Gastrointestinal Parasites in Dogs & Cats


Worms don’t discriminate. Even the cleanest, most pampered pets are targets for these gastrointestinal parasites. That’s why it’s so important to take the necessary steps to protect your pets – and yourself.

Gastrointestinal parasites can cause serious illness and even death in dogs and cats. The infection can be spread from pet to pet, and even to humans. When humans become infected, worms can cause blindness, itchy skin lesions, and other serious health issues.

What are gastrointestinal parasites?

Gastrointestinal parasites in dogs and cats are worms and microscopic organisms that invade your pet’s body, taking up residence in the stomach or intestinal tract. These worms come in many different types, shapes, and sizes – some can grow to lengths up to six inches. Although some worms are large enough to be seen, many are so small that they can only be detected under a microscope.

The most common gastrointestinal parasites found in pets include:

  • Roundworms
  • Hookworms
  • Tapeworms
  • Whipworms
  • Giardia
  • Coccidia

Only roundworms and tapeworms can be seen with the naked eye. Roundworms in your pet’s stool will look like small pieces of spaghetti. Tapeworms are long, flat worms with many different body segments. In time, these segments break off and are passed through your pet’s stool. They look similar to a piece of rice.

If your pet has gastrointestinal parasites, what symptoms will you see?

It can be difficult to tell when a pet has gastrointestinal parasites. While some infected pets may experience diarrhea, vomiting, weakness, or weight loss, others have no symptoms at all. Although the parasites may be too small to be seen, your veterinarian can look for the actual parasites or their eggs by examining your pet’s feces under a microscope. Often this is an effective way to diagnose the condition – but it doesn’t always work. If no parasites or eggs have been shed in the particular fecal sample you take from your pet, the parasitic infestation will not be discovered. If you suspect parasites, but nothing shows up on the feces scan, your veterinarian will need to continue testing regular samples of your pet’s stool. Alternatively, it may be prudent to simply administer the deworming medication anyway, as they are very safe for the pet.

How do parasites spread?

Gastrointestinal parasites enter the body of pets and people in many different ways, and the infection can be transmitted to other pets and people in a variety of ways.

  • Mother to puppy or kitten – Pups and kittens are often born with worms. Infected mothers can pass the parasites to her young in the womb, or through the milk during nursing.
  • Faeces – Parasite eggs and larvae leave the host’s body in the stool. Contact with infected feces can transmit the infection to pets and people.
  • Contaminated soil – Infected feces will contaminate the soil. Parasites can survive in the environment for a long time. Some can survive for years. When pets or people come into contact with contaminated soil – or with contaminated water, food, or plants – they become infected. Parasites can enter the body through the paws, the mouth, or the skin.
  • Prey – Parasites infect rodents and small animals. When your pets prey on or eat these animals, the parasite is passed to your pet.
  • Fleas – Tapeworms can be transmitted to pets and people by fleas. Developing tapeworms live inside fleas. Pets swallow fleas during grooming. When killing prey, they also swallow fleas. When your pets swallow the flea, they also swallow the tapeworm that is living inside the flea. Eventually that tapeworm hatches and grows inside your pet.

What kind of treatments do my pets need?

When properly used, preventive medications and de-worming treatments are a safe and effective way to control parasites. There is no single treatment or medication that works for all parasites. Different medications must be used to treat different types of gastrointestinal parasites. Your veterinarian can advise you on the appropriate treatment for your pet.

Taking the right precautions can help protect your pets (and you) from dangerous parasites. Here are some helpful tips:

  • Test and treat new pets for parasite infestations before bringing them home. De-worm new puppies and kittens before bringing them home.
  • Reduce the risk of soil contamination by picking up your dog’s feces. Handle the feces carefully and always wash your hands afterwards.
  • Use regular flea preventives to reduce the risk of tapeworms.
  • Many heartworm preventives also target gastrointestinal parasites – treat your pet monthly.
  • Don’t let your pets roam. Try to keep them away from rodents and small animals.
  • Don’t let your pets drink from streams where water may have been contaminated by animal feces.
  • Always wash fresh fruits and vegetables before eating them.
  • Make sure children wash their hands after playing outdoors, and before eating.
  • Visit the vet often, and always take a stool sample along for parasite screening.