FAQ: How Often Should I Deworm My Pet?

By:  Dr. Hilary Slaven

We get this question a lot, especially for routine yearly exams for our patients.  How often should we be deworming our pets?  The answer is:  it depends!  Let’s discuss.

First of all, we need to understand which ‘worms’ we are talking about.  What enemies are we fighting?  After all, nobody wants these guys in our pets and in our homes.


I mean, seriously.  This hookworm is scary.

  1. Hookworms.  Primarily a concern in dogs, this worm has eggs that are shed by infected animals and live in the soil, waiting for your furry friend to gobble them up as they nose around in your yard.  These worms are also passed from mother to baby through the placenta or milk.  They live in the intestines and suck blood, which over time causes low red blood cell counts (anemia), weight loss, diarrhea, lethargy and death.
  2. Roundworms. Seen in both dogs and cats, this worm looks like spaghetti when shed out with stool.  Often puppies and kittens get them from mom through the placenta, so we see babies shedding worms even as early as 6 and 8 weeks old.  They primarily live in the small intestine and cause weight loss, poor hair coats, intestinal blockage and rarely can cause nerve and eye disease.  This worm can be spread to people, especially children, making it a top priority to keep dogs dewormed in homes with families.
  3. Whipworms.  Primarily a concern in dogs, this worm lives in the large intestine and is shed in the stool.  Furry friends ingest the worm eggs and they grow into the adult worm stage in the intestine.  Causes diarrhea, dehydration, blood loss, weight loss, lethargy and death.
  4. Tapeworms.   Our furry friends can pick up tapeworms from fleas, soil and from hunting rodents in the backyard.  We see little bitty segments of worms in the stool that look like rice.  These are actually only small pieces of the actual worm, which is roughly 6 inches long and are attached by a mouth part to the inside of the intestinal wall.  To get rid of these, a critter needs to be de-wormed and de-flea’d too.
  5. Heartworms.  Both cats and dogs can get heartworms, which as adults live in the lungs and heart.  They are spread through mosquitoes.  The insects take a blood meal from an infected critter, thereby ingesting the immature form of the worm (called a microfilaria).  Then the mosquito moves down the road and takes another blood meal from an uninfected animal, where the microfilaria break through the skin and get into the bloodstream of the newly infected dog or cat.  Over several months, the microfilaria grow into 6 inch long spaghetti-like worms that settle into the large blood vessels of the lungs and cause disease.  Signs of disease include weight loss, shortness of breath, coughing and death.


Ok, take a minute and catch your breath.  Like, wow.  These things are not only gross, but they spread disease (they could even spread disease to you!).

Now that we know what we’re fighting, get your battle gear on.  We’re going into battle against these buggers.

First things first.  We need to figure out if your furry friend actually is carrying any of these parasites.  It’s important to note that these worms don’t shed in the feces every time the dog or cat stools.  In fact, it’s common for there to only be eggs shed in the stool, which are microscopic and unable to be seen with the human eye.  Bottom line:  Your furry friend could be infected without you even seeing any sign of worms. 

So let’s do a simple test.  Look at a fresh stool sample under the microscope and see if we find any worm eggs.  This is a 15 minute test called a “fecal flotation”  that can be done here in the vet clinic.  Once we know what we’re dealing with, we can pick a dewormer that best suits your pet’s situation.

Keep in mind, heartworms are the worms on the list that cannot be simply killed by an oral dewormer.  Heartworms need a more complex treatment involving injections and hospitalization.

Like most battles, the best defense is a good offense when it comes to parasites.  That’s why we really like these monthly chewable pills that we give that can kill intestinal parasites AND kill heartworm microfilaria, too.  So every month your pet is protected from these nasty critters.  An alternative way to approach them is to give a heartworm prevention injection (Proheart 6) every 6 months, and check your pet’s stool with a fecal flotation at the same time, deworming if necessary.

We would love for you to call and come into the clinic!  We can test your pet for parasites and come up with the best plan for your family to prevent infection and disease.