ABSTRACT
Amebic Meningoencephalitis (AM) and Primary Amebic Meningoencephalitis (PAM) are infectious diseases essentially confined to the Central Nervous System (CNS) and caused by free-living amebas of the genus Acanthamoeba (A.) and Naegleria (N.) respectively. AM due to A. sp. (Acanthamoeba castellanii and Acanthamoeba culbertsoni) have been reported in chronically ill debilitated individuals, some of them under immunosuppressive therapy, or in immunologically impaired patients without a history of recent swimming in contrast to cases due to N. sp. which usually occurs in healthy, young individuals with a recent history of swimming in man-made lakes or heated swimming pools. AM due to A.sp. is characterized by a subacute or chronic granulomatous meningoencephalitis involving mainly the midbrain, basal areas of the temporal and occipital lobes and posterior fossa structures. CNS lesions in AM are perhaps secondary and the portal of entry in humans is probably from the lower respiratory tract, genitourinary system or skin reaching the CNS by hematogenous spread. The predominant host reaction is usually composed of lymphocytes, plasma cells, monocytes and multinucleated foreign body giant cells. Necrosis is moderate and hemorrhage scant or absent. Cysts as well as trophozoites may be seen within the CNS lesions. PAM is due to Naegleria fowleri and is characterized by an hemorrhagic necrotizing meningoencephalities with an acute inflammatory response. Only trophozoites are found in lesions. The portal of entry is through the olfactory neuroepithelium. CNS tissues fixed in formalin may be used for further identification and taxonomical classification of the causative protoza using immunofluorescent antibody techniques (IFAT) and electron microscopic methods.
Subject(s)
Amebiasis , Meningoencephalitis/etiology , Amebiasis/pathology , Amoeba/ultrastructure , Brain/pathology , Meningoencephalitis/pathology , Microscopy, ElectronABSTRACT
A simple precipitin test (CAP) using cellulose acetate membrane has been devised and evaluated against the gel diffusion precipitin (GDP) test. In 251 sera tested by both methods, the CAP was never negative when the GDP was positive (110 sera). 34 sera were negative by the GDP but positive by the CAP; in all of these the patients either had a past history of amoebiasis or were considered to have active amoebiasis. The CAP is technically very simple, the result is available within four and a half hours, and the membranes can be impregnated with antigen and stored for several months. The CAP is slightly more sensitive than the GDP and remains positive longer after the patient has been cured; it seems to be equally specific.
Subject(s)
Amebiasis/diagnosis , Precipitin Tests/methods , Evaluation Studies as Topic , Humans , ImmunodiffusionSubject(s)
Amebiasis/pathology , Meningoencephalitis/etiology , Adolescent , Adult , Amebiasis/epidemiology , Amoeba/immunology , Amoeba/isolation & purification , Child , Female , Fluorescent Antibody Technique , Humans , Male , Meningoencephalitis/epidemiology , Meningoencephalitis/pathology , United States , VirginiaABSTRACT
One hundred sera from army patients who had had amoebiasis in the past and 113 sera from coloured immigrants attending a venereal diseases clinic were examined by four serological techniques. The indirect haemagglutination and the latex agglutination tests showed almost complete correlation; they are useful epidemiological tools but too sensitive and the antibodies on which they depend are too persistent for clinical use. The indirect fluorescent antibody test is a good clinical screening test, and in an area of low endemicity the gel diffusion precipitin test shows a close correlation with clinical disease.
