Advise clients that they should collect and store feces in a container that will exclude air. A plastic bag or container with
a lid will suffice. Samples should be stored in a cool, dry location out of direct sunlight. Storage in a standard refrigerator
is ideal, although most pet owners are reluctant to place samples in a refrigerator with food. Samples can be refrigerated
for several days to a week without affecting most parasites; however, samples should always be delivered to the veterinarian
and examined as soon as possible. Trophozoites of Giardia and Tritrichomonas species and certain nematode larvae will not survive storage. When these parasites are suspected, the sample must be examined
Table 2 Examples of Commercially Available Centrifuges with Fixed-Angle Rotors*
In preparing fecal samples for centrifugation, eliminate as much large debris as possible (see an overview of sample preparation in Figure 1). First, add the fecal sample (Figure 2) to an amount of flotation solution that will fill the tube into which the mixture will be poured to about 80% of its capacity.
Stir the mixture to distribute the fecal material throughout the flotation solution. If sucrose is used, take care not to
stir the mixture too vigorously to avoid creating air bubbles. Then pour the mixture through a strainer into another clean
container (Figure 3) and into a test tube (Figure 4), or pour the mixture through one or two layers of gauze sponge into another clean container or directly into a test tube.
The filtrate is ready for centrifugation.
CONDUCTING CENTRIFUGAL FLOTATION
Centrifugal flotation can be performed by using either a swinging bucket or fixed-angle centrifuge. We prefer a swinging bucket
centrifuge because it decreases the number of times the sample must be handled.
Swinging bucket centrifuge
For an overview of the swinging bucket centrifuge technique, see Figure 5. Place the prepared sample into a tube holder (bucket) in the centrifuge (Figure 6). Add flotation solution (Figure 7) to form a rounded meniscus at the top of the tube. Gently place a coverslip on the tube (Figure 8). It is important to avoid trapping air bubbles under the slide. This can be prevented by placing one side of the coverslip
in contact with the tube and then slowly lowering the coverslip by gradually reducing its angle over the meniscus of the sample.