METHODS: Using Eimeria tenella oocysts as a model parasite, the present study evaluated three check points: (1) the proportion of parasites that remain floating in flotation solution (sucrose or saturated saline) during centrifugation, (2) the proportion of oocysts that naturally float after addition of flotation solution after centrifugation, and (3) the rate of recovery on cover slips after completion of the flotation protocol.
RESULTS: After centrifugation in sucrose solution and saturated saline solution, 82.4% and 60.3% of oocysts floated, respectively. After addition of flotation solution after the final centrifugation step, the recovery rates for oocysts that naturally floated again for 30 min in sucrose and saturated saline were 39.2% and 38.2%, respectively. The recovery rate on cover slips as the final step after performing a commonly used flotation method was 36.4% in sucrose solution (the rate for saturated saline solution could not be assessed due to rapid crystallization).
CONCLUSION: Our results suggest that floating oocysts could have become dispersed by the addition of flotation solution, and not all of these oocysts remained floating after an additional 30 min of settling time although collection on cover slips could be effective for accurate recovery.