Evaluation of Parasite Egg and Cyst Recovery Using Devices Designed for Centrifugal or Stationary Flotation

Two new devices (OT, ST), were recently introduced for the recovery of parasite eggs and cysts for microscopic examination. These devices, two stationary flotation devices, and a standard double-centrifugal sugar-flotation were compared using common flotation solutions and methods recommended by the manufacturers for the recovery of hookworm, ascaridoid, and whipworm eggs from companion animal fecal samples. Additionally, the recovery of Giardia cysts in the OT device using a zinc sulfate versus sodium nitrate solution was evaluated. Double-centrifugal sugar-flotation (1.30 specific gravity) was the most sensitive method for the recovery of the nematode eggs from feces of companion animals. Overall, centrifugation increased the recovery of eggs as compared with standing flotation methods, with the ST performing equivalently to the OT. Although these more recently introduced tests have good sensitivities for the nematodes tested, egg recovery was routinely markedly less than that achieved by standard double-centrifugal sugar-flotation, and false-negatives did occur. Still, the OT and ST generally have increased recoveries over the two standing flotation devices, and are significantly better than these for the recovery of ascaridoid and whipworm eggs from dog and cat samples. Zinc sulfate (1.18 specific gravity) is recommended for the recovery of Giardia cysts when using the OT device.