Angiostrongyliasis is a zoonotic disease resulting from infection with two species of a parasitic nematode (roundworm), Angiostrongylus cantonensis (also known as rat lungworm) and Angiostrongylus costaricensis. The predominant clinical manifestations in humans are eosinophilic meningitis for A. cantonensis and enteritis for A. costaricensis. This summary focuses on angiostrongyliasis resulting from infection with A. cantonensis.

Angiostrongylus cantonensis is endemic in South Asia, Australia, and islands of the Caribbean, Pacific (including Hawaii), and Indian Ocean. Eosinophilic meningitis due to A. cantonensis has been reported in US travelers to these regions. Angiostrongylus cantonensis lungworm has been reported in wildlife hosts in southeastern United States.

The life cycle is similar for both species. In the definite host (rats), adult worms lay eggs, and larvae hatch from them, migrate, and get excreted in the rat's feces. These larvae are then swallowed by snails and slugs. These slugs may then be eaten by a variety of creatures including frogs, crabs, fish, etc. The predominant manner in which humans become infected is ingestion of raw snails that are harboring the larva. Similarly, ingestion of other uncooked or undercooked freshwater species that have consumed infected snails or slugs such as frogs, shrimp, crabs, and fish can also lead to disease. Fruits and vegetables can also carry larvae and cause infection. Children may infect themselves by putting their hands in their mouth after playing with affected creatures.

After A. cantonensis ingestion, larvae migrate from the gastrointestinal tract and hematogenously arrive in the central nervous system (CNS). This is the most common cause of eosinophilic meningitis worldwide. Patients develop symptoms when inflammation increases in conjunction with the worms dying. Symptoms typically occur 7-35 days after ingestion of the larvae and include headache, nausea, vomiting, and paresthesias of the extremities. Many of the symptoms are due to increased intracranial pressure. Focal signs are uncommon except for cranial nerve palsies. Typically, patients recover without sequelae in several weeks. Angiostrongylus cantonensis occasionally presents with blurred vision due to the worm invading the vitreous chamber.