A simple and economical direct agglutination test for the detection of visceral leishmaniasis is described. Trypsin-treated, Coomassie Brilliant Blue-stained, formalin-preserved promastigotes were used as antigen in re-usable V-well microtitre plates. In 21 patients with recent kala-azar, titres of 1:51200 or higher were found. Cured kala-azar patients treated 4 to 14 months before testing, showed titres in the range of 1:3,200 to greater than 1:51,200. Healthy and diseased controls had titres below 1:1,600 with the exception of African trypanosomiasis patients who showed titres of 1:200 to 1:12,800, overlapping with the titres of cured kala-azar patients. Where trypanosomiasis is not a consideration, a titre of 1:1,600 could be considered indicative of visceral leishmaniasis, the sensitivity and specificity were then 100%. The test was applied to sera of 280 inhabitants of Baringo District, a known focus of visceral leishmaniasis in Kenya. When treated cases were included, the test showed a sensitivity of 100% and specificity of 99.3%. This test could be used in district hospitals and health centres in endemic areas as an aid in diagnosis of kala-azar and in the field for sero-epidemiological studies.
A newly developed direct agglutination test (DAT) for visceral leishmaniasis, IFAT and ELISA were applied to sera of patients with visceral leishmaniasis, African and American trypanosomiasis, other parasitic infections and healthy controls. The sensitivities of the 3 tests were comparable (96.3% to 100%); excluding patients with African and American trypanosomiasis, the specificities of DAT and IFAT were 100% and ELISA 87.3%. When trypanosomiasis sera were included, the specificities were 72.6%, 94.3% and 79.4% in DAT, IFAT and ELISA respectively. In 273 sera from a leishmaniasis endemic area (Baringo District, Kenya), the sensitivity was 80% in DAT and IFAT and 60% in ELISA, specificities being 99.6% (DAT), 98.5% (IFAT) and 62.5% (ELISA). As the new DAT is economical and easy to perform, it is recommended for sero-epidemiological field work on visceral leishmaniasis.
Six fresh Giardia lamblia strains were isolated by in vitro excystation and subsequent culturing of excysted parasites in bile-supplemented BI-S-33 medium. The cysts passed in faeces appeared to differ in structure when observed using differential interference contrast microscopy. Sometimes the enclosed organisms were closely applied to the cyst wall; in most stool specimens, however, the parasites were separated from the cyst wall by a space. Cysts with parasites closely applied to the wall were the most viable type, with excystation rates up to 90%. Cysts with organisms detached from the wall displayed low excystation rates, 0-15%. During exposure to the induction solution of hydrochloric acid (pH 2), parasites initially closely applied to the cyst walls completely detached, and after transfer into culture medium vigorous flexing movements of the organisms were observed. Stool samples from 42 symptomatic and asymptomatic giardiasis patients were examined; in 26 of the samples parasites hatched, and 6 new strains were established in axenic culture.
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