The Acid-Ether Centrifugation and the Zinc Sulfate Flotation Techniques as Methods for the Recovery of the Eggs of Schistosoma Mansoni

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Summary and Conclusions

A uniform suspension was prepared from each of 46 fecal specimens selected because they were known to contain relatively large numbers of eggs of Schistosome mansoni. The number of eggs per cc. in each suspension was then determined by the Stoll dilution egg counting technique. The suspensions were examined by the routine diagnostic modification and also a semiquantitative modification of the acid-ether centrifugation technique and the zinc sulfate flotation technique and counts were made of the eggs recovered by the four methods. For twenty-five specimens found to contain over 400 eggs per cc., the results of the counts obtained by the various techniques were expressed in terms of the percentage of the available eggs that were actually recovered.

The acid-ether technique was found to be superior to the zinc sulfate flotation technique as a routine method for the isolation of schistosome eggs, recovering a greater number of eggs from 41 of the 46 specimens. In the group of 25 specimens, the acid-ether routine method gave an average percentage of 20.6% while the zinc sulfate counterpart gave an average of 4.6%. The semiquantitative modification of the acid-ether technique gave an average recovery of 48.2% while the zinc sulfate semiquantitative method gave an average recovery of 22.2%. The acid-ether preparations showed no distortion of the eggs, and usually contained less extraneous fecal debris than did the zinc sulfate preparations.

Although the acid-ether technique has inherent disadvantages the simplicity and efficiency of the method are such that it would appear to deserve further investigation as a routine diagnostic and survey procedure for the recovery of the eggs of Schistosoma mansoni.

Author Notes

Captain, Med. Corps A. U. S.

Major, Med. Corps A. U. S.