Biomedical subjects
Publications and source records attributed to J J Laarman.
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Findings are described of small (8-10 microns) coccidian oocysts in the stools of 9 patients presenting with diarrhoea, all of whom with a history of travelling in South Asia and/or South America in the years 1986 and 1987. There was no indication of immunodeficiency. These oocysts, which were immature in freshly excreted stools, could be induced to sporulate into a two-sporocysts stage and are now recognized as Cyclospora spec.
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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In situ hybridization techniques develop rapidly into diagnostic tools of considerable value for detection of viruses and bacteria. Here we report the application of this technique for the detection of Leishmania parasites. Biotin-labelled total promastigote DNA was hybridized to cultured Leishmania parasites and to blood and impression smears of infected mice. In promastigotes kinetoplasts were strongly stained, nuclei somewhat more diffuse. In amastigotes both nuclear and kinetoplast DNA hybridized strongly. Amastigotes were easily detected in tissue of infected mice by their stable configuration of kinetoplast and nuclei. Cross-hybridization was observed between Leishmania donovani and L. tropica, but not between these two and L. braziliensis or Trypanosoma cruzi. A minor aspecific staining of host cell nuclei in the smears did not interfere with the detectability of the parasites.
Promastigotes of Leishmania donovani cultured in liquid media gradually changed from a majority of elongated forms through a predominance of intermediate spindle-shaped parasites to a majority of round forms, often aflagellate. Quantitative and qualitative differences among these subpopulations, separated on Percoll gradients, could be demonstrated when they were run on SDS-PAGE gels and stained from proteins or carbohydrates. When cultures containing a majority of one or other form were used as antigenic substrate in serological tests (ELISA and immunofluorescence) the older, round forms were more highly reactive with patients' sera. These forms may represent different phases of the parasite, related to function, and the density variations would provide a convenient method to separate them.
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.
A microagglutination test using trypsin-treated and Coomassie blue-stained Trypanosoma cruzi epimastigote antigen was adapted for the diagnosis of Chagas' disease. When incorporated in the test, 2-mercaptoethanol treatment of chagasic sera had no influence on antibody titer. In contrast, titers in sera from patients with visceral leishmaniasis, African trypanosomiasis, and autoimmune disorders, subjected to similar treatment, showed remarkable decline. Accordingly, a lower cut-off point for Chagas' disease serological negativity could be taken resulting in a higher sensitivity (95.6%); the specificity was 94.7%. Similar specificities were obtained with Leishmania donovani chagasi and L. d. donovani antigens applied to homologous visceral leishmaniasis and heterologous Chagas' sera. Of 316 nonchagasic sera, only 3 with leptospirosis and 1 with leprosy showed seropositive titers prior to and after 2-mercaptoethanol treatment.
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Two established immunodiagnostic techniques, immunofluorescence and indirect haemagglutination, were compared with ELISA (enzyme-linked immunosorbent assay) using intact promastigotes as antigen for the detection of specific antibodies against Leishmania in the serum of patients with visceral or mucosal leishmaniasis from the Sudan. The ELISA was found to be more sensitive and more specific than either of the other two tests.
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.
The commonly used diagnostic methods for visceral leishmaniasis (kala-azar) have many disadvantages. ELISA appears to be a more easily applied test for diagnosis, follow-up of treatment and epidemiology. The preparation of the ELISA antigen has given rise to difficulties in standardization since these are usually soluble. Intact cultured promastigotes have been used to develop an ELISA which is sensitive and specific while avoiding the extra handling which is a source of variability and lack of reproducibility. When tested on sera from kala-azar patients and patients with other tropical diseases, this ELISA was able to detect specific antibodies at very high serum dilutions. It is thus promising as a screening method applicable in the field.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
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Muscular sarcosporidiosis is reported for the first time in the common European weasel, Mustela nivalis. The morphology of the sarcocysts is described from fresh and stained histological preparations. Attempts to complete the sexual cycle of this mustelid parasite in a tawny owl, Strix aluco, are reported and the results discussed in the light of hypothetically likely sources of infection with muscular sarcosporidiosis for carnivores or omnivores, including man and other primates.