HORSE SPECIES SYMPOSIUM: Contagious equine metritis: An insidious threat to the horse breeding industry in the United States1

Taylorella equigenitalis in Icelandic intact males compared with other horse breeds using natural cover

BACKGROUND

Contagious equine metritis (CEM) is caused by Taylorella equigenitalis. It is a venereal disease that is detected in some breeds more than others and can cause temporary infertility with substantial costs for regular testing, sanitation and retesting. There was a perceived increase in T. equigenitalis-positive cases in Icelandic intact males where natural cover is common.

OBJECTIVES

We aimed to investigate the prevalence of T. equigenitalis in Icelandic intact males and compare to draught horse and Haflinger intact males. We hypothesised that prevalence of T. equigenitalis is higher in Icelandic compared with draught and Haflinger intact males.

STUDY DESIGN

Cross sectional.

METHODS

Swabs from 76 Icelandic, 35 Haflinger, and 51 draught horse intact males were collected on 38 different farms and analysed by qPCR. Animals were further stratified into active breeding and non-breeding animals and age groups (1.5-7.0 and 8.0-26.0 years). Fisher's exact tests and mixed effect logistic regression with 'farm' as random effect were used to estimate differences in odds for T. equigenitalis-positive test results.

RESULTS

The overall prevalence of T. equigenitalis in included intact males was 16.7% (27/162). The odds for T. equigenitalis-positive intact males were significantly higher in Icelandic compared with draught and Haflinger intact males (Odds ratio [OR] = 6.42, 95% confidence interval (CI) = 1.43-28.8, p = 0.02). Odds for T. equigenitalis-positive intact males were significantly lower in active breeding compared with non-breeding animals (OR = 0.09, 95% CI = 0.01-0.54, p = 0.009). Age had no significant influence on test results.

MAIN LIMITATIONS

Convenience sampling with regional restrictions to Southern Germany and Austria, small sample size.

CONCLUSIONS

Significantly higher odds for T. equigenitalis-positive intact males were found within Icelandic over draught and Haflinger and within non-breeding animals compared with active breeding animals. Findings suggest that non-breeding animals could be a reservoir for T. equigenitalis. Testing for CEM should therefore be routinely performed in Icelandic horses prior to breeding and investigations into epidemiology and reservoirs on affected farms should be initiated.

Core genome multilocus sequence typing analysis of Finnish Taylorella equigenitalis isolates

In Finland, Taylorella equigenitalis, the causative agent of contagious equine metritis (CEM), was first detected in 1992. The aim of this study was to genotype Finnish T. equigenitalis isolates to investigate the epidemiology of the infection in the Finnish horse population. A total of 34 T. equigenitalis isolates from 24 horses obtained during 1992-2021 were subjected to whole genome sequencing (WGS) and subsequent local ad hoc core genome multi-locus sequence typing (cgMLST) targeting 1259 loci. Classical MLST profiles were extracted from the whole-genome sequence data. Three novel MLST types, ST81, ST82 and ST83, and four previously described sequence types, ST16, ST17, ST50 and ST63 were detected among the isolates. cgMLST minimum spanning tree analysis using 12 allele difference as threshold, resulted in five clusters and three singletons. cgMLST clusters were congruent with the MLST-defined groups, except for the ST83 isolates which were divided into two clusters. However, the high discriminatory power cgMLST allowed differentiation between isolates of the same MLST type as each isolate had a unique core genome ST. Our study suggests that cgMLST has the prospective for being a standardised typing method for T. equigenitalis in the future, and further contributes to worldwide phylogenetic and spatio-temporal analyses needed to better understand the epidemiology of the bacterium.

