Intestinal parasite infections are common everywhere and even more so in dogs living in Fort Lauderdale, Florida where I own my small veterinary practice. For years, I evaluated and diagnosed pets with in-house fecal flotation with centrifugation but always saw variability in my test results, misdiagnosis of parasites, and false negative results. Recognizing the importance of accurately diagnosing intestinal parasites, I made the change from in-house fecal flotation tests with centrifugation to fecal antigen testing and fecal flotation with centrifugation at the reference lab. This transition drastically increased the number of patients I diagnose with intestinal parasites. Because of this, I now feel confident that I am practicing the best quality medicine.
Limitations to fecal flotation testing
The most common method for diagnosing intestinal parasites is fecal flotation, either by passive or centrifugation. There are limitations to fecal flotation testing caused by the following factors:
- Misidentification – Identifying pollen and other debris as eggs as well as inaccurate identification of eggs from other species (coprophagy) occurs frequently.
- Egg detection – There is a lack of ability to detect eggs when the pet is infected either during the prepatent period or with single-sex infections.
- Egg shedding – Because parasites shed eggs intermittently, fecal floatation is not reliable as a single test. An infected animal may have a false-negative diagnosis especially if only one fecal flotation test is performed.
- Egg density – The density of different eggs differs which makes it difficult for the clinician to select the ideal fecal flotation solution to ensure adequate recovery of eggs, further creating less confidence in proper diagnosis.
Advantages to fecal antigen testing
Fecal antigen testing has essentially eliminated the above-mentioned limitations seen with fecal flotation testing, and there are numerous advantages:
- Better Accuracy – Fecal antigen testing detects proteins produced by the parasite independent of egg production for hookworm, roundworm, and whipworm in feces. These antigens are secreted by the worm and do not rely on eggs being present in the sample.
- Earlier detection – Single-sex infections, infections during prepatent periods, and intermittent egg laying can result in a positive antigen test and negative egg detection on fecal flotation.
- Less contamination – By detecting and treating parasitic infections earlier and more frequently, environmental contamination with infectious eggs can be reduced.
- Error reduction – Errors are often caused by misidentification of eggs from other species due to coprophagy, pollen, debris, or pseudoparasites as infectious eggs. Errors can also come from improper fecal flotation procedures.
As a clinician, since switching from in-house fecal flotation testing to fecal antigen testing and fecal flotation with centrifugation at the reference lab, I have seen a large spike in the number of patients that are testing positive for intestinal parasites and thus being treated and protected correctly. Intestinal parasites are everywhere so it’s important to always test for them. For me, practicing small animal medicine in an area where intestinal parasite infections are very common, along with the potential for zoonosis, I am much more confident that I am practicing the best quality of medicine and protecting my pets and their families.