The purpose of this study was to describe the epidemiological and clinicopathologic findings of hospitalized adult horses and foals with Eastern Equine Encephalitis.
Medical records of adult horses and foals admitted to a Veterinary Teaching Hospital from 1979 through 2017 were examined for cases presenting with signs of diffuse brain disease, and serological or post-mortem diagnosis of Eastern Equine Encephalitis. There were 104 cases that met the inclusion criteria. Data retrieved included season at admission, signalment, physical examination, neurologic evaluation, and clinicopathologic findings at presentation; as well as duration of hospitalization, treatment, and case outcome. Where available, historical information (i.e. vaccination status, treatment prior to referral) was also included.
The median age at presentation was 1.4 years (range: 0.1-13.4 years), with Thoroughbred and Quarter Horse breeds most common. Cases were typically admitted during summer (63 %), and less frequently during spring (17 %), fall (11 %), and winter (9 %). Common findings upon physical examination were abnormal mentation (n = 100/104, 96 %), with dementia seen in 32/94 (34 %) cases. Fever (≥ 101.5°F) prior to presentation was reported in 67/68 (99 %) cases (mean: 104.4°F; range: 98.9-107.0°F), but only evident at admission in 42/92 (46 %) cases (mean: 101.3 F, range: 96.4-107.0 F). Approximately half (51/100, 51%) were recumbent; seizure-like activity was reported in 38/68 (56 %) cases.
Cerebrospinal fluid analysis revealed gross discoloration in 51/84 cases (61 %), and a high protein concentration (> 85 mg/dL) in 65/82 (79 %) cases. Total nucleated cell count (> 6/uL) was typically high (80/90, 89 %), with a high neutrophil count (> 5%) in 71/83 (86 %) cases.
Median duration of hospitalization was 1 day (range: 0-13 days), attributed to rapid progression of neurologic disease resulting in recumbency. Mortality rate was high (90 %), with only 10 horses (10 %) surviving to discharge.
Eastern Equine Encephalitis in horses is a severe, rapidly progressive, and typically fatal neurologic condition.
Large Animal Internal Medicine Resident
University of Florida
Dr. de Tonnerre is from Sydney, Australia, and obtained her veterinary degree from The University of Sydney in 2013. After spending a few months in mixed practice, she completed a 1-year internship at UQ VETS Equine Specialist Hospital in Queensland. Following this, Dr de Tonnerre moved to the US in July 2015 to commence a residency in Large Animal Internal Medicine at the University of Florida. Her clinical interests include all aspects of large animal internal medicine, particularly neonatology and critical care. Current research interests include Eastern Equine Encephalitis.
Thursday, June 14
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