Distribution of Equine Encephalosis Virus in Israel

Abstract

typing. During the study period there were 2235 admissions (1705 different horses), with 2783 MRSA surveillance samples obtained. Samples were collected from 1239/1277 (97%) of horses that were hospitalized for a duration of at least one day; 728 horses (59%) were screened according to protocol and 511 (41%) were screened, but less frequently than protocol. MRSA was isolated from 80 samples during 50 visits by 40 horses (first positive visits: CA–19; CO-HA– 3; HA–17; IN–1; range 0-7 per month). Overall, 3.0% of horses were positive (monthly range 0-8.6%). The prevalence at admission (CA and CO-HA combined) was 1.7% (monthly range 0-7.1%). Three horses had MRSA infections at admission and all were also colonized. No HA clinical MRSA infections were identified. Sixteen (89%) isolates were spa type t064, an ST8 strain commonly found in horses. spa types t002 and t1779 were also identified. Results for first-time positive animals were available for only 7 (18%) prior to discharge. However 11 (28%) colonized horses were later re-admitted, and 7 were still colonized. Within 6 months of the first positive result, 5 owners of MRSA-positive horses brought 14 additional horses to the OVC (range 1-4). Three horses from one of these owners were also colonized. Compliance with MRSA surveillance was good. The prevalence of MRSA colonization varied throughout the study period; however, the 1.7% admission prevalence is similar to previous reports from this facility. The time required for culture hampers the effectiveness of screening as most horses were discharged by the time results were known. However, screening can identify subsequent high risk cases (e.g. previously positive horse, horse from a farm with a colonized horse) and enable the use of enhanced infection control practices while awaiting test results. Screening also allows for detection of changes in MRSA risk posed by the referral population and early identification of within hospital transmission. Ultimately, rapid testing is required to optimize MRSA screening in horses. At defined periods, MRSA colonization was relatively common among equine patients. Screening can be an effective tool to identify high risk cases and reduce transmission, especially if risk analysis incorporates positive results from previous visits and other horses on the farm.