What You Need to Know About Pet Parasite Prevention

Parasites can be unwelcome guests in your pet’s internal organs, and you might not even know it. Your pet can appear totally healthy and have some secret foreign invaders inside or on them, which is why parasite prevention is so important. It’s easier to proactively protect your pet rather than race around trying to fix the problem via medicines later. Did we mention that pets can sometimes pass these pests to you, too? So it’s in everyone’s best interest to be on alert and cautious. 

Adopt a Pet spoke with Dr. Heidi Cooley, DVM, senior manager of client experience and advocacy at Banfield Pet Hospital, about why it’s imperative to safeguard your pet from parasites, which parasites you should be looking out for, and how you can prevent them from leeching onto your pets.

Why is parasite prevention important?

Even if you’re still prepping for adoption and haven’t yet met your future dog or cat, it’s worth thinking about this stuff early. Why? If your dog or cat contracts a parasite, it can steal all of their nutrients and cause irreversible organ damage. 

They can also spread disease to other pets and family members. “A pet with parasites can lose weight, have a poor hair coat, be more prone to infection, and even have life-threatening illness,” Dr. Cooley says. That’s why it’s so important to factor parasite prevention into your pet prep — it’s not just something to deal with after your first vet visit.

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Common types of parasites

There are two different types of pet parasites: external and internal. Mites, fleas, and ticks are external parasites, while tapeworms, roundworms, hookworms, whipworms, and single-celled organisms, such as giardia and coccidia, are internal parasites. Each parasite affects the body in its own way, and the symptoms of an infection can vary. Here are some signs to watch for.

Fleas

If your dog or cat has fleas, they will itch constantly and over-groom themselves in an effort to get rid of the blood-sucking parasites. Fleas can cause hair loss and skin infections, which are identified by small, red bumps or flaky skin. Check the base of your pets’ tails and between their legs for signs of irritation. Fleas can easily pass to other pets and can carry diseases.

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Mites

Similar to fleas, mites can cause intense itching on areas such as the face, belly, paws, and ears. Symptoms of a mite infestation include inflamed red skin, dandruff, scabs, dark and “dirty” ears, and ear discharge.  

Ticks

Ticks are particularly insidious. If your dog or cat has a tick attached, the area around the bite will be red, swollen, and itchy. Your pet will try to chew, lick, or scratch the area. From there, ticks can cause skin irritation, fever, diarrhea, loss of appetite, lethargy, rapid breathing, neurological issues (including tick paralysis), and weight loss. 

Tapeworms

Unlike many internal parasites on this list, you will be able to see segments of tapeworms (they look like grains of rice) in the stool of your pet or around their anus. Pets will scoot on their butts and lick the area to try to relieve the itchiness. Tapeworms can cause vomiting, diarrhea, weight loss, and lethargy, though sometimes a pet may not have any symptoms. 

Roundworms

Roundworm infections most often show up in the puppy-kitten stage because they lie dormant in adults and can be passed on during pregnancy to an unborn children. Symptoms include a pot-bellied appearance, malnutrition, vomiting, diarrhea, and coughing. Sometimes roundworms can be spotted in vomit: They are long, skinny, and pale in color. Roundworms can make their way into the human system and cause serious diseases. 

Hookworms

Another parasite often contracted during babyhood, hookworms can wreak havoc on a dog or cat’s system. Signs of an infection include lethargy, GI distress, blood in the stool, weight loss, pale gums, coughing, vomiting, as well as skin itchiness. Humans can contract hookworms, too. 

Dirofilaria immitis (aka heartworm)

Dirofilaria immitis is the parasite that causes the deadly heartworm disease. Dogs contract it via mosquito bites, the only way that heartworm is spread. Heartworms take six months to mature, so your dog will not show symptoms right away. Early signs of a heartworm infestation include coughing, loss of appetite, lethargy, and weight loss. Later symptoms consist of fainting, a swollen belly, irregular heartbeat, difficulty breathing, and heart failure. Heartworms can be fatal. Cats can get heartworm, but most heartworms will die before they reach adulthood. 

