Abstract. Samples of lung, liver, kidney, pancreas, spleen, and lymph node from pigs with postweaning multisystemic wasting syndrome from California (USA) and samples of mesenteric lymph nodes from similarly diseased pigs from Brittany (France) were examined by light microscopy, in situ hybridization (ISH), and/or virus isolation. Whole genomic probes for porcine circovirus (PCV) and chicken anemia virus (CAV) were used for ISH. Tissue homogenate supernatants were inoculated onto PK/15 cells for virus isolation, and the presence of viral antigen and viral particles was verified by indirect immunofluorescence, ISH, and electron microscopy. Histologic examination of lung from pigs from California revealed interstitial pneumonia, alveolar epithelial hyperplasia, and basophilic nuclear and cytoplasmic inclusions in mononuclear cell infiltrates and various pulmonary epithelial cells. Granulomatous lymphadenitis with syncytial cells typified the lesions seen in the pigs from France. PCV-like nucleic acid was detected by ISH in lung, pancreas, lymph node, kidney, and liver in pigs from California. Positive signal was also obtained in lymph node sections from pigs from France. Probes for CAV were consistently negative. PK/15 cell cultures inoculated with lung preparations from diseased California pigs and mesenteric lymph node preparations from pigs from France had positive fluorescence by indirect staining for PCV using pooled polyclonal pig sera and hyperimmune rabbit serum and had variable staining with a panel of 7 monoclonal antibodies specific for cell culture contaminant PCV. PCV-like nucleic acid was also detected by ISH in cell cultures. Cytopathic effect was not observed. Electron microscopic examination of inoculated cell cultures revealed 17-nm viral particles morphologically consistent with PCV. No other virus particles were observed. Although genomic analysis for the definitive identification of these viral isolates remains to be done, the evidence provided strongly suggests that these tissue isolates are closely related to, although antigenically distinct from, the original PCV cell culture contaminant.

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.

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.

Abstract. Bovine fetuses submitted to the California Veterinary Diagnostic Laboratory System were evaluated during a 2-year period (1987 to 1989) for the presence of multifocal necrotizing nonsuppurative encephalitis, nonsuppurative myocarditis, or tissue protozoa. Eighty-two of 445 (1 8%) fetuses submitted met these histologic criteria. Fetuses were from 54 dairy and two beef herds located throughout the state. In 17 fetuses (2 1 Yo) protozoa were found in fetal tissues. Protozoa were found in brain parenchyma of ten fetuses (1 2%), in endothelial cells in four fetuses (5%), in cardiac myofibers in one fetus (lYo), and were associated with endothelial cells in two fetuses (2%). In most fetuses there were no significant gross pathologic findings other than autolysis. While aborted fetuses were from 3 to 9 months gestation, the majority were between 5 and 7 months gestation. They were submitted year round, but more were seen in the fall and winter months. Additional salient histologic features included portal nonsuppurative hepatitis, focal hepatic inflammation and necrosis, and focal nonsuppurative myositis. Nonsuppurative inflammation was also found in decreasing frequency, in the adrenal medulla, kidney, mesentery or abdominal fat, placenta, and lung. In two fetuses (Nos. 1 and 2), the location and morphology of the protozoa were compatible with Sarcocystis spp. The identity of protozoa in the remaining 15 fetuses is unknown. The histopathologic changes in these 82 fetuses and the presence of protozoa in 2 1 Yo of the fetuses suggest these abortions are due to fetal protozoal infections.