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Internal Parasite Analysis

Randy Walker DVM

About Internal Parasite Analysis...

Internal Parasite Analysis (often referred to as a fecal sample, stool sample, stool check, fecal flotation or just "a fecal") is a commonly performed laboratory procedure in the veterinary clinic. We use this procedure to detect "worms" and other intestinal parasites.

Briefly, How Is A Fecal Flotation Performed?

There are many different methods used for fecal flotation but the basic principle behind all of them is the same. In general, we first mix up a small amount of the patient's stool in a heavy saltwater solution. This solution is allowed to sit for approximately 5 minutes during which time the parasite eggs (if they are present) will float to the surface layer of the solution and are caught on a microscope slide. Then the parasite eggs (if they are present) can be viewed and diagnosed under the microscope.

Can't A Person Just Check The Stools Visually At Home To Determine If Worms Or Other Parasites Are Present?

Although visually checking the stools at home periodically is important for several other reasons, this is really not a very reliable way to determine if internal parasites are present. Of the common parasites encountered, tapeworms are the only ones that can be reliably diagnosed through visual inspection. Of the other common parasites encountered, (roundworms, coccidia, hookworms whipworms, giardia, etc) only the roundworms are readily visible in the stools as adults and these adults are only encountered in the stool in perhaps 5-10% of roundworm infections (as opposed to finding the eggs with the microscope which will be present in approximately 98-99% of roundworm cases). The other common parasites will not be readily visible in the stool and two of them (coccidia and giardia) are microscopic even in the adult stage.

How Reliable Is Fecal Flotation In Testing For Internal Parasites?

Fecal flotation is the most reliable way to determine the parasite status of a patient. The reliability of fecal floatation varies with the type of parasite encountered. With roundworms and coccidia (two of the most common internal parasites), fecal flotation is 98-99% reliable, meaning that these parasites can be either diagnosed or ruled out conclusively in 98-99% of cases. Hookworms can be diagnosed reliably over 95% of the time. Whipworms (which are found most commonly in the humid areas of the southeast U.S.) can be diagnosed about 50% of the time through fecal flotation (this is because whipworms only shed eggs sporadically). Giardia is a delicate, one-celled, microscopic parasite which usually can't be detected by routine fecal floatation and requires special procedures to detect. As noted above, tapeworms are the exception as being the one type of worm that is best diagnosed by visual inspection of the rectal area (rear end) and stool to look for the "cucumber-seed-like" worm segments. All other parasites require fecal flotation for reliable diagnosis.

If Tapeworms Are Diagnosed In My Dog Or Cat, Is It Still Recommended That Fecal Flotation Be Performed?

Yes. It's recommended to conduct a complete parasite analysis because where you see one type of internal parasite (such as tapeworms) you will often see others (such as roundworms, coccidia, etc).

How Often Should A Routine Stool Sample Be Run?

Most veterinarians prefer to test all puppies and kittens at least once when they are young and also when they change households. If no parasites are detected, then veterinarians usually recommend a routine fecal flotation once-a-year. Your veterinarian may recommend internal parasite analyses more or less often than this based on the parasite situation in your area. Although these parasites occur nationwide, they tend to be more of a problem in the more humid, temperate regions of the country.

Will The Internal Parasite Analysis Tell Me Whether My Dog Is Infected With Heartworms?

No. You need a blood test to tell if your dog has heartworms.

- Randy Walker DVM
Sun Lakes Animal Clinic
May 16,2004

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