When our office staff calls to confirm your appointment with your pet, you may have noticed that we always ask you to bring a stool sample. It’s not because we like to see you walk in with a plastic bag in hand, or because we are in a contest to have the stinkiest trash can ever (although we would win that contest easily!). We ask for this sample because a fecal test sent to the outside lab is one of the most common tests we run. The fecal flotation test/fecal ELISA test is a powerful diagnostic tool for sick pets, as well as a screening test for pets who appear to be healthy.
We track all the specimens we send to the lab and for the month of June 2015 we sent 132 samples out for testing. Most of them, 76%, were all clear, showing no parasites or parasite eggs and a negative ELISA test. 15% were positive for giardia and the remaining 9% were positive for roundworms, hookworms, coccidia or tapeworms.
Below are the answers to six frequently asked questions about fecal testing and parasites.
What is a fecal test? What does this test screen for? A fecal test requires sending a sample of stool to the lab. Only a small sample is needed to run the test. Most owners bring more than enough! Samples should be fresh (within a day old) and soft. Stool that is hard or dry will not yield good results. The first half of the test is called a flotation test. The sample is mixed with a special solution and spun in a centrifuge. Any parasite eggs present in the solution rise to the top and stick to a cover slip which is then examined under a microscope to identify the eggs. This part of the test screens for intestinal parasites like tapeworms or roundworms, as well as the cysts seen in giardia infection.
The second half of the test is an immunology test called an ELISA test. This test detects immune response and is used to diagnose pregnancy, identify viral infection or exposure to an infectious agent. This part of the test for cats and dogs looks specifically for exposure to giardia.
My pet doesn’t have diarrhea or vomiting. Does he still need a test? Yes. Vomiting and diarrhea can be signs of infection with an intestinal parasite, but it is also possible for an animal to have a parasite and show no clinical signs. We submit a sample for pets that have new cases of vomiting and diarrhea, but also submit samples as part of the yearly vaccination and testing visit. Pets that are positive for a parasite without showing any signs of sickness still need to be treated, as they can infect other pets and the environment with the parasite. It is important to note that several parasites seen in cats and dogs can also infect humans.
Wouldn’t I know if my pet was infected with parasites? Not really. Pets without symptoms don’t always pass adult worms out in their stool. The eggs and cysts that are part of the life cycle of parasites usually can’t be seen without a microscope, so you wouldn’t know they were there. Tapeworm segments are sometimes visible (they look like pieces of rice) and from time to time, a puppy will vomit an adult roundworm or pass one with their stool, but most of the time it’s not obvious that a cat or dog is carrying intestinal parasites.
Why does my indoor pet need a fecal test? Indoor pets are less likely to become infected with intestinal parasites than outdoor animals, but it does happen. Crickets, cockroaches and other insects can carry roundworm eggs on their legs and transmit them to a cat or dog that eats the bug. Indoor pets that share a water bowl with a pet that goes outside can pick up giardia or coccidia from the water. Pets that drink from puddles on decks or patios or dig in houseplants can become infected from the water or the soil. Cats that hunt and eat mice that find their way inside can become infected with parasites. Finally, fleas are the vector for tapeworms and indoor pets are still at risk for flea infestation.
My pet takes a monthly medication to prevent parasites. Why does he still need a test? Some heartworm preventives also contain medication to remove intestinal parasites. However, none of these products provides protection against all types of parasites. Plus, compliance among pet owners isn’t always 100% when it comes to giving these medications as directed. Giving a dose even a week late leaves a window of opportunity for parasites. And even if you are sure you gave the medication on time, pets have been known to vomit a pill or spit it out when no one is looking.
I’m seeing parasites in my pet’s stool, but the test was negative. Why? As mentioned above, the flotation part of the test screens for eggs present in the stool. A pet can have parasites visible but still have a test come back negative. Some eggs are dense, such as tapeworm eggs. Larger, heavier eggs don’t always rise to the top of the solution. It’s possible to submit a portion of the stool that doesn’t have any eggs in it. That’s why we ask for a decent sized sample, so we can fill the specimen container with as much sample as possible. Finally, seeing eggs in the fecal solution requires the parasites to be actively shedding eggs. If the pet has an infection but the parasite hasn’t developed to the point where it is shedding eggs, or the pet is infected with parasites that are too far apart in the intestinal tract to reproduce, or if the pet is infected with literally one worm, no eggs will be seen.
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