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At least 127 records · Page 7Linked to original sources
PubMed1977

The epidemiology of infection with Entamoeba histolytica in the Gambia, West Africa.

A country-wide stool survey of The Gambia showed the prevalence of Entamoeba histolytica cysts to range from 13.7% up-country in the dry season to 52.3% near the coast. A longitudinal survey showed a near 100% infection rate over one year and a sharp rise in prevalence as the rains commence with an equally sharp fall as the rains progress. Specific antibody levels are elevated and reasonably constant through the year. Carriers generally show no specific lymphocyte reactivity to amoebic antigen but consistently parasite-negative individuals tended to show elevated lymphocyte reactivity. Attempts to discover the presence of cysts in the environment of villages by cultivation of specimens of water, soil, food, flies and washing from clothes and hands generally failed though E. histolytica was recovered once from a well.

Amebiasis↗
PubMed1980

Protective effects of crude and chromatographic fractions of axenic Entamoeba histolytica in guinea-pigs.

Axenic amoebic antigen was chromatographed on Sephadex G-200. Two peaks divided into three fractions were obtained which were concentrated by lyophilization. Guinea-pigs were given a series of subcutaneous injections of crude Entamoeba histolytica antigen and its chromatographic fractions mixed with Freund's complete adjuvant. After three immunizing doses, the animals were challenged with intracaecal injection of a virulent isolate of amoebae (Strain No. H-25) and were killed seven days later. The antibody response was studied by indirect haemagglutination (IHA) and counter-current immunoelectrophoresis (CIEP) before intracaecal inoculation and at the time of killing. Fraction I, which had the highest molecular weight, stimulated high levels of antibodies in guinea-pigs and showed 92% protection. Only one animal of 12 inoculated had gross lesions and these were very mild. The caecal contents of three of the 11 animals without gross lesions were positive for amoebae but no tissue invasion was observed. Partial protection was observed with other antigens--30% with whole amoebae, 18% with Fraction II and 30% with Fraction III. In most there were multiple ulcers of the deep penetrating type and amoebae either penetrating and invading the muscular layer or the lytic process extending up to the muscular layer. In one animal, immunized with whole amoebic antigen, multiple hepatic lesions were also observed and trophozoites of E. histolytica were demonstrated histologically.

Amebiasis↗
PubMed1980

Experimental amoebic infection in guinea-pigs immunized with low grade amoebic infection.

Guinea-pigs were immunzied with a low grade amoebic infection, either intracaecally or intramesenterically. The immunized animals were challenged with a virulent strain of Entamoeba histolytica. Some of the animals, immunized via the intracaecal route were challenged repeatedly. 10 to 30% of immunized animals developed caecal lesions compared with 92.8% of non-immunized animals. The percentage of protection in animals challenged repeatedly was greater than in those challenged once. Neither immunized nor non-immunized guinea-pigs developed hepatic abscesses. It appears that prior low grade infection could lead to resistance to subsequent amoebic challenge.

Amebiasis↗
PubMed1980

Specific anti-amoebic immunoglobulins and the cellulose acetate precipitin test in Entamoeba histolytica infection.

Using the indirect fluorescent antibody test and sera from 10 proved cases of invasive amoebiasis, the effects of absorption of IgG on observed titres of amoeba-specific IgM and IgA were investigated. In addition, results of cellulose acetate precipitin tests were compared with anti-amoebic antibody levels. Antiamoebic IgM was found at titres of 1:14 to 1:112 after IgG absorption in four cases. Anti-amoebic IgA was detected in sera from four cases, but the maximum titre was 1:28. There was no relationship between the presence of amoeba-specific IgM or IgA and the result of the precipitin test, but a raised anti-amoebic IgG level was consistently found where the precipitin test was positive. However, sera with raised amoeba-specific IgG levels did not invariably give a positive precipitin reaction.

Amebiasis↗
PubMed1981

Effect of specific and non-specific prior sensitization on the outcome of amoebic infection.

