Keeping Your Pet (and You) Free of Worms

Keep your pets worm free with your VetBox subscription

Common Gastrointestinal Parasites of Dogs and Cats

It’s probably safe to say that every pet owner wants their pet to be worm free. When I say worms, I’m talking about gastrointestinal (GI) parasites. Those pesky worms that we think only puppies and kittens get can actually infect pets of all ages. There are several types of parasites that infect our furry family members, but in this post we’re going to focus on a few common GI parasites you should be aware of as a pet owner. 


Among our friends in the GI parasite family, roundworms are extremely common among dogs and cats. They are one of the most widely recognised, resembling spaghetti on their best days. Species causing infection are usually Toxocara, though others exist in the environment as well. But where do these parasites come from? Transmission between pets is typically faecal-oral, meaning your dog/cat gets faecal material from an infected animal in their mouth and swallows the eggs. You may think, “well my dog doesn’t eat other dogs’ poo” and that may be true. We have to remember that contact with faeces can be in many forms such as sniffing another animal’s rear end in the park, or even just stepping in soil that had faeces in it and then your dog licks its paws to clean them. The egg grows into an adult worm along the gut and then sheds eggs to be passed out in your pets faeces. Not very nice! Now let’s think about the sheer number of eggs that are passed. We’re talking thousands of parasite eggs from one adult worm, with the worst part being these eggs are microscopic. You won’t be able to see these with the naked eye. Not all pets will pass adult worms into the faeces, meaning that your pet could be infected and you may not even realise. This can end up being a problem for your pet, you and your family (we’ll talk more about this in our “Zoonosis” blog), and other pets that could become infected. Puppies and kittens can also be infected directly in the uterus from their mother, making roundworms in our young babies common and important to address. In addition to the roundworm issue being disgusting, it can cause medical issues for your pet including diarrhoea, vomiting, weight loss, and potentially even intestinal blockage in severe cases. Roundworms are found far and wide including places like the park, the beach, walking paths; anywhere that dogs might poo. It is important we recognise this is a risk and make sure we are deworming our pets regularly with the direction of a licensed vet.


Similar to roundworms, hookworms are also in the same family, however they contain a hook like mouth on the adult worm that allows them to behave a little more aggressively. Hookworms are also spread via the faecal-oral route. Signs of infection may include diarrhea, but in severe cases we may also see blood in the stool or anemia (low red blood cell count) due to bleeding in the intestinal tract from the parasite. Both hookworms and roundworms may also try to migrate  to other organs and cause serious disease. Hookworms in particular are known to cause conditions in humans called visceral larval migrans (migration and trauma to other organs) and cutaneous larval migrans (migration to worms under the skin). This makes deworming your pet even more essential for you both.


There are thousands of parasites that can infect our pets, but I think one that people recognise above others are tapeworms. Tapeworms are commonly spotted by owners with or without clinical signs like diarrhea. Vets get many calls about “small worms coming out of the patient’s behind”. These little worms resemble moving grains of rice, and are the major indicator of tapeworm infestation. The most common origin of tapeworm infestation is actually a flea infestation. Fleas harbour the immature form of the tapeworm Dipyllidium, and when pets groom/lick themselves and swallow adult fleas, they also consume the tapeworm egg. The worm then matures in the gut and both segments of the adult worm as well as eggs are passed in the faeces. There are other common species of tapeworms, primarily of the Taenia family, that our pets contract by consuming what is called the intermediate host. This is a host that helps the parasite complete its life cycle and mature, such as a rabbit or rodent. 

Some other common gastrointestinal parasites include coccidia, giardia, whipworms, and lungworms (these are actively passed through faeces even though they reside in the lung). I could write pages and pages on these, however I think that it’s important pet owners are familiar with some of the most common to help them be proactive when it comes to prevention. Prevention is always better than treatment if we can help it.

Top Five Parasite Tips for Pet Owners

  1. Make sure a vet is involved in deciding which wormer is best for your pet.
  2. There is not ONE dewormer that treats ALL parasites, meaning there is not a one shot treatment for all species. This makes #1 all the more important. 
  3. Most intestinal parasites are NOT visible to the naked eye and may or may NOT cause clinical signs like diarrhea. It is important that we regularly deworm our pets AND regularly have a faecal sample checked by a vet to make sure we aren’t missing low grade infections. 
  4. Prevention is typically cheaper and safer than treatment after a problem is detected. 
  5. HUMANS can also become infected and ill from parasites that infect our pets, making awareness and treatment essential to all of our health. 

Dr. Kirsten Ronngren, DVM – MRCVS

Want to get started on your worm free journey? Get your first VetBox subscription today.