Babesiosis in Dogs

What Is Babesiosis in Dogs?

Babesiosis is caused by infection with Babesia, a protozoal parasite. It is found across the world in domestic dogs and cats. In North America, most cases of babesiosis in dogs occur in the Southern United States. The disease is considered uncommon in healthy, spleen-intact adult dogs, but is considered an emerging infection in dogs.

Babesia attacks red blood cells in the body. Infection is spread through tick bites and/or exposure to infected dog blood. Dogs with babesiosis, even those without any clinical signs, can spread infection to other dogs, most commonly in kennels.

Veterinarians often diagnose babesiosis incidentally after owners bring their dogs to be examined due to sudden illness.  Because babesiosis is a tick-borne infection, it is not uncommon for infected dogs to have other tick-borne infections, such as ehrlichiosis, Rocky Mountain spotted fever, Lyme disease, and others. These infections may interact with each other, making the condition more severe.

The most common mode of transmission of Babesia in dogs is by a tick bite. The Ornate dog tick, the Brown dog tick, and the American dog tick, among other tick species, have been implicated in transmitting Babesia to dogs. The tick must bite, attach, and feed on a blood meal from the dog for 2 to 3 days.

Several disease-causing species of Babesia have been identified as causing infection in dogs, including Babesia canis (subspecies vogeli, canis, rossi), Babesia gibsoni (most prominent in the US), Babesia vulpes, and Babesia conradae. Babesia gibsoni is believed to transmit disease in dogs directly through infected blood from dog fights and bites or blood transfusions. It may even spread into a puppy’s bloodstream from an infected mother dog (transplacental transmission).

The incubation period, or time from tick bite to when symptoms start, averages about two weeks, but symptoms may remain mild. Some cases are not diagnosed for months or even years.

Babesia organisms are usually classified as large or small:

• Babesia canis is a large blood parasite that infects dogs, and it is distributed worldwide

• There is also a genetically distinct small blood parasite that can infect dogs.

  • Babesia gibsoni—worldwide distribution; emerging disease in the US. Mostly attacks Pit Bull Terriers and is transmitted by bite wound and from mother to unborn puppies. This is the most common Babesia in North America.

Specific breeds, such as Greyhounds and members of the Terrier group, have an increased risk of infection. Babesiosis is considered a serious threat to racing Greyhounds and Pit Bull Terriers. Young dogs tend to be most severely infected.

Symptoms of Babesiosis in Dogs

Signs of infection vary from a mild illness that passes quickly to a severe disease that rapidly results in death. Signs can be highly variable, depending on the area of the body that is infected. Common clinical signs include:

• Lack of energy, lethargy, depression

• Lack of appetite

• Pale gums and other mucous membranes

• Fever

• Enlarged lymph nodes or spleen

• Abnormally dark-colored urine, usually dark red or orange

• Yellow or orange skin, jaundice

• Enlarged or swollen abdomen

• Weight loss

• Discolored stool

• Neurologic signs, including

  • Imbalance and/or wobbly gait

  • Seizures

  • Neck pain

Ticks are typically found near a dog’s neck, head, and ears, and in the creases under the legs.

Ticks are generally tiny and feel like a hard bump on your dog’s skin. They are typically dark brown or black. Depending on the life stage, ticks will have six legs (larvae) or eight legs (nymphs and adults). If they have been on your dog for a while, they might be engorged from feeding on your dog’s blood and appear to be a light brown or gray color. Dogs can still get ticks even if they are up to date on monthly flea and tick preventatives. It’s best to check your dog often if you live in an area where ticks are prevalent, and after spending time in wooded areas and parks with other dogs.

Causes of Babesiosis in Dogs

Once a tick bites a dog, blood-borne parasites such as Babesia enter the bloodstream. A tick must feed for 2-3 days to infect a dog with Babesia. It replicates in red blood cells, resulting in anemia. The infected red blood cells are broken down and hemoglobin is released into the body. This can lead to jaundice (yellow discoloration of skin and whites of the eyes) and to anemia when the body cannot produce enough new red blood cells to replace those being destroyed.

Dogs that spend a lot of time outdoors, especially in wooded areas, are at an increased risk for tick bites and for contracting this parasite.