Current and Future Advances in the Detection and Surveillance of Biosecurity-Relevant Equine Bacterial Diseases Using Loop-Mediated Isothermal Amplification (LAMP)

Horses play an important role throughout the world, whether for work, culture, or leisure, providing an ever-growing significant contribution to the economy. The increase in importation and movement of horses, both nationally and internationally, has inevitably allowed for the global equine industry to grow. Subsequently, however, the potential for transmission of fatal equine bacterial diseases has also escalated, and devasting outbreaks continue to occur. To prevent such events, disease surveillance and diagnosis must be heightened throughout the industry. Current common, or "gold-standard" techniques, have shown to be inadequate at times, thus requiring newer technology to impede outbreaks. Loop-mediated isothermal amplification (LAMP) has proven to be a reliable, rapid, and accessible tool in both diagnostics and surveillance. This review will discuss equine bacterial diseases of biosecurity relevance and their current diagnostic approaches, as well as their respective LAMP assay developments. Additionally, we will provide insight regarding newer technology and advancements associated with this technique and their potential use for the outlined diseases.

Surveillance of Contagious Equine Metritis: Results of the First 5-Year Period of French Proficiency Tests for Taylorella equigenitalis Detection by Real-Time PCR

Contagious equine metritis (CEM) detection by PCR is recognized by the European Union according to Commission Implementing Regulation (EU) No 846/2014, and real-time PCR is now recommended by the World Organisation for Animal Health Terrestrial Manual at the same level as the culture method. The present study highlights the creation of an efficient network of approved laboratories in France in 2017 for CEM detection by real-time PCR. The network currently consists of 20 laboratories. A first proficiency test (PT) was organized by the national reference laboratory for CEM in 2017 to evaluate the performance of the early network, followed by annual proficiency tests organized for ongoing periodic assessment of network performance. Results of the 5 PTs organized from 2017 to 2021 are presented, during which 5 real-time PCRs and 3 DNA extraction methods were used. Overall, 99.20% of the qualitative data corresponded to expected results and the R-squared of global DNA amplification calculated for each PT varied from 0.728 to 0.899. DNA extraction is also an important step in the analytical process, and results were more favorable with direct lysis compared to column extraction. Focusing on the most commonly used PCR (PCR 1: 86.4% of results) showed lowest cycle threshold values with direct lysis compared to column and magnetic bead extractions, and with magnetic bead extraction compared to column extraction, but neither of these differences were statistically significant.

A new strain of Taylorella asinigenitalis shows differing pathogenicity in mares and Jenny donkeys

BACKGROUND

Three horse mares inadvertently inseminated with semen from a Tayorella asinigenitalis-positive Jack donkey developed severe, purulent endometritis whereas two Jenny donkeys mated naturally to the same Jack donkey did not develop clinical signs of infection.

OBJECTIVES

To isolate and identify the causative agent.

STUDY DESIGN

Case report.

METHODS

Endometrial swabs from the infected mares were cultured on selective and non-selective media under aerobic and microaerophilic conditions. Isolates were subjected to Gram staining, oxidase and catalase tests, the Monotayl Latex Agglutination test and PCR to test for both T. equigenitalis and T. asinigenitalis. In vitro antimicrobial susceptibility testing was performed and the bacterial isolate was genotyped using MLST.

RESULTS

A new sequence type of T. asinigenitalis was confirmed.

MAIN LIMITATIONS

A limited numbers of mares and donkeys are described.

CONCLUSIONS

This strain of T. asinigenitalis causes a severe venereal infection in mares but not in Jenny donkeys.

Cost-effective horse breeding in the Republic of Bashkortostan, Russia

Background and Aim:

There is a lack of reliable data in agribusiness regarding the economic efficiency of horse breeding, and this limits its further development. The purpose of this study was to create rational parameters for the development of productive horse breeding as an effective agricultural business, in particular, in relation to farms.

Materials and Methods:

The methods of investigation used were induction and deduction, as well as analytical, statistical, and economic-mathematical analysis. We also used the dynamics of time series, CVP analysis, direct costing, and microeconomic analysis. Data were taken from the Russian Federation’s official statistics on animal husbandry as well as closed (commercial) data of agricultural enterprises from our study region.

Results:

Horse ownership in the Republic of Bashkortostan is higher than in the rest of Russia with about 9% of the total number of horses in Russia. We found that landowners need one hectare of arable land to ensure profit and that the highest economic income occurs on farms specializing in kumis production. The production of kumis under intensive farming is less profitable than with free-range horses kept in pastures. Family farms need a large amount of arable land with natural foliage to balance space and profit.

