POSTMORTEM EXAMINATION PROGRAM

Transcription

1 POSTMORTEM EXAMINATION PROGRAM Conducted for the California Horse Racing Board January 1, 2005 December 31, 2005 California Animal Health and Food Safety Laboratory System J.D. Wheat Veterinary Orthopedic Research Laboratory School of Veterinary Medicine University of California, Davis August 2006

2 TABLE OF CONTENTS Postmortem Examination Program California Animal Health and Food Safety Laboratory System J.D. Wheat Veterinary Orthopedic Research Laboratory School of Veterinary Medicine University of California, Davis Davis, CA (916) August 2006 Equine Welfare and Racing Injury Prevention Committee William Bell, DVM Cherie Harter Bud Johnston Richard Mandella, Chair Roy Minami Skip Park, DVM Alan Severinsen Donald Smith, DVM Lawson Williams Steve Wood Alex Ardans, DVM Introduction 2 Submissions 3 5 Figure 1. Number of Horses Submitted by Year Table 1. Submissions by Activity Table 2. Submissions by Breed and Month Figure 2. Number of Horses Examined by Month Submissions by Breed and Age 5 Table 3. Submissions by Breed and Age Figure 3. Number of Horses Examined by Age Injuries Categories of Injury 6 Table 4. Category of Injury by Age Table 5. Category of Injury by Breed Category of Injury by Breed 7 Figure 4. Category of Injury: All Breeds Figure 5. Category of Injury: Quarter Horses Figure 6. Category of Injury: Thoroughbreds Organ Systems Affected by Injuries 8 12 Table 6. Organ Systems Affected Figure 7. Organ Systems Affected Table 7. Musculoskeletal Injuries by Breed Figure 8. Musculoskeletal Injuries Table 8. Limbs Affected Cardiovascular System Integumentary (skin) Gastrointestinal System Respiratory System Central Nervous System Whole Body Milestones 12 Research Support 12 Research publications insert 1

3 POSTMORTEM EXAMINATION PROGRAM Introduction Since its inception in February 1990 through the end of calendar year 2005, the Postmortem Examination Program has performed examinations on 3,820 horses. Initiated by the California Horse Racing Board (CHRB), the program is a partnership with the California Animal Health and Food Safety Laboratory System (CAHFS). This program was established to meet three primary objectives: 1) to determine the nature of injuries occurring in racehorses, 2) to determine the reasons for these injuries, and 3) to develop injury prevention strategies. To accomplish these objectives, a broad, cooperative approach was organized through which the CAHFS performs a necropsy on every horse that dies or is euthanized on racetracks or training facilities under CHRB jurisdiction. This visionary partnership has become a national model for the racing industry in an effort to improve the safety and welfare of racehorses. Pathologists at the Davis, Tulare and San Bernardino laboratories of the CAHFS conduct postmortem examinations and compile detailed information on each horse, which is then reported to the CHRB. A broad range of specimens are collected and shared with veterinary scientists in the School of Veterinary Medicine (SVM) at the University of California, Davis (UC Davis). In-depth analyses of these specimens helps to more precisely determine the causes and risk factors that lead up to catastrophic injuries in racehorses resulting in their death or euthanasia. During the past year, funding for postmortem examinations was provided by the CHRB. Racing associations provide transportation of the horses to the nearest laboratory facility, and additional studies are funded by the Center for Equine Health at UC Davis along with private donors. Information from the tests and data gathered from the postmortem examinations are analyzed in efforts to elucidate the specific cause of catastrophic injuries. An advisory board, composed of horse owners, trainers, veterinarians, track maintenance people and CHRB officials, gives insight into injury investigations, as well as sharing program findings and prevention strategies with the horse racing industry. In-depth studies of catastrophic musculoskeletal injuries in Thoroughbred horses have prompted studies by the Equine Orthopedics Laboratory Group within the UC Davis School of Veterinary Medicine that focus on a variety of fractures and failures of the suspensory apparatus of the front limb. With a detailed database representing more than 8,460 diagnostic findings, a valuable resource is available to help develop preventive strategies on racehorse injuries. Other states have begun their own programs using the CAHFS Postmortem Examination Program model. 2

