Download Babesia Infection in Dogs

Babesia Infection in Dogs
Kristi S. Lively, DVM, DABVP
BASIC INFORMATION
Description
Babesia is a blood parasite that causes anemia (an abnormally
low red blood cell count) in dogs all over the world. The anemia arises from destruction of red blood cells. Babesia rarely
affects cats. It is spread by ticks and occurs most commonly in
the southeastern United States and in the Great Lakes region.
Babesial infections affect greyhounds and pit bulls more often
than other breeds. Puppies younger than 8 months of age may be
more susceptible.
Causes
Even though more than 100 species of Babesia species exist, currently Babesia canis and Babesia gibsoni are the only two species
known to infect dogs. Babesia infection (babesiosis) occurs most
commonly when a tick carrying the Babesia organism attaches to
a dog (for at least 2 days) and releases the infection into the dog’s
bloodstream. The organisms multiply and infect red blood cells.
New ticks pick up the infection from an infected dog and spread
it to other dogs. Pregnant dogs can spread the infection to their
unborn puppies. Infection may also be transmitted from dog to dog
through bite wounds and via blood transfusion.
The dog’s immune system recognizes the infected red blood
cells and destroys them in an effort to kill the parasite. The resulting anemia may be mild to severe.
Severe inflammation may also arise in other body systems,
including the liver, kidneys, eyes, neurologic system, and respiratory system.
Clinical Signs
The infection typically incubates 10-21 days before clinical signs
develop. Most infected dogs clear the infection and never become
ill, but they may become carriers. Signs may occur in carrier dogs
when they are stressed. Babesiosis may be classified as uncomplicated or complicated.
In uncomplicated cases, dogs are acutely ill, with fever, loss
of appetite, depression, pale gums, enlargement of the spleen,
and dark urine. Signs may be mild to severe, depending on the
extent of the anemia. Symptoms of the anemia include weakness,
jaundice, fever, depression, sudden collapse, and red- or orangecolored urine.
Complicated babesiosis may manifest as acute kidney failure,
neurologic or blood clotting disorders, liver or breathing problems,
inflammation of the heart muscle, low blood pressure, inflammation of the pancreas or eyes, or swelling of the legs. Shock, severe
weakness, vomiting, and death may also occur.
Diagnostic Tests
The best diagnostic test for babesiosis is demonstrating the parasite on a blood smear; however, the parasite may not always be
present in the sample, so a negative blood smear does not rule
out infection. Because the organisms are hard to find, alternative
testing is often necessary and may require sending samples to a
laboratory. Some tests to confirm the diagnosis do not differentiate well among the various Babesia species and may give falsenegative results early in the infection. These false-negative results
complicate the screening process for carriers of the disease.
Other laboratory tests may be needed to detect problems in
other organs, to evaluate blood clotting, to rule out other causes of
anemia, and to assess the immune system’s reaction to the disease.
TREATMENT AND FOLLOW-UP
Treatment Options
Treatments are aimed at reversing the anemia and suppressing or
clearing the infection. To stabilize the anemia, many dogs require
a blood transfusion. A steroid (such as prednisone) may be given
to decrease destruction of the red blood cells. Other complicating
factors must also be addressed with appropriate therapy.
No known treatment clears all Babesia infections. Imidocarb
dipropionate is the only drug approved in the United States for
treatment of babesiosis. A single injection of the drug often clears
B. canis and probably B. gibsoni. Side effects include pain at the
injection site, tremors, elevated heart rate, fever, drooling, facial
swelling, vomiting, and breathing problems. For B. gibsoni and the
other small Babesia species, multiple injections may be needed.
A vaccine is available in France that is 89% effective against certain strains of Babesia. The best prevention is strict tick control.
Follow-up Care
All blood donors should be screened for babesiosis before donating, especially greyhounds and dogs from areas of the country
where Babesia species are known to exist. Dogs that clear the initial
infection but become carriers may have relapses when subjected to
stress, such as surgery, pregnancy, or other illness. Females that test
positive should not be used for breeding.
Prognosis
Prognosis is best when the infection is caught before the anemia
becomes severe. Severe and complicated cases require more supportive care, and prognosis depends on the severity of anemia,
severity of other organ involvement, and response to treatment.
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