Potomac horse fever in Ontario: Clinical,geographic, and diagnostic aspects |
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| Authors: | Luis G Arroyo Alison Moore Sofia Bedford Diego E Gomez Omid Teymournejad Qingming Xiong Khemraj Budachetri Hannah Bekebrede Yasuko Rikihisa John D Baird |
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| Institution: | Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, Ontario N1G 2W1 (Arroyo, Bedford, Gomez, Baird); Ontario Ministry of Agriculture, Food, and Rural Affairs, Guelph, Ontario N1G 4Y2 (Moore); Laboratory of Molecular, Cellular, and Environmental Rickettsiology, Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio 43210, USA (Teymournejad, Xiong, Budachetri, Bekebrede, Rikihisa) |
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| Abstract: | Clinical findings, geographic locations, laboratory diagnoses, and culture isolation of Neorickettsia spp. 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 Neorickettsia risticii. Agreement between both laboratories for detection of N. risticii DNA 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). Neorickettia spp. were isolated from 16 of 41 (39%) blood samples. DNA analysis confirmed 14 isolates were N. risticii and 2 were N. findlayensis, a novel species of Neorickettsia recently demonstrated to cause PHF. |
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