes neural angiostrongyliasis, is discussed here.

Hosts

The main definitive host for A. costaricensis is the hispid cotton rat (Sigmodon hispidus); but adult worms have been found in other rodent species, such as black rats (Rattus rattus), short-tailed zygodonts (Zygodontomysbrevicauda), spiny pocket mice (Heteromys adspersus), and pygmy rice rats (Oligoryzomys fulvescens). Slugs in the families Veronicellidae and Limacidae are the typical intermediate hosts.

Aberrant abdominal infections have been documented in humans, non-human primates, and other mammals, including raccoons and one opossum.

Geographic Distribution

Abdominal angiostrongyliasis has mainly been reported from parts of Latin America and the Caribbean. Although A. costaricensis has been found in various animals in the southern United States, the sporadic human cases identified in the United States are thought to have been travel associated.

Clinical Presentation

The clinical manifestations of abdominal angiostrongyliasis (A. costaricensis infection) arise from the parasite’s invasion of the gastrointestinal wall, and may mimic those of other conditions, such as appendicitis, Crohn’s disease, or Meckel’s diverticulum. Eosinophilia is commonly noted. Intestinal obstruction, perforation, and other complications may occur, as may ectopic infection (e.g., in the liver).

Causal Agent

The nematode (roundworm) Angiostrongylus (=Parastrongylus) cantonensis, also called the rat lungworm, is a common cause of human eosinophilic meningitis (neural angiostrongyliasis) and occasionally ocular disease.

Hosts

A. cantonensis is known to use multiple rat species as definitive hosts, including black rats (Rattus rattus), brown rats, (Rattus norvegicus), and cotton rats (Sigmodon hispidus). Gastropod (snail and slug) intermediate hosts are numerous and include Achatina spp., Biomphlalaria spp., Bulinus spp., Lymnaea spp., Pomaecea spp., and more. Apart from humans, aberrant infections have occurred in several species of wild and domestic mammals and birds.

Geographic Distribution

Most cases of A. cantonensis-associated eosinophilic meningitis originate from Southeast Asia and Pacific Islands. The parasite has also been reported from Africa, the Caribbean, Australia, Hawaii, and recently the southern United States.

Clinical Presentation

The most notable manifestation of A. cantonensis infection is eosinophilic meningitis caused by the presence of larvae in the brain and resultant local host reactions. Somatic symptoms (e.g. headache, fever, malaise) as well as varying degrees of neurological dysfunction are usually noted. A. cantonensis infection may occasionally prove fatal. Ocular angiostrongyliasis is associated with uveitis, blurred vision, and a substantial loss of visual acuity.

What is Angiostrongylus cantonensis?

Angiostrongylus cantonensis is a parasitic worm of rats. It is also called the rat lungworm. The adult form of the parasite is found only in rodents. Infected rats pass larvae of the parasite in their feces. Snails and slugs get infected by ingesting the larvae. These larvae mature in snails and slugs but do not become adult worms. The life cycle is completed when rats eat infected snails or slugs and the larvae further mature to become adult worms.

Can people get infected with this parasite?

Yes. People can get infected, under unusual circumstances. However, even if infected, most people recover fully without treatment.

How can people get infected?

People can get infected by eating raw or undercooked snails or slugs that are infected with this parasite. In some cultures, snails are commonly eaten. Some children, in particular, have gotten infected by swallowing snails/slugs “on a dare. ” People also can get infected by accident, by eating raw produce (such as lettuce) that contains a small snail or slug or part of one.

Certain animals such freshwater shrimp, crabs, or frogs, have been found to be infected with larvae of the parasite. It is possible that eating undercooked or raw animals that are infected could result in people becoming infected, though the evidence for this is not as clear as for eating infected snails and slugs. Of note, fish do not spread this parasite.

Can an infected person infect other people?

No.

In what parts of the world have people become infected with this parasite?

In many parts, but most of the known cases of infection have been in parts of Asia and the Pacific Islands. Some have been in other areas of the world, such as in the Caribbean and Africa.

Have cases of this infection occurred in the United States?

Yes. Cases have occurred in Hawaii (and other Pacific Islands). Very few cases have been reported in the continental United States. In 1993, a boy in New Orleans got infected by swallowing a raw snail “on a dare. ” The type of snail he swallowed isn’t known. He became ill a few weeks later, with muscle aches, headache, stiff neck, a slight fever, and vomiting. His symptoms went away in about 2 weeks, without treatment of the infection.