Giardia

The giardia parasite can spread through water, food, and infected surfaces in both humans and animals. It’s an intestinal parasite that causes diarrhea, vomiting, fatty or mucus-y stool, weight loss, and lethargy. 

Coccidia

Coccidia is another intestinal parasite that more often than not affects puppies or kittens. It can cause dehydration, weight loss, vomiting, and diarrhea. If not caught and treated, it can lead to death.

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How do you prevent parasites in dogs and cats?

All of the above parasites might have you worried for your pet, but not all is lost. There are simple steps you can take to ensure that parasites stay far away from your BFF. “Pet owners should also give [their] pet monthly prevention to ensure pets do not become infected with parasites that are spread in ways we cannot control as easily,” Dr. Cooley says.

What do veterinarians recommend for flea and tick control?

“There are a number of products that are topical or oral,” Dr. Cooley says. “They are usually monthly, but some last as long as 12 weeks. There are some that are flea only, and some that do both flea and tick. Prescription products tend to be the most effective as they are the newest scientific medication, which has the least resistance from fleas.”

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Some natural parasite prevention methods may work, but not as well as prescription medicines. Because fleas can spread fast, it’s in your best interest to contain and eradicate the fleas as quickly as possible. 

Parasite prevention tips for dogs​

• Give your dog monthly topical, oral, or ingestible preventable medicines year-round, even if your dog is mostly indoors. 

• Pick up poop promptly, whether in your yard or on walks. Parasites spread fast through contaminated soil.

• Don’t let your dog drink from puddles, ponds, or standing water. That’s prime real estate for giardia and other nasties.

• Regular baths or trips to the groomer will keep your pet’s coat parasite-free.

• Make sure to check your dog for ticks, fleas, and other parasites regularly. 

• Get regular fecal tests done at the vet, even if your dog seems fine.

Parasite prevention tips for cats

• Give your cat vet-recommended topical, oral, or ingestible preventable medicines.

• If you have a kitten or a cat who roams outside, regular deworming is crucial. 

• Avoid giving your cat raw meat, because parasites can live in raw meat. 

• It’s important to keep your cat’s litter box clean, especially if you have multiple cats, to avoid the spread of worms.

• Keep your cat indoors or limit outdoor time to reduce exposure to fleas, ticks, and infected prey.

Is monthly worm prevention really necessary?

Dr. Cooley absolutely recommends monthly heartworm prevention, in particular. “Heartworm disease can result in severe illness and death,” Dr. Cooley says. “It not only has an extreme cost to address, but is a very painful condition for the pet. Heartworm prevention is easy to administer and also prevents other intestinal parasites. It can be given as a six-month or 12-month injection if you prefer not to do monthly oral medication.”

Strategies to prevent parasites around the home

“Parasites can be prevented by a combination of controlling environmental exposure and providing preventative medication,” Dr. Cooley says. “Environmental prevention can [mean] keeping your pet from dirty water sources, other pets’ waste, and infected animals.”

1. Clean up after your pet

This might seem obvious, but it’s crucial to clean up your yard, clean the litter box, and regularly clean the surfaces that your pet (and the rest of your family) steps on, especially if you have an animal that’s going outside regularly. 

2. Check your pet for parasites after coming inside

If you’re a hiker, you know that you do a tick check on yourself after you’re done, so why wouldn’t you do the same for your dog or cat? It’s a good habit if your pet is roaming in any grass at all or coming in from the dog park. 

3. Learn about parasites in your area

Check your local news sources and Facebook groups (especially dog park groups) to know which parasites might be living in your area. Internal parasites can spread in dog parks due to shared water bowls. 

4. Regular vet checkups

It’s important to schedule appointments with your vet for yearly check-ups. Even if you and your pet hate trips to the vet, you’d be doing them a grave disservice by skipping them. The vet is the one who finds microscopic parasites in your dog’s stool or ear mites in your cat’s ears. And if your dog or cat does have recurring diarrhea, it’s a smart idea to take them to the vet to rule out any parasites or get treatment ASAP.

Commonly asked questions

Is topical or oral flea and tick control safer?

