Neurognathostomiasis

The worms nematodes (Gnathostoma spinigerum) reside in the stomach of cats and dogs. They release eggs in the faeces. The eggs hatch after 10-12 days after reaching water. The first-stage larvae are taken up by Cyclops crustaceans and moult to second stage larvae. After an infected Cyclops is swallowed by a second intermediate host, such as freshwater fish, frogs, snakes, chickens or pigs, a third stage larva develops. People infect themselves by eating raw of undercooked freshwater fish, poultry or pork. The disease is less commonly acquired through drinking water containing infected copepods. In humans, the third-stage larvae (10-25 mm in length) penetrate the gastric wall and migrate through the soft tissues of the human body for as long as 10 to 12 years. Unlike Angiostrongylus, this parasite is not neurotropic, and involvement of the central nervous sytem is an accidental featuere of infection. The clinical presentation is more fulminant than that of angiostrongyliasis. Gnathostoma spinigerum penetrates the central nervous sytem by migrating along nerve roots. The most characteristic feature is radiculitis, with excruciating nerve root pain in the limbs or trunk. Subarachnoid haemorrhage and intracerebral haematoma can develop. Paralysis and urinary retention often develop, followed by involvement of the cranial nerves. Other findings are myelitis and meningoencephalitis. There is important mechanical damage from the migrating larvae, with necrotic tracts in the brain and spinal cord and often haemorrhages. Focal lesions are visible on MRI-scan of the brain. Antihelminthic agents are not effective. Corticosteriods are often used to diminish the inflammation. Permanent neurological deficits are common. Mortality is between 7 and 25%.

Category: Medicine Notes