Rhodococcus equi was isolated from soil samples obtained from seven Hokkaido native horse farms in Hakodate, Hokkaido. R. equi was prevalent in all 59 soil samples collected from the seven farms at concentrations of between 7.5 × 102 and 7.5 × 104 colony-forming units per gram of soil. The isolates were examined for presence of the gene that encodes the virulence-associated 15-17 kDa antigen protein, VapA, using PCR. VapA-positive R. equi was isolated from 1-6% of isolates from three of the farms. This represents 1.4% of isolates from all farms examined (8 out of 590). The eight virulent isolates were characterized by plasmid profiling, restriction fragment length polymorphism analysis, and pulsed-field gel electrophoresis. All of the virulent isolates contained an 87-kb type II plasmid, but there were eight distinct VspI profiles. These results suggest that, although the Hokkaido horses of Hakodate are exposed to a variety of distinct types of virulent R. equi, the incidence of exposure is low or zero. An 87-kb type II plasmid was strongly associated with Hokkaido native horses as has already been observed in virulent isolates from Hokkaido native horses at Bekkai, Hokkaido.
We aimed to determine the safety, immunogenicity and efficiency of an inactivated equine rotavirus vaccine. The vaccine was prepared with G3 serotype equine rotavirus. A dose of 2 ml was inoculated twice with a 1-month interval into the cervical muscles of 60 pregnant mares (40 on farm T and 20 on farm M). The first vaccination was conducted 2 or 3 months before full term. No abnormal signs were observed in the whole body or the inoculated area in any of the mares vaccinated. Serum neutralization antibody rose in 56 (93.3%) of the 60 vaccinated mares. The 60 foals born to the vaccinated mares possessed neutralization antibody titers of 1:320 to 1:10240. Sixteen foals on farm T developed diarrhea caused by serotype G14 rotavirus infection, but no foals on farm M developed diarrhea. Diarrhea in the foals born to vaccinated mares was a slight illness in comparison with that in foals born to unvaccinated mares. The vaccine is safe and immunogenic for pregnant mares, and vaccine-induced maternal antibody in the foals can reduce the signs of diarrhea caused by rotavirus infection.
Granulosa-theca cell tumor (GTCT) is the most common ovarian tumor in mares. Two adult Arabian mares presented with a history of persistent estrus (No. 1) and aggressive behavior (No. 2). Large unilateral polycystic ovarian masses were identified in each mare on rectal and ultrasound examinations. The masses were surgically removed and subjected to immunohistochemical staining. The histopathologic features of both ovarian masses were consistent with GTCT. Both tumors displayed positive immunoreactivity for inhibin α-subunit, but were negative for inhibin βA and βB subunits. This report indicates that appearance of inhibin α-subunit can be used as an immunohistochemical marker in the diagnosis of GTCT in equine.