What's your pet's fecal test for, anyway?
So what’s that embarrassing caca test for, anyway?
It’s stressful enough to have your pet’s backside violated by a plastic rod, right? So what’s the point?
You say: If the goal is to make my pet healthier and parasite-free then I’ll trust your judgment, but I have to say, stool checks are a kind of cruel and unusual sort of punishment. I don’t get that sort of humiliation until I’m male and forty, right? And fecals aren’t that helpful, right?
I say: For starters, you need not have your pet succumb to the dastardly rod. A fresh sample is usually easily obtained the morning (or afternoon) before your annual visit or any time your pet suffers gastrointestinal symptoms. It’s not so tough, really. And if the timing’s not exactly right (stool should be no older than an hour for best results), your vet hospital will surely not deny you the right to bring in a super-fresh sample at your convenience. Promise.
And yes, fecal examinations, though relatively cheap and routine, are indispensable. But as this post will demonstrate, it’s also true that not all fecal tests will pick up a parasite infection in your pets. That’s why annual and/or serial fecal examinations may be necessary.
Now for the primary goal of the test:
Veterinarians are always on the lookout for parasites that may find their way into your pets’ gastrointestinal tracts. Sure, we humans can get parasites, too, but our modern lifestyles tend to be less conducive to parasite infection. (When was the last time you went snuffling in the yard, lips to the ground, just so you could inhale a feline turd or two?)
Yes, pets get lots of parasites. Here’s a sampling of the most common gastrointestinal parasites I see here [in the parasite heaven that is semi-tropical South Florida]:
Hookworms in pets
Whipworms in pets
Giardia in pets
Liver flukes in pets
Coccidia in pets
I’ll not go into the gory details on each but you can click on the links and check out the info for a better understanding of how these parasites can potentially affect your pets and even your human family.
Sure, pet-popular parasites don’t often infect humans in the so-called, “developed” nations all of you reading this likely live in, but that doesn’t mean it doesn’t happen. Roundworms and hookworms are still a factor in humans in the US, as is Giardia, which will give you the nastiest case of diarrhea you can imagine short of amoebic dysentery.
Since veterinarians are also on the front lines when it comes to public health, consider that fecal exams are not just necessary for healthy pets, they’re essential for healthy humans, too, more so if your family members are very young children, very old adults or otherwise immunocompromised (transplant patients, HIV-positive humans, chemo recipients, etc.).
How do we identify these critters in the fecal exam?
The short answer: With a microscope.
The long answer: We take a tiny sample of your pet’s stool (very fresh is always best). A few grams is enough (think an eighth of a teaspoon if that’s easier). Then we put it through one of three processes.
1. The smear: We take about a half gram of stool and smear it onto a microscope slide to search for parasites (and bacteria) directly. Many times we’ll see them swimming about. Finding evidence of parasites in a simple smear is often indicative of severe infection.
2. The float: This method relies on mixing the stool with a special solution. It filters out the big pieces of stool in a tube or other cylindrical vessel and allows the eggs and other small critters to float up to the top, buoyed by the solution’s specific gravity. A microscope slide’s cover slip is typically used to recover the floaters. Some parasites, however, aren’t amenable to flotation. Eggs seem to do best through this method.
3. Centrifugation: Spinning the heck out of stool in a centrifuge when it’s mixed in a sugar solution picks up about 50% more parasite eggs and oocysts than through flotation. Therefore, I like this method best for worm eggs, Giardia, and coccidia––though I’d never go without a smear. Problem is, most hospitals don’t yet use this method. It’s more expensive than others and research demonstrating it’s much greater efficacy is fairly recent.
So now you know the truth: Not all fecal exams are created equal. Not only does this test rely on careful selection of materials and methods, it also requires a trained eye. In our practice, for example, one of our techs detects parasites about 50% more often than the veterinarians and other techs/assistants. (That’s why we also do floats so that she can check them all at her convenience when she comes back from her day off.)
It’s also true that even a parasite-infected animal will often not come up positive on a fecal test. Human error and equipment choice are factors, but so is the parasite itself. Sometimes they do not make themselves known in the stool. Worms sometimes aren’t shedding their eggs and subclinical (low-grade or smoldering) infections may not reveal much, either.
Again, that’s why it’s important to perform this test as often as is reasonable. For all dogs and cats at least three times during the first few months of life. I want to see at least two negative tests in a row, a month apart, before I’ll feel comfortable that my patient is parasite-free.
For adults, once a year is great––that is, unless they show gastrointestinal illnesses. In this case, serial fecal tests make sense––or at least one every time the symptoms recur until a definitive diagnosis is made (whether it’s parasites or something else).
Ultimately, fecal tests are a critical component of our veterinary hat of tricks. Doing without may seem like the economically wisest thing in the absence of gastrointestinal symptoms, but consider: parasites can wear pets down in ways you might not expect. And it’s never wrong to be too safe in the presence of diseases that may also affect your family. ‘Nuff said.