4 SUBMISSIONS During the 2005 calendar year, 342 horses were submitted to CAHFS as part of the CHRB Postmortem Examination Program. This is an increase of 27 percent (73) over 2004 and the largest number of horses submitted to the program since its inception. The graph below shows the number of horses that have been submitted to the program since The Davis, Tulare and San Bernardino branches of the CAHFS performed the necropsies, with horses being brought directly to the closest CAHFS facility. At the time of submission, the CHRB official at the track categorized the activity of the horse at the time of injury into one of four types (Table 1). The majority of catastrophic injuries, 45.9 percent, occurred during a race or immediately following a race. A total of 33.9 percent of the fatal injuries occurred during or immediately following a training session. The third most frequent category of fatalities, accounting for 19.3 percent of submissions, included horses in the non-exercise group. These were horses suffering primarily from colic or infectious diseases. Only 3 (0.9%) recorded deaths were due to accidents, which are typically fatal injuries due to mishaps that are considered one-of-a-kind events. Figure 1. Number of Horses Submitted to the Postmortem Program by Year Table 1. Activity at Time of Injury Accident 3 Non-exercise 66 Racing 157 Training 116 Total 342 3

5 SUBMISSIONS BY BREED AND MONTH Table 2. Submissions by Breed and Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total Appaloosa Arabian Not Reported Paint Quarter Horse Standardbred Thoroughbred Welsh Pony & Cob Total The vast majority of submissions (77.2 percent) during 2005 were Thoroughbreds (Table 2). With fewer numbers of the other breeds racing, not enough data exist to allow comparison of injury rates among breeds for any predisposition to any particular type of injury. The number of horses submitted per month was highly variable, with statistically higher than average submissions in March, July and October, and significantly lower than average submissions in February, June and August (Figure 2.). SUBMISSIONS BY MONTH Figure 2. Number of Horses Examined by Month Number of Submissions Month 4

6 SUBMISSIONS BY BREED AND AGE Table 3. Submissions by Breed and Age Breed/Age in years NG* < >9 Total Appaloosa Arabian Not Reported Paint Quarter Horse Standardbred Thoroughbred Welsh Pony and Cob Total *(NG=not given) The largest proportions of submissions (50.3 percent) were 3- or 4-year-old racehorses (Table 3). Only 17.3 percent of all racehorses submitted were 2-years-old or less. The number of horses submitted with catastrophic injuries drops dramatically after the fourth year of age (Figure 3). We cannot conclude if horses 5 years of age and greater are less susceptible to the athletic injuries of racing because the numbers of each age group racing and training on facilities controlled by CHRB are not known. Figure 3. Number of Horses Examined by Age Number of Submissions Years of Age 5

7 INJURIES As mentioned earlier, the categories of injury represent the activity of the horse or circumstances at the time of the fatal or catastrophic injury. The largest cluster of fatal injuries, 45.0 percent, occurred during racing and training in 3- and 4-year-old racehorses (Table 4). The 2-year-old horses had more fatalities related to training than either racing or non-exercise, as would be expected for young horses. The 2 and 3-year-old group accounted for 46.1 percent of all fatalities of the non-exercise type. Table 4. Category of Injury by Age Age (Years) NG* <= >9 Total Accident Non-exercise Racing Training Total *(NG=not given) Unlike 2004, Thoroughbred horses suffered a nearly equal number of catastrophic injuries while racing when compared to training, but significantly more than non-exercise (Table 5). Typical of previous years, the Quarter Horses infrequently suffer a catastrophic injury during a training session and in 2004 there were no fatalities suffered during training by this breed. Table 5. Category of Injury by Breed Breed/Injury Class Accident Non-exercise Racing Training Total Appaloosa Arabian Not Reported Paint Quarter Horse Standardbred Thoroughbred Welsh Pony and Cob Total

