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Signs and Symptoms of Parasites in Dogs

Tick on Dog

Parasites are part and parcel to a dog’s life. Over the course of your dog’s years, they’re likely to become infected at one point or another.

Many (if not most) will go undiagnosed, unacknowledged and untreated. That’s a good thing: Large numbers of canine parasites are relatively benign, and may come to pass as quickly as they arrived.

However, there are parasites that demand pet parents’ immediate attention. Many of which you’ve heard the names of before, but maybe haven’t been acquainted with their signs and symptoms. For those of you in that boat, we put together a quick handguide of the most common parasites in dogs, what they’re indicators are and what you can do about them.

First, what’s a parasite?

As the medical dictionaries put it, a parasite is any plant or animal that lives upon or within another living organism at whose expense it obtains some advantage. Parasites span the bacterial and animal kingdoms, coming in all shapes, sizes and difficult-to-pronounce distinctions that outrank the purposes of this article. 

In the world of dogs, we can simplify parasites into two broad categories:

External parasites like ticks, fleas and mites that are often visible to the naked eye and live on the hair or skin of your dog, and internal parasites like roundworms, tapeworms and heartworms that are tougher to see, sometimes microscopic and live inside your dog’s body.


Ticks are eight-legged, spider-like invertebrates that spend their lives wandering from host to host, feeding off their blood for nutrition. Disgusting, for certain. But more importantly, ticks can pose real dangers to your dog. Many carry diseases such as Lyme disease, Rocky Mountain spotted fever and others. Not to mention the redness, rashes and general irritation that can come from a tick clamping down on your dog’s skin.

Be sure to check for ticks anytime you and your dog take a stroll through the woods or a heavy brush. If you find a tick, the Humane Society recommends using a pair of tweezers to gently remove it, then rinsing your dog’s wound with isopropyl alcohol to help prevent infection.


Fleas, like ticks, live off of dogs’ bloodstreams. The good news is that identifying them is often easier, as you may even be able to see them dancing across your dog’s fur with only your naked eye. It’s likely your dog will experience persistent itching when they catch fleas, which is another telltale sign.

Oftentimes, fleas can be removed through a thorough bathing with a specialized flea shampoo, followed by a thorough brushing with a specialized flea comb. If your dog’s fleas persist, speak to your vet about medication.


Mites carry many of the same properties as fleas and ticks: microscopic, fur-dwelling and stubborn. However, they may crawl into even less detectable areas such as your dogs folds and ears.

Dogs often catch mites from one another at boarding stays, animal hospitals and dog parks, though they may also live within carpets, bedding and other spots within your home environment. Prevention is all about keeping your dog away from potentially infested areas, though if your dog does come down with mites, treatment typically requires only a simple antiparasitic shampoo you’ll be able to find online or at your local pet store. Speak with your vet if the infection persists or you notice mites in a sensitive location such as their ears.


Roundworms are perhaps the most common internal parasite, living inside their intestines and feeding off the food your dog eats.

Know to science as Toxocara canis and Toxascaris leonine, roundworms take their everyday name from their shape, and if it were up to us, their bizarre and circular lifecycle. If infected, dormant roundworm larvae can live inside your dog’s body tissue near permanently. 

While oftentimes benign, this nesting capability makes roundworms extremely important to catch early. Look out for a distended stomach, vomiting or presence of worms within your dog’s stool. Talk to your vet about treatment — deworming medications are available to help them pass the infection in as little as days.


Flat, segmented and usually transmitted via fleas, tapeworms attach themselves to dogs’ intestinal lining, nourishing themselves through your dog’s intake much the same way roundworms do.

Dogs suffering from a tapeworm infection often tip their hand by doing the trademark butt scoot. Tapeworms occasionally latch to a dog’s outer anus, causing irritation and the need to itch.

Tapeworms are somewhat easily prevented with specialty collars and medications. Though in the instance your dog becomes infected, treatment is often just as simple. Speak with your vet about an oral dewormer.


Heartworms are perhaps the most pressing common worm infection that dog parents need to keep in mind. Different from tapeworms or roundworms, heartworms can cause potentially fatal complications.

The associated heartworm disease is a serious cause for concern, as it can lead to organ failure if left untreated. 

Heartworms are also unique in their transmission via mosquitos. Once inside a dog, Heartworms are not contagious, but may live up to seven years. Make sure you get your dog tested at your next routine vet appointment, as mild heartworm infections may difficult to detect without professional evaluation.

The greater number of heartworms that live and reproduce inside your dog’s arteries and vital organs, the greater the risk. So be sure to stay current with their anti-heartworm medication and look out for any severe signs of illness.

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