Superficial digital flexor tendon (SDFT) injury leading to tendonitis is the most frequent soft tissue injury in racehorses. As tendonitis has been noted to heal slowly and imperfectly, injured tendons require long periods of rest, and the rate of recurrence of tendonitis upon return to training is high. Between 1, 100 and 1,200 of the 6,400 to 7,000 racehorses currently registered with the Japan Racing Association (JRA) suffer from tendonitis, and some 70% of these return to racing without making a comeback in a single race. In view of this statistic, the JRA has conducted investigational and clinical research from various perspectives. This paper will review the results of these studies, thus providing insight into practical methods of treating and preventing tendonitis. The study results are summarized under the following headings: 1) Introduction; 2) Impacts and loads on the lower limb at the track; 3) Occurrence of tendonitis at JRA training centers; 4) The hoof and tendonitis; 5) Ultrasonic diagnostic criteria; 6) Therapeutic regimens; 7) Conclusion. We concluded that tendon injuries represent irreversible structural alterations that are unlikely to be significantly altered by therapy, so that the best outcome may be achieved by minimizing the damage done by the original injury. From this viewpoint, research efforts will be directed toward prevention and early diagnosis, rather than therapy of established lesions.
The D4 dopamine receptor gene (DRD4) polymorphic region, which is possibly related to the personality trait known as Novelty Seeking in humans, was examined in equids. Partial nucleotide sequences in exon 3 of DRD4 gene were compared among several species in genus Equus. Inter-and intra-species differences were observed, as well as between two domestic horse breeds, Thoroughbred and Kiso pony (Japanese native pony). In equids, these variations were consisted of as many as 9 fold repeats of 18 bp variable number of tandem repeat (VNTR) type polymorphisms and single nucleotide polymorphisms (SNPs).
Isotype-specific antibody responses in 13 foals to Rhodococcus equi were studied during the first 20 weeks of life on a horse-breeding farm with a persistent incidence of R. equi infection. The levels of immunoglobulin (Ig) classes and IgG subclasses specific for R. equi antigens in the 13 foal sera were determined by ELISA and Western immunoblotting. Kinetics of the total amount of IgG and the number of WBC in the blood of 13 foals were also monitored. Soluble extract from R. equi strain ATCC 6939 was used as a routine EISA antigen. During the observation period, 8 of the 13 foals showed >0.3 OD value against ATCC 6939 antigen by a routine ELISA, which was tentatively fixed to be positive on the basis of readings made of healthy horse sera in previous studies. R. equi-specific IgGa was predominantly detected in these foals at 6 to 10 weeks after birth by ELISA with Tween 20-extracted ATCC 6939 antigens. Specific serum IgGb, and IgA were also detected, but they showed lower titers than IgGa antibodies in the foals. Specific IgG(T), IgGc and IgM was present consistently at low levels in most foals. On the other hand, IgGa and IgGb antibodies specific for 15-to 17-kDa antigens (VapA) were detected by immunoblotting at 5 to 7 weeks of age in most foals. Out of the 13 foals, 3 foals had a serum IgG concentrations less than 1,000 mg/dl (650 to 900 mg/dl) at the first week of birth. WBC counts tended to increase by 8 weeks with age in all foals. Virulent R. equi was isolated from the feces of foals during this study. This study suggests that R. equi-specific IgGa was predominantly measured by ELISA, and VapA-specific IgGa and IgGb were predominantly detected by immunoblotting in foals naturally exposed to R. equi on a farm with a persistent incidence of R. equi infection.
A sero-epidemiological survey was conducted using a serum neutralization test in order to better understand the level of circulation of three equine rotavirus strains, HO-5 strain (G3, P), FI23 strain (G14, P), and L338 strain (G13, P), among horses in the Hidaka region of Hokkaido, Japan. Sera used for the survey were collected from 50 1-year-old horses at 10 thoroughbred stud farms in the Hidaka region in February and March of 1999. Two horses were excluded from the study because they did not possess antibodies against any of the 3 strains. Of the remaining 48 horses, 35 (73%) showed highest antibody titers against HO-5 strain while 8 horses (17%) demonstrated highest titers against FI23 strain. The remaining 5 horses (11%) possessed similar antibody titers against HO-5 strain and FI23 strain. Predominant antibody titers against L338 strain were not observed in any of the horses. These results suggest that G3, P type was the predominant rotavirus among horses in the Hidaka region of Hokkaido although G14, P type also circulated. There was no evidence that horses in the Hidaka region were infected with the L338 strain.