Parasitic diseases of the nervous system in Thailand.

In Thailand there are 3 parasites that commonly cause neurological diseases in man. 1) In gnathostomiasis man becomes an accidental host by eating infected under-cooked fresh water fish. The tissue nematode involved, Gnathostoma spinigerum, because of its high motility, may cause widespread damage in the spinal cord and brain stem. The common presenting neurological symptoms are severe nerve root pain, paralysis of limbs and urinary retention. Less frequently seen are cranial nerve palsies and symptoms of subarachnoid haemorrhage. The disease has significant morbidity and mortality. 2) Eosinophilic meningitis caused by Angiostrongylus cantonensis, the lungworm of rats, has a more benign, self limiting course. It occurs in Thai people of lower socio-economic groups who acquire the parasite by eating infected raw Pila snails. 3) Cysticercus cellulosae, caused by Taenia solium, commonly results in epilepsy, and sometimes increased intracranial pressure from intraventricular obstruction or from basal arachnoiditis. Spinal cord and cauda equina involvement occurs much less frequently. Cysticercus complement fixation tests on the CSF and computerised axial tomography have been found to be of great diagnostic value.