Testing for Tick Borne Diseases

In our experience with Greyhounds over the past 17 years, the prevalence of TBDs has decreased markedly, likely due to better tick control. For example, 15 years ago approximately half of the retired racing Greyhounds evaluated as potential blood donors at OSU tested positive for Babesia canis or Ehrlichia canis serology, whereas now only 1-3% of the dogs are positive for any TBD. However, in some diagnostic laboratories, the prevalence of positive dogs using serology is still high, even though the results are frequently not reproducible when the same sample is analyzed by a different lab or method ("the never-ending conundrum..."). Interpretation of test results may differ in healthy versus sick patients, and depending on whether serology or PCR are used (examples will be used during the lecture). Dogs with symptomatic TBDs usually have one or more of the following: weight loss, fever, anemia, thrombocytopenia, neutropenia, lymphadenopathy, ocular signs, splenomegaly, and polyarthritis.