Prevalence of Taylorella equigenitalis in an Icelandic horse population

Abstract

Contagious Equine Metritis (CEM) is an infectious disease caused by Taylorella equigenitalis (TEq). In mares, clinical as well as subclinical infections have the potential to cause short-term infertility. Stallions are generally believed to be asymptomatic carrier of TEq. Transmission commonly occurs venereally and therefore poses a risk for horses in less controlled natural mating programs (Timoney, Comp. Immun. Microbiol. Infect. Dis. 1996, 3: 199-204). In the Icelandic breed, pasture breeding is routinely performed. Therefore, the aim of this study was to investigate the prevalence of TEq in intact stallions, mares and geldings of the Icelandic breed. We hypothesized that there is a high prevalence of TEq in Icelandic horses independent of their breeding purpose. In total, 437 Icelandic horses from 16 randomly selected farms in southern Germany and Austria were examined. In a first trial, 76 intact Icelandic males from 10 farms were compared to a reference group (n=86) consisting of 35 Haflinger and 51 Draft intact male horses from 31 farms. Breeds of the reference group are also known to be used in natural mating programs. In a second trial, 105 geldings and 256 mares from 11 farms were tested for presence of TEq. In both trials, swabs from standardized localizations of the male (penis) or female (clitoris) genital tract were collected (WOAH for TEq). The presence of TEq DNA was determined using quantitativePCR. There was a significant higher prevalence of TEq-positive samples in Icelandic intact males (n=23) compared to the reference group (n=4; p=0.0001). Both groups were further differentiated regarding their actual use for breeding. Pairwise comparison of both groups resulted in a significantly lower number of TEq-positive intact males used for breeding compared to the horses without breeding (reference group: p=0.019; Icelandic group: p=0.006). In the second trial, a higher prevalence of TEq-positive geldings compared to mares (36.2% and 5.5%, respectively) was detected. Mares were further differentiated in mares with breeding history (n=134) and mares without (n=122). A higher prevalence in mares without breeding history could be found (2.2% and 9.0%, respectively). The hypothesis could be confirmed that in the Icelandic breed a higher prevalence of TEq-positive stallions compared to stallions also used in natural mating programs exists. Furthermore, TEq has a higher prevalence in geldings compared to mares of Icelandic horses. Therefore, geldings might represent a reservoir of TEq in this breed. The spread of CEM is of economic importance and should be considered even in horses never used for breeding. Further studies investigating the genotype of the CEM strains in the Icelandic breed might help to understand further ways of transmission.