By Michael Dryden, DVM, MS, PhD, DACVM, Professor at Kansas State University & Mike Thomas, V.P. of Sales for LW Scientific

It’s not often that veterinary professionals discover a simple change in daily routine that will improve diagnosis, speed up treatments, and keep profits in the clinic. Spinning fecals is coming back… coming back into the clinic as the new standard for intestinal parasite detection and treatment.

Coprologic (fecal) examinations for parasite eggs, cysts, and oocysts are important for the diagnosis of diseases in animals, several of which could also be transmitted to people. Using the best technique is imperative for accurate diagnosis, and a multi-year study performed by Dr. Michael Dryden and Dr. Patricia Payne from Kansas State University has shown the swing-out centrifuge fecal method to be hands-down the best technique for sensitivity and accuracy. If you are not using this technique you may have a much higher rate of false negatives and overlook parasitic and zoonotic diseases.

The Solutions
Which floatation solution you choose is a big part of the solution! Parasite eggs and oocysts have different densities ranging between 1.05 and 1.23, and they will not float in water. However, if the solution is denser than the eggs, they will float to the top. Common floatation solutions include Zinc Sulfate, Sodium Nitrate, and Sugar Solution (Sheather’s). The BEST solution to float most eggs is Sheather’s solution, because the specific gravity is the highest at SG 1.27. The other solutions have lower specific gravities, which will not float some of the heavier eggs, such as Taenia tape worm eggs and the eggs of the stomach worm Physaloptera sp. Sheather’s solution (J1028G) is now available in various-sized bottles from Jorgensen Laboratories.

The Methods
Some clinics are performing fecals in-house, but are using the Passive Floatation (standing float) method. This method uses 1 g-force to float the eggs (1 force of gravity is what keeps your feet on the ground). With 1 g-force some of the eggs will slowly make their way up to the top of the tube and lightly touch the coverslip, leaving you wondering if you recovered all the eggs (likely not). Imagine if you could apply 280 g-force to the solution…more eggs would be accelerated upward and would push onto the coverslip with much greater force. So take that Passive Floatation, turn it sideways, and spin it in a swing-out centrifuge! Using the Swing-out Centrifuge Method with the coverslip on top of the tube produces a much higher yield and recovery, thus more accurate diagnosis.

The Procedure
For the Swing-out Centrifuge Method: mix 2g to 5g of feces with 10ml of Sheather’s solution in a paper cup, and pour the solution through a strainer (or cheese cloth) into a 15ml conical test tube. Top off the 15ml test tube with a slightly positive meniscus and set the coverslip onto the top of the tube. Place the test tube and coverslip into the centrifuge and give the coverslip one last tap down to seat it. Spin at approximately 1,300 rpm (280 g-force) for 5 minutes, then leave the coverslip on the tube for an additional 10 minutes to allow the eggs to stick. Next remove the coverslip and perform a complete scan using the 10x objective and the 40x objective for a closer look at questionable eggs.

*Note: One exception is Giardia cysts which are more readily recovered and identified using Zinc Sulfate solution

The Mess
Here are a few helpful tips that will keep your hands and workspace clean, and extend the life of your centrifuge:

• The Squeeze Test (J1250) from Jorgensen Laboratories is a collection and transport device which includes the collection spoon, container, mixing chamber, and strainer all in one sealed unit for safety, hygiene, and convenience.

• Always train your staff to prepare and fill their test tubes and set the coverslip in a rack over a paper towel by the sink first, and then transfer the tube to the centrifuge. Never fill the test tubes inside the centrifuge, because spilling excess fecal solution can make the centrifuge spin off balance due to fluid filling the sleeves. Excessive spilling can also damage and corrode the centrifuge internally…especially the salt solutions.

How well does the coverslip stay on the tube? Great question … this should help:

The Test Tube
Through studies done at LW Scientific, many different types of test tubes were tested with coverslips placed on top in swing-out centrifuges. The conclusion is that Polypropylene tubes are by far the best tubes for holding coverslips. Polypropylene tubes are opaque with a somewhat “rubbery” feel, and the top rim is very flat and smooth, creating a perfect seal for the coverslip. Glass tubes were second best, with a smooth top rim, but sometimes the top rim is not as wide and flat. Polystyrene tubes, the cheapest tubes available, tested the worst. Polystyrene tubes are clear, with a “hard” feel, and often they have rough top rims with sharp edges or bumps - not good for seating a coverslip.

