KAKUDA Tsutomu KITASATO UNIVERSITY, SCHOOL OF VETERINARY MEDICINE AND ANIMAL SCIENCES, LECTURER, 獣医畜産学部, 講師 (80317057)
TSUBAKI Shiro KITASATO UNIVERSITY, SCHOOL OF VETERINARY MEDICINE AND ANIMAL SCIENCES, PROFESSOR, 獣医畜産学部, 教授 (70050507)
MADARAME Hiroo AZABU UNIVERSITY, TEACHING ANIMAL HOSPITAL, ASSOCIATE PROFESSOR, 獣医学部, 助教授 (20173768)
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¥7,100,000 (Direct Cost : ¥7,100,000)
Fiscal Year 2004 : ¥2,300,000 (Direct Cost : ¥2,300,000)
Fiscal Year 2003 : ¥2,300,000 (Direct Cost : ¥2,300,000)
Fiscal Year 2002 : ¥2,500,000 (Direct Cost : ¥2,500,000)
There are eight native horse breeds in Japan (Hokkaido, Kiso, Noma, Misaki, Tokara, Taishu, Miyako, and Yonaguni) and each is thought to have originated principally from the Mongolian horse. On the island of Cheju, the native horse has been present for about 700 years since the Mongolians introduced their horses to the island. We hypothesized that the transmission to Japan of the virulent form of R.equi, with its various virulence plasmid types, may have occurred with the migration of native horses from the Mongolian grasslands. However, there has been no information about the distribution of virulent R.equi in native horses in Korea, China and Mongolia.
Rbodococcus equi was isolated from fecal and soil samples from four native Jeju horse farms and six Thoroughbred farms in Jeju, Korea. The isolates were examined for the presence of virulence-associated 15 ミ 17-kDa antigens (VapA) by colony blotting, using the monoclonal antibody 10G5, and for the gene encoding VapA by PCR. R.equi was i
solated from all 36 soil samples collected from the 10 farms with between 5.0 to 10^2 and 7.5 to 10^4 colony-forming units (cfu) per gram of soil, and from 37 of 40 fecal samples with between 5.0 to 10^1 and 1.1 to 10^5 cfu per gram of feces. Virulent R.equi was isolated from seven farm and appeared in 2.0% of isolates (10 of 508). Of the 10 virulent isolates, four contained a 90-kb type II plasmid, which has been found in isolates from the Kiso native horses of Japan, and the other six contained a new variant, which did not display the EcoRI and EcoT22I digestion patterns of the 10 representative plasmids already reported (85-kb types I, II, III, and IV ; 87-kb types I and II ; 90-kb types I, II, III, and IV). We designated the new variant as the 90-kb type V plasmid, because its EcoRI digestion pattern is similar to that of the 90-kb type II plasmid. This is the first report of the prevalence of virulent R.equi in Jeju, Korea. The same virulence plasmid type is found in both Korean and Japanese isolates, providing insight intro the origin, ancestry, and dispersal of native horses in Korea and Japan.
In native Mongolian horses, the incidence and distribution of Rhodococcus equi are poorly understood. One hundred and fourteen equine fecal samples and 71 soil samples were collected from the camp sites of 26 nomadic families located in three areas less than 100 km from Ulaanbaatar, Mongolia. Five fecal samples were also collected from foals of Przewalski's Horses introduced into the Hustai National Park, Mongolia. No R.equi was isolated from the Mongolian horses or the soil samples. However, three colonies of R.equi were isolated from two fecal samples collected from foals of Przewalski's Horses. These isolates were avirulent, with neither 15- to 17-kDa antigens (VapA) nor a 20-kDa antigen (VapB) being detected. We concluded that native Mongolian horses and their environment appear free from contamination with R.equi.
In conclusion, further studies on the molecular epidemiology of native horses in Mongolia, China, and Korea are needed. Less