Biosecurity in equestrian activities

Equestrian events, gatherings or activities come with an inherent risk of contagious disease introduction and its subsequent spread. Risk comes with any form of mixing and mingling, while risk increases with event size, grounds and set-up, event duration, and stocking densities. There is an increased risk of transmission during events with a focus on young stock because of an immunologically naïve population, and last, but not least, there is a human factor to consider on either side of an event: organizers and participants. Biosecurity measures reduce the risk of introduction and spread of contagious organisms. Biosecurity aims to prevent any direct or indirect contact between horses coming from different backgrounds. Biosecurity regulates static components like building structures, the set-up and size of boxes and aisles, ventilation, the number of wash stalls and outdoor paddocks, cleaning & disinfection protocols, quarantine space, but it also regulates dynamic aspects of an event: movement of horses on the premises, strategic occupation of barn space, but also humans: participants (riders, grooms, supporters with access to horses and facilities), the organizers and primary and secondary personnel. Biosecurity can only be of success if the static components fulfill the requirements and if there is broad compliance and adherence to protocols and procedures by the human component. Breeches most likely will occur on the dynamic side when there is low to moderate compliance only due to a lack of information, lack of planning, distraction, detachment, indifference, panic.

Biosecurity relies on early detection of a suspicious animal, and entry to the showg rounds is a very important filter station in the prevention of disease introduction, but it is not the first. Horses to be admitted should travel with a current health certificate and up-to-date mandatory vaccinations. Sick animals should not travel - should not attend an event. Horses should not travel from premises with undiagnosed cases of acute cough, diarrhea, ataxia/recumbency, or abortion unless tested appropriately (and in seclusion) for relevant contagious diseases. A check-in exam should be a routine part of admittance in case there is stabling in a shared barn environment. This exam should include, but is not limited to findings like abnormal rectal temperature, nasal discharge, coughing, mandibular lymph nodes, diarrhea, unexplained sudden ataxia/ recumbency, symmetrical limb/ventral edema, abortion, petechial hemorrhage.

Early recognition of a suspicious animal during competition is germane to spread prevention. However, this requires reporting by the participants to the event management, which on their side requires a plan of action.

Any contagious disease is of concern during an event. Many diseases spread through direct contact, albeit via fecal – oral transmission or through nose-to-nose contact. Most of them can also be transmitted via fomites. Simple measures ‘no contact’, ‘no touching’ unless barrier precautions (gloves, gowns, shoe cover) are in place, will quite effectively prevent transmission. Airborne transmission, however, is ‘complicating matter’, and several pathogens are capable of spread via airspace: Equine Influenza, Equid alphaherpesvirus 1/ 4 (EHV-1, -4), Strep equi spp. equi and Equine Arteritis virus (EAV). Effective containment and mitigation can only be achieved by increasing distance between horses, erecting barriers between horses, but above all, transferring a shedding animal into a separate quarantine barn. Furthermore, many of the airborne pathogens can be shed by subclinically infected animals. Any pathogen on the list can be picked up at home and is travelling with the animals on the same transport. This highlights the importance of clinical evaluation at home, the importance of an official health certificate, and the key function of an intake exam at the event grounds which may be expanded to additional targeted testing in the (near) future. EHV-1 (and EHV-4) is exceptionally different as it is present in many horses in its latent (silent, non-replicative) form. Latent virus can be reactivated during times of transportation and stress. Reactivation is followed by replication in the respiratory tract, which will lead to shedding of infectious virus. However, several days will go by until a horse starts to shed, and this infection is likely to bypass the travel precautions and intake exam at the event grounds.

Conclusion: preparedness, compliance to protocols and early detection is key to outbreak prevention and mitigation.

Lutz S Goehring

University of Kentucky, USA

I graduated as a veterinarian from Utrecht University, the Netherlands in 1993. Since then I became a board-certified Equine Internal Medicine Specialist in 2 specialty colleges, ACVIM and ECEIM. I was a faculty member at Utrecht University (Netherlands), Colorado State University (USA) and Ludwig-Maximilians University in Munich (Germany). Through all these years my research focused on Equid alphaherpesvirus 1 (EHV-1), on equine infectious diseases in general, and on neurological conditions and anomalies in horses. My focus on EHV-1 brought me to Kentucky, where I am a faculty member now at the M.H. Gluck Equine Research Center at the University of Kentucky in Lexington, Kentucky (USA). Here I can focus on my research areas EHV-1 latency, acute disease pathogen-host interaction, transmission, epidemiology and vaccine/treatment efficacy testing (gluck.ca.uky.edu/directory/lutz-goehring).