Whether they call it a “fecal sample” or “stool specimen”, pet owners often wonder why their animal doctors have such a fascination with something that should be left in the backyard or litter box. As it turns out, checking your pets’ feces just might keep the people in your family from getting seriously sick!
It might be the look on the person’s face or maybe the way they are carrying the bag, but our staff can always tell when our clients arrive with a stool sample for testing. Dozens of specimens arrive each day, some in Ziploc baggies, others triple wrapped in aluminum foil and some are tucked neatly in plastic containers. People may not realize it, but that smelly sample brought in for testing may help prevent an illness in their pet…or in them!
Why do we have such an interest in your pet’s stool?
The Centers for Disease Control (CDC) state that 3,000 to 4,000 human serum samples are sent to their labs every year with a presumptive diagnosis of toxocariasis, or, infection with roundworms or hookworms. The illnesses caused by these parasites are not reportable in the United States, so true numbers of human cases are not known. What is known is that 36% of dogs across the country and 52% in the southeastern states carry these zoonotic worms. Many pet owners are unaware that their furry family members are capable of harboring these parasites.
Some pet owners don’t believe that their pet could have worms. But, pets can come into contact with these parasites in the yard, in potting soil, at the dog park or even on our hands or feet after we come inside from working in the garden or after taking a walk. The larva and eggs of these parasites, which are microscopic, are simply abundant in many places.
In fact, a single female worm can shed more than 100,000 eggs per day and most puppies and kittens are infected with more than just one worm! That’s millions of eggs spreading through areas where dogs and cats go to defecate. Pets infected with a protozoan parasite, like coccidia or giardia, can shed over a billion cysts each and every day!
So, what do we do with the sample you brought? Most people understand that veterinarians are checking fecals as a means to find intestinal parasites, more commonly known as “worms”. What is less well known is that the veterinarian is not looking for whole adult parasites. They are looking for microscopic eggs and protozoans that may inhabit your pet.
First, the feces are mixed with a sugar or salt solution, a liquid that is slightly denser than regular tap water. Breaking up the stool allows any infective eggs to enter the solution. Next, the mixture is carefully poured into conical tubes that are placed in a centrifuge. The spinning action helps separate the organic debris of the feces from the parasites and the parasite eggs.
After about 10 minutes, the suspension is then allowed to sit with a microscope coverslip placed on top. The eggs and most parasites will float to the top and adhere to the coverslip. A veterinary technician or assistant can then take this sample and review it under a microscope. Any positive specimens are discussed with the pet owner and an appropriate deworming medication is prescribed.
This process may not sound appetizing to most readers, but these tests are an important part of a veterinarian’s dedication to your pets, but also to public health as a whole. The CDC, the Companion Animal Parasite Council and the American Animal Hospital Association all recommend regular fecal testing for all pets. This means you can expect to package up a stool sample once or twice each year per pet. Fortunately, most of the monthly heartworm preventive medications do a good job of preventing a lot of these parasites.