Worms That Can't Be Detected in Dog Stool Tests

by Catherine Troiano
    Stool, blood and skin samples are used to detect different parasites.

    Stool, blood and skin samples are used to detect different parasites.

    Dean Golja/Photodisc/Getty Images

    Over the course of your dog's annual veterinary examination, you will be asked for stool sample from your furry friend. Your veterinarian will also collect a blood sample to check for heartworm disease. Not all worms and parasites are found in your dog's stool. As you start to ponder the array of parasites that your dog could be carrying, consider the fact that they can be found in his stool, his blood and even in his skin.

    Worms, mites and other organisms that live inside your dog or on his skin in order to thrive are called parasites. The most common parasites in dogs are intestinal parasites. While the adult worms reside within your dog’s gastrointestinal tract, eggs are passed through the stool when he defecates. Some eggs can also be passed from a mother to her puppies. When your veterinarian orders a fecal analysis on your dog’s stool, he is looking for the eggs of roundworms, hookworms, whipworms and protozoans, such as coccidia and giardia. Your vet may run various tests on the stool sample to detect the presence of parasites. Other parasites in dogs cannot be detected in stool, however.

    Adult heartworms, as the name implies, reside in your dog’s heart. The immature offspring, called microfilaria, are released to circulate through your dog’s bloodstream and his lungs. Adult female heartworms also release specific proteins into the dog’s bloodstream. Since heartworms are limited to your dog’s cardiopulmonary system, they will not show up on a fecal analysis. A blood heartworm antigen test is the most accurate method for detecting the presence of heartworm disease, which is transmitted by mosquitoes. There is a 5 to 7 month incubation period following a mosquito bite before a heartworm antigen test can reveal a positive result.

    A number of parasites can attack a dog’s skin, leading to infection or mange. Dracunculus infections are caused by a type of roundworm that burrows along the connective tissue of your dog’s skin. Pelodera dermatitis is a skin infection that occurs when the larvae of certain roundworms, pelodera strongyloides, infiltrate your dog’s skin. A more common skin affliction is called demodectic mange. All dogs harbor some demodectic mites, but the mite population is kept low by your dog’s immune system. If the number of these mites escalates, demodectic mange can result. The sarcoptic mite is another skin parasite that can cause inflammation and mange. Pelodora strongyloides larvae, demodectic mites and sarcoptic mites can all be detected when your veterinarian views a skin scraping sample under the microscope.

    The term “ringworm” is actually a misnomer. Although the condition is parasitic in nature, ringworm is not caused by a worm at all. Ringworm is the clinical term assigned to a skin infection caused by the spores of dermatophyte fungi. The fungi feed off of dead cells from your dog’s skin and fur. Ringworm can often be detected when a veterinarian observes your dog’s skin through a fluorescing Woods lamp, through which the fungus appears fluorescent green. Confirmation of a ringworm diagnosis can be made by examining damaged hairs under a microscope to look for spores. Another testing method is to collect hair and skin scales to grow for several days in a fungal culture medium.

    Photo Credits

    • Dean Golja/Photodisc/Getty Images

    About the Author

    Based on Long Island, Catherine Troiano has been writing pet-related articles since 2011. As a former veterinary technician of more than 10 years, she has amassed extensive knowledge and is versed in an array of health topics pertaining to cats and dogs.

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