The development and performance of a simple, sensitive method for the detection of Cryptosporidium oocysts in faeces.

Features are described of a new staining method for the detection of Cryptosporidium oocysts in faeces. Smears, fixed in acid-methanol, are stained with heated safranin and counterstained with methylene blue. Oocysts stain a vivid orange-pink and are easily recognized. The method is rapid and simple with little source of error. The method is more sensitive than currently recommended Ziehl-Neelson methods; of 26 cases of cryptosporidiosis diagnosed by the new method only 19 were detected by acid-fast and only 11 by acid-alcohol-fast methods. Oocysts can be stained by safranin-methylene blue after concentration by various methods, in paraffin-embedded material, and after storage for months at various temperatures.