Your guide to understanding parasitic diseases in dogs

Parasites survive by feeding on animals and people. Know what to look for and how to treat.

Lyme disease



Heartworm disease




How does my dog
get infected?

Deer tick or black-legged tick (Ixodes spp.) carries bacteria and bites dogs, spreading infection.

Lone star tick (Amblyomma americanum) or brown dog tick (Rhipicephalus sanguineus) carries bacteria and bites dog, spreading infection.

Mosquito transfers worm larvae from infected dog to your dog; larvae develop into worms that live in the heart and its vessels.

Ingestion of parasite eggs or rodents or direct contact with parasite larvae in contaminated environment. Also spread through mother’s milk and placenta.

Ingestion of parasite eggs from a contaminated environment (soil, kennels, dog parks, etc.)

Most common signs of infection

May not show any signs, or:

  • Lameness

  • Fever

  • Swollen joints

  • Kidney failure

  • “Not himself”

  • Loss of appetite

May not show any signs, or:

  • Lack of energy

  • High fever

  • Swollen, very painful joints

  • Loss of appetite

From mild to severe:

  • Loss of appetite

  • Depression

  • Fever

  • Painful joints

  • Bloody nose

  • Pale gums

No signs at first, then:

  • Mild, persistent cough

  • Reluctance to move or exercise

  • Tiredness after moderate exercise

  • Reduced appetite

  • Weight loss

May not show any signs, or:

  • Diarrhea

  • Pale gums

  • Poor health

  • Poor hair quality

May not show any signs, or:

  • Diarrhea

  • Pot-bellied appearance

  • Poor hair quality

  • Cough

  • Vomiting

May not show any signs, or:

  • Intermittent diarrhea

  • Loose poop

  • Blood in poop

Disease progression if left untreated

Damaged joints, fatal kidney disease (rare), neurological signs (rare)

Very low numbers of platelets and white blood cells, chronic joint pain, neurological signs (rare)

Permanent blindness, autoimmune diseases, bleeding complications, death

Heart failure, lung disease, sudden death

Intestinal inflammation, failure to grow/thrive, weight loss, severe anemia

Intestinal inflammation, failure to grow/thrive, weight loss

Chronic bloody diarrhea, dehydration, weight loss and anemia


Coinfection with Lyme disease and anaplasmosis is possible. In addition, it’s possible for your dog to become infected with any combination of parasitic diseases—including those not listed here.

Roundworm, whipworm

Hookworm, whipworm

Hookworm, roundworm


Simple blood test: Laboratories, Inc. SNAP® 4Dx® Plus Test

(can detect six infections in one blood sample in less than 10 minutes)

Other tests: Complete blood count, chemistry profile, urinalysis, other special tests (depending on initial findings and clinical signs)

Test poop sample for presence of parasites (eggs, larvae, antigen)


Antibiotics: doxycycline, tetracycline

Antibiotics: doxycycline, tetracycline

Antibiotics: doxycycline, tetracycline

Adulticides (kills adult heartworms), monthly products licensed to treat microfilaria

Source: Companion Animal Parasite Council

Deworming medication


If caught and treated early, the outcome is usually very good for a full recovery from symptoms. Some of these infections cannot be cured completely, but early intervention usually provides the best prognosis.




Vaccine available?








Other prevention

Daily tick inspection and removal, and the use of oral or topical preventives. Ask your vet for more information.

Oral and topical preventives

Monthly parasite control products (available from your veterinarian), often included in your monthly heartworm preventives. Also remember to pick up your dog’s waste regularly.

No prevention is 100% effective. Test your dog every year.

Ask your veterinarian about testing and prevention for parasites.


Babesiosis is a disease transmitted by ticks. It is caused by protozoan parasites of the genus Babesia, which infect the red blood cells. Babesiosis affects a wide range of domestic and wild animals and, occasionally, humans. While the major economic impact of babesiosis is on the cattle industry, infections in dogs occur at various rates throughout the world.

