Causes of Babesiosis
Babesiosis is caused by a tiny parasite that infects the red blood cells of dogs and other mammals. Two species of this parasite have been identified in the United States: Babesia canis (“large babesia”) and Babesia gibsoni (“small babesia”). Babesia organisms are transmitted to dogs in the saliva of ticks. Ticks pick up these parasites when they bite infected rodents, like mice, rats, rabbits and squirrels. The infective form of the parasite is called a “sporozoite.” Sporozoites are carried in the salivary glands of ticks – especially the brown dog tick. Brown dog ticks like to live on mice and deer. When an infected tick bites a dog, it transfers the organisms into the dog through its saliva. Babesia can also enter a dog’s blood stream through blood transfusions and dog bite wounds. Unborn puppies can become infected with Babesia across the placenta (this is called “transplacental transmission”), if their mother is infected during her pregnancy.
Regardless of how they get into a dog, these parasites invade its red blood cells and multiply there over an incubation period of about two weeks. During this time, they stimulate the production of “fibrin-like proteases,” which cause the infected dog’s red blood cells to become sticky and clump together. Eventually, the damaged red blood cells rupture. This is called “hemolysis.” Hemolysis causes the contents of the red blood cells to spill into the dog’s blood stream. The dog’s immune system will also attack the abnormal RBC clusters that are caused by Babesia.
Prevention of Babesiosis
The best way to prevent babesiosis is to control the tick population. Ticks must remain attached to a dog for many hours before they can transfer disease to it through their saliva. Any ticks found on a dog should be physically removed as quickly as possible. Special tick-removal devices are widely available. Tweezers can also be used. Because microorganisms in the blood of ticks can be dangerous to people, gloves should be worn whenever removing ticks from dogs or other animals. Before disposing of the tick, it may be worth a call to the dog’s veterinarian, to see whether the tick should be brought into the clinic for identification and determination of whether it is carrying any infectious diseases. It is best to dispose of ticks in a tightly closed container, such as a jar or a sealed plastic bag, containing a bit of rubbing alcohol or dish detergent. The container should be discarded in an outdoor garbage receptacle. Believe it or not, ticks can survive and infect other animals after being flushed down a toilet, so that is not the best disposal route.
A number of topical products that can protect dogs from being bitten by ticks are available over-the-counter or from a veterinarian. These come in liquid form, as well as in collars. Discuss these products with a veterinarian to determine whether they are appropriate and safe for use on your dog, especially if you have young children and/or other pets in the household. Outdoor tick control should include regular cutting of tall grass, brush and weeds, because this type of vegetation is a prime habitat for adult ticks. Pet-safe outdoor insecticides are also commercially available.
Potential blood donor dogs should all be screened for babesiosis before their blood is accepted for donation to a veterinary blood bank.
Babesia gibsoni is considered to be an emerging pathogen in North American companion dogs. It is particularly common in Greyhounds and American Pit Bull Terriers. Babesia has been detected from the deep south (Texas and Florida) to the far north (Wisconsin and Michigan), as well as in other states. Certain species and subspecies of Babesia are widespread throughout Asia, while others cause extremely severe disease throughout the South African dog population.