Dog Parasites

How to Prevent, Diagnose, and Treat Internal and External Dog Parasites

While there are many wonderful benefits of being a dog owner, the possibility of your pooch getting internal or external parasites is certainly not one of them. You’ve already turned to the internet for answers on how to prevent or treat dog parasites, so you're obviously a conscientious pet owner. If you suspect your dog currently has parasites, we urge you to seek immediate medical care.

At GeniusVets, we believe that pet care information should come from veterinarians and not from Dr. Google. That’s why we’ve taken FAQs on dog parasites, sent these questions to renowned veterinarians across the U.S., and compiled their replies to get you useful information that you can trust.

While we've sourced all of the dog parasite information and recommendations below directly from leading veterinarians across the country, please make sure to seek out the advice of your own veterinarian or find a trusted vet near you using the GeniusVets Directory.

How old does my dog need to be before I start parasite prevention?

Most veterinarians will recommend deworming dogs every two weeks until 12 weeks of age. Roundworms are extremely common in puppies and kittens. Your vet should start with the deworming process at two weeks of age and then repeat that every two weeks until your dog is 12 weeks of age. At that point, your vet will recommend monthly deworming for intestinal parasites and, of course, flea and tick prevention.

What are intestinal parasites in dogs?

Intestinal parasites are primarily worms that live in dogs' intestinal tracts. For instance, there's a roundworm and hookworm that live in the stomach and the small intestines of dogs, and there are tapeworms that live in the large intestines of dogs. There are intestinal parasites that are not worms, such as coccidia and Giardia, which are one-celled organisms that are also considered parasites in the intestinal tract.

Intestinal parasites are typically transmitted through a fecal-oral mode of transmission. The eggs are present in the stool of an infected animal, and when a dog steps in that stool and then cleans their paws or somehow ingests fecal material with eggs in it, then those parasites develop in the dog. When the adult worms are present, then those eggs are shed through the stool and can go on and infect other animals.

What are external parasites, and what can I do to prevent them?

The most common external parasites seen in dogs would be fleas and ticks, but they can also get ear mites and even lice. There are monthly preventatives that can help with those external parasites, and there is monthly prevention for intestinal parasites—what's exciting is some newer products combat all of that. They combine a preventive for heartworm disease, which is a blood parasite transmitted by mosquitoes, with a preventive for intestinal parasites, along with a preventive for fleas and ticks and external parasites. It's ultra-convenient that a single pill or chewable taken once a month can work to prevent all of those things.

What everyone is most used to seeing are fleas and ticks, and, as with all parasites, the best thing to do about fleas and ticks is to prevent them in the first place. If you already suspect your dog may have fleas and/or ticks, however,  let your veterinarian diagnose what they have and then look into the whole situation. How many pets do you have at home? Are they indoor, outdoor? What are their conditions? After getting answers to those questions, your vet can help pick out the best preventative and treatment plan for your dog.

How soon should I bring my dog to the veterinarian if I suspect that they may have parasites?

Get them to the veterinarian right away because some parasites are zoonotically transmitted to humans. Your vet certainly doesn’t want children being exposed to roundworms or hookworms, so it’s best to err on the side of caution with an immediate trip to the vet. Also, the sooner you start your dog on treatment, the sooner your dog will be free of those parasites. If your dog is vomiting or having diarrhea, which are the most common signs of intestinal parasites, your veterinarian will want to check a stool sample right away. With external parasites, your dog might be experiencing itching, skin problems, and you might see live fleas or ticks on your pet, and any of these things are indications to get treatment right away.

How will a veterinarian diagnose parasites in my dog?

Your vet can usually visualize external parasites. With ear mites or some skin mites, like scabies or Demodex, they may take a skin scraping or an ear smear of your dog and look under the microscope. To test for intestinal parasites, your vet will quite often ask for or take a fecal sample—a small amount of the stool—and send it into a lab or conduct the test in-house. They’ll use that sample to look under a microscope and diagnose intestinal parasites. About 10% of the stool samples that vets look at in a given year are positive for some intestinal parasites, and many of these patients are asymptomatic. The dog can be carrying a very low worm burden and not have any symptoms at all, yet they’re shedding those eggs. Some of those eggs are transmissible to people, which is why it's essential to keep up with that monthly deworming.

It's much easier to prevent blood parasites and heartworm disease than it is to treat them. The heartworm disease medication is somewhat toxic to the patient—thankfully, it’s more toxic to the worms. Veterinarians highly recommend monthly heartworm prevention, but if a dog is positive for heartworm disease, they will go through a lengthy protocol to get rid of those worms.

Is ringworm a parasite?

Ringworm is not a parasite, despite having the word “worm” in it. It's a saprophytic fungus, which means it comes from the soil, and it often causes circular lesions and infects the hair. Your dog might get these circular lesions on the skin with hair falling out or patchy hair loss.

Why is early detection and diagnosis of parasites so important?

The sooner your veterinarian can detect and treat heartworm disease, the less chance of permanent damage to the heart and lung vasculature there is. Dogs can live with up to five heartworms with no symptoms yet that ongoing damage occurs. Many pet owners will tell vets, "My dog can't have heartworm. He's acting totally normal." That's not the case, which is why they stress that heartworm testing on an annual basis is an excellent idea.

In addition, early detection of intestinal parasites is also essential to reduce the chance that those parasites are spread to people, especially young people in a household. Think of toddlers who may be crawling around on the floor, exploring their environment, and putting things in their mouths that older people would not. Or think of a cat using a play sandbox outside for a litter box—all this fecal material may be washed away, but those eggs can remain in that sand for up to five years. Keeping those pets in the household free of parasites is extremely vital for the health of the family.

Another reason why early detection of parasites in your dog is so critical is that roundworms, hookworms, and whipworms are all in the dog’s gastrointestinal system. They generally get the nutrition from your dog first, and your dog gets the leftover nutrition. That’s why the infected dogs may be unthrifty, may not be gaining weight, and may have bloody stools—all very unhealthy situations.

Fleas can cause flea allergy dermatitis. The fleas can jump off of one animal onto another animal. They can also jump off of a dog and bite people. Ticks can transmit many diseases. The deer tick can transmit Lyme disease. Some other ticks can transmit Ehrlichia, anaplasmosis, Babesia, and Rocky Mountain spotted fever. The bottom line is that all ticks can carry diseases, so it's essential that your veterinarian knows right away if you know or even suspect that a tick bit your dog.

In sum, here is why early detection of dog parasites is so critical:

  • The sooner the dog is treated, the less chance of damage to the heart and lungs
  • Parasites can be zoonotic, meaning they can be transmitted to humans, so you need to protect your family members
  • Parasites steal your dog's nutrition, leaving them unhealthy
  • Fleas can cause allergy dermatitis and ticks can carry many terrible diseases

The ideal situation for prevention in the eyes of veterinarians would be for you, the pet owner, to bring your dog in as a puppy or an adult (whenever they get it) to ensure that they're negative for parasites to start with—at that point, they’ll want to get them on some preventatives so that they won't get intestinal parasites, heartworms, fleas, or ticks.

The AVMA is also an excellent resource for the prevention and treatment of dog parasites. If you have any further questions about how to prevent your dog from getting internal or external parasites, please reach out to your vet. Don’t have one? We can help you find a local veterinarian!