Chapter 27 Taylorella equigenitalis and the recently described Taylorella asinigenitalis (Jang et al. 2001), are Gram-negative rods about 0.8 × 5.0 µm in size. Both species are facultative anaerobes, non-motile, oxidase-positive, catalase-positive, phosphatase-positive and produce no acid from carbohydrates. Taylorella species are fastidious and slow-growing bacteria; optimal growth is obtained on chocolate agar with a rich base (Eugon or Columbia agar) at 37°C under 5–10% CO2, with T. asinigenitalis growing more slowly than T. equigenitalis. Taylorella species do not grow on MacConkey agar. Transmission of T. equigenitalis is essentially venereal, but mares can also be infected by attendants and via veterinary instruments. The organisms can be isolated from neonatal and virgin animals. A purulent metritis develops within a few days of infection and the mare often has a copious mucopurulent uterine discharge. The infectious process is limited to the mucous membranes of the uterus, cervix and vagina. There is erosion and degenerative change in the endometrium. After endometrial repair is complete, within a few weeks, the organism may still be present in the clitoral sinuses and fossa, remaining there for long periods. No clinical signs occur in the stallion but T. equigenitalis can be found on the surface of the penis, in preputial smegma and in the urethral fossa. The infection in mares causes a temporary infertility and occasionally abortion within the first 60 days of pregnancy. Little is known of the virulence mechanisms of T. equigenitalis although studies attempting to characterize pathogenic properties such as adherence and invasion have been described (Bleumink-Pluym et al. 1996, Lapan et al. 1991). The genomes of both Taylorella species have been sequenced recently and these studies identified a number of putative virulence genes including genes encoding Type II, III, IV and VI Secretion Systems, haemagglutinins and iron acquisition systems (Hauser et al. 2012, Hébert et al. 2012). However, the role of these genes in vivo remains to be confirmed. In addition, use of PCR-based techniques for the detection of the organism indicates that carriage of the organism may be more widespread than cultural techniques would suggest and genotyping procedures have demonstrated the existence of several different strains of T. equigenitalis. These findings suggest that differences in pathogenicity exist between strains. Application of molecular techniques such as microarray analysis should increase our understanding of the relationship between infection with T. equigenitalis and the pathogenesis of contagious equine metritis in the future. In many countries contagious equine metritis is controlled by a government body or by a thoroughbred breeders’ association. These bodies lay down the method of sample taking, the type of samples to be taken and the culture media to be used, when examining asymptomatic stallions and mares for the carrier state of the disease. Many of the recommendations are based on the Code of Practice of the Horserace Betting Levy Board in the UK (Horserace Betting Levy Board 2012). Requirements may be amended periodically. Often only approved laboratories are licensed to process and culture the specimens. Details of required sampling and cultural techniques are also available from the OIE (2012). In general, acceptable samples are swabs or biopsies from: • Mares: cervix, uterus, clitoral fossa and clitoral sinuses • Stallions: urethra, urethral fossa and diverticulum, prepuce and pre-ejaculatory fluid.
Taylorella species
Pathogenesis and Pathogenicity
Laboratory Diagnosis
Specimens
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Taylorella species
