Lyme borreliosis, also known as Lyme disease, is a chronic multiorgan disease of humans and animals transmitted by ticks of the Ixodidae family and caused by a group of spirochetes Borrelia burgdorferi sensu lato. Dogs are one of the most susceptible animal species to Lyme disease. Symptoms of the disease in dogs can range from mild lameness and fever to more severe and potentially life-threatening conditions, such as kidney damage and neurological disorders. Due to the variety of clinical manifestations and the lack of a universal diagnostic approach, veterinarians often face difficulties in accurately diagnosing the disease. Therefore, improving the algorithms for diagnosing Lyme borreliosis in dogs remains an urgent issue for practical veterinary medicine. The article describes and analyzes data on two cases of dogs from Kyiv (Ukraine) that presented with musculoskeletal disorders, including lameness, swelling of the knee joints, and tenderness, which raised suspicion of Lyme borreliosis. The diagnostic tests used to confirm the diagnosis of Lyme borreliosis included clinical blood test, C-reactive protein test, cerebrospinal fluid cytology, enzyme-linked immunosorbent assay for IgM and IgG antigens to Borrelia burgdorferi sensu lato, computed tomography and PCR analysis of synovial fluid for the presence of Borrelia burgdorferi sensu lato DNA. As a result, the clinical blood test, C-reactive protein test, and cerebrospinal fluid cytology were not diagnostically important for the diagnosis of Lyme borreliosis. In both cases, serological tests for antibodies to Borrelia burgdorferi sensu lato were not positive. Computed tomography showed the development of an inflammatory process in the knee joints with the formation of osteophytes, enthesophytes, sclerosis of the articular surfaces, and an increase in the volume of synovial bursa. The final diagnosis of Lyme arthritis in both dogs was established by PCR analysis of synovial fluid from the affected joints for the presence of Borrelia burgdorferi sensu lato DNA. This study emphasizes the importance of considering Lyme borreliosis as a potential cause of musculoskeletal disorders in dogs. We also propose an expanded algorithm for the diagnosis of Lyme borreliosis in dogs with a pronounced symptom complex of Lyme arthritis using the method of PCR analysis of synovial fluid to detect the DNA of Borrelia burgdorferi sensu lato spirochetes.

Key words: Lyme borreliosis in dogs, clinical cases, diagnosis, polymerase chain reaction, Borrelia burgdorferi sensu lato.