Routine Fecal Testing: FAQs for Dog Owners

What is the purpose of routine fecal parasite testing?

Routine fecal examinations are used to detect intestinal parasites in your dog. These parasites may include worms (such as hookworms, roundworms, and whipworms) and microscopic parasites (such as Giardia or Coccidia). Parasites not only cause intestinal disease in dogs, some of them can also be infectious to humans (hookworms, roundworms, and Giardia).

How does my veterinary hospital perform fecal parasite testing?

Fecal testing must be performed on fresh feces. Your veterinarian may have you bring a fresh sample from home or they may collect a small sample directly from your dog’s rectum.

A fresh fecal sample is mixed with a special solution in a vial and either centrifuged (spun at high speeds) or allowed to sit undisturbed for a set time. The purpose of centrifugation or undisturbed fecal flotation is to isolate parasite eggs at the top of the vial. The material that rises to the top of the vial is then examined under the microscope to look for the presence of worm eggs and other microscopic parasites.

In some cases, your veterinarian may also perform a fecal smear, which involves placing a small amount of your dog’s feces on a microscope slide and examining it directly under the microscope, without any special processing. Fecal smears are primarily used to diagnose Giardia, although they can also be used to obtain other information about your dog’s intestinal health.

How often should my dog’s feces be tested for parasites?

Puppies should have several fecal parasite exams during their first year of life. Intestinal worms are very common in puppies and can cause more problems in younger dogs, so early detection is important. Not all intestinal parasites are addressed by common dewormers, so fecal parasite exams are important even in puppies receiving regular deworming.

In adult dogs, fecal parasite testing should be performed every six months, even they are on heartworm prevention or other parasite prevention.

How can my dog have worms if I can’t see any in his stool?

Most intestinal worms remain within the body and are not shed in the stool. Instead, these worms lay microscopic eggs that are shed into the environment. A fecal parasite examination searches for these eggs.

Can my dog have intestinal worms even though he is on heartworm prevention?

While most monthly heartworm preventatives are effective at preventing intestinal worms, breakthrough infections can occur. Additionally, not all heartworm preventives are designed to prevent all intestinal worm preventions. For example, ivermectin-based heartworm preventatives do not prevent whipworms, and long-acting heartworm prevention injections have only short-lived efficacy against intestinal worms. Therefore, even pets receiving consistent heartworm prevention may develop intestinal worms.

How serious are intestinal parasites?

The effects of intestinal parasites can vary significantly, depending on the parasite and the overall health of the dog.

• Roundworms: Roundworm infections in adult dogs are often asymptomatic (they have no signs). In young dogs or severely infected adults, signs may include vomiting, diarrhea, weight loss, a dull coat, and a potbellied appearance. Roundworm larvae also migrate through the lungs as a part of their life cycle, so coughing may be observed.
• Hookworms: Hookworms embed in the wall of the intestine, sucking blood from their host. Therefore, the most significant effect of hookworms is anemia, resulting in lethargy, weakness, and pale gums. Weight loss and bloody diarrhea are also commonly observed.
• Whipworms: Whipworms often cause bloody diarrhea in dogs. Affected dogs may also be weak and may become increasingly debilitated over time.
• Giardia: This protozoal parasite often causes severe watery diarrhea, which may or may not be accompanied by vomiting and weight loss.
• Coccidia: Infection with this protozoal parasite is often asymptomatic in healthy adults, but it may cause diarrhea and other signs of illness in puppies or debilitated adults.

How will my veterinarian treat intestinal parasites found on routine fecal testing?

If your veterinarian finds evidence of intestinal parasites on routine fecal testing, they will recommend appropriate treatment to eliminate the parasites. Depending on the parasite, your dog’s treatment may include as little as one to two doses of dewormer or a prolonged course of oral medication. Each intestinal parasite has unique treatment requirements.

Your veterinarian may also recommend a change in your dog’s heartworm preventive if it is not effectively preventing a particular parasite in your dog’s environment.