Report of the third Havemeyer workshop on infection control in equine populationsby P. S. Morley, M. E. C. Anderson, B. A. Burgess, H. Aceto, J. B. Bender, C. Clark, J. B. Daniels, M. A. Davis, K. W. Hinchcliff, J. R. Johnson, J. McClure, G. A. Perkins, N. Pusterla, J. L. Traub-Dargatz, J. S. Weese, T. L. Whittem

Equine Vet J




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Report of the third Havemeyer workshop on infection control in equine populations


Infectious diseases are an ever present threat to the health of individual horses, local, regional and national herds and the equine industry as a whole. Treating infectious disease has always been one of the foundations of veterinary medicine. However, infectious disease prevention is becoming increasingly important because of the high visibility of recent outbreaks of infectious disease, the increasing frequency and ease of national and international horse movement and emergence and re-emergence of equine pathogens. This is especially true in large, transient horse populations. For many veterinarians and facility managers, infection control remains a subject they are reluctant to discuss for fear of it reflecting poorly on them, yet management of infectious diseases is an unavoidable issue that must be addressed by all equine practitioners regarding every equine population under their care.

The field of veterinary infection control, although still young compared with equivalent efforts in human medicine, has advanced considerably in the last decade thanks to those that have willingly and openly shared their experiences – both good and bad – with regard to hospital and field-based outbreaks of infectious diseases and subsequent mitigation efforts. In veterinary hospitals, infection control is often not considered until after individual patient care is addressed and thus prevention of infectious disease transmission can become a secondary activity relative to the treatment of individual horses and a tertiary activity relative to the care of the larger hospital population. Thus infection control has oftenbeen largely reactive rather than proactive in many equine facilities. Control efforts are sometimes hurriedly implemented after a disease outbreak is well underway, rather than being used to prevent sporadic cases from escalating into an outbreak. It is clear that outbreaks of infectious disease can occur with alarming frequency, even in highly controlled environments such as veterinary teaching hospitals. A survey of personnel responsible for infection control at 38AmericanVeterinaryMedical Association (AVMA) accredited veterinary teaching hospitals found that 82% had identified at least one outbreak of hospital-associated disease in the previous 5 years with 32% reporting outbreaks so significant that hospital closure was utilised to aid inmitigation efforts [1].

Outbreaks are undoubtedly under-reported in the scientific literature but a variety of organisms have been previously documented as causes of epidemic disease in equine hospitals, including Salmonella enterica [2–5], methicillin-resistant Staphylococcus aureus (MRSA) [6–8], equine herpesvirus type 1 [9–11] and Cryptosporidium [12]. However, equine infectious diseases are not solely associated with veterinary hospitals. The last decade has seen the epidemic spread of West Nile virus in North

America, a major equine influenza epidemic in Australia, outbreaks of contagious equine metritis in the USA and South Africa, the re-emergence of piroplasmosis in the USA and dramatically increasing concerns regarding equine herpesvirus myeloencephalopathy and multidrug resistant bacterial pathogens (e.g. MRSA). There are several significant differences with regard to the practice of infection control in equine populations outside of veterinary hospitals (i.e. ‘in the field’). The focus in field situations is likely tobe theprotectionof a relatively healthypopulation of horses from disease incursion, rather than protection of hospitalised patients with varying degrees of compromised health. The differences are similar to those between protection of public health in the community and infection control in human hospitals. Infection control in the field has often focused heavily on vaccination; however, effective vaccines cannot fully protect all horses as vaccines are not available for many diseases and vaccination cannot be used to control emerging diseases. A fundamental shift in the mindset of clinicians and horse owners must occur whereby vaccination is considered a last line of defence and overall infection prevention emphasises implementation of other control measures. This is particularly critical in large, transient horse populations that gather for specific events due to the potential for serious and widespread repercussions when these populations disperse, as was seen following the

National Cutting Horse Association Western National Championship in

Ogden, Utah, in May 2011. It is likely that exposure to a single horse shedding equine herpesvirus-1 (EHV-1) at this event resulted in over 165 horses developing clinical disease that was known or suspected to be caused by EHV-1 and at least 13 of these horses were subjected to euthanasia. The outbreak spanned at least 10 western US states and 2

Canadian provinces ([13], P.S. Morley, personal communication 2012).

Clearly infectious diseases have a tremendous impact on equine populations and efforts to control and prevent spread are critical to the well-being of individual horses and horse populations. The Dorothy

Russell Havemeyer Foundation Inc. (http://www.havemeyerfoundation. org) is a private foundation that supports scientific efforts to improve the health and welfare of horses. To this end, the foundation conducts workshops in a variety of different subject areas, including the control of infectious diseases.

Themost recent Havemeyerworkshop conducted on infection control in equine populations was held in September 2010, bringing together a diverse group of internationally recognised experts in fields related to infection control. The overarching goal of the workshop was to advance the discipline by providing guidance and inspiration to those currently involved in equine infection control and insight to those who may still be on its periphery. More specifically, the objective of this workshop was to identify the most urgent and critical priorities in equine infection control so that these might be targeted for research and resource development. In this report, we summarise the consensus opinions, major ideas and recommendations developed during the workshop.