Primary amoebic meningoencephalitis in Britain.

Primary amoebic meningoencephalitis is caused by amoebae of the genera Naegleria and Hartmannella (Acanthamoeba), which ordinarily are free-living saprophytes. The infection may be acquired from fresh water-for example, while bathing-the amoebae invading the nasal mucosa and reaching the meninges and brain along the olfactory nerve filaments. The disease is designated "primary" to distinguish it from meningocerebral infection caused by the parasitic amoebae, particularly Entamoeba histolytica, which invade the central nervous system only as a result of dissemination in the blood stream from lesions in other parts of the body.During histological reappraisal of old specimens in a medical museum in London an instance of amoebic meningoencephalitis histologically indistinguishable from the published cases has been found. The specimen dates from 1909. The patient was said to be from Essex. What may have been another case, seen in Northern Ireland in 1937, is also described briefly. These observations may indicate that this disease occurs in the British Isles.Primary amoebic meningoencephalitis should be considered in the differential diagnosis of every case of acute meningitis.