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5 Key Facts You Want to Know About Internal and External Parasites in Dogs

5 Key Facts You Want to Know About Internal and External Parasites in Dogs

The simple word parasite might make you shiver, and for good reasons! Google's definition of parasites is as follows: "an organism that lives in or on an organism of another species (its host) and gets its food from or at the expense of its host". It makes sense that we don't want to get parasites or our pets to have them. But unfortunately, our world is filled with them: worms, fleas, and ticks, to name a few.




External and internal parasites in dogs: what is the difference?

On the one hand, external parasites are found on your dog, on the surface of their skin. 

The most common ones are fleas and ticks, but you'll also find mosquitoes, flies, and sandflies (phlebotome).

On the other hand, you'll rarely see internal parasites because they live inside your dog. Internal parasites are mostly worms in the body's cavities( GI tracks, heart, or lungs). However, some parasites that live in your dog's body cells (intracellular) also exist. 

All types of worms exist, and veterinarians will diagnose and treat them based on the organs they live in and their kind. The most common in the USA are intestinal worms (particularly roundworms) and heartworms.


What are the common parasites in dogs?

Here are the parasites you want to know. We also broke the list down by category:

  • External parasites
    • Fleas
    • Ticks
    • Mosquitoes
    • Flies
  • Internal parasites
    • Intestinal worms
      • Roundworms
      • Tapeworms
      • Whipworms
    • Heartworms
    • Lungworms
    • Blood parasites

Parasites most often found in dogs are fleas, ticks, roundworms, tapeworms, and heartworms.


What does fleas on a dog look like?


Are parasites dangerous for my dog?

Not to be alarming, but yes, every parasite is dangerous for dogs! Many diseases and illnesses come from parasites. They will make your dog sick, and sometimes they can lead to death (heartworm, for example). 

On a larger scale, parasites are a public health problem. Indeed an animal with parasites can contaminate a human. We call these parasites "zoonotic parasites."

You might think mosquitoes are not dangerous for your dog, as their bites are just temporary itchy problems. But mosquitoes can transmit Dirofilariosis, also called heartworms, to your dog. Dirofilariosis will cause heart and lung problems in your dog and can lead to a painful death. 

The most common and hated parasites are fleas. Flea bites will significantly decrease your dog's quality of life, especially if your dog is allergic. 

Furthermore, fleas can transmit Dipylidum caninum, a tapeworm also called flea tapeworm and which look like rice grains in your dog’s poop. Tapeworms are zoonotic, meaning we humans can have them.


For what parasites do I need to treat my dog?

It would help if you treated all your pets and house against fleas year-round because they are everywhere, even in Alaska. 

Below are a few examples that can impact your dog's parasites treatment needs:

  • Where you live: parasites love various conditions of temperature, humidity, or even different animals. So the place you live in will change the type of parasites your dog will encounter.
  • Is your dog leaving with other animals, and if so, which ones?
  • Does your dog have direct access to a garden or often goes to a park?
  • Is your dog a (rodent or another animal) hunter?

All these different scenarios might feel overwhelming, but your veterinarian is a great resource to help you see clearer! They will ask you a list of questions, and together, you will identify the parasite risk for your pup and create a treatment plan that makes sense for you. Also, if you want to dig deeper into the world of parasites, check out our article.


How often should I treat my dog against parasites? 

You should know that treating your dog against parasites is part of what veterinarians call preventive medicine. Preventive medicine means you take action to keep your dog from getting sick. Preventative medicine is always better than curative medicine because:

  • you decrease the risk of getting sick,
  • you decrease or delay the consequences of getting sick,
  • you increase your chances of living longer and,
  • it costs you less!

Here are a veterinarian's main principles for dog parasites treatments and frequency: 

External parasites

US Map of the fleas and ticks presence
  • Flies and mosquitoes: it depends on your location. 
    • They are highly active in the south of the USA, less in the northeast. 

Internal parasites

  • Heartworms: All year round, depending on where you live.
    • Mosquitoes transmit heartworms, so it's a real threat to pets in the south, where mosquitoes are most prevalent. Monthly and yearly treatment options exist. It would be best if you asked your vet for the best option for you and your dog. Injectable or chews exists; you'll want to explore your choices with a professional.

Explicit - Photo of heartworms in a dog

  • Roundworms and whipworms: Once a quarter, but depending on your dog's lifestyle
    • Most of the time, once a quarter is a good frequency. 
    •  If your dog doesn't go out much and doesn't play with other dogs, you could consider them "low-risk" and decrease your treatment frequency to once or twice a year. You can also ask your veterinarian for a coproscopic examination to treat on an as-needed basis.
    • If you have children under six years old or people with a low immune system (older people), you should treat your dog monthly to avoid any risk.
  • Tapeworms: again, it depends on your dog's situation. You'll want to treat regularly if:
    • If your dog is a hunter or can meet little prey
    • If you live in an area with echinococcus where your dog can meet cattle, or you feed raw food to your dog.

We find parasites fascinating, but we don't want them to harm your dog or family. Therefore, it's essential to understand how to protect your family against them adequately.

Contact your veterinarian if you have questions about your dog and their potential risk exposure. Also, if you have any general questions about your dog's preventive care! We love to hear from you!


Author: Dr. Jeremy

Doctor of Veterinary Medicine (DVM), MS

Meet Jeremy, a passionate veterinarian and co-founder of Jope, with a decade of experience—7 years in the nutraceutical and pharmaceutical industry and 3 years as a veterinarian. Passionate about enhancing the well-being of pets, Jeremy's mission is to provide practical, evidence-based advice and products that support pet parents and their furry companions. His favorite breed, the Australian Shepherd, holds a special place in his heart for their playfulness, cleverness, and beauty.

Join Jeremy on an insightful journey through the world of pet health and discover how science and compassion come together to improve the lives of pets.

The content presented here is for informational purposes and reflects Jeremy's own opinions, expertise, and experience. It is not intended to replace professional veterinary consultation, diagnosis, or treatment. For personalized advice and care for your pets, always consult with your veterinarian.



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