To clarify the microbiological causes of dermatosis in racehorses, clinical samples were collected from the skin lesions of dermatosis in racehorses and cultured. Trichophyton equinum was isolated purely from 26 of 87 racehorses (29.9%) and Microsporum equinum from 3 of 87 (3.4%). Staphylococcus hyicus was isolated predominantly from 22 racehorses (25.3%) and Staphylococcus aureus from 21 (24.1%) in cases except dermatophytosis. S. hyicus was most frequently isolated from the skin regions in contact with a harness in large amounts of sweat, suggesting secondary infection to eczema. S. aureus was isolated predominantly from most of the skin lesions of dermatosis with scabs in the white areas of the fetlocks and pasterns. Thus, S. aureus was considered to play an important role in this dermatosis. The present study suggests that two kinds of dermatophytes and two kinds of Staphylococcus are important as causal pathogens of infectious dermatosis in racehorses.

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We investigated a method of culture for the establishment of equine long-term culture cell lines. The tissues tested were equine fetus tissues; right abdomen epithelium, the umbilical artery, the umbilical ring, the pulmonary artery, the renal cortex and the fetal placenta. To decide on a suitable primary culture method, we compared two methods of primary culture: tissue fragment culture and low-temperature trypsin cell-dispersal. On the other hand, to decide on a suitable culture medium, we compared 11 culture media: BME, MEM, D-MEM, IMDM and HFM (commercially completed culture media, available Human Foreskin Melanocyte). These were supplemented with 10% or 20% FCS when used as culture media. Moreover, HFM medium was used with no FCS, 10% and 20% FCS. Culture conditions were 37°C, 100% humidity, 5% CO₂ and 95% air. We obtained the following results: 1) The tissue fragment culture method was suitable for preparing primary cell culture from fetal tissue. 2) High-nutrition culture media such as D-MEM and IMDM were suitable for the culture of fetal tissues. 3) We established a cell line from cells of renal cortex, named “TEK-1”.

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A 13-year-old Anglo-Arabian stallion showing signs of lumber paralysis for four months suddenly developed priapism and was autopsied five days after the onset of priapism. Pathological examinations revealed that lumber paralysis was caused by spinal nematodiasis with parenchymal destruction in the spinal cord and severe infiltration of eosinophils and gliosis caused by the migration of nematode parasites. Leucodystrophy of the lumbosacral spinal cords and axonal dystrophy of the peripheral nerves such as the N. femoralis, N. ischiadicus, N. pudendus, and N. dorsalis penis were also observed. In the swollen penis, severe venous congestion and multiple thrombosis were frequently observed in the corpus spongiosum, necrotic changes and diffuse infiltration with neutrophils in the cavernous trabeculi. Secondary peripheral neuropathy in the penis which resulted from the parasitic spinal injury was discussed histopathologically. This is the first case report of priapism due to spinal nematodiasis.

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We studied the superoxide-scavenging ability (SOD-like ability) of the plasma of mares and foals before and after delivery through the use of the ESR method, with which superoxide radicals (O₂^-) can be detected more specifically than with conventional methods. Superoxide-scavenging ability was measured in the plasma of seven mares before delivery, and in the plasma of seven pairs of mares and foals immediately after delivery and three days, seven days, and 21 days after delivery. In the foals, a significant change was observed, with the highest superoxide-scavenging ability level seen immediately after delivery, followed by a sudden decline to three days after birth, and a gradual decline to seven days after birth. In the mares, no significant change was observed between before and after delivery. It was also shown that SOD-like ability tends to be high in mares after they develop diseases. This suggests a close association between disease and superoxide-scavenging ability.

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Glycolytic enzyme activities and expression of glucokinase (GK) were investigated in leukocytes (WBC) from Thoroughbreds, racehorses undergoing continuous training exercise and riding horses. Glycolytic enzyme activities in WBC from racehorses were higher than those from riding horses. Especially activities of GK, rate-limiting enzyme of glycolysis, were significantly higher in WBC from racehorses than in those from riding horses. Analysis of reverse transcription-polymerase chain reaction (RT-PCR) with specific primer for GK showed that expression of mRNA of GK was remarkably increased in WBC from racehorses. This suggested that activities and gene expression of some kinds of glycolytic enzymes including GK in WBC are possibly a good indicator for assessing glucose metabolism in Thoroughbreds undergoing training exercise.

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