Outbreak management

The meaning of ‘outbreak’ is when 2 or more horses suffer from similar disease. Outbreak management tries to mitigate the progression of an outbreak, while prevention should be our goal. While outbreaks also can be caused by toxicants or deficiencies, we will focus in the following discussion on the management of outbreaks caused by infectious and transmissible pathogens. However, regardless of the outbreak’s cause clinical signs in combination with environment/season (what is common in this area, region, country), and/ or similar genetic background of affected needs to be taken into consideration for a diagnosis, which needs to be confirmed by specific testing.

There are no winners with outbreaks. However, the ill-prepared will suffer most… Outbreak management will differ between premises. It will depend on size, stabling type and on the organizational (management) structure of the operation. It is fact, that premises that experienced an outbreak of a contagious disease before will respond faster at an early stage to an outbreak than those without experience. ‘Never again’ is the phrase that drives an immediate outbreak response. Outbreak prevention and mitigation strategies should be tailored to individual premises and their needs. What helps in outbreak prevention and mitigation is simple preparedness: i) a strategic plan in place; ii) regular communication of this strategic plan with all stakeholders, ii) an emergency fund for diagnostics and mitigating adaptations; iii) routine sequestration and testing of new additions to the herd or returning horses from an event of mixing and mingling prior to joining the rest of the herd; iv) availability of (temporary) quarantine facilities; v) earliest recognition of an infected/shedding animal.

In greater detail:

i) Procedures on paper on ‘who needs to do what and when’, assigning responsibilities and organizing practice rounds with mandatory presence.

ii) Many horse owners are not willing to pay for diagnostic testing when their horse is apparently healthy. A monthly contribution to an emergency fund during #healthy times’ will allow the testing that is necessary, and funds can also be used for purchase of materials/products of transmission inhibition.

iii) protocol of sequestration (= no direct contact, 4+ m to the next horse, ideally a separate airspace) and testing for any new addition(s) to the herd, or for returning horses from an event of mixing and mingling. I recommend 10 days for ‘new additions’ and 3 - 5 days for the returners.

iv) availability of (temporary) quarantine facilities. ‘Temporary’ refers to the use of alternative space or temporary stable rental.

v) 4x I of infection control Identify a suspicious animal (fever, acute cough, nasal discharge, lymph node enlargement, petechial hemorrhage, symmetrical limb edema/ ventral edema, ataxia/recumbency, abortion, diarrhea).

Isolate/ sequester a suspicious animal immediately. During this time: Investigate into the cause of the abnormal presentation (initiate testing).

Inform stakeholders (internal and external) as quickly as possible if a contagious cause has been identified. Check and start testing horses in the vicinity of the affected and other in-contact horses. ‘Inform’ also includes quarantine for the entire operation. No horses/animals in, and horses ‘off’ only under specific circumstances.

Furthermore- Implementation of procedures (see item i) for outbreak scenario: Close the affected unit for through traffic; relocate other shedding animals and create space (or barriers in case of airborne transmission) between the remainders. Mark vacated boxes as ‘unavailable for use’ until further notice. Implement for all animals on the farm: twice daily temperature collection; written recording & report data to management. All other horses are advised to avoid contacts with others (includes shared grooms & riders, feeding and barn crew) as much as possible. Avoid bottlenecks and traffic jams; stop activities for 72 hours (hand walking only and in an organized manner, ‘as previously discussed during mock outbreak exercises’), let go of contact routines with others. Cancel farrier and routine veterinary appointments. Initiate treatments or prophylaxis if indicated or appropriate. The duration of quarantine is variable and depends on the cause of an outbreak. Negative testing prior to lifting quarantine is advised.

Conclusion: be prepared, be pro-active and follow the 4xIs.

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).