Conclusion:

Successful implementation of these parameters will make it possible to turn agriculture into successful horse breeding businesses. The expected volume of agricultural production may be approximately 9-11 thousand US dollars per employee.

Comparative Semen Microbiota Composition of a Stallion in a Taylorella equigenitalis Carrier and Non-Carrier State

Simple Summary

Contagious equine metritis carriers have become a new cause of concern in horse stud farms. Their detection can result in significant financial loss and force owners to have their animals undergo antibiotic treatment. Current research has not been able to satisfactorily explain the appearance of carriers in agent-free farms. Studies made on microbial flora have given new insights into the diagnosis and treatment of different issues in animal systems. Next-generation sequencing (NGS) is a powerful tool that can draw an accurate picture of microbial flora. Therefore, the aim of this study was to compare the seminal bacterial composition of one stallion before and after being diagnosed with Taylorella equigenitalis using NGS. Our results show that the microbial seminal flora visibly changed between the samples analyzed. Corynebacteriaceae, an opportunistic bacterial family, was more common in the infected sample. However, Porphyromonadaceae, a natural component in several tissues, was more abundant in the negative sample. Despite the constraints of a single-case study, these findings can open the door to new therapeutic tools, as flora transplants. Similarly, seminal flora analysis may foresee microbial shifts, letting practitioners take preventive actions before a potential outbreak. Furthermore, these actions would have the extra benefit of reducing the administration of antibiotics to treat an infection.

Abstract

Contagious equine metritis is receiving renewed attention due to the continuous detection of carriers in apparent agent-free farms. Interactions of Taylorella with the seminal microflora may be the plausible cause behind these spontaneous changes of the carrier state. Accordingly, the aim of this study was to compare the differences in the seminal microbiome composition of one stallion in the contagious equine metritis carrier state and non-carrier state. Samples were cryopreserved after their extraction. Cell disruption was performed by high-speed homogenization in grinding media. Bacterial families were identified via V3 amplification of the 16S rRNA gene and Ion Torrent sequencing. Only bacterial families with relative abundance above 5% were taken into consideration. The positive sample contained a strong dominance of Corynebacteriaceae (37.75%) and Peptoniphilaceae (28.56%). In the negative sample, the Porphyromonadaceae (20.51%), Bacteroidaceae (19.25%) and Peptoniphilaceae (18.57%) families prevailed. In conclusion, the microbiome seminal composition varies when an individual carries Taylorella from when it is free of it. The wider differences were found in the Corynebacteriaceae, Porphyromonadaceae and Bacteroidaceae families. Due to the limitations of a single-case analysis, further studies are needed for a better understanding of the stallion seminal microflora interactions.

Overview of spatio-temporal distribution inferred by multi-locus sequence typing of Taylorella equigenitalis isolated worldwide from 1977 to 2018 in equidae

The accurate identification of Taylorella equigenitalis strains is essential to improve worldwide prevention and control strategies for contagious equine metritis (CEM). This study compared 367 worldwide equine strains using multilocus sequence typing according to the geographical origin, isolation year and equine breed. The strains were divided into 49 sequence types (STs), including 10 described for the first time. Three major and three minor clonal complexes (CCs), and 11 singletons, were identified. The genetic heterogeneity was low (0.13 STs/strain) despite the wide diversity of geographical origins (n = 16), isolation years (1977-2018) and equine breeds (n = 18). It was highest outside Europe and in the 1977-1997 period; current major STs and CCs already existed before 1998. Previous data associated the major CC1 with the first CEM outbreaks in 1977-1978 in the United Kingdom, Australia and the United States, and revealed its circulation in France. Our study confirms its circulation in France over a longer period of time (1992-2018) and its distribution in Spain and Germany but not throughout Europe. In addition to CC1, relationships between non-European and European countries were observed only through ST4, ST17 and ST30. Within Europe, several STs emerged with cross-border circulation, in particular ST16 and ST46 from the major complexes CC2 and CC8. These results constitute a baseline for monitoring the spread of CEM outbreaks. A retrospective analysis of a higher number of strains isolated worldwide between 1977 and the early 2000s would be helpful to obtain an exhaustive picture of the original CEM situation.

