Information on internal and external parasites in cats and dogs.

Select a Topic

  1. What are Parasites?
  2. What Causes Parasites?
  3. Diagnosing Parasites
  4. Help for Parasites
  5. More Information on Parasites

What are Parasites?

A parasite is “an organism that lives on or in a host organism and gets its food from or at the expense if its host,” according to the Centers for Disease Control and Prevention.  Unfortunately, it’s common for our beloved pets to become these unwilling host organisms. Parasitic infection in dogs and cats can cause symptoms ranging from mild to life threatening.

Common dog and cat parasites can be broken down into two main groups, external and internal. External parasites live outside the pet’s body, while internal parasites live inside the body and can affect the intestinal tract and other organs.

External parasites:

  • Fleas and ticks
  • Ear mites
  • Mange

Internal parasites:

  • Heartworm disease
  • Intestinal parasites
    • Hookworms
    • Ringworms
    • Roundworm
    • Tapeworm
    • Whipworms
    • Coccidia, giardia and spirochetes (non-worm parasites)

External parasites, especially fleas, can be a big headache for pet owners and pets alike. Getting rid of fleas can be difficult, and sensitive pets can develop an allergy to flea bites called flea-bite dermatitis. Other parasites, such as ticks, can cause significant health risks from tick-borne diseases including Lyme Disease. The good news is, most external parasites can be avoided with preventive treatments and regular grooming.

Internal parasites are a common problem in kittens and puppies, and also occur in adult cats and dogs. Most pets have some type of intestinal worms within the first few months of life, which are unpleasant but easily treated. It’s better to preventively treat animals against internal worms before an infestation, if possible, than to eradicate worms once the cat or dog becomes infected. Heartworm prevention provides effective protection against heartworm disease, which can be life-threatening.

What Causes Parasites?

External parasites are part of the environment. They look for any opportunity to attach to a comfy host, such as your pet. Keeping pets out of long grass and making sure their immediate environments are parasite-free helps prevent external parasites like fleas and ticks.

Internal parasites have many methods of infecting your pet. Often intestinal worms are contracted when a pet eats the infected larvae in the environment, such as eating infected food or raw meat, or an infected mouse or flea. Intestinal worms can also enter the body through the skin, the bottom of the pet’s feet and through direct contact with bodily fluids. Kittens and puppies can be infected in the uterus before birth or when they are suckling from their mothers.

Diagnosing Parasites

Your veterinarian will typically check for signs of parasites at regular vet checkups. The signs and symptoms vary greatly, though, so be sure to mention anything unusual to your vet.

Common symptoms of parasites:

  • Vomiting
  • Weight loss
  • Loss of appetite
  • Diarrhea
  • Coughing
  • Mucous or blood in feces
  • Dull coat
  • Pale mucous membranes
  • Potbellied appearance

External parasites are usually visible to the naked eye, so when grooming your dog or cat check for any signs of fleas or ticks.

Internal parasites are not as easy to spot, but worm segments or eggs can often be seen in your pet’s stool or on the fur around the anus. Your vet will probably take a stool sample to determine the type of parasite and appropriate treatment.

Treatment for Parasites

No single treatment kills all parasites, but different products provide parasite prevention and parasite control. 

Conventional Treatments

Products such as Frontline Plus, Revolution and Advantage help keep pets free from external parasites like ticks and fleas.

Internal parasite treatment depends on the type of parasite your pet has. Different medications kill different internal parasite types. Over-the-counter de-wormers are usually less effective and can be more dangerous than veterinarian prescribed de-wormers, but all de-wormers can cause side effects and dangerous interactions with other medication. It’s important to know the facts and be aware of alternatives before giving your pet any new medication.

Natural Treatments

Consider natural parasite control options for your pet. Parasite Dr. ™ for Cat & Dog Digestive Detoxification is an herbal supplement that promotes digestive functioning and detoxification in cats and dogs. It’s used to expel internal parasites and restore health after infection.

More Information on Parasites

Tips for managing Parasites
  • Make sure your pet is on some form of preventative program for both internal and external parasites. Preventing infestation is much more effective than treating one.
  • Wash your pet’s bedding frequently and make sure their immediate environment is parasite-free. Regularly vacuum floors and wash curtains and drapes, where fleas and parasite larvae can hide.
  • If possible, keep your pet away from long grass and open fields where ticks are likely to be found. Avoid letting your pet have contact with animals who may be infected or are not on parasite preventives.
  • Make sure your pets have a healthy sanitation area. Litter boxes should be cleaned regularly and stools should be removed from the yard at least once a week.


1. “Dog Parasites.” American Kennel Club. Accessed March 22, 2019.

2. “6 Most Common Cat Health Problems.” WebMD. Accessed March 22, 2019.

3. “Gastrointestinal Parasites of Cats.” Cornell Feline Health Center. Accessed March 22, 2019.

4. Maciorakowski, L. “Intestinal Parasites in Dogs and Cats.” MSPCA. Accessed March 22, 2019.

5. “Intestinal Worms in Dogs and Cats.” PetMD. Accessed March 22, 2019.

6. “Common Intestinal Parasites in Cats and Dogs. Kansas State University. Accessed March 22, 2019.

.tinymce-seo h1, .tinymce-seo h2, .tinymce-seo h3, .tinymce-seo h4, .tinymce-seo h5, .tinymce-seo h6 { font-family: inherit; font-size: inherit; color: inherit; padding: 10px 0; } .well h4 { color: white; margin-bottom: 1em; } .well a { font-weight: bold; color: white; text-decoration: underline; } .well p{ margin-bottom: .5em; } .well__content { text-align: left; } .category.text-center{ width: 100% }