Biliary fever (Tick fever)

Biliary Fever or Tick Fever (Babesiosis)

Babesia canis

Babesia canis (photo courtesy of ProProfs)

Babesiosis (also called Biliary fever or Tick fever) is one of the most common tick-borne diseases in dogs. Due to the high number of ticks found in our area it is a disease that we diagnose very commonly. Biliary fever can be fatal if not treated promptly.

Biliary fever is caused by a protozoan parasite (Babesia canis) which is carried by ticks. When the tick is attached to your dog for 48 hours or more and has a blood meal, the parasite is transmitted from the tick to the dog. (Remember that not all ticks will carry the biliary parasite).

The parasite can take 10-14 days (but even up to 28 days in some cases) before it has multiplied enough to cause visible disease in your dog. The ticks might thus already be gone by the time your pet gets sick.

The parasites infect the red blood cells, eventually leading to their destruction. This can lead to various organs having to work harder and sometimes failing to keep up with the increased demands.

Clinical signs

The first visible signs are usually lethargy/depression and a loss of appetite. You might also notice the gums looking pale or yellowish and a colour change of the urine to dark yellow or red.

If you see any of the above signs your pet needs to be taken to the vet.


 The vet will examine your dog for the clinical signs mentioned above. He will also look for fever and possible enlargement of the spleen and liver.

Biliary fever is confirmed by making a blood smear and looking for the parasites in the red blood cells under a microscope.

Normally a red blood cell count and ISA test will be performed if biliary fever is diagnosed. This is done to determine the correct treatment needed for the specific pet.


 Treatment is most successful if done promptly.

Treatment consists of a drug that kills the parasites in the blood stream. The drug is potentially toxic and thus needs to be given at the correct dose and by a qualified veterinarian.

Depending on each individual case and the severity of the disease other treatments might be necessary. These include,but is not limited to intravenous fluid therapy, anti-inflammatory drugs, blood transfusions and liver supportive therapy.


 Prevention is always better than cure. Effective and regular tick control will reduce the chances of your dog being infected with biliary fever. Please see our article on external parasites for more information.