Why fecal centrifugation is better - Veterinary Medicine
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Why fecal centrifugation is better


VETERINARY MEDICINE SUPPLEMENT


Fixed-angle rotor

If your centrifuge has a fixed-angle rotor, add the mixture of feces and flotation solution to a tube, filling it to within about 1 in of the top. Spin the preparation at about 1,200 rpm for five minutes. Remove the tube, add flotation solution to form a reverse meniscus, and carefully place the coverslip, as described above. Allow the preparation to stand for an additional 10 minutes, remove the coverslip, and examine the sample.

AN IN-CLASS EXPERIMENT

So what proof do we have that centrifugal flotation is better than passive flotation? I perform an interesting exercise every year in my parasitology class by using a fecal sample from a dog with a hookworm burden typical of what practitioners would see in pet dogs. The students are divided into three groups. One group performs a direct smear, another group mixes 2 g of feces with flotation solution and performs a passive flotation procedure, and the third group uses 2 g of feces and performs the centrifugal flotation procedure.

Each year the results are graphic. Usually only 25% of the students performing the direct smear recover hookworm eggs. About 70% of the students performing the passive flotation procedure report seeing hookworm eggs. And every year, without exception, 100% of the students performing the centrifugal flotation procedure report recovering hookworm eggs. This simple exercise convinces my students of the improved sensitivity of centrifugation. Improved recovery rates using centrifugal flotation procedures are also substantiated by published studies.1-4

CONCLUSION

Now that prepared flotation solutions and high-quality, inexpensive swinging bucket centrifuges can be purchased from several commercial sources, it is much easier to adopt centrifugal flotation techniques. It doesn't require much cost, effort, or time to improve your parasite detection technique with this important diagnostic procedure.

Byron L. Blagburn, MS, PhD, Department­ of Pathobiology, College of Veterinary Medicine, Auburn University­, Auburn, AL 36849. Dr. Blagburn is immediate­ past-president of the Companion­ Animal Parasite Council.

REFERENCES

1. Blagburn BL, Butler JM. Optimize intestinal parasite detection with centrifugal fecal flotation. Vet Med 2006;101(7):455-464.

2. Dryden MW, Payne PA, Ridley R, et al. Comparison of common fecal flotation techniques for the recovery of parasite eggs and oocysts. Vet Ther 2005;6:15-28.

3. Dryden MW, Payne PA, Smith V. Accurate diagnosis of Giardia spp and proper fecal examination procedures. Vet Ther 2006;7:4-14.

4. Zajac A, Johnson J, King S. Evaluation of the importance of centrifugation as a component of zinc sulfate fecal flotation examinations. J Am Anim Hosp Assoc 2002;38:221-224.


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