Common Parasites of the Dog

Bugs and Your Dog

Dog scratching on sofa
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Any dog can get parasites. There are two main categories of parasites that affect dogs: external and internal. The external parasites generally affect the dogs skin and coat, but can lead to internal problems. The internal parasites often affect the gastrointestinal system or the heart and lungs.

While parasitic infestations can be treated medically, some are easier to manage than others. In addition, some canine parasites can be transmitted to humans. Prevention is the best way to protect your dog, yourself and your family.

Learn about the most common types of parasites that affect dogs and find out how to prevent them.

  • 01 of 05


    Flea on blade of grass, close-up
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    The flea is a hard-bodied, wingless insect that is as small as the tip of a pencil. Its strong legs are designed to jump great distances and its narrow body is perfect for navigating through the hair coats of mammals. The flea's mouthparts are used to suck the blood of its host (often a dog or cat). Fleas can cause a variety of problems for your dog, including Flea Allergic Dermatitis, anemia, and tapeworm infection. A serious flea infestation can be difficult to deal with. The best option is to keep your dog on flea prevention all year long.

  • 02 of 05


    Pictures of Ticks
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    Fleas are not the only little vampires lurking in your dog's world. The tick is an arthropod that feeds on the blood of its host, including dogs, cats, and humans. The tick jumps onto a host, attaches its mouthparts into the skin, and sucks blood until it becomes engorged. Ticks are well-known vectors of some serious diseases. Lyme Disease, Ehrlichia, and Rocky Mountain Spotted Fever are a few of the more common tick-borne diseases. Ticks typically live in tall grasses and wooded areas. Certain preventive products can prevent ticks from attaching to your dog. However, it is still important to check your dog regularly for ticks, especially after spending time where ticks may lurk.

  • 03 of 05


    Photo of Mosquito - Heartworm Disease in Dogs
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    Heartworms (Dirofilaria immitis) are parasitic nematodes that are among the most dangerous parasites affecting dogs. Heartworm larvae are transmitted to dogs via mosquitos. Once inside the dog, the larvae migrate and mature in dog's heart and lungs. Adult heartworms look something like spaghetti and can be 9 to 16 inches in length. Heartworm infection is a serious condition in dogs that leads to death if untreated. In addition, the treatment to rid a dog of adult heartworms is risky to the dog and rather expensive. The best approach is heartworm prevention (generally given monthly) to kill the tiny heartworm larvae before they mature into dangerous adults. Every dog should be on heartworm prevention all year long.

  • 04 of 05

    Intestinal Worms

    Dog roundworm, illustration

    There are a variety of intestinal parasites that your dog can pick up from his environment. The "big four" are roundworms, hookworms, whipworms, and tapeworms. Tapeworms come from fleas, but the other three are typically contracted after contact with contaminated soil. They may also be passed on from a mother dog to her puppies.

    Intestinal parasites may cause a variety of symptoms, most of which are uncomfortable for your dog, such as diarrhea, vomiting, and lethargy. However, a dog with intestinal parasites may show no signs at all. Some of these intestinal parasites can affect humans too. Protect your dog, yourself and your family by learning about these intestinal parasites and how to prevent them.

    Continue to 5 of 5 below.
  • 05 of 05

    Mites (Mange)

    Scabies mite, artwork
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    There are a few types of mites that typically affect dogs. The most common are demodex and scabies. Both can cause skin irritation and hair loss.

    Demodectic mange, or Demodex, are mites that live on the skin or in the hair follicles and oil glands of a host (often a dog or cat). Small numbers of mites can live on many dogs without causing problems because the immune system keeps the population under control. However, when Demodex numbers get high, they can cause localized areas of hair loss and itching. This most often occurs in young animals or those with compromised immune systems. Demodex is treated with prescription medication (oral and/or topical) and can take weeks to months to resolve.

    Sarcoptic mange, also called Scabies, is a highly contagious mite that burrows into the skin. These mites cause intense itching, hair loss, and scabs on the skin. Scabies can be difficult to diagnose. Treatment is lengthy and often requires a combination of oral medications and, in some cases, special medicated baths. Scabies is contagious to both pets and humans.

If you suspect your pet is sick, call your vet immediately. For health-related questions, always consult your veterinarian, as they have examined your pet, know the pet's health history, and can make the best recommendations for your pet.