7 Types of Parasites in Dogs

Dogs can be affected by several different types of parasites. These tiny creatures can cause minor to severe illnesses in dogs.

Jan 5, 2024By Heather Jarek, BA Veterinary Technology
types of parasites in dogs

Parasites are living organisms that survive by taking the nutrients they need from other living organisms called hosts. Many parasites favor or require a specific host to be able to thrive and complete their life cycle. Unfortunately, many parasites prefer dogs as their primary host. They will live on or inside a dog, causing various health issues for our canine companions. For owners, it’s helpful to be aware of the common parasites that can infect dogs.

7. Roundworms

puppies playing on grass

There are over 15,000 different types of roundworms. Toxocara Canis is a species of roundworm that commonly infects dogs. They live in the intestinal tract and get their nutrients from partially digested food. You may have noticed that many puppies have large potbellies. This is because many puppies are born with worms that they get from their mother during pregnancy or when nursing. Adult dogs become infected when they sniff or lick infected feces or ingest other infected animals, such as rodents or birds.

In the early stages of infestation, it can be difficult to notice that your dog has roundworms. For this reason, veterinarians usually recommend a fecal test every six months to check for worms. Fortunately, roundworms are treatable with a dewormer. Puppies are generally put on a deworming schedule starting two weeks after birth.

6. Tapewor

dog sniffing mouse


Tapeworms are another common intestinal parasite found in dogs. A dog can get tapeworms by ingesting an infected flea or rodent. This is why many dogs that have fleas end up with tapeworms. Tapeworms are flat, segmented worms. When a segment breaks off, it can pass through the dog’s feces and be seen by owners. This is usually the first sign that a dog has a tapeworm infestation.

Tapeworm eggs can be difficult to find on fecal testing and are more commonly diagnosed by the segments found in the feces. They are easily treated with a dewormer, but it’s essential to rid the dog of fleas to prevent reinfection. Your veterinarian may recommend flea prevention along with treating your dog with a series of dewormings.

5. Heartworms

labrador dog outside with misquito bugs

Heartworms (Dirofilaria immitis) are thread-like worms that infect dogs, cats, and ferrets. They are spread by mosquitos, which are needed to complete their life cycle. As their name indicates, they live in the heart and, if not promptly treated, will clog the heart and major arteries. A significant heartworm infection can take years to develop and cause major organ failure and death in untreated dogs.

Dogs don’t show symptoms of heartworm disease until it has progressed into the later stages. For this reason, veterinarians recommend yearly heartworm tests. Treatment for heartworm disease is an expensive and lengthy process. Fortunately, you can give your dog medications to prevent this disease. It’s best to talk with your veterinarian to decide which prevention best suits your dog and lifestyle.

4. Fleas

beagle dog scratching itself

Fleas are the most common parasite treated by veterinarians. They are external parasites, meaning they live outside a dog’s body. They are tiny creatures, but if you look close enough, you will be able to see them scurrying through your dog’s coat. You may also notice flea dirt (flea feces) throughout your dog’s fur. Flea bites cause an intense itch, so excessive scratching is usually an early indication of a flea infestation. Some dogs are allergic to fleas, and one flea bite can cause these dogs to develop severe skin infections.

If you suspect your dog is infected with fleas, it’s essential to seek out veterinary help quickly to prevent the fleas from multiplying. A flea infestation can be challenging to treat as they can lay thousands of eggs inside the home. You must treat your home and your dog to eradicate a flea infestation. The best way to keep fleas out of your home and off your dog is to keep your dog on a flea preventative all year round!

3. Hookworms

weimaraner dog sniffing grass

Hookworms are another common canine intestinal parasite. Instead of feeding off partially digested food, they use tiny hooks to anchor themselves to the intestinal wall, where they ingest large amounts of blood. Significant hookworm infections can cause inflammation of the intestines and anemia (decrease in red blood cells), which can be life-threatening.

Adult dogs can get hookworms from sniffing or digesting infected soil. Puppies are commonly born with hookworms, as they can be passed from mother to puppy during pregnancy or while nursing. Keeping puppies on a deworming schedule will ensure they don’t develop life-threatening hookworm infections. Routine veterinary visits and fecal exams are vital to detecting hookworm infections, as adult dogs won’t show symptoms until the infestation has progressed. If hookworms are detected, your veterinarian will prescribe a dewormer. Other treatments may be needed for advanced infections.

2. Whipworms

dog licking paw outside

Whipworms are similar to hookworms and attach themselves to the intestinal walls. They are named after their long, thin, posterior end that looks like a whip. A dog infected with whipworms may not show symptoms in the early stages of infection but can suffer from anemia, diarrhea, and weight loss in the later phases of the disease.

Dogs get whipworms when they ingest infected soil, usually when grooming themselves. A whipworm infection can be challenging to detect, making routine veterinary and fecal exams vital to diagnosing it. Whipworm eggs are hardy and can live for years in the soil, so your veterinarian may recommend parasite prevention to prevent reinfection. Are you noticing a pattern here? Prevention is key when keeping your dog parasite free!

1. Giardia

dog drinking from dirty puddle

Giardia is yet another intestinal organism. Unlike the other parasites, it is not a worm, bacteria, or virus but a microscopic protozoan, a simple one-celled species. Dogs can be infected with Giardiasis by drinking dirty, infected water or sniffing infected soil. A dog’s symptoms can range from none to diarrhea, weight loss, vomiting, and lethargy.

Detecting Giardia can be difficult as their cysts are shed intermittently. A fecal smear may be recommended if your veterinarian suspects your dog is infected with Giardia. Treatment may include an antiparasitic, and other medications may be necessary to treat the symptoms of the infection. Keeping your dog from drinking out of puddles and ensuring their drinking water is clean can go a long way in preventing Giardiasis.

Heather Jarek
By Heather JarekBA Veterinary Technology

Heather is a lover of all animals, big and small. She graduated with a bachelor’s degree in veterinary technology in 2014. She has been working as a licensed veterinary technician for the last eight years. Her favorite hobby is horseback riding, and she has been riding horses since the age of eight. She enjoys spending time with her family at the lake with their golden retriever Calista in her free time.