Signs of infection vary from a mild illness that passes quickly to a severe disease that rapidly results in death. In some cases, the parasite causes a longterm disease with severe and progressive anemia as the main symptom. Babesiosis can be confused with other conditions that cause fever, anemia, destruction of red blood cells, jaundice, or red urine. Therefore, laboratory tests should be performed to confirm the diagnosis.

Your veterinarian will be able to prescribe the appropriate medication. Supportive treatment is helpful and may include the use of anti-inflammatory drugs, antioxidants, and corticosteroids. Blood transfusions may be life-saving in very anemic animals.

A vaccine based on some types of Babesia is available, but it does not protect against all types. Preventing exposure to ticks by using appropriate tick control products and removing any ticks promptly will help keep your dog from being exposed to this parasite.

A small number of cases of human babesiosis have been reported, but it is unclear whether the species of Babesia that infect dogs are the same as those that cause infection in people. Fatal cases have been reported in people whose spleen had been removed or who had a weakened immune system. Human Babesia infections are acquired by way of bites from infected ticks or through contaminated blood transfusions.

Dog Diseases and Symptoms

Knowing the symptoms of certain common diseases gives you an idea as to whether your dog’s condition is serious enough to warrant a visit to the vet, or whether home care is sufficient.

Educating yourself and learning some common dog diseases and symptoms can make you a better dog parent!

As you will see, different dog diseases and health problems can result in similar canine illness symptoms. The key is to observe your dog and identify as many symptoms as you possibly can. Usually, that will give you a better idea at least as to whether the problem is a serious one.

The bottom line is, when in doubt, and when the symptoms persist, consult a veterinarian before considering or attempting any type of treatment.

This page gives a list of some common dog diseases and symptoms for your quick reference. New information will periodically be added to this page, so be sure to check back regularly!

Parasitic Blood Infection (Haemobartonellosis) in Dogs

Your guide to understanding parasitic diseases in dogs - pets

1. Roundworms are nematodes that commonly affect young puppies. These worms live in the stomach and intestines of dogs. Puppies can pick up a roundworm infection while they are still in the womb of their mother or from her milk after they are born. Or dogs can become infected by ingesting soil contaminated with roundworm eggs. The soil becomes contaminated from the feces of a dog who has these worms.

2. Hookworms are another nematode that like to infect puppies. Of course, a dog of any age can certainly get them. These worms are microscopic and live in the small intestine of their host. Hookworms are dangerous to dogs, especially puppies, because they can potentially cause anemia. They feed on blood, so large infections of hookworms are problematic. Hookworms are zoonotic, which means people can get them too. And did you know that they can actually pass through your skin? That's why your mother told you to wear shoes out in the yard when you were young.

3. Whipworms are also passed through dog stool. And they happen to be one of the hardest parasites to get rid of once their eggs get in your yard. It could potentially take several months to rid your dog of a whipworm infection. They get their name because they look like whips. One end is fat, like a whip handle and the rest of the worm is very long and skinny. These worms are microscopic. They also have the coolest looking eggs. (Can you tell I am a little too into my parasitology?)

4. Giardia is not a worm. It's a protozoal parasite. It causes dogs and cats to become sick with symptoms such as diarrhea and vomiting. It makes them feel pretty crummy. It's not easy to get rid of, either. Many dogs and cats pick up giardia by drinking from contaminated water puddles. Contaminated poop that's left un-scooped washes away with rain water and then other animals drink it. This can infect people also.

5. Parvo is a life threatening virus that infects puppies and young dogs. This viral infection is no joke. Puppies with parvo will be extremely lethargic, have bloody diarrhea, vomiting, and dehydration. Parvovirus can live in the environment for years and there isn't much that can kill it. Bleach is an effective method of killing this virus in it's environment. Parvo is not something that people get.

Watch the video: Vet Guide. General Info About Heartworm Disease in Dogs and Cats (August 2021).