8 INJURIES continued Figure 4 Category of Injury: All Breeds Figure 5 Category of Injury: Quarter Horses Figure 6 Category of Injury: Thoroughbreds 7

9 INJURIES continued In 2005, approximately 83.0 percent of the fatal injuries were due to musculoskeletal problems (Table 6). Of this group, 88.7 percent of injuries involved problems affecting the front or rear legs (Table 7). The injuries listed in this table represent the primary injury to the horse. In many cases, multiple related injuries, such as tendon and ligament ruptures are identified concomitantly. Musculoskeletal injuries are most likely to occur during racing or training. Because these injuries are by far the most common, most of the investigative efforts at the University of California, Davis, have focused on causes and prevention of limb injuries. Table 6. Organ Systems Affected Organ System CV GI Skin MS Nerv Resp WB Total Appaloosa Arabian Not Reported Paint Quarter Horse Standardbred Thoroughbred Welsh Pony and Cob Total (CV=cardiovascular; GI=gastrointestinal system; Skin=Integumentary system; MS=musculoskeletal; Nerv=nervous system; Resp=respiratory system; WB=whole body) Figure 7 Organ Systems Affected 8

10 INJURIES continued Table 7. Musculoskeletal Injuries by Breed Injury by Breed Appaloosa Arabian Not Reported Quarter Horse Standardbred Thoroughbred Welsh Pony and Cob Arthritis 1 1 Connective Tissue Hemorrhage 1 1 Degenerative Joint Disease 1 1 Fracture, Carpal Fracture, Femur 2 2 Fracture, Humerus Fracture, Metacarpal Fracture, Metatarsal Fracture, P Fracture, P2 1 1 Fracture, Pelvis Fracture, Radius Fracture, Ribs 1 1 Fracture, Scapula Fracture, Sesamoid Fracture, Sesamoid - Biaxial Fracture, Skull Fracture, Tibia Fracture, Ulna 1 1 Fracture, Vertebrae Joint Disarticulation 1 1 Joint Luxation Laminitis 7 7 Ligament Rupture 5 5 Muscle Rupture 1 1 Myodegeneration 1 1 Osteochondritis Dissecans 1 1 Suspensory Apparatus Failure Tendon Rupture 1 1 Tenosynovitis 1 1 Vertebral Instability 1 1 Total Total 9

11 INJURIES continued Figure 8 Musculoskeletal Injuries Table 8. Injury by Primary Limb Affected Limb Affected Accident Non-exercise Racing Training Total Bilateral Left Front Right Front Left Rear Right Rear Total Vertebrae (11) Ribs (1) Pelvis (10) Scapula (5) Skull (6) Humerus (18) Femur (2) Radius (3) Ulna (1) Carpus (26) Tibia (5) Metacarpal (54) Cannon Bone P1, Long Pastern (3) P3, Navicular (0) Metatarsal (8) Sesamoid (95) P2, Short Pastern (1) Laminitis (7) 10

