Use of large-scale veterinary data for the investigation of antimicrobial prescribing practices in equine medicine


E. Welsh, T. D. H. Parkin and J. F. Marshall



This retrospective cohort study aimed to determine the rate of prescription of ‘reserved’ antimicrobials, enrofloxacin, ceftiofur and clarithromycin. Electronic medical records of 116,600 horses treated in nine first opinion equine practices in the US and Canada between 2006 and 2012 were analysed.


Antimicrobial prescriptions were made in 207,325 cases, of which 7.5% were for reserved antimicrobials. Of these, 9,856 (4.8%) were for ceftiofur, 5,016 (2.4%) were for enrofloxacin and 664 (0.3%) were for clarithromycin. Of all antimicrobials prescribed, 44.7% were done so during a period of hospitalisation, and 46.6% of reserved antimicrobials were prescribed during hospitalisation. Ceftiofur and enrofloxacin were both significantly associated with hospitalisation. Only 3.3% of antimicrobial prescriptions were associated with a culture and sensitivity result, with only slightly higher percentage of reserved antimicrobials being informed by culture and sensitivity (5.2%).


There were fluctuations in the use of individual antimicrobials with enrofloxacin and clarithromycin prescriptions apparently on the increase. A strong seasonal association between clarithromycin and summer months was found, thought to be due to its use for Rhodococcus equi infections in foals. The increasing use of this drug in the latter years of the study may indicate that it is superseding erythromycin as macrolide of choice in these foals.


Veterinary surgeons in certain practices were more likely to prescribe reserved antimicrobials than in other practices. The low uptake of culture and sensitivity may be due to a desire to avoid additional expense for the client and the delay in obtaining results; however, this is especially important in new infections and where use of reserved antimicrobials is being considered.



Bottom line:


Use of certain reserved antimicrobials is stable or increasing; however, this is rarely informed by a culture and sensitivity result. There is a continued need to modify the prescribing habits of equine vets in regard to the use of reserved antimicrobials.




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