Overview

Babesia are parasitic protozoans that are transmitted by tick bites. Babesia infections can occur in conjunction with other tick-transmitted infections such as Lyme disease. When a dog is bitten by Babesia-carrying ticks, the protozoans enter the new host’s bloodstream and penetrate the red blood cells, where they can reproduce. The dog’s own immune system will begin to destroy the infected red blood cells, which will result in anemia. Localized inflammations can occur when the parasites are carried to other parts of the body with the bloodstream. If untreated, the infection can become chronic. A dog with chronic Babesia infection may only display mild symptoms and become a carrier of the disease.

Generally speaking, for a dog to become infected via tick bites the tick must remain attached to the dog for 2 to 3 days. A dog may also become infected if bitten by another dog carrying the parasite. Greyhounds and Pit Bull Terriers are especially susceptible to Babesia infections, and the symptoms may be very severe, especially in younger dogs.

Symptoms and Diagnosis

Early symptoms of a Babesia infection include fever, general weakness, and loss in appetite. When more red blood cells are destroyed the animal becomes jaundice, which will be most pronounced in the whites of the eyes; as well, the urine becomes orange or red due to the pigments from destroyed red blood cells. A blood test will show substantial anemia. There may be neurological signs if the infection becomes sequestered into the central nervous system. In severely infected dogs there may be upper respiratory symptoms such as coughs or labored breathing.

It is possible to diagnose Babesia infection by direct observation of the blood, such as a blood smear; however the parasites are often difficult to detect. If the symptoms are suggestive of a Babesia infection, PCR testing is currently the most reliable method to make a positive diagnosis.

Treatment

Several anti-Babesia drugs are available, and they are administered via injections or as IV drips. Some drugs carry significant side effects including muscle tremors and fever. Usually only one or two treatments are needed to clear the infection. In very severe cases a blood transfusion will be needed to alleviate the anemia. For a dog with very mild to no symptoms, treatments may not be necessary; however it will remain a carrier of the disease and can infect other dogs with its bite.

After a dog recovers from a Babesia infection, relapses are still possible since no currently available drugs can fully eliminate the parasite. The most effective method to control the disease is to prevent contact with ticks, and to remove them promptly when found.