12 INJURIES continued Organ Systems Affected by Injuries Cardiovascular: A single horse was submitted with significant bleeding in the musculature of the atrium of the heart. The cause for the bleeding was determined to be heart failure, but an inciting cause was not identified. Integumentary (Skin): It is unusual for diseases of the skin to result in the death or euthanasia of an animal; however, in the cases listed above, one was due to bacterial cellulitis, a wound infection that spreads along tissue planes and causes tremendous inflammation of the skin and subcutaneous tissues. Release of bacterial toxins may result in sloughing of the skin or a serious systemic illness leading to shock and death. There was a single case of death where the primary finding was substantial hemorrhage around the front of the head with no other significant findings. Due to the postmortem decomposition of the horse, it was not possible to determine additional causes of death. Gastrointestinal: Of the digestive system diagnoses, severe colitis (inflammation of the intestinal tract) was most frequently identified. There were similar numbers of intestinal strangulation (due to a variety of non-infectious causes) and gastrointestinal rupture to those seen in The single case of cecal impaction lead to leakage of intestinal contents and severe infection of the abdominal cavity leading to death. Respiratory: Several cases of pneumonia, often with a severe pleuritis occurred in The primary cause in ten cases was Streptococcus zooepidemicus. Two cases were due to Klebsiella sp., with a mixture of bacterial species responsible for the remaining cases. The horse dying from pulmonary hemorrhage succumbed shortly after administration of Lasix, while pulmonary edema was the only significant finding in two horses that died acutely. Central Nervous System: Horses with neurological disorders presented a diverse set of primary causes. The first case of West Nile virus encephalitis in a race horse was identified along with a single case of equine protozoal myelitis (EPM), caused by the protozoal parasite Sarcocystis neurona. There was also one case of cerebral hemorrhage due to trauma to the skull and one case of encephalitis due to a bacterial infection. Whole body: The number of sudden deaths in horses increased slightly over In none of these cases could the cause of death be determined. One case of severe infection of the abdominal cavity caused the death of a single horse while another died from a penetrating wound to the abdomen leading to infection and death. Atrial Rupture... 1 Bacterial Cellulitis... 1 Skin Hemorrhage... 1 Colitis...7 Cecal Impaction...1 Gastrointestinal Rupture...6 Intestinal Strangulation/ Obstruction...4 Diaphrahm Rupture...1 Pneumonia/Pleuritis Pulmonary hemorrhage/ edema...3 Sinusitis...1 Cerebral hemorrhage...1 Bacterial encephalitis...1 Equine Protozoal Myelitis...1 West Nile Virus encephalitis..1 Sudden/unexplained death.. 11 Peritonitis...1 Abdonimal Trauma

13 MILESTONES Publications 2005 Nevens, A.L., Stover, S.M., Hawkins, D.A. Evaluation of the passive function of the biceps brachii muscle-tendon unit in limitation of shoulder and elbow joint ranges of motion in horses. American Journal of Veterinary Research, 66(3): Swanstom, M.D., Zarucco, L., Hubbard, M., Stover, S.M., Hawkins, D.A. Musculoskeletal modeling and dynamic simulation of the Thoroughbred equine forelimb during stance phase of the gallop. Journal of Biomechanical Engineering, 127: Swanstom, M.D., Zarucco, L., Stover, S.M., Hubbard, M., Hawkins, D.A., Driessen, B., Steffey, E.P. Passive and active mechanical properties of the supervicial and deep digital flexor muscles in the forelimbs of anesthetized Thoroughbred horses. Journal of Biomechanics, 38: RESEARCH SUPPORT Sponsors Center for Equine Health, with funds provided by: Oak Tree Racing Association State of California Satellite Wagering Fund Southern California Equine Foundation private donors Dolly Green Foundation Grayson-Jockey Club Research Foundation, Inc. Marcia MacDonald Rivas Niarchos Foundation USDA Veterinary Orthopedic Society Researchers Mark Anderson Lucy Anthenill Alex Ardans Bradd Barr Patricia Blanchard Ian Campbell James Case Tim Carpenter Barbara Daft Larry Galuppo Ian Gardner Jeff Gibeling Diane Gross Dave Hawkins Ashley Hill Mont Hubbard Hailu Kinde Sarah Lejeune Ziqi Liu Melinda MacDonald Bruce Martin Janet Moore Bob Norrdin Sarah Pollock Sarah Puchalski Deryck Read Susan Stover Mike Swanstrom Helen Thomas Mark Thurmond Francisco Uzal Hsin-Yi Weng Dana Whitlock Leslie Woods 12

14 California Animal Health and Food Safety Laboratory System J.D. Wheat Veterinary Orthopedic Research Laboratory School of Veterinary Medicine University of California, Davis West Health Sciences Drive Davis, California 95616