Angiostrongyliasis

Angiostrongyliasis is an infection with the larvae of the worms called Angiostrongylus cantonensis and A. costaricensis.  This is the most common cause of eosinophilic meningitis.

LIfe Cycle

The adult worms of A. contonensis live and reproduce in the arteries of the lungs of rats.  Following hatching, the larvae migrate to the pharynx where they are swallowed and passed in the feces.  These penetrate or are swallowed by intermediate hosts, like snails, where they become infective to mammals.  When the host (ie, snail) or food items that have been contaminated by the host is ingested, the larvae migrate to the brain and ultimately die.  A. costaricensis, on the other hand, stay in the arteries of the intestines, particularly in the ileocecal valve.  They often reach sexual maturity and release eggs into the intestinal tissues.  These degenerate and the human body responds by causing a severe inflammatory reaction.

Humans are incidental hosts of these worms as they cannot reproduce in humans.

Epidemiology

Infection by A. cantonensis occurs frequently in Southeast Asia and the Pacific Basin, however, other locations have also been reported like in the Caribbean.  A. costaricensis has been reported from Costa Rica.

Clinical Features

The incubation period is usually from 1 week to 1 month.  A. cantosinensis larvae migrate to the meninges or the outer covering of the brain, inciting an inflammatory reaction.  Eosinophilic meningitis initially present with severe headaches, nausea and vomiting, neck stiffness, fever, and neuropathic pain.  Progression is heralded by weakness, paralysis, seizures, respiratory failure, and muscle atrophy.  Occasionally, ocular symptoms like visual impairment, pain, and edema may be present, indicating eye invasion.  A. costarisensis infection affects the intestines, presenting with abdominal pain, fever, and vomiting.

Diagnosis

Diagnosis may be difficult and may require a high degree of suspicion especially if there has been a previous history of ingestion or exposure to snail hosts.  Lumbar puncture, wherein a sample of cerebrospinal fluid is taken for studies, would show eosinophilia.  Rarely, parasites can be seen in the CSF.  Brain imaging using a CT scan or an MRI can be performed.  Lesions indicating invasion in the brain can be seen, and occasionally a hemorrhagic lesion produced by migrating worms may be present.

Diagnosis of gastrointestinal infection cause by A. costaricensis is difficult since the eggs and larvae are not passed in the feces, although during surgery, these may be identified in the intestinal tissues.

Management

Currently, there are still no medications that have been proven to be effective in the treatment of Angiostrongyliasis.  Symptomatic treatment is given; analgesics, corticosteroids (to reduce the inflammatory reaction), and lumbar taps to reduce the CNS pressure.  Most infections resolve spontaneously or without serious sequelae, however, there have been cases where permanent damage to the CNS has been reported.  Possible negative outcomes include chronic pain and death.  Antihelmintics to kill the worms may be given, however this may cause the condition to worsen because of the toxins released by the dying worms, however, studies show that this class of drugs may limit the course of the disease.