Test your own tubes in your clinic: Fill the test tube with water over the sink, set a coverslip on top and tap it down, then turn the tube 90 degrees and even upside down. You will be amazed that the coverslip will stay on the Polypropylene tube even upside down! Be careful with the other types of tubes!

The Centrifuge
Most clinics already own a fixed-angle centrifuge for spinning bloods and urines. Yes, fecals can be spun in an angled centrifuge, but you cannot top off the test tube and you cannot set a coverslip on the test tube while spinning. You can fill the test tube short of the top and spin it so the eggs all come to the surface. Next, move the test tube to a rack, then use a pipette to raise the meniscus, and place a coverslip on top. At this point you have reverted to a passive float, but at least you forced the eggs upward before you set the coverslip.

The BEST centrifuge is a swing-out horizontal centrifuge that is designed for spinning fecals. This means the tube holders must hang vertical at rest, swing out horizontal while spinning, and have clearance for the coverslips. The centrifuge also must have very smooth acceleration and deceleration so the coverslips are not jarred loose. Not every swing-out centrifuge is designed for spinning fecals.

• USA C5 Centrifuge: Jorgensen Laboratories offers the C5 centrifuge (J0501SQ): the premium choice for spinning fecals. The C5 is the one and only centrifuge that can spin everything (blood, urine, fecals, crits, microtubes, semen, IRAP, PRP, stem cells, etc). Plus the C5 centrifuge is manufactured in Atlanta, GA by LW Scientific, ensuring American quality and pride.

• USA Ultra Digital Centrifuge: In 2014, Jorgensen Laboratories introduced the new USA Ultra Digital swing-out centrifuge (J0501WCH), which, at only $795 list, has made spinning fecals affordable to every clinic. Although designed as the low-cost leader, this centrifuge features digital touch-pad controls and super quiet operation. The USA Ultra Digital is also manufactured in Atlanta, GA by LW Scientific.

The Payback
Sending fecals to the commercial lab usually costs around $8-9 each and takes 24+ hours to get results. Bringing fecals back in-house could put roughly $800-900 back into the profit of the clinic each month, plus clients can be diagnosed and treated on the spot. Therefore, the investment into the centrifuge and supplies could pay for itself within the first month.

The Proof
In the extensive multi-year study by Doctors Dryden and Payne, the swing-out centrifuge method using Sheather’s solution resulted in significantly higher fecal egg counts than the simple passive floatation method.

• Passive Floatation produced false negatives 21% of the time vs. only 5% with centrifugation

The Conclusion
Covetrus, Jorgensen Laboratories, and LW Scientific provide the products and the expertise to ensure your success bringing fecal exams back into the clinic:

Now it is easier than ever to adopt swing-out centrifuge fecal floatation procedures for more accurate diagnosis, instant treatment, and added profitability for the clinic.

Dryden MW, Payne PA, Ridley R, Smith V. Gastrointestinal Parasites: The practice guide to accurate diagnosis and treatment. Supplement to Comp. Cont. Ed. Pract. Vet. 28 (8A): 3-13, 2006.

About the Authors
Michael Dryden, DVM, MS, PhD, DACVM is a University Distinguished Professor of Veterinary Parasitology, in the Department of Diagnostic Medicine and Pathobiology at Kansas State University, Manhattan, Kansas. He received his DVM from Kansas State University College of Veterinary Medicine, and his M.S. & PhD in Parasitology from Purdue University. He is the author or co-author of over 125 journal articles, 9 book chapters and over 100 presentations at scientific meetings. He has lectured in 22 countries, presenting over 1,000 invited seminars at regional, national and international meetings.

Mike Thomas is the Vice President of Sales for LW Scientific, a medical device manufacturing company based in Atlanta, Georgia. Mike has been employed at LW Scientific for 16 years, and is responsible for strategic business development, sales, and marketing of medical and laboratory equipment worldwide into doctor offices, laboratories, hospitals, and veterinary clinics. Mike has enjoyed a long partnership with Jorgensen Laboratories, his expert sales force into the veterinary industry. He and his team at LW Scientific, along with helpful advice from veterinarians and experts like Dr. Dryden, have developed a full line of centrifuges for veterinarians, which are manufactured in Atlanta, GA. Additionally, he has been married 25 years, raised 4 children, and now enjoys his grandbaby girl when he’s not traveling to veterinary conferences.