Human gnathosomiasis is characterised by space-occupying inflammatory lesions and haemorrhage as a result of the migration of, very often, a single larva of G. spinigerum. It produces intermittent cutaneous migratory swellings that continue for many years (Rusnak and Lucey, 1993). The worm is able to migrate into deeper tissues, so other organ systems may become involved.
Patients may present with nausea, vomiting, abdominal cramps and diarrhoea as little as 24 hours after ingestion of infected meat (Rusnak and Lucey, 1993). This may later be associated with weakness, pruritis and migratory swellings and myalgia. The swellings are found in cutaneous tissues, and this is the most common and characteristic manifestation. The oedema is typically intense and non-pitting and is associated with pain, pruritis and redness. Infection is usually due to a single gnathostome but multiple infections have been reported. Over time the episodes of migration occur less frequently, the intensity diminishes and recurrent migratory swellings have been known for up to 12 years, but re-infection cannot be excluded (Rusnak and Lucey, 1993). On some occasions, cutaneous gnathosomiasis presents as a skin abscess, skin nodule or creeping eruption that is in a position that allows surgical resection. At present this is the only possible means of cure.
Gnathosomiasis can involve the lung, when infection presents as cough, pleuritic chest pain, dyspnoea, haemoptysis, lobar consolidation, pleural effusions, pneumothorax and hydropneumothorax. Some patients may expectorate the worm and if this occurs it is followed by resolution of the symptoms. Visceral gnathoso-miasis is associated with peripheral blood eosinophilia. Gastrointestinal involvement is rare, presenting as a right lower quadrant mass or acute abdominal pain mimicking appendicitis or intestinal obstruction. Diagnosis is often made by pathological examination of the material after resection. The genitourinary system is rarely involved. As in the case of other migratory worms, the eye may become involved and infection with gnathosomiasis is associated with uveitis, iritis, intra-ocular haemorrhage, retinal scarring, detachment and blindness. The immediate symptoms can be relieved by topical steroids but the definitive treatment is removal of the worm (Punyagupta et al., 1990).
Cerebral involvement by gnathosomiasis is probably quite common and is thought to be the most important parasitic disease of the central nervous system in Thailand. Patients present with myelitis, signs of encephalitis or hemiplegia. The case fatality rate is high, up to 12%. Cerebral gnathosomiasis can be differentiated from eosinophilic meningitis caused by Angiostrongylus cantonensis, as gnathosomiasis is suggested by focal neurological findings, often beginning with severe neuritic pain followed by paralysis, or multiple cranial nerves can be involved, whereas in Angiostrongylus, infection is characterised by low-grade fever, headache, meningitis and lowered cerebral function associated with cerebrospinal fluid (CSF) eosinophilia. Cranial nerve involvement is less common and, when it occurs, usually involves cranial nerves VII or VIII.
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