Special issue on racehorse pathology: In the service of equine and human welfare

Despite the plethora of information produced over the years through the increasing number of racehorse postmortem programs in North America and elsewhere, little of this information is readily available to the diagnostic community. We prepared this special issue to put the postmortem examination of racehorses in the spotlight and to provide diagnostic pathologists with tools that will help them in their daily work. If pathologists follow the procedures outlined in this special issue, they can be all but assured that a complete examination has been performed. Accurately observing and documenting musculoskeletal injuries in racehorses helps the racing industry to better understand the circumstances leading to those injuries and to hopefully find ways to prevent them.

A postmortem examination program for racehorses was initiated in 1990 by the California Horse Racing Board (CHRB) in partnership with the California Animal Health and Food Safety Laboratory System (CAHFS)–UC Davis, to determine the nature and cause of injuries in racehorses and to develop injury prevention strategies. To date, close to 7,000 autopsies of racehorses have been performed as part of the CHRB postmortem program in California. Several other states and provinces in the United States and Canada, including but not limited to Kentucky, New York, Oklahoma, Ontario, Pennsylvania, Texas, and Washington have instituted racehorse postmortem programs, mostly in collaboration with local racing authorities. Similar programs have also been created in several other countries of the world. The overall goal of these programs is to improve the welfare of jockeys, drivers, and horses.

These programs have generated a large amount of new knowledge, not only on the nature and causes of musculoskeletal injuries of racehorses, but also on medical conditions. Undoubtedly the number one lesson learned is that the great majority (~90%) of racehorses experiencing catastrophic musculoskeletal injuries have preexisting lesions that correlate with, and predispose to, the fatal injury. As Dr. Scollay points out in her paper in this special issue: “This is a vital piece of data that undermines the timeworn adage that the horse simply ‘took a bad step.’ The reality is that the ‘bad step’ is the point when the bone failed as a consequence of aggregated bone lesions resulting from cyclic loading. So, a racehorse submitted for autopsy signals failure on more than one level. It is not just the obvious musculoskeletal failure, but the more complex and insidious failure of the trainer, exercise rider, groom, attending veterinarian, and/or regulatory veterinarian to recognize, acknowledge, and/or respond appropriately to the horse’s orthopedic health, or lack thereof.” ⁶

The development of the many racehorse postmortem programs in North America and elsewhere has also brought up discussion about the need to have pathologists trained to examine and recognize musculoskeletal injuries. Although musculoskeletal pathology is a specialty within veterinary pathology, recognizing and documenting musculoskeletal injuries does not necessarily require a “musculoskeletal specialist,” and any well-trained pathologist should be able to recognize and document these lesions. This is supported by a statement in another manuscript of this special issue by Diab et al.: “In fact, at CAHFS, the racehorse autopsy program has been carried out by anatomic pathologists with a very diverse set of skills.” ³

Obtaining useful information from racehorse autopsies is facilitated by the information that has been coming to light over the past several years. For instance, we now know that most stress fractures of the humerus of young racehorses are located on the proximo-caudal surface, immediately below the head of the bone. While removing the soft tissues and examining the whole bone might be of some use, directing the examination to areas known to be frequently affected by preexisting lesions, such as the proximo-caudal part of the humerus, in both the ipsilateral and contralateral pair of bones, will suffice in most cases. The same applies to many other preexisting lesions of the skeletal system.

The good news is that the various postmortem examination programs are already benefiting equine welfare. As noted in the report in this issue from the New York program, ⁵ “The general distribution of these findings was very similar to that reported by the California Animal Health and Food Safety Laboratory System during the same period. These findings, used in conjunction with a comprehensive mortality review process and regulatory reform have contributed to a significant reduction of the incidence of Thoroughbred racing fatalities at NYRA racetracks during the period of this review.” This is a very positive outcome. As awareness of underlining lesions expands, and mitigating strategies improve, we can expect continuing improvement in the welfare of racehorses.

A final remark on the great value of the many racehorse postmortem programs that have originated over the past 26 plus years is that they have also allowed pathologists to gather valuable information on diseases of systems in addition to the musculoskeletal system. Examples of these are papers included in this special issue by Carvallo et al., ¹ DeLay, ² and Diab et al. ⁴