There is evidence of direct dog-to-dog transmission of Babesia under certain circumstances, including:

• An infected dog with oral lesions or abrasions bites another dog. This is particularly true for Babesia gibsoni, which primarily affects Pit Bull Terriers.

• An unborn puppy is infected in the uterus of the mother.

• A dog is unintentionally infected through a contaminated blood transfusion from another dog.

• When dogs are housed in kennel settings with poor tick control.

How Veterinarians Diagnose Babesiosis in Dogs

Your veterinarian will obtain a full history of symptoms, including when a tick bite might have occurred or a dog fight. The vet will do a complete physical examination including:

• Complete blood count

• Blood biochemical profile

• Urinalysis

• Electrolyte panel

Low blood protein levels, a decreased number of blood platelets, and anemia are often noted.

Babesiosis can be confused with other illnesses that cause fever, anemia, destruction of red blood cells, jaundice, or red urine. One or more of the following laboratory tests should be performed to confirm the diagnosis:

• Wright’s stain, a stain used on a dog’s blood sample and then examined by microscope, helps your veterinarian differentiate blood cells, making an infection of the blood more apparent as it allows for the protozoa to be seen on the blood smear.

• Immunofluorescent antibody (IFA) tests look for antibodies in the serum of the blood that react with the Babesia organism. The serum is the part of the blood left behind when all of the cells are removed by high-speed spinning of a blood sample. IFA tests are limited because they cannot usually distinguish between different species and subspecies of Babesia.

• Enzyme-linked immunosorbent assay (ELISA) is another blood test. A positive test result is dependent on an antibody response by the infected dog, which may take up to 10 days to develop.

• Polymerase chain reaction (PCR) tests look for the presence of Babesia DNA in a biological sample, usually whole blood in dogs. The PCR test has the advantage that it can detect all four species of Babesia. It is more sensitive because it does not use a microscope.

Treatment of Babesiosis in Dogs

The FDA-approved treatment for babesiosis is imidocarb dipropionate, an antiprotozoal drug commonly used for treatment of large Babesia species. This is an injection given by a veterinarian. In some cases, antibiotics will also be recommended, such as azithromycin and/or clindamycin.

Specific treatment depends on the babesia species identified and the severity of the disease. More severely affected dogs will require anti-inflammatory or steroid medications, hospitalization, IV fluids, blood transfusions, oxygen therapy, anti-nausea medications, and other supportive care. Blood transfusions may be lifesaving in very anemic animals and are commonly performed in dogs.

Recovery and Management of Babesiosis in Dogs

If an imidocarb injection is used, a single dose is usually successful for eliminating Babesia canis (large organism), but two injections given two weeks apart are needed for the smaller Babesia species. The injection is often painful and it can cause muscle tremors, drooling, elevated heart rate, shivering, fever, facial swelling, tearing of the eyes, and restlessness.

Your veterinarian will want to monitor your dog’s progress and will schedule regular follow-up appointments to repeat blood work and urine testing. Two to three consecutive negative PCR tests beginning two months after treatment should be performed to make sure your dog’s treatment was successful and infection does not persist.

Most cases of babesiosis will not be diagnosed until the disease is fairly progressed. The prognosis for a dog diagnosed with babesiosis is guarded, depending on what body systems are affected at the time of diagnosis.

Pet parents should be aware that dogs that have survived babesiosis often remain subclinically infected and may suffer a relapse of disease in the future. These persistently infected dogs serve as a source for the further spread of disease in each area. Dogs that have recovered from babesiosis should never be used as donors for blood transfusions because the recipients may develop the disease.

Prevention of Babesiosis in Dogs

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. Prevention also centers around control of dog-to-dog transmission through blood, such as in dog bites, mother dog to puppies, and blood transfusions.

Dogs should receive regular tick prevention with a collar, a topical medicine applied to the skin, or a chew/pill taken by mouth. Products that prevent ticks, including parasite preventatives such as Revolution, Bravecto, and NexGard or tick collars such as Preventic and Seresto, can be used. Be sure to follow your veterinarian’s advice when using these products.

Keep grass and brush trimmed in your yard. In areas where ticks are a considerable problem, you can treat the yard and kennel area for ticks as well.