Introduction
Angiostrongyliasis also known as the rat lungworm is commonly found in Southeast Asia and tropical islands in the Pacific. These worms show a coiled pattern formed by the red, blood-filled intestines, and white uterine tubes. The prevalence of this infection has been increasing over time. Cases of this infection have also been documented in the United States, the Caribbean, and Africa.
The infection is caused by two nematodes Angiostrongylus cantonensis and Angiostrongylus costaricensis. Angiostrongylus cantonensis causes eosinophilic meningitis whereas Angiostrongylus costaricensis leads to eosinophilic gastroenteritis.
What Are the Clinical Features of Angiostrongyliasis?
Angiostrongylus cantonensis: The incubation period of A. cantonensis usually ranges from one to three weeks. Symptoms of this infection include:
The infection can also affect the eyes sometimes. When an individual is tested positive for bacterial meningitis by taking a sample of the cerebrospinal fluid, it does not show high levels of the polymorphonuclear leukocytes (cells that help fight against bacterial infections). However, another cell type called eosinophils is found though these cells may be absent early and late in the course of the infection. Hence, the infection is also known as eosinophilic meningitis.
Sometimes abnormal sensations in the legs and arms may also be seen. The symptoms of the infection generally remain for two to eight weeks but may last longer sometimes. Most infections of A. cantonensis resolve over time without any treatment as the parasite cannot survive in the human body for a long time. In rare cases, serious complications might occur that can lead to neurologic disorders and can also be fatal.
Angiostrongylus costaricensis: The exact incubation period of this parasite is still unknown, but it might range from several weeks to months and can be as long as one year. A. costaricensis is generally present in the ileocecal region of the intestine. The symptoms of the disease include:
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Abdominal pain.
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Nausea.
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Vomiting.
Abdominal findings in this infection resemble those of appendicitis, and infection is often detected after the removal of the appendix surgically. In some rare cases, the larvae enter the mesenteric arteries present in the abdominal cavity and mature into adults. Here these worms can cause an infarction, arteritis, thrombosis, and gastrointestinal hemorrhage. Eggs produced by adult worms enter the capillaries and degenerate causing an inflammatory reaction. The immune system may respond to the eggs, larvae, and adults resulting in an eosinophilic inflammatory reaction, with the eosinophils invading the intestinal wall and leading to eosinophilic vasculitis. Rare cases of intestinal obstruction and perforation have occurred, and fatalities have been reported in some cases. The infection may be recurrent and occur for several months. However, most cases resolve on their own without any treatment.
What Are the Epidemiology of Angiostrongyliasis?
This parasitic nematode or worm is transmitted between rats and mollusks like slugs or snails during its natural life cycle. The worms can be transmitted to other animals like land crabs, frogs, and freshwater shrimp, that act as transport hosts but are not required for the multiplication of the parasite. However, these infections might transfer this infection to humans if they are consumed undercooked or raw. Human beings do not transfer the infection to others. Most cases of Angiostrongyliasis have been reported in Southeast Asia and the Pacific Basin. However, certain cases have also been found in Australia, Africa, the Caribbean, Hawaii, and Louisiana. Outbreaks of angiostrongyliasis have involved over 2,800 cases from around 30 countries.
What Are the Risk Factors Associated With Angiostrongyliasis?
1. Risk factors for infection with A. cantonensis include:
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The consumption of raw or undercooked infected snails and slugs accidentally chopped up in vegetables or salads. It can also occur through the consumption of foods containing the slime of infected snails or slugs. In addition, hands might get contaminated during the preparation of uncooked infected snails and leading to the consumption of the parasite.
2. Risk factors for infection with A. costaricensis are not specified exactly but infection can occur through the consumption of infected slugs or raw vegetables contaminated with slugs that contain A. costaricensis larvae. Some studies suggest that the risk of the infection is higher in:
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Children between the age group of 6 to 12 years.
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Males.
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In individuals of higher socioeconomic status.
How Is Angiostrongyliasis Diagnosed?
Angiostrongyliasiscan be difficult to diagnose when there are no readily available blood tests. Proper history helps in the diagnosis of infection as it may reveal a recent trip to a region where this parasite is commonly found and ingestion of raw or undercooked snails or slugs. Other diagnostic features include:
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A high level of eosinophils (white blood cells that can be raised in the presence of a parasite).
How Is Angiostrongyliasis Treated?
Angiostrongyliasis has no specific treatment. Generally, certain supportive treatments may decrease the severity of headaches and the duration of symptoms. Individuals with severe symptoms should consult their healthcare provider immediately.
A. cantonensis meningitis is cured with analgesics, removal of cerebrospinal fluid (CSF) at regular intervals to decrease central nervous system (CNS) pressure, and corticosteroids can decrease the frequency of therapeutic lumbar puncture. The inflammatory response can be increased by anthelmintic therapy as it leads to the release of parasite antigens. However, most cases are self-limiting and usually show complete recovery.
How Can Angiostrongyliasis Be Prevented?
Prevention of Angiostrongyliasis involves:
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People living in or traveling to regions where the parasite is commonly found should be educated about the consequences of eating raw or undercooked snails, freshwater shrimp, land crabs, frogs, potentially contaminated vegetables, or vegetable juice.
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The infection can be further prevented by removing snails, slugs, and rats from houses and gardens.
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Hands and utensils should be washed properly after handling raw snails.
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Raw vegetables should be washed thoroughly before consuming them.
Conclusion
Strategies should be adopted for decreasing human infection. Emphasis should be given to public education so that individuals do not consume raw infectious hosts and precautions should be taken before consuming raw vegetables. The spread of intermediate and definitive hosts should be controlled and managed to reduce the incidences of accidental consumption.
