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Necropsy of Racehorses

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General Guidelines 
The AAEP recommends that all racehorses that die or are euthanized at a racetrack or training facility undergo a complete necropsy by, or under the supervision of, a board-certified veterinary pathologist at an accredited veterinary diagnostic laboratory. Field necropsy is not appropriate for exercise-related fatalities, cases of sudden death or cases resulting in human injury. 

The AAEP encourages collaboration among operators of diagnostic laboratories to elevate and harmonize exam protocols and information management to facilitate intermural research into the etiology of catastrophic musculoskeletal injuries and other conditions resulting in the death of racehorses. The Special Issue on Racehorse Pathology in the Journal of Veterinary Diagnostic Investigation (2017, 29(4) is a useful resource.

Ante- or immediately post-mortem blood samples (and urine, when available) should be collected, maintained under chain of custody protocols, and submitted to the official racing laboratory. The laboratory should be notified of any medications administered prior to sample collection (inclusive of euthanasia solutions if collection is performed post-mortem). Other fluids or tissues can be collected at necropsy, if warranted. The regulatory veterinarians in each state should be familiar with legal chain of custody requirements so that a case is not withdrawn as a result of a procedural deficiency.

Transportation options for necropsy cases should be identified prior to need. Storage, pending transport, and transportation of the body should be managed in such a way that tissue degradation and the development of post-mortem artifacts are minimized. Care should also be taken to employ good infection control practices with respect to equine infectious and/or zoonotic disease. 

It is recommended that regular communication and interaction between the on-site regulatory veterinarian(s), practicing racetrack veterinarians, and the pathology staff at the diagnostic laboratory be established. This will enhance the necropsy process and the resultant information. It will also facilitate collaborative efforts when specific research interests are identified. 

Providing pathologists with information (e.g., medical/surgical/treatment and exercise history) related to each case submitted allows for an examination of relevant scope. The ability of a pathologist to adapt the necropsy protocol to the individual case facilitates an efficient and informative exam.

  • For catastrophic musculoskeletal failure, examination of the contralateral limb is critical to understanding a horse’s musculoskeletal health prior to injury. Additionally, when possible, the examination of all 4 limbs is recommended. An assessment of the failed boney and/or soft tissues solely in the affected limb does not provide adequate information for discussion at the mortality review, nor does it provide the necessary data for epidemiological studies of catastrophic injury.  

  • For cases of sudden death, in addition to a general exam of all organ systems, a thorough examination of cardiac muscle, toxicologic analysis of blood/urine/aqueous humor for heavy metals and rodenticides are recommended.

  • In all cases, a gross assessment of the lungs and gastric mucosa will provide additional information to inform discussions at the Mortality Review. 

Necropsy findings for Thoroughbreds, Quarter Horses, and Arabians should be entered into The Jockey Club’s Equine Injury Database. The AAEP supports the development of a similar database for harness racing.

Exercise-related Fatalities 
For exercise-related fatalities, a best practice inquest or mortality review protocol is recommended that incorporates ante-mortem information (examples include: interviews with personnel relevant to the horse and/or the incident, exercise history, race replay video, medical history) and post-mortem findings. A framework for implementing a mortality review protocol can be found in the Mid-Atlantic Strategic Plan to Reduce Equine Fatalities.

Revised by AAEP Racing Committee in 2020.