Comparison of passive fecal flotation run by veterinary students to zinc-sulfate centrifugation flotation run in a diagnostic parasitology laboratory.

The sensitivity of fecal examination methods can be influenced by both technician error and methodology. In this analysis, we compared the results of 335 passive fecal flotation examinations performed on the feces of stray dogs by 3rd-yr veterinary students at the University of Pennsylvania, School of Veterinary Medicine, to the results obtained through zinc-sulfate centrifugation performed by the diagnostic parasitology laboratory on the same fecal samples. The students' passive flotation results agreed with the laboratory zinc-sulfate centrifugation for only 62.4% of samples. Students were able to diagnose 75.0% of Ancylostoma caninum cases, 71.4% of Toxocara canis cases, 54.2% of Trichuris vulpis cases, 26.7% of Cystoisospora spp. (C. ohioensis-like and C. canis) cases, and 14.7% of Giardia lamblia cases. There were also 70 instances where students reported the presence of parasites in the sample that were not diagnosed by zinc-sulfate centrifugation. Based on the overall study findings, passive fecal flotation examinations run in private practice could be missing up to 50.5% of infected dogs, due to either technician error or inherent limitations to the passive fecal flotation technique.