How to Approach an Equine Infectious Disease Outbreak

1. Introduction

In 2005, the American Association of Equine Practitioners (AAEP) assembled a task force assigned to develop guidelines for the management of equine infectious disease outbreaks. To date, the task force has developed three sets of symptom-based guidelines. These flow charts contain specific, expanded biosecurity and diagnostic information and are available to members on the AAEP website or through the AAEP office. The purpose of this paper is to address universal considerations in health management wherever a large group of horses is assembled.

Effective management of equine infectious disease outbreaks must be initiated before the onset of clinical disease. Outbreak management begins with the development and commitment to a plan developed well before any horse arrives at the facility. In addition to the existence of a plan, risk assessment, resource management, and horse management should be evaluated before each equine event. Risk assessment requires an awareness of on-going disease outbreaks elsewhere and potential for spread. Resource management includes establishing a "chain of command" with clearly defined responsibilities. Isolation and biosecurity capabilities both on- and off-site should be identified. Diagnostic sampling materials, disinfectants, and biocontainment materials should be inventoried and upgraded as necessary. If the facility was recently used for another equine (or livestock) event, it should be inspected for adequate sanitation and waste removal before readmitting animals. Horse management includes the publication (and enforcement) of health requirements for access to the facility and the implementation of a horse identification and tracking system.

After an infectious disease is suspected, the veterinarian’s responsibilities are to

1. Do no harm. Do not rush into a stall/barn without a plan to leave it.
2. Respond to the "worst-case scenario" until a diagnosis is made.

The veterinarian’s actions should address (in order of importance)

1. Biosecurity
2. Dissemination of the established plan
3. Diagnostic testing

If a diagnosis is made, the veterinarian can proceed to management based on disease-specific guidelines. If no diagnosis is made, the biosecurity measures remain in place for a minimum of 21–28 days after last case development, the differential diagnosis list is expanded, and the infectious-disease experts are contacted.