Summary Necropsies were performed on 496 horses that had a fatal injury or illness at a California racetrack during the period February 20th 1990 to March 1st 1992. The primary cause of death was categorised by breed, activity at time of injury or illness and organ system affected. Most of the submissions were Thoroughbred horses (432) and Quarter Horses (46). Most of the injuries occurred while racing (42%) and in training sessions (39%); with fewer non‐exercise (12%) and accident (7%) related injuries or illnesses. Musculoskeletal injuries accounted for 83% of the Thoroughbred and 80% of the Quarter Horse submissions. The Thoroughbred horses incurred 306 fractures with 263 in the limbs and 90% of those in the forelimbs. The proximal sesamoid bone(s), third metacarpal bone and humerus were the most common bones fractured in Thoroughbred horses and Quarter Horses. Other major causes of death included respiratory, digestive and multi‐organ system disorders.

Abstract. Canine distemper virus (CDV) infection occurred in captive leopards (Panthera pardus), tigers (Panthera tigris), lions (Panthera leo), and a jaguar (Panthera onca) in 1991 and 1992. An epizootic affected all 4 types of cats at the Wildlife Waystation, San Fernando, California, with 17 mortalities. CDV-infected raccoons were thought to be the source of infection in these cats. Two black leopards died at the Naibi Zoo, Coal Valley, Illinois, and 2 tigers died at the Shambala Preserve, Acton, California. Initial clinical signs were anorexia with gastrointestinal and/or respiratory disease followed by seizures. Canine distemper virus was isolated from 3 leopards, 3 tigers, and 3 lions that died or were euthanized when moribund. Monoclonal antibody testing identified the virus isolates as CDV. Gross and histopathologic findings were similar to those found in canids with distemper with a few exceptions. There were fewer lesions in the brain, and there was a pronounced type 2 cell proliferation in the lung, with inclusion bodies and CDV antigen demonstrated by immunohistology. Neutralizing antibody to CDV was found in high titers in serum from most animals but was absent or was found only in low titers in some cats that succumbed after CDV infection. There was a marked difference in neutralizing antibody titers when tests were done with different strains of CDV.Canine distemper virus (CDV) is a common pathogen in dogs and is well known in canids, mustelids, procyonids, and viverrids.2 Encephalitis in javelinas (collared peccaries) after natural infection with CDV occurred in Arizona. 4 Experimental infection with CDV in domestic cats and pigs resulted in seroconversion but no clinical disease. 6 Morbilliviruses closely related to CDV have been isolated from epizootics in seals, 26 dolphins, 14 and porpoises. 32A major outbreak of canine distemper (CD) There are other reports of encephalitis in large cats. A fatal nonsuppurative encephalitis in lions and tigers was observed in a safari park in Germany. It was believed to be caused by an infectious agent that has not been isolated but was found to be unrelated to CDV by serology and immunohistology. 30 A similar encephalitis of unknown origin is seen in domestic cats in the United States and Europe.21,31 A paramyxoviruslike agent was associated with demyelinating lesions in the CNS and optic neuritis in cats. 13 This agent has 277

Summary Twenty‐one horses had a complete unilateral humeral fracture during race training or racing at a California racetrack during the period 24 February 1990 to 10 July 1991. Fractures occurred approximately equally in left and right limbs, and in males and females. Most fractures occurred during training, and in 2‐ and 3‐year‐old horses. Only 5 of 16 Thoroughbred horses with known racing records had previously raced more than once, and their mean time between races was less than the time between their last race and fracture (P = 0.07). Ten of 13 humeri studied further had gross evidence of periosteal callus bridging one portion of the fracture line, indicative of a pre‐existing stress fracture.

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