Potomac horse fever in Ontario: Clinical, geographic, and diagnostic aspects.

Abstract

Clinical findings, geographic locations, laboratory diagnoses, and culture isolation ofspp. in Potomac horse fever (PHF) cases diagnosed in Ontario between 2015 and 2019 are described. Forty-six confirmed PHF cases occurred from late June to early September. Of 41 horses admitted to the Ontario Veterinary College, 28 (68%) survived and 13 (32%) were euthanized due to poor prognosis or financial constraints. Most cases were in southern Ontario along the Canada-USA border. Blood and fecal samples from 43 suspect PHF cases were submitted to 2 laboratories for polymerase chain reaction (PCR) testing for. Agreement between both laboratories for detection ofDNA was excellent for feces [κ = 0.932, 95% confidence interval (CI): 0.80 to 1], and fair for blood samples (κ = 0.494, 95% CI: 0.13 to 0.85).spp. were isolated from 16 of 41 (39%) blood samples. DNA analysis confirmed 14 isolates wereand 2 were, a novel species ofrecently demonstrated to cause PHF.