Taylorella equigenitalis
[11][2][12][13] Due to specific genomic characteristics and DNA hybridization results, Sugimoto et al., proposed the change from Haemophilus genus to Taylorella in 1983.
[14] Gross morphology and growth rates of T. equigenitalis and T. asinigenitalis are too similar to differentiate the two species without the use of molecular identification techniques such as PCR.
[19] Taylorella equigenitalis tests positive on oxidase, catalase, phosphatase and phosphoamidase reactions and negatively on glucosidase, indole, hydrogen sulfide and production of chemoorganotrophic acid from carbohydrates.
Experimental reports have noted intrauterine infection of rodents with Taylorella equigenitalis, but not with cattle, sheep, swine or cats.
[12][7] Taylorella equigenitalis can be isolated from the urethral fossa, distal urethra, prepuce, free-part of the penis and uncommonly from the pre-ejaculatory fluid.
[7] Taylorella equigenitalis can persist on equine genitalia for years and still be transmitted to susceptible mares or stallions through natural service or artificial insemination.
[5] More significantly, stallions are frequently asymptomatic when carriers, with T. equigenitalis harbouring in the urethral fossa, urethra or penile sheath.
[7] Biosecurity standards including good hygiene, cleaning of fomites and use or sterile and disposable materials should be considered when handling horses for breeding and semen collection.
[2][7] Taylorella equigenitalis does not survive long off of horse reproductive tissue and is sensitive to disinfectants, UV light, high temperatures and humidity.
The genomic structure of T. equigenitalis strain MCE9 contains one chromosome consisting of 1,695,860 base pairs and with a G+C content of approximately 37.42%, with no plasmids.
The preferred method of differentiation is to examine the serological specificities of T. equigenitalis lipopolysaccharides by performing Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and silver staining.
[26] Taylorella equigenitalis untreated will invade the endometrial lining and cause edematous, suppurative endometritis characterized by a hyperemic cervix, which may consist of a mucopurulent exudate.
[27][28] Pathogenic strains are better equipped to invade the host cells and replicate causing lesions characteristic of CEM, mechanisms which need further investigation.
[25] Research has taken a closer look at some conserved protein regions in the genome to gain a better understanding of their role in the pathogenesis of T. equigenitalis and how the bacterium is able to manifest into a clinically significant disease, CEM.
Flp pili aid in adherence to epithelial cell cilia of the genital mucosal, which allows T. equigenitalis to quickly establish residence in that host.
[25][28] Although there are proteins being identified in conserved and variable regions that may contribute to the varying pathogenicity of strains, the true mechanism and their relatedness to virulence is still under investigation.
[7][9] In particular, colts infected in utero via a transplacental route may become a source of future T. equigenitalis transmission to susceptible mares.
No clinical signs that were indicative of infection developed in trials where cattle, sheep, pigs, and cats were inoculated.
[31] The clinical signs associated with Taylorella equigenitalis infections in mares include abnormally cloudy vaginal or cervical discharge, vulvar inflammation, increased size and hardness of the ovaries and uterus upon rectal palpation, as well as abnormalities in the length and/or stages of the mare's estrous cycle.
[32] These signalments are extremely similar to other bacterium which cause infections of the equine reproductive tract, and so diagnosis of T. equigenitalis cannot be based solely on clinical signs.
[7][36] Daily washing of the external genitalia with a solution of 4% chlorhexidine, followed by application of nitrofurazone antibiotic ointment has been stated to be an effective treatment option for stallions and colts.
[7][34] In endemic areas, environmental hygiene and restrictive breeding programs are effective in preventing transmission from fomites and asymptomatic stallion carriers, respectively.
[7] Due to the possibility of asymptomatic carriers of Taylorella equigenitalis leading to CEM, the economic impact can be substantial.
[9][16] Overall, an outbreak of T. equigenitalis can cost upwards of millions of dollars in lost revenue from semen and embryos, as well as import and export limitations.
