Canine babesiosis is a tick-borne disease caused by infection with protozoa of the genus Babesia. During over 20 years of studies on canine babesiosis at the Faculty of Veterinary Medicine of the Warsaw University of Life Sciences, the researchers have identified the species of the parasite and its vector in Poland, determined the cause of azotemia and observed other pathological changes, such as endocrine disorders, changes in the de Ritis quotient, as well as biochemical and hematological changes. It was shown that the tick Dermacentor reticulatus is the only vector of canine babesiosis in Poland and the disease is caused by Babesia canis (formerly known as Babesia canis canis). The first studies of pathological changes confirmed the results of previous research in other countries, in which the most prevalent changes in canine babesiosis were thrombocytopenia, anemia leucopenia, increased activity of liver enzymes (ALT, AST, ALP), azotemia, hypoalbuminemia, hypoglycemia, hyponatremia and hypokalemia. Research on azotemia in dogs infected with B. canis showed the contribution of TNF-α overproduction to hypotension and its influence on renal ischemia, hypoxia and the development of azotemia. Moreover, in research on endocrine disorders in canine babesiosis, it was shown that IL-6 overproduction leads to the suppression of the hypothalamic-pituitary-thyroid axis resulting in euthyroid sick syndrome, and that secondary hyperaldosteronism results from decreased renal blood flow and leads to hypokalemia. The results of the research were published in 27 original papers, 6 case reports and many review articles in veterinary journals. These studies provided veterinary surgeons in Poland with improved procedures for diagnosing canine babesiosis, as well as allowed them to better understand some pathogenic mechanisms of the disease and to develop more efficacious therapies..