Angiostrongylius cantonensis. was first described in 1945 in Taiwan from a boy with suspected meningitis. Since then it has been recognised throughout the Pacific areas with sporadic cases reported in other parts of the world including Central America and Cuba It is associated with easinophilic meningitis.

Life cycle

The definitive host of A. cantonensis is the rat. Adult worms reside in the pulmonary arteries Eggs

are released, carried to the lungs and then swallowed.  The eggs hatch in the intestine and the larvae are passed in the stools and invade slugs and snails These crustaceans are eaten by rats where the larvae can complete the cycle.  Human infection occurs by the ingestion of infective larvae in the slugs, snails or on vegetation.  The larvae migrate to the brain and cannot continue their growth cycle. It is the death of the larvae which invoke the inflammatory response in the meninges resulting in eosinophilic meningitis.

Morphology

A.cantonensis is a long slender worm measuring between 17 and 25 mm long by 0.26 to 0.34 mm wide.

Clinical Symptoms

The incubation period is usually about 20 days but can be up to 47 days Infection in man is usually self-limiting but can result in fatalities.  The main symptom is severe headache but other symptoms include convulsions, vomiting, facial paralyses, parasthesia, neck stiffness and fever.  It is accompanied by moderate eosinophilia in the CSF i.e. the cell count is 100 – 2000/mm³.  Blood eosinophilia is also common. Eye involvement is accompanied by visual impairment, ocular pain, keratitis and retinal oedema.  Living worms have been reported and are removed surgically.

Diagnosis

Presumptive diagnosis can be made on the basis of the patients symptoms i.e. fever, meningitis, ocular involvement and severe headache.  Eosinophilia in CSF and peripheral blood is also suggestive.  Larvae or young adults can be recovered in the CSF ELISA can also provide confirmation.