Both topical and oral flea and tick medications are safe. “There is not a ‘safe’ or ‘unsafe’ option,” Dr. Cooley explains. “There are a number of [flea and tick control] options, so veterinarians can recommend what is best for the individual pet based on their health status. It would be best for any pet owner to speak to their provider about their recommendation.”

Does an indoor cat need flea treatments?

Dr. Cooley confirms that indoor cats need flea treatments, too: “Fleas can travel inside on other pets as well as on clothing and items. We also have flea control that includes heartworm prevention.” Heartworm prevention is also important for indoor cats, because mosquitoes (the way heartworms are spread) can easily get inside the home.

How do you protect your pup from ticks and worms?

“There are many products that protect against fleas, ticks, and heartworms, all in one product,” Dr. Cooley says. “That may be an option for your pet. There are also oral dewormers that your vet can prescribe in the hospital after a fecal exam looking for intestinal parasites. Monthly prevention is best to keep your pet tick and worm-free.”

How do you deal with an infestation in a multi-pet household?

Here’s how to deal with an infestation in a multi-pet household. “Identifying what parasite[s] your pets have is important, and then treating every pet in the household with veterinary-prescribed medication monthly consistently will stop the cycle of infestation,” Dr. Cooley says. “You should also treat the environment with the instructions of a pest professional with pet-friendly products. It is important to continue monthly pet parasite prevention on your pet even if you do not see any parasites.”

References

AKC Staff, et al. “What Is the Best Flea and Tick Prevention for Dogs?” American Kennel Club, www.akc.org/expert-advice/health/best-flea-tick-prevention-dogs.

Cohen, Aly. “Giardia: Infection, Treatment and Prevention.” Cornell University College of Veterinary Medicine, 2024, www.vet.cornell.edu/departments-centers-and-institutes/riney-canine-health-center/canine-health-information/giardia-infection-treatment-and-prevention.

‌“Dog Parks May Be Fueling Parasite Outbreaks.” Earth.com, 2024, www.earth.com/news/dog-parks-may-be-fueling-parasite-outbreaks.

FDA. “The Facts about Heartworm Disease.” Fda.gov, 2019, www.fda.gov/animal-veterinary/animal-health-literacy/keep-worms-out-your-pets-heart-facts-about-heartworm-disease.

‌“Geography Pet Parasites Changing.” Boehringer-Ingelheim.com, 2025, www.boehringer-ingelheim.com/animal-health/companion-animals-horses/pets/geography-pet-parasites-changing. 

Giannelli, Alessio, et al. “Control of Companion Animal Parasites and Impact on One Health.” One Health, 1 Jan. 2024, pp. 100679–100679, https://doi.org/10.1016/j.onehlt.2024.100679.

Kustritz, Margaret Root. “Parasite Control.” Pressbooks.umn.edu, 1 Jan. 2022, pressbooks.umn.edu/vetprevmed/chapter/chapter-5-parasite-control.

“Prevent the Big Three Pet Parasites.” Veterinary Medicine at Illinois, vetmed.illinois.edu/pet-health-columns/pet-parasites.

“Protecting Your Pet from Parasites - Veterinary Teaching Hospital.” Veterinary Teaching Hospital, 5 Nov. 2020, vetmedbiosci.colostate.edu/vth/animal-health/protecting-your-pet-from-parasites. 

“Puppy Parasites: Preventing, Diagnosing, and Treating Parasites in Puppies.” Kinship.com, 2020, www.kinship.com/dog-health/puppy-parasites. 

‌Purdue Veterinary Medicine. “Heartworm and Other Internal Parasite Prevention.” Purdue University College of Veterinary Medicine, 2025, vet.purdue.edu/hospital/small-animal/primary-care/services/heartworm-and-other-internal-parasite-prevention.php. 

‌“Tapeworms | Cornell University College of Veterinary Medicine.” Www.vet.cornell.edu, www.vet.cornell.edu/departments-centers-and-institutes/riney-canine-health-center/canine-health-information/tapeworms.

“Vet Times: Latest Veterinary News, Jobs & Clinical Resources.” Vettimes.com, 2025, www.vettimes.com/clinical/small-animal/parasite-surveillance-vital-role-in-uk-cats-and-dogs-cpdparasitology. ‌