Angiostrongyliasis

Definition

Definition of Angiostrongyliasis
Angiostrongyliasis is an infection by a nematode from the Angiostrongylus genus of kidney and alimentary tract roundworms. For example, infection with Angiostrongylus cantonensis can occur after consuming raw Giant African land snails, Great Grey Slugs, or other molluscs.

Symptoms

Symptoms of Angiostrongyliasis
Infection first presents with severe abdominal pain, nausea, vomiting, and weakness, which gradually lessens and progresses to fever, and then to CNS symptoms and severe headache and stiffness of the neck.

Causes

Causes of Angiostrongyliasis
Ingested larvae can migrate to the central nervous system and cause eosinophilic meningitis. Typically, the incubation period is about 1–3 weeks but has ranged from approximately 1 day to >6 weeks. Common manifestations include headache, photophobia, stiff neck, nausea, vomiting, fatigue, and body aches. Abnormal skin sensations (such as tingling or painful feelings) are more common than in other types of meningitis. A low-grade fever might be noted. The symptoms and signs may persist for weeks or months but are usually self-limited. Severe cases can be associated with sequelae such as paralysis or blindness or death.

Diagnosis

Diagnosis of Angiostrongyliasis
Diagnosis of Angiostrongyliasis is complicated due to the difficulty of presenting the angiostrongylus larvae themselves, and will usually be made based on the presence of eosiniphilic meningitis and history of exposure to snail hosts. Eosiniphilic meningitis is generally characterized as a meningitis with >10 eosiniphils/µL in the CSF or at least 10% eosiniphils in the total CSF leukocyte count. Occasionally worms found in the cerebrospinal fluid or surgically removed from the eye can be identified in order to diagnose Angiostrongyliasis.

Treatment

Treatment of Angiostrongyliasis
Treatment of angiostrongyliasis is not well defined, but most strategies include a combination of anti - parasitics to kill the worms, steroids to limit inflammation as the worms die, and pain medication to manage the symptoms of meningitis.

1. Anti-Helminthics: Anti-helminthics are often used to kill off the worms, however in some cases this may cause patients to worsen due to toxins released by the dying worms. Albendazole, ivermectin, mebendazol, and pyrantel are all commonly used, though albendazole is usually the drug of choice. Studies have shown that anti-helminthic drugs may shorten the course of the disease and relieve symptoms. Therefore anti-helminthics are generally recommended, but should be administered gradually so as to limit the inflammatory reaction.
2. Anti-Inflammatories: Anti-helminthics should generally be paired with corticosteroids in severe infections to limit the inflammatory reaction to the dying parasites. Studies suggest that a two week regimen of a combination of mebedizole and prednisolone significantly shortened the course of the disease and length of associated headaches without observed harmful side effects. Other studies suggest that albendazole may be more favorable, because it may be less like to incite an inflammatory reaction. The Chinese herbal medicine long-dan-xie-gan-tan (LDGXT) has also been shown to have a similar anti inflammatory effect, and in mild cases may be used alone to relieve symptoms while infection resolves itself.
3. Symptomatic Treatment: Symptomatic treatment is indicated for symptoms such as nausea, vomiting, headache, and in some cases, chronic pain due to nerve damage or muscle atrophy.

Prognosis

Prognosis of Angiostrongyliasis
Meningitis is usually mild and resolves spontaneously over six weeks. Occasionally, cases are severe and may lead to long-term neurological complications.

Prevention

Prevention of Angiostrongyliasis
No vaccine is available. Preventive measures are aimed at reducing the risk of ingesting the parasite.