Eosinophilic meningitis. An unusual cause of headache.

Human parasitic infections are uncommon outside the tropical north but common in animals throughout Australia. The rat lung worm, Angiostrongylus cantonensis, can invade the human brain to cause a chronic meningitis with prolonged headache. This condition can be diagnosed by finding a high eosinophil count in cerebrospinal fluid (CFS), the lumbar puncture also provides symptomatic relief. The outcome is usually benign but death has been reported.