Direct culture-independent sequence typing of Taylorella equigenitalis obtained from genital swabs and frozen semen samples from South African horses

We report herein the use of crude extracts obtained from samples of Taylorella equigenitalis-infected horses for the purpose of multi-locus sequence typing (MLST). Samples (n = 36) were collected from horses in South Africa from 1996 to 2017: 34 from genital swabs (stored at -20°C for 2-3 y) and 2 from cryopreserved raw semen aliquots (stored at -70°C for 18 y) prior to assay. The MLST assay showed a single sequence type (ST), designated ST4, that supported a point introduction and thus a common source for the South African outbreak of contagious equine metritis.

Acute Endometritis due to Taylorella equigenitalis Transmission by Insemination of Cryopreserved Stallion Semen

Taylorella equigenitalis can be transmitted during artificial insemination. This report describes clinical T. equigenitalis transmission by cryopreserved stallion semen. T. equigenitalis isolates from a mare's vaginal discharge and semen from the same batch of the cryopreserved semen used for the insemination gave identical API ZYM, antibiotic susceptibility, and multilocus sequence typing results (ST-46); furthermore, the multilocus sequence typing lineage ST-46 is known to circulate in the country of semen collection. These results support the need for strict contagious equine metritis screening of processed semen before use for artificial insemination.

Towards European harmonisation of contagious equine metritis diagnosis through interlaboratory trials

The performance of culture and PCR methods routinely used to diagnose contagious equine metritis (CEM) was evaluated and compared by two interlaboratory trials involving a total of 24 European laboratories, including 22 National Reference Laboratories for CEM. Samples were swab specimens artificially contaminated with bacteria present in the genital tract of Equidae, some with and some without Taylorella equigenitalis, the causative agent of CEM, and T asinigenitalis, responsible for possible misidentification as T equigenitalis Throughout both interlaboratory trials, PCR performed better in terms of specificity and sensitivity than the culture method, supporting the assertion that PCR should be accepted for CEM diagnosis. However, the culture performance during the second interlaboratory trial was better than during the first one, suggesting that the expertise of participants improved. This reveals the advantage of regular interlaboratory trials to constantly improve the expertise of laboratories. It also shows the need to develop new culture media that are more selective and/or better geared to the metabolism of T equigenitalis in order to improve the bacteriological diagnosis of CEM.

Contagious equine metritis in Portugal: A retrospective report of the first outbreak in the country and recent contagious equine metritis test results

Contagious equine metritis (CEM), a highly contagious bacterial venereal infection of equids, caused by Taylorella equigenitalis, is of major international concern, causing short-term infertility in mares. Portugal has a long tradition of horse breeding and exportation and until recently was considered CEM-free. However, in 2008, T. equigenitalis was isolated at our laboratory from a recently imported stallion and 2 mares from the same stud. Following this first reported outbreak, the Portuguese Veterinary Authority (DGVA) performed mandatory testing on all remaining equines at the stud (n=30), resulting in a further 4 positive animals. All positive animals were treated and subsequently tested negative for T. equigenitalis. Since this outbreak, over 2000 genital swabs from Portuguese horses have been tested at our laboratory, with no further positive animals identified. The available data suggests that this CEM outbreak was an isolated event and we have no further evidence of CEM cases in Portugal, however, an extended and wider epidemiological study would be needed to better evaluate the incidence of the disease in Portuguese horses.

Reproductive Disorders in Horses

Reproductive disease is relatively common in the horse, resulting in a variable, yet significant, economic impact on individual horsemen as well as the entire industry. Diverse expertise from the veterinary community ensures and improves individual and population health of the horse. From a pathology and diagnostics perspective, this review provides a comprehensive overview of pathology of the male and female equine reproductive tract. Recognition by clinical and gross features is emphasized, although some essential histologic parameters are included, as appropriate. Where relevant, discussion of ancillary diagnostic tests and approaches are included for some diseases and lesions.

Polymerase chain reaction-based national surveillance programme to determine the distribution and prevalence of Taylorella equigenitalis in South African horses

REASONS FOR PERFORMING STUDY

The response to the first outbreak of contagious equine metritis in South Africa included pioneering a web-based platform to coordinate key aspects of a national, real-time polymerase chain reaction (qPCR)-based stallion screening programme to determine the distribution and prevalence of Taylorella equigenitalis in stallions and exposed mares.

