Common Parasites of the Dog

Bugs and Your Dog

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All dogs are vulnerable to parasites. Learning about the risks of parasites can help you protect your dog, yourself, and others.

There are two main categories of parasites that affect dogs: external and internal. External parasites generally affect the skin and coat. Internal parasites affect the gastrointestinal system or the heart and lungs.

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 in the US and find out how to prevent them.

  • 01 of 05

    Fleas

    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. The flea's strong legs are designed to jump great distances. 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 and take several months to eradicate. The best option is to keep all pets in the home on flea prevention all year long so you can avoid a flea infestation altogether.

  • 02 of 05

    Ticks

    Pictures of Ticks
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    Fleas are not the only tiny 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 medications can prevent ticks from attaching to your dog. These should be used on your dog if ticks are prevalent in your area. However, it is still important to check your dog regularly for ticks, especially after spending time where ticks may lurk.

  • 03 of 05

    Heartworms

    Photo of Mosquito - Heartworm Disease in Dogs
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    Heartworms (Dirofilaria immitis) are internal parasites that are among the most dangerous to dogs. Heartworm larvae are transmitted to dogs via mosquitoes. Once inside the dog, the larvae migrate through the bloodstream and mature in the dog's heart and lungs. Adult heartworms look something like angel hair pasta and can be 9 to 16 inches in length.

    Heartworm infection is a serious condition in dogs that can lead to death if untreated. In addition, the treatment to rid a dog of adult heartworms is risky to the dog and very expensive for you. The best approach is heartworm prevention to kill the tiny heartworm larvae before they mature into dangerous adults. Every dog in the US should be on heartworm prevention all year long, regardless of the region.

  • 04 of 05

    Intestinal Worms

    Dog roundworm, illustration
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    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 or infected feces. Some may also be passed on from a mother dog to her puppies.

    Intestinal parasites may cause a variety of symptoms. The most common signs are diarrhea, vomiting, lethargy, and weight loss. 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 following your veterinarian's recommendations for screening and prevention.

    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 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 is called demodicosis and is somewhat common in puppies and young adult dogs. It can also affect dogs with compromised immune systems. Demodicosis is treated with prescription medication (oral and/or topical) and can take weeks to months to resolve.

    Sarcoptic mange, also called Scabies, is a 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. Fortunately, sarcoptic mange is less common than demodicosis.

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.