Why Tapeworms Sometimes Don’t Show Up On Fecal Flotation

A client asked me this morning, “Just last week my pet was in to see you and you reported a negative fecal flotation test result. Why, then, am I seeing worms in my pet’s stool?”

A dried tapeworm proglottid, waiting to release its eggs.
A dried tapeworm proglottid, waiting to release its eggs.

This is an excellent question and one that is asked more often than you might imagine.

The fecal flotation test is designed to find the eggs of intestinal parasites. Common canine and feline tapeworms, including Taenia pisiformis and Dipilydium caninum, pass their eggs via proglottids.

Proglottids can be thought of as “egg packets,” sealing and holding the eggs of the tapeworm and assisting in their spread. Proglottids actually graduate from the tail end of the tapeworm as individual worm-looking, worm-acting creatures. They have a temporary ability to crawl around like an inch-worm for a short time before they dry out. Upon complete drying, the package releases the eggs with the intention of infecting more fleas, which act as the intermediate host of the tapeworm. Then, the cycle begins again.

Therefore, you can easily see that the tapeworm’s eggs are sealed away from showing up in the fecal flotation’s result unless one of the proglottids ruptures in the intestinal tract or in the processing of the stool for the test.

That is why we say tapeworms are best diagnosed by our clients, the pets’ owners. You should try to see your pet’s bowel movement at least once daily to know when it is abnormal, such as loose stool or containing visible parasites.

Routine grooming at home can also reveal a tapeworm’s presence. Proglottids, upon crawling from the anus, can dry up and stick to the hair on the perineum. When they do, you or we can see a little particle that looks very much like a small, tan grain of rice.

Treatment can then be administered by injection or tablet. Usually only a single treatment is required.

See you tomorrow, Dr. Randolph.

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