Babesiosis in Dogs

By Malcolm Weir, DVM, MSc, MPH; Ryan Llera, BSc, DVM; Ernest Ward, DVM

What is babesiosis?

Babesiosis is a tick-borne infection due to Babesia protozoal parasites. Babesia invades mammalian red blood cells, causing anemia. Babesia species are found worldwide. n North America, most canine cases of babesiosis occur in the southern United States; however, reports in other areas of the US and Canada are increasing. Babesiosis is considered a serious threat to racing greyhounds and fighting dogs, such as pit bull terriers.

How does a dog contract babesiosis?

Babesiosis primarily spreads through an infected tick's bite (multiple tick species can carry the disease). There is also evidence that some direct animal-to-animal transmission may occur, such as when an infected dog with oral lesions or abrasions bites another dog. This is particularly true for Babesia gibsoni, which primarily affects Pitbull Terriers. Recent studies show that Babesia may be transmitted to unborn puppies in their mother’s uterus. Dogs may also be inadvertently infected through a tainted blood transfusion. Dogs housed in kennel settings with poor tick control are at a higher risk for developing babesiosis.

"Dogs housed in kennel settings with poor tick control are at a higher risk for developing babesiosis."

What are the clinical signs of babesiosis?

Dogs infected with babesiosis may present with a wide variety of clinical signs ranging in severity from sudden collapse with systemic shock, to a hemolytic crisis (the body attacks and destroys red blood cells), to a subtle and slowly progressing infection with no apparent clinical signs.

Dogs typically present with the acute and severe form of babesiosis, characterized by abnormal dark urine, fever, weakness, pale mucous membranes, depression, swollen lymph nodes, and an enlarged spleen. Blood and urine tests may reveal anemia, thrombocytopenia (low platelets), hypoalbuminemia (low albumin, a blood protein), and bilirubinuria (a pigment from breaking down red blood cells found in the urine).

How is babesiosis diagnosed?

In the past, babesiosis was diagnosed by seeing the parasite on a blood smear. Other diagnostic tests are becoming more readily available, including FA (fluorescent antibody) staining of the organism and ELISA (enzyme-linked immunosorbent assay) tests. A PCR (polymerase chain reaction) test is also available and is commonly used to diagnose babesiosis. The PCR test has the advantage of detecting all four species of Babesia.

"The PCR test has the advantage of detecting all four species of Babesia."

Serologic or antibody titer testing has limitations. A positive test result depends on an antibody response in the infected dog, which may take up to ten days to develop. Once a dog has developed antibodies to babesiosis, they may persist for years, and this must be considered when performing follow-up tests.

How is babesiosis treated?

A combination therapy of azithromycin and atovaquone is the preferred treatment method for some Babesiosis species. Unfortunately, atovaquone is expensive and may be difficult to obtain in smaller quantities. As a result, an older treatment called imidocarb (Imizol®) is often used. The treatment of babesia is often dependent on what species of Babesia is present in your dog.

Clindamycin, the treatment of choice for Babesia microti, the main Babesia species to infect humans, can also be used against Babesia in dogs. Clindamycin is a readily available antibiotic and is an excellent starting point for treatment in many dogs. Your veterinarian will discuss any alternative and adjunctive treatments with you.

Depending on the severity of your dog’s condition, other supportive treatments, such as blood transfusions and intravenous fluids, may be recommended.

What is the prognosis for a dog diagnosed with babesiosis?

The prognosis for a dog diagnosed with babesiosis depends on which body systems are affected at the time of diagnosis. Owners should be aware that dogs who survive babesiosis often remain sub-clinically infected. These dogs may suffer a disease relapse in the future or may serve as a source for further spreading disease in a given area. Dogs that recover from babesiosis should never be used as donors for blood transfusions because the recipients may develop the disease.

Currently, there is no effective vaccine available to protect dogs against babesiosis.

Can humans get babesiosis?

Yes, humans can develop babesiosis. Although several species have been reported, the most common species infecting humans is Babesia microti, transmitted by the deer or black-legged tick.

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