Babesia canis in Dogs: Signs, Smear and RT-PCR

Babesia canis is a tick-borne parasite that lives inside a dog's red blood cells and can cause sudden anaemia, fever and dark urine. A blood smear can show the parasite under the microscope, and RT-PCR (real-time PCR, a test that finds the parasite's genetic material) can confirm it when the smear is unclear. A registered veterinarian reads the results with your dog's signs.

Why is it called the large babesia?

Babesia are tiny parasites that live inside red blood cells. Under the microscope, the ones that infect dogs come in two broad sizes. Babesia canis is the larger kind. It often looks like a pear, and it is frequently seen as a pair sitting inside one red cell. The smaller kind looks like a tiny ring and has its own article, linked at the end.

Ticks carry the parasite from one dog to another. After an infected tick feeds, the parasite settles in the red cells and multiplies until the cells burst. The body then loses red cells faster than it can replace them, and that loss is what makes the dog ill.

What signs should make you call your vet?

Common signs include:

• tiredness, and a dog that does not want to walk or play
• fever and a poor appetite
• pale gums or pale inner eyelids, which may point to anaemia (the normal colour is pink)
• urine that looks dark orange, brown or red-brown, because broken red cells release their colour into it
• a yellow tint to the gums or the whites of the eyes
• fast breathing or weakness

These signs are not special to babesia. Other tick fevers, liver trouble and immune problems can look much the same, so a lab test is needed. A dog with pale gums and dark urine is an emergency: see a registered veterinarian without waiting for any report.

What does a blood smear show?

For the Blood Protozoa (Blood Parasite Smear), a drop of blood is spread thin on a glass slide, stained with a dye and checked under the microscope. A trained pathologist looks inside the red cells for parasites and notes their size and shape. The smear is quick to prepare, and in a dog that is very ill it can give the vet a first answer.

Its weakness is that it only shows what is on the slide. If the parasites are few at the moment the blood is drawn, they can be missed, so a negative smear does not always rule babesia out.

What does RT-PCR add?

The Babesia Canis RT-PCR looks for the parasite's genetic material in a blood sample instead of looking for the parasite itself. It can find small amounts, so it is often asked for when the signs fit but the smear looks clear. The lab confirms what the test covers, the sample needs and the reporting time when you book.

RT-PCR has limits too. It tells you the parasite's genetic material is present, but it does not show how sick the dog is or how much blood has been lost. Your vet needs the other results for that.

Why add a blood count and a reticulocyte count?

A Complete Blood Count (CBC) counts the red cells, white cells and platelets. In babesia the red cells are usually low, and the platelets, which help blood to clot, are often low as well. The count shows how deep the anaemia has gone.

A Reticulocyte Count adds a second clue. Reticulocytes are young red cells that the bone marrow has only just released. When a dog loses red cells, a healthy marrow answers by sending more of them into the blood, so a rising count suggests the body is rebuilding. If the dog is anaemic but the count stays low, the marrow may not be responding, and the vet looks for the reason. Your vet may repeat both tests to follow progress and decides on any treatment.

The Tick Bone Panel typically groups a blood parasite smear, a blood count and checks of the liver and kidneys for a dog with tick-fever signs. The exact list is confirmed when you book.

Read next

The smaller cousin of this parasite is easy to overlook on a slide, and Babesia gibsoni in Dogs: The Small Parasite That Hides on a Smear explains why it needs extra care. To see how the same kind of tick-borne blood parasite is tested for in another animal, read Tick Fever in Horses: Equine Piroplasmosis Testing.

Testing in Bhopal

If your dog lives in Bhopal, the lab can collect the blood at your door without a collection charge, or you can bring the dog to C-200, C Sector, Shahpura. Owners in other districts can send samples by courier, bus parcel or through their own vet. Call or WhatsApp +91 88175 01118, and the lab confirms the method, sample needs and reporting time when you book.