Retrospective analysis of anamnesis, clinical signs, therapy, and outcome in 342 dogs with acute Babesia canis infections.

Babesia canis is a protozoan vector-borne pathogen causing infections in dogs. Acute B. canis infections are emerging in central and eastern Europe. Clinicopathological abnormalities include fever, thrombocytopenia, and pigmenturia. This retrospective study aimed to analyse anamnesis, stays abroad, clinicopathological abnormalities, therapy, and outcome in dogs with acute B. canis infections in Germany. Three hundred and forty-two dogs with positive piroplasmid-PCR results (B. canis identified after sequencing) and negative Anaplasma phagocytophilum-PCR results between January 2018 and December 2024 were included if data on hematocrit, platelets, and leukocytes were available. Information about anamnesis, clinical findings, therapy, and outcome was collected through questionnaires. Acute B. canis infections occurred mainly in autumn (218/342; 63.7%), followed by spring (67/342; 19.6%), winter (34/342; 9.9%), and summer (23/342; 6.7%). Most dogs tested positive in northern federal states (259/342; 75.7%), with Berlin/Brandenburg, Saxony, Saxony-Anhalt, the Saarland, the Rhine-Main area and the Ruhr area classified as high-risk areas. Lethargy (147/220; 66.8%) and fever (127/228; 55.7%) were most frequently reported. Pigmenturia was detected in 53/204 dogs (26.0%). All 164 dogs with available information on treatment received imidocarb dipropionate (median dosage 3.3 mg/kg; 1.7-6.8 mg/kg body weight). An uncomplicated course of disease was reported in most dogs (169/193, 87.6%). The mortality rate was 6.7%. Acute B. canis infections are most often uncomplicated if prompt treatment is initiated and represent a differential diagnosis in case of thrombocytopenia throughout the year, even when presented without fever and pigmenturia, especially in high-risk areas.