Guinea-pigs were sensitized with monoaxenic amoebic antigen (Group I), bacterial associate antigen (Group II) and axenic amoebic antigen (Group III). All animals in Group I, 95% in Group II and 70% in group III, developed caecal lesions on intra-caecal inoculation of Entamoeba histolytica trophozoites; 92.8% of control (unsensitized) animals developed lesions in their caeca. Lesions were more severe in sensitized animals than in controls. Hepatic abscesses were found in 7.6% of group I, 11.1% of group II and 7.1% of group III. No animal from the untreated but infected group developed hepatic abscess. It thus appears that specific (amoebic) and non-specific (bacterial) prior sensitization may render the host more susceptible to hepatic amoebic infection.

Amebiasis↗
PubMed1981

Virulence of Entamoeba histolytica in rat and its comparison with the serological responses of the amoebic patients.

The virulence of 70 isolates of Entamoeba histolytica was studied in the Wistar strain of albino rat by intracaecal inoculation of amoebae. The results were evaluated by the Neal scoring system, histopathological grading of ulcers and virulence indices. It was found that isolates from acute amoebic cases could infect and produce ulcers in significantly more animals than could the isolates from asymptomatic cyst passers. The virulence indices of isolates from acute cases were also significantly higher as compared to those from asymptomatic cyst passers. However, there was no significant difference between virulence indices of isolates from acute cases and non-dysenteric amoebic colitis. This study also showed that Neal scores failed to correlate with the type of pathology produced by the amoebae in the caecum. It is felt that virulence indices which depend upon the histopathological lesions should also be taken into consideration. The serological response of the patients tended to correlate with the virulence indices of isolates but only minimally. The results thus contradict a common belief amongst clinicians that higher levels of anti-amoebic antibodies reflect severe disease, as compared to low levels of antiamoebic antibodies.

Acute Disease↗
PubMed1981

Prevalence of intestinal helminths and protozoans in a rural population segment of the Dominican Republic.

There are few reports of parasitic disease prevalence in the Dominican Republic. The most recent study was that by Mackie et al. (1951). Examination of purged specimens from individuals employed by two sugar plantations demonstrated generally high prevalences of a number of helminths and protozoans. We report here the findings of a prevalence study using a population sample of 453 individuals. Ascaris lumbricoides, Trichuris trichiura, hookworm, Enterobius vermicularis, Giardia lamblia and Entamoeba coli were found.

Adolescent↗
PubMed1982

Preliminary observations using a multi-layer ELISA method for the detection of Entamoeba histolytica trophozoite antigens in stool samples.

A method for detecting Entamoeba histolytica trophozoite antigens in aqueous solution is described. This involves coating plastic microtitre plates with a 'catching antibody', specific rabbit anti-E. histolytica antibody (SRAE). After adding the test material the presence of antigen is determined using two additional heterologous antibody layers, one of 'developing antibody', in this case human anti-E. histolytica immunoglobulin (HAE), which is followed by a final layer of peroxidase conjugated sheep anti-human immunoglobulin antibody (SH-HRP). The specificity and sensitivity of the assay was investigated both in the model system and using stool samples from infected patients. In the model system, the test had a sensitivity equivalent to detection of approximately one amoeba per microscope coverslip (18 mm X 18 mm). Little cross reaction was observed with other intestinal parasites common to the area of Bangladesh from which the stool samples were taken. The possible use of this method in large scale screening of stool samples and in the detection of circulating antigens is discussed.

Amebiasis↗
PubMed1982

A zymodeme study of Entamoeba histolytica in a group of South African schoolchildren.

Using a biphasic culture medium, stocks of intestinal amoebae were isolated from a group of children attending school in Durban, South Africa. These were compared with stocks collected in other areas of the world already characterized using the electrophoretic patterns of four enzymes: glucose phosphate isomerase (GPI), phosphoglucomutase (PGM) L-malate: NADP+ oxido-reductase (oxalacetate-decarboxylating) (ME) and hexokinase (HK). 33% of 94 samples grew Entamoeba histolytica, only one of which gave a pattern indicative of a pathogenic stock. Entamoeba hartmanni, Dientamoeba fragilis and Entamoeba coli were also grown from some samples, increasing the total positive samples for all species isolated to 40%.

Adolescent↗