EFFICIENCY AND SENSITIVITY OF TECHNIQUES FOR RECOVERING NEMATODE EGGS FROM BOVINE FECES

  • 1 January 1981
    • journal article
    • research article
    • Vol. 45  (3) , 243-248
Abstract
H. contortus eggs were extracted from sheep feces and known numbers were added to helminthologically sterile bovine feces to provide samples with 7, 30 and 60 eggs/g (epg). At 60 epg, dilution techniques (modified Cornell-McMaster and modified McMaster) tended to overestimate the number of eggs and more eggs were recovered (mean of 121 and 88%, respectively) with these techniques than with centrifugal concentration procedures (modified Cornell 63% and Wisconsin 69%). At 30 epg, all techniques were comparable (modified Cornell-McMaster 67%, modified McMaster 63%, modified Cornell and Wisconsin 64%). At 7 epg, the Wisconsin (61%), modified Cornell (60%) and Cornell-McMaster (94%) techniques were comparable and better than the modified McMaster technique (16%). At all levels of epg, the modified Cornell and Wisconsin techniques recovered eggs from 100% of the samples. The Cornell-McMaster and modified McMaster techniques recovered eggs from 90 and 100% of samples at 60 epg; 40 and 100% at 30 epg; and 21 and 11% at 7 epg. With a gravitational concentration procedure, the standard vial, no more than 16% of the eggs at any level of epg were recovered and at 7 epg eggs were recovered from only one-half of the samples. Five gravitational concentration techniques were assessed over 66-490 epg. The ovassay, fecalyzer and modified standard vial techniques were comparable in efficiency (28, 25 and 24%, respectively) but the standard vial technique was less efficient (11%). Introduced into diagnostic parasitology is the concept of predictive values which is the proportion of samples that a technique correctly identifies as being negative for parasite eggs. At 7 epg this was calculated to be 0 for the modified Cornell-McMaster, modified McMaster and standard vial techniques and 100 for the Wisconsin and modified Cornell techniques.