Persistence of virus-neutralizing antibodies in horses inoculated with two doses of a live equine herpesvirus type 1 vaccine with different vaccination intervals.

The antibody response in horses inoculated with 2 doses of a live equine herpesvirus type 1 vaccine with different vaccination intervals (1 to 3 months) was evaluated with regard to the persistence of virus-neutralizing (VN) antibodies. The durations for which the geometric mean VN titers were maintained significantly higher than those before the first vaccination (P<0.05) were up to 5 months in horses that received the vaccination with a 1-month interval (n=17) and 7 months for those that received it with a 2-month (n=17) or 3-month interval (n=14 or 17). The vaccination program with the 2-month interval was the most effective in maintaining VN antibodies for a long duration with the smallest gap of antibody decline between the first and second vaccinations.

Application of a wearable GPS unit for examining interindividual distances in a herd of Thoroughbred dams and their foals.

Global positioning system (GPS) units are now lightweight and compact. They have proven useful for analyzing the behavioral characteristics of horses in pastures. Because the GPS records data in latitude and longitude, it may be feasible to calculate the distance between GPS units. The present study aimed to confirm the applicability of GPS units in behavioral studies on horses. For this, we analyzed the accuracy of the distances calculated from GPS units using Hubeny's distance formula and of the monthly changes in interindividual distances obtained from GPS units worn by Thoroughbred dams and their foals in a pasture until weaning. The calculated inter-GPS distances were highly accurate. The regression line was linear, and the squared correlation coefficient (r2) was 0.9998. During the first month of age, the interindividual dam-dam and foal-foal distances were significantly greater than the dam-foal distance. During the second month of age, the dam-foal distance increased once and gradually decreased up to the fifth month of age. During the sixth month of age, the dam-foal distance was significantly greater than the foal-foal distance. The GPS distances calculated using Hubeny's distance formula were useful for analyzing changes in interindividual distances in a herd of Thoroughbred dams and their foals. Most likely, calculation of the distance between GPS units worn on equine head collars is likely to become a very useful tool as an objective index for quantifying equine behavioral observations.

Histopathological findings of apical fracture of the proximal sesamoid bones in young Thoroughbred foals.

Although radiographic findings at the apical portion of the proximal sesamoid bone (PSB) are often observed in young Thoroughbred foals, conflicting findings, either fractures or apparent secondary ossifications centers, have been reported. Three cases (aged 2, 5, and 7 weeks) were identified in 30 necropsied foals (0-31 weeks old). Histopathologically, the subchondral trabecular woven bone was fractured and exhibited focal necrosis of woven bone, fibrin exudate, and/or fibrosis within the foci. In the 7-week-old case, proliferations of chondrocytes were also observed. These findings suggest that the radiographic findings represented a healing process of the apical PSB fractures associated with the mechanically damaged subchondral trabeculae. Developmental PSB injuries should be taken into consideration during the management of young Thoroughbred foals.

Characteristic findings of magnetic resonance imaging (MRI) and computed tomography (CT) for severe chronic laminitis in a Thoroughbred horse.

A Thoroughbred horse with severe chronic laminitis of both forelimbs was evaluated on the same day with magnetic resonance imaging (MRI) and computed tomography (CT). Both MRI and CT revealed loss of the dorsal aspect of the cortical bone of the 3rd phalanx and sclerosis. CT reflected the status of the horny layer and bone of the affected feet, while MRI depicted inflammation of the laminar corium, together with tendon edema. On the 3-dimensional CT venogram, vessels were visualized in both the right and left forelimbs, although there was a difference in the vasculature of the coronary plexus and circumflex vessels between the right and left forelimbs. A combination of both MRI and CT provides detailed information regarding pathological conditions.

Evaluation of Antibody Response in Horses After Vaccination With an Inactivated Getah Virus Vaccine Using an Accelerated Immunization Schedule.

Antibody response in horses after accelerated-schedule Getah virus vaccination was evaluated for its potential adoption during outbreaks. One-year-old Thoroughbred horses received two doses of priming vaccinations following an accelerated schedule (accelerated group: 14-day interval, n = 30) or the conventional schedule (control group: 28-day interval, n = 30). At Day 14, both groups showed similar seropositive rates (66.7% in control group and 73.3% in accelerated group) and geometric mean (GM) virus-neutralizing titers (5.2 [95% confidence interval (CI), 3.0-8.8] in control group and 5.3 [95% CI, 3.1-8.9]). At Day 28, the controls showed a lower seropositive rate (40.0%) and GM titer (2.2 [95% CI, 1.5-3.3]), whereas these figures were significantly higher in the accelerated group, at 80.0% and 7.0 (95%CI, 4.2-11.6, P < .05). The control group's antibody response peaked on Day 42, with a seropositive rate of 80.0% and GM titer of 11.3 (95% CI, 5.6-24.0). From Day 42, the accelerated group showed a faster decline in seropositive rate and GM titer than the control group. Despite the relatively short persistence of antibodies after a second vaccination, the accelerated vaccination schedule proved effective in bridging the detrimental immunity gap that is observed in conventionally vaccinated horses, suggesting the potential usefulness of this accelerated vaccination schedule as an emergency control measure.