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Sodium azide preservation of faecal specimens for Kato analysis

Published online by Cambridge University Press:  06 April 2009

D. A. P. Bundy
Affiliation:
Department of Zoology, University of the West Indies, Kingston 7, Jamaica
J. D. M. Foreman
Affiliation:
Wellcome Trace Element Research Group, Tropical Metabolism Research Unit, Kingston 7, Jamaica
M. H. N. Golden*
Affiliation:
Wellcome Trace Element Research Group, Tropical Metabolism Research Unit, Kingston 7, Jamaica
*
*Author for correspondence.

Extract

The modified Kato technique has the advantages of reproducibility, simplicity and economy: the disadvantage is that it cannot be used in conjunction with traditional faecal preservatives. Sodium azide has been evaluated as a preservative for human faeces for subsequent Kato analysis. More than 400 faecal samples (from normal and malnourished children, and from mixed-age participants in a field survey of the Turks and Caicos Islands) were each mixed with 2–5 mg of sodium azide powder and stored in 2 or 4 ml autoanalyser cups at ambient tropical temperature. At intervals up to 30 weeks, aliquots were prepared for Kato analysis. Trichuris trichiura, Ascaris lumbricoides and Necator americanus eggs were well preserved without degenerative or developmental changes in morphology. Quantitative analyses of 18 samples indicated that the mean egg count/sample did not change significantly after storage for 1, 2, 4, 8, 12 and 16 weeks in preservative. The use of azide preservative extends the applications of the Kato technique to field and clinical studies in which delays may occur between specimen collection and examination. The direct costs of azide preservation are substantially lower than for traditional methods and the preserved specimens are more compact and resistant to leakage.

Type
Research Article
Copyright
Copyright © Cambridge University Press 1985

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