The effect of repeated transport stress over a period of 60 hours on secretion of gonadotropins was investigated by transporting three cyclic mares in a trailer. The experiment involved ten 5-hour transport periods, each followed by one hour of rest. Ultrasound observation of ovaries and measurement of levels of circulating progesterone indicated that two mares (Horse Nos. 1 and 2) were in the luteal phase and the remaining one horse was in transition from the luteal phase to the follicular phase (luteolysis). Levels of plasma cortisol in all horses increased in response to each transport periods, but the cortisol response much leveled off during the last three transport periods (41 hr after the experiment began). Levels of plasma LH in Horses Nos. 1 and 2 remained low throughout the period of transport experiment. In Horse No. 3, however, levels of plasma LH increased during the first 2 transport periods, followed by a gradual decrease until the end of the experiment. There were no obvious changes in levels of plasma FSH in any of the animals. These results suggest that transport stress suppresses basal secretion of LH in cyclic mares and the pattern of this suppression may depend on the estrous cycle.

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During the 3-years period from 1989 to 1991, 15 methicillin-resistant Staphylococcus aureus (MRSA) strains were isolated from 13 mares with metritis in Hidaka District, Hokkaido, Japan. All these isolates proved to possess mec A gene and showed MICs of 25-100 μg/ml for methicillin. The isolates were found to be multidrug resistant to erythromycin, tetracycline and aminoglycoside antibiotics as well, to exhibit the same antimicrobial sensitivity patterns and to have common characteristics of being phage type III, coagulase type IV and enterotoxin type A. The organisms therefore were strongly suggested to have originated from the same source. Then, bacteriological examinations were performed at a stud farm suspected to be the source of MRSA infection. As the result, MRSA was not detected from reproductive organs of stallions, their environment or farm employees but was done consistently from cutaneous lesion of pastern in the hind leg of a stallion in that farm over a period longer than two months. The MRSA isolates obtained from the skin lesion of the stallion were found to be identical in the characteristics with the isolates from metritis in the mares. It was thus inferred that the organism was persistently infecting the cutaneous lesion in the stallion eventually contaminated the stud farm environment, resulting in infections in the mare received for mating.

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Interstitial pneumonia associated with multinucleated giant cells was noted in an aborted 9-month-old Thoroughbred horse fetus in a routine postmortem examination. The multinucleated giant cells were considered to have originated from interstitial macrophages and blood monocytes that migrated into the bronchiolar lumen and alveolar space. There were no increases in any of the maternal serum titers of antibodies against equine rhinopneumonitis virus, Getah virus, adenovirus or equine arteritis virus, and no pathogenic organisms or metals were detected in the fetal lung tissues. The histopathologic findings of pulmonary lesions offered similarities to “desquamative interstitial pneumonia, ” or “usual interstitial pneumonia” in man.

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The sequence of the VP7-encoded gene of a serotype G3 equine rotavirus strain HO-5 isolated in Japan was determined. The VP7 was amplified by a reverse transcription-polymerase chain reaction from the segment 8 RNA of the HO-5 strain by using a synthetic primer pair for the rotavirus VP7 gene. The gene segment 8 of the HO-5 strain was also sequenced and the deduced amino acid sequence was determined. The results indicate that the VP7 of the HO-5 strain is encoded by the gene segment 8 and the deduced amino acid sequence of the HO-5 VP7 has an overall high sequence homology more than 95% to those of two known equine rotavirus strains.

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