Can giant African land snails be infected with this parasite?

Yes. This type of snail, which can grow larger than a person’s hand, is just one of many types that can be infected. But snails can be infected only if they have ingested contaminated rat feces. We don’t know if any of the giant African land snails in the continental United States are infected.

What are the signs and symptoms of infection with this parasite?

Some infected people don’t have any symptoms — or have only mild symptoms that don’t last very long. Sometimes the infection causes a rare type of meningitis (eosinophilic meningitis). The symptoms can include headache, stiff neck, tingling or painful feelings in the skin, low-grade fever, nausea, and vomiting.

What should I do if I think I might be infected with this parasite?

You should see your health care provider, who will examine you and ask about any symptoms, travel, and exposures you’ve had (for example, to snails/slugs). You might have some blood tests, as well as tests for meningitis.

Does infection with this parasite need to be treated?

Usually not. The parasite dies over time, even without treatment. Even people who develop eosinophilic meningitis usually don’t need antiparasitics. Sometimes the symptoms of the infection last for several weeks or months, while the body’s immune system responds to the dying parasites. The most common types of treatment are for the symptoms of the infection, such as pain medication for headache or medications to reduce the body’s reaction to the parasite, rather than for the infection itself. Patients with severe cases of meningitis may benefit from some other types of treatment.

How can I keep from getting infected with this parasite?

Don’t eat raw or undercooked snails or slugs, frogs or shrimp/prawns. If you handle snails or slugs, wear gloves and wash your hands. Always remember to thoroughly wash fresh produce. When travelling in areas where the parasite is common, avoid eating uncooked vegetables.

Angiostrongylus cantonensis

Angiostrongylus cantonensis, also known as the rat lungworm, is a parasitic nematode (worm) that is transmitted between rats and mollusks (such as slugs or snails) in its natural life cycle. Other animals that become infected such as freshwater shrimp, land crabs, frogs, and planarians of the genus Platydemus, are transport hosts that are not required for reproduction of the parasite but might be able to transmit infection to humans if eaten raw or undercooked. Humans are accidental hosts who do not transmit infection to others. Most cases of infection are diagnosed in Southeast Asia and the Pacific Basin, but the parasite has also been found in Australia, some areas of Africa, the Caribbean, Hawaii and Louisiana. Outbreaks of human angiostrongyliasis have involved a few to hundreds of persons; over 2,800 cases have been reported in the literature from approximately 30 countries. It is likely that the parasite has been spread by rats transported on ships and by the introduction of mollusks such as the giant African land snail (Achatina fulica). In addition, the semi-slug, Parmarion martensi (native of Southeast Asia)has spread in regions of Hawaii and is found to often be infected with A. cantonensis, and the freshwater snail Pomacea canaliculata (native of South America) has been introduced into Taiwan and China and has been implicated in outbreaks of disease in those countries.

Risk factors for infection with A. cantonensis include the ingestion of raw or undercooked infected snails or slugs; or pieces of snails and slugs accidentally chopped up in vegetables, vegetable juices, or salads; or foods contaminated by the slime of infected snails or slugs. It is possible that ingestion of raw or undercooked transport hosts (freshwater shrimp, land crabs, frogs, etc. ) can result in human infection, though this is less certain. In addition, contamination of the hands during the preparation of uncooked infected snails or slugs could lead to ingestion of the parasite.

Angiostrongylus costaricensis

Angiostrongylus costaricensis is a parasitic nematode (worm) that resides in rodents and uses mollusks, such as slugs, as an intermediate host. Rats, such as the cotton rat, transmit the larvae through their feces. Slugs then ingest the larvae. Humans are accidental hosts of the parasite. The parasite is not able to complete its life cycle in humans and eventually dies in the abdomen. Human infection principally occurs in Latin America and the Caribbean, with a few cases suspected in the United States and in the Republic of Congo. The organism is also found in animals in the Southern U.S. (Texas).

Risk factors for infection with A. costaricensis are not well established but are likely to be ingestion of infected slugs or raw vegetables or vegetable juices contaminated with slugs or their slime, which can contain A. costaricensis larvae. The infection of transport hosts, which are not essential to the lifecycle of the parasite, has not been identified and any role in human infection is not known, in contrast to A. cantonensis. Some reports have shown the case rate to be higher in children 6 to 12 years of age, males, and in persons of higher socioeconomic status. There has been one food-related outbreak in Guatemala that affected primarily adults.

