Babesiosis is not particularly difficult to diagnose, although the more advanced diagnostic techniques will require sending blood samples out to a specialized veterinary pathology laboratory. Standard blood work performed on dogs suspected of having babesiosis includes a complete blood count and a serum biochemistry profile. In dogs with babesiosis, the results of these tests typically reveal low numbers of circulating red blood cells (this is called a low packed cell volume [PCV], or anemia). The test results also usually show a low number of circulating platelets (thrombocytopenia) and an increase in the amount of circulating bilirubin (hyperbilirubinemia). Bilirubin is one of the break-down products of red blood cells that is released when those cells rupture. Increased levels of glucose in the blood (hyperglobulinemia) are common in dogs with chronic babesiosis. Sometimes, this is the only identifiable blood abnormality.
A stained blood smear – which is a blood sample that is streaked very thinly across a glass slide, dipped in a special stain and examined under a microscope – will show either large or small Babesia organisms that can be identified by their distinctive shapes. However, the reliability of a diagnosis based on a blood smear depends upon the experience of the person examining the slide and the randomness of how many infective organisms are present in any given sample of blood. Analysis of a urine sample may reflect elevated levels of bilirubin (bilirubinuria) and/or hemoglobin (hemoglobinuria), due to the breakdown of red blood cells.
Another blood test, called a Coombs’ test, is positive in up to 85% of dogs with babesiosis. This test can be used to differentiate between various types of hemolytic anemia. “Hemolytic” means something that pertains to the rupture of red blood cells. When red blood cells break down, they release bilirubin, hemoglobin and other substances into circulation. A dog with a positive Coombs’ test will need additional tests to determine why it became anemic in the first place.
Advanced testing can be done with a polymerase chain reaction (PCR) test, which usually assesses a sample of uncoagulated whole blood for the presence of the genetic material (DNA) of Babesia organisms. PCR is highly sensitive and can not only identify the microscopic Babesia parasites, but also can differentiate between their species and even subspecies. Unfortunately, PCR tests for Babesia are only available at a few places in the United States. An immunofluorescent serum antibody test (IFA) is available at some laboratories. However, it does not differentiate between Babesia species or subspecies.
Since babesiosis can be transmitted across the placenta from an infected mother to her unborn fetuses, it should be on the list of differentials if all or most puppies in a litter are chronically weak, lethargic and pale. If one dog in a multi-dog household or kennel situation is diagnosed with babisiosis, the other dogs in that environment should also be tested for the presence of the infective organisms.