Babesia species, such as B. canis and B. gibsonii, can cause an acute hemolytic anemia in dogs. In a high percentage of dogs with acute or potentially chronic babesiosis, will contribute to immune-mediated hemolytic anemia. Unless Babesia infection is diagnosed by visualization of the protozoa within the red blood cell, or through blood testing or, the cause of the immune- mediated anemia will not be determined in these cases. Although immunosuppressive drug therapy may be necessary to halt immune-mediated erythrocyte destruction, the influence of prolonged immunosuppressive therapy on the clinical course of chronic babesiosis has not been clearly established. In this example, short duration immunosuppressive therapy for babesiosis may be prove initially life-saving; however, recovery may be only temporary, or a fatal outcome can occur if anti-Babesia drug therapy is not used in conjunction with immunosuppression.

Until recently, there has not been an approved anti-babesia drug available in the United States for treatment of canine babesiosis. Imidocarb diproprionate (Imizol7, Schering-Plough Animal Health) is currently available for the treatment of babesiosis in dogs. The drug is administered at a dosage of 6.6 mg/kg of body weight by intramuscular or subcutaneous injection and the same dose is repeated in 2 weeks for a total of 2 treatments. In acute babesiosis, the therapeutic response is rapid, with increasing production of new red blood cell values documented within 12 to 24 hours. In Africa and other regions of the world, imidocarb diproprionate is considered efficacious for treatment of E. canis, as well as B. canis infections.

Following recovery from the acute infection, dogs develop premunition or Ainfection immunity. Recent limited observations related to B. microti infection in human patients and B. canis infection in racing Greyhounds suggest that people and dogs may pay a biological price for premunition. For example, until diagnosed and treated with anti-babesia drugs, chronic B. microti infection caused a chronic fatigue-like syndrome in a female marathon runner previously diagnosed with Lyme disease. Following treatment for babesia, the woman was able to resume training and long distance running. A potentially similar observation was made in racing Greyhounds. Dogs that were competing successfully as racers had significantly lower seroreactivity to B. canis antigens than dogs that were less successful racers. Potentially, premunition, associated with chronic babesiosis, may interfere with the performance of athletes, whereas the consequences of infection may not be recognized in less athletic individuals.

Babesia gibsonii

Historically, B. gibsonii was considered endemic in Asia, Africa and the Middle East, but was not recognized in the United States until 1979. Subsequently, B. gibsonii infection was recognized in dogs from California. Currently, there are no reports of the identification of the organism from the southeastern United States. Recently, a diagnoses B. gibsonii infection in 10 dogs from North Carolina was made. In most instances, the presenting problem was immune- mediated hemolytic anemia. To date, a competent tick vector for the organism has not been identified in the United States; therefore, establishment of the organism within the tick population may not be possible. As the efficacy of currently available drugs for treatment of B. gibsonii is limited, veterinarians should report any suspected cases to the State Veterinarian. Should B. gibsonii become established within a tick population in the United States, the consequences could be serious.

Excerpts From Article Written By

Edward B. Breitschwerdt, DVM, Diplomate, ACVIM
Professor Veterinary Medicine
North Carolina State Veterinary School