The prevalence of virulent Rhodococcus equi in environmental isolates from 31 horse-breeding farms in Hidaka, Hokkaido was investigated: isolates were tested for the presence of virulence plasmid DNA and 15- to 17-kDa antigens by immunoblotting. R. equi was isolated from almost all of the soil samples obtained from the 31 farms with 102 to 105 colony forming units per gram of soil. However, virulent R. equi at various levels (ranging 1.7 to 23.3 %) was isolated from 24 of the 31 farms and appeared in 6.5% of the isolates (121 of 1, 865). The ratio of 85-kb and 90-kb virulence Plasmids in the 121 isolates was about 3:1, which was similar to that previously reported about clinical isolates from infected foals in Hidaka. The similarity between the amounts of virulence Plasmids obtained from the environment and from infected foals indicates that soil-borne virulent R. equi, which is thought to be a major source of the infection, constitutes a great risk to foals in horse-breeding farms. This study shows that plasmid profiles are useful markers in epidemiological surveys of R. equi infection in foals.
We surveyed the distribution o f antibodies to Japanese encephalitis, Getah and equine influenza viruses in racehorses at the Utsunomiya Racecourse. The racehorses have been annually inoculated with vaccines against these infectious diseases. I t was confirmed that most racehorses possessed sufficiently high antibody levels to prevent Japanese encephalitis and Getah virus infection during the epidemic season. Among 2- and 3-year-old horses not yet inoculated annual equine influenza vaccine, antibody titers to equine influenza viruses were distinctly low. On the other hand, horses older than 4 years had relatively high antibody titers.
A rapid and reliable procedure for molecular cloning and nucleotide sequencing of PCR product is described. PCR amplified fragment recovered from agarose gel by centrifugation through siliconized sterilized glass wool was further puri fled in sequential extraction with phenol, phenol/chloroform and chloroform. This was ligated into Thanged plasmid vector and transformed E. Coli was isolated. The plasmid recovered by the alkali denature method was purified by means of spun columns containing Sepharose CL-4B. This step is critical in obtaining a reading >500 by with an automatic DNA sequencer.
A method for grinding thin sections o f resin-embedded hooves for histological analysis is described. Ten percent neutral formalin fixed material is dehydrated in a graded ethanol series, then embedded in resin. After polymerization, sections are cut to a width of 0.5-1.0 mm with diamond blade saw, and then ground to a thickness of 30-40 μm. The ground sections thus obtained are considered to be suitable for histological study of hooves.
Two pregnant mares, at 5 and 6 months gestation were inoculated intranasally with the Bucyrus strain of equine arteritis virus (EAV). Both mares aborted at 1 1 days after the inoculation. Multi focal and necrotizing myometritis was found histopathologically in the uterus. Large numbers o f mononuclear cells had infiltrated the smooth muscle and interstitium o f the myometrium. The smooth muscle cells showed signs o f degeneration with sarcoplasmic vacuolation, and necrosis with acidophilic sarcoplasm and pyknosis or karyorrhexis. EAV antigens were detected in the smooth muscle cells o f the myometrium. These findings suggested that a replication o f EAV had occurred in the smooth muscle cells o f the uterus, resulting in the myometritis.
An attempt was made as a preliminary examination to establish the carrier state o f equine viral arteritis (EVA) in 5 colts infected intranasally with the 84KY-Al strain of the equine arteritis virus (EAV). Persistent infection was monitored by virus isolation and its longest duration was positive in the plasma of a colt one to three weeks after infection. EAV was distributed through all body tissues and high titered virus was detected in the lymphoid tissue rather than the reproductive tissue one week after infection. However, no virus was recovered from any site in the body tissues, including the reproductive tract of 4 colts 4 months after infection. This suggested that persistent infection would not occur in young colts. The carrier state of EVA was discussed with regard to essential conditions, e.g. whether the presence of testosterone, testes or both are involved.
A survey was conducted on the prevalence of internal parasites in 450 racehorses necropsied in Tokyo, Japan, during the period 1980 to 1989. Large strongyles were found in 31.8% and verminous aneurysms in 36.4% o f the horses. Parascaris equorum was found in 14.4% o f all the horses, but in 19.4% of those less than three years old. Setaria equina was found in the peritoneal cavity of 16.2% of the horses. Oxyuris equi, Anoplocephala perfoliata and larvae of Gasterophilus intestinalis were found in 0.4%, 33.1 % and 9.3% o f the horses, respectively. The rate o f in fection with each parasite was less than that in the previous surveys and this might result from the proper application o f highly effective anthelmintic drugs to racehorses in recent years.