Angiostrongylus cantonensis

Prevention of A. cantonensis infections involves educating persons residing in or traveling to areas where the parasite is found about not ingesting raw or undercooked snails and slugs, freshwater shrimp, land crabs, frogs, and monitor lizards, or potentially contaminated vegetables, or vegetable juice. Removing snails, slugs, and rats found near houses and gardens should also help reduce risk. Thoroughly washing hands and utensils after preparing raw snails or slugs is also recommended. Vegetables should be thoroughly washed if eaten raw.

Angiostrongylus costaricensis

Prevention of A. costaricensis infections involves educating persons residing in and traveling to areas where the parasite is known to be found about not ingesting raw or undercooked slugs or potentially contaminated vegetables or vegetable juices. Removing slugs and rats found near houses and gardens should help reduce risk. Thoroughly washing hands and utensils after preparing raw slugs is also recommended. Vegetables should be thoroughly washed if eaten raw.

Angiostrongylus cantonensis

The incubation period of A. cantonensis averages 1 to 3 weeks, but has ranged from 1 day to greater than 6 weeks. Illness from A. cantonensis usually lasts between 2-8 weeks but can last longer. People present with symptoms of bacterial meningitis, such as nausea, vomiting, neck stiffness, and headaches that are often global and severe. Additionally, abnormal sensations of the arms and legs can occur. Sometimes the eyes can be affected. When patients are tested for bacterial meningitis by taking a sample of the fluid that surrounds the brain, the fluid does not show high levels of the cells that help fight off bacterial infections (polymorphonuclear leukocytes) as one might expect. Instead, another cell type called eosinophils are found (this is called eosinophilic meningitis), though these cells may be absent early and late in the course of disease. Most infections of A. cantonensis resolve spontaneously over time without specific treatment because the parasite cannot survive for long in the human body. However, serious complications can rarely occur, leading to neurologic dysfunction or death.

Angiostrongylus costaricensis

The incubation period is not specifically known, but is thought to usually range from several weeks to several months, possibly even up to 1 year. A. costaricensis is usually found in the intestine (especially the ileocecal region) and can cause abdominal pain, fever, nausea and vomiting. Abdominal findings can often mimic appendicitis, and infection is identified after surgical removal of the appendix. In rare cases, the larvae enter the mesenteric arteries found in the abdominal cavity where they mature into adults and can cause arteritis, infarction, thrombosis, and gastrointestinal hemorrhage. Eggs produced by adult worms lodge in capillaries and cause an inflammatory reaction as they degenerate. The immune system’s response to the adults, larvae, and eggs can result in a massive eosinophilic inflammatory reaction, with eosinophilic invasion of the intestinal wall and eosinophilic vasculitis. Intestinal obstruction and perforation can occur, and deaths have been reported. Recurrent episodes of illness may occur over several months. Most cases resolve spontaneously.

Angiostrongylus cantonensis

Diagnosing A. cantonensis infections can be difficult, in part because there are no readily available blood tests. Important clues that could lead to the diagnosis of infection are a history of travel to where the parasite is known to be found and ingestion of raw or undercooked snails, slugs, or possibly transport hosts (such as frogs, fresh water shrimp or land crabs) in those areas. A high level of eosinophils, a blood cell that can be elevated in the presence of a parasite, in the blood or in the fluid that surrounds the brain can be another important clue. Persons worried that they might be infected should consult their health care provider.

Angiostrongylus costaricensis

Diagnosing A. costaricensis infections can be difficult, in part because there are no readily available blood tests. Important clues that could lead to the diagnosis of infection are a history of travel to where the parasite is known to be found and ingestion of raw or undercooked slugs or food contaminated by infected slugs or their slime. A high blood level of eosinophils, a blood cell that can be elevated in the presence of a parasite, can be another important clue. Persons worried that they might be infected should consult their health care provider.

Angiostrongylus cantonensis

There is no specific treatment for A. cantonensis infection. There is some evidence that certain supportive treatments may reduce the severity of headache and the duration of symptoms. Persons with symptoms should consult their health care provider for more information.

Angiostrongylus costaricensis

There is no specific treatment for A. costaricensis infections. Most infections resolve spontaneously though sometime surgical treatment is necessary to removed portions of inflamed intestine. Persons with symptoms should consult their health care provider for more information.