A clinical and pathological description of 320 cases of naturally acquired Babesia rossi infection in dogs

•This is the largest cohort of PCR confirmed, natural Babesia rossi infections published.•Clinical, hematological, biochemical and pathology is described.•Odds ratios confirmed which clinical and biochemical measures associat.e with poor outcome.•ROC curves identified TT4, bilirubin, urea and cortisol are most predictive of death.•Cut-offs for these measures allow clinicians and researchers to objectively classify cases. Babesia rossi causes the most severe clinical disease in dogs of all the babesia parasites. We included 320 naturally-infected dogs that presented for care at the Onderstepoort Veterinary Academic Hospital between 2006 and 2016. All dogs had mono-infections confirmed by multiplex PCR. The data allowed more accurate clinical classification of the disease and identified parameters that were associated with disease severity and death. Odds ratios for dying were significant (P