OBJECTIVES

To define the hypothesised pre-existing status of T. equigenitalis in the South African equine population and progression of the epidemiological investigation via the implementation of a molecular diagnostic-based surveillance programme.

STUDY DESIGN

Retrospective case series.

METHODS

Screening for T. equigenitalis was via a qPCR assay on genital swabs obtained from predilection sites in stallions and mares with subsequent confirmation using bacterial culture according to prescribed methods.

RESULTS

The initial outbreak investigation identified 4 horses including the index stallion and mare. Traceback of in-contact horses identified 26 horses, including a subpopulation focus at the South African Lipizzaner Centre where 24/33 resident stallions tested positive for T. equigenitalis on qPCR. The national screening programme identified an additional 9 stallions. A total of 39 horses (36 stallions and 3 mares) tested positive for T. equigenitalis by qPCR and T. equigenitalis was isolated from 23 of these stallions and 2 of these mares. In addition to the index property, an artificial breeding centre where the index case was first identified, an additional 12 properties with infected horses were identified in 3/9 provinces. Horses on 11 of these 12 properties were directly linked to the index property. Two incidents of T. equigenitalis transmission associated with artificial insemination were recorded.

CONCLUSIONS

T. equigenitalis was present in a subpopulation focus within the South African horse population prior to the outbreak identification in April 2011. Horizontal fomite-associated spread was the most probable route of transmission between stallions. The targeted surveillance of stallions and exposed mares using a qPCR-based screening programme expedited investigation of the distribution and prevalence of T. equigenitalis infection in South African horses. The application of qPCR provided a sensitive and practical screening test for identification of T. equigenitalis-positive animals as part of an emergency response to the first identified cases of T. equigenitalis infection in South African horses.

Development of loop-mediated isothermal amplification methods for detecting Taylorella equigenitalis and Taylorella asinigenitalis

Taylorella equigenitalis is a causative bacterium of contagious equine metritis (CEM), and Taylorella asinigenitalis is species belonging to genus Taylorella. The authors developed two loop-mediated isothermal amplification (LAMP) methods, Te-LAMP and Ta-LAMP, for detecting T. equigenitalis and T. asinigenitalis, respectively. Using experimentally spiked samples, Te-LAMP was as sensitive as a published semi-nested PCR method, and Ta-LAMP was more sensitive than conventional PCR. Multiplex LAMP worked well without nonspecific reactions, and the analytical sensitivities of multiplex LAMP in the spiked samples were almost equivalent to those of Te-LAMP and Ta-LAMP. Therefore, the LAMP methods are considered useful tools to detect T. equigenitalis and/or T. asinigenitalis, and preventive measures will be rapidly implemented if the occurrence of CEM is confirmed by the LAMP methods.

Survival of taylorellae in the environmental amoeba Acanthamoeba castellanii

Background

Taylorella equigenitalis is the causative agent of contagious equine metritis, a sexually-transmitted infection of Equidae characterised in infected mares by abundant mucopurulent vaginal discharge and a variable degree of vaginitis, cervicitis or endometritis, usually resulting in temporary infertility. The second species of the Taylorella genus, Taylorella asinigenitalis, is considered non-pathogenic, although mares experimentally infected with this bacterium can develop clinical signs of endometritis. To date, little is understood about the basic molecular virulence and persistence mechanisms employed by the Taylorella species. To clarify these points, we investigated whether the host-pathogen interaction model Acanthamoeba castellanii was a suitable model for studying taylorellae.

Results

We herein demonstrate that both species of the Taylorella genus are internalised by a mechanism involving the phagocytic capacity of the amoeba and are able to survive for at least one week inside the amoeba. During this one-week incubation period, taylorellae concentrations remain strikingly constant and no overt toxicity to amoeba cells was observed.

Conclusions

This study provides the first evidence of the capacity of taylorellae to survive in a natural environment other than the mammalian genital tract, and shows that the alternative infection model, A. castellanii, constitutes a relevant alternative system to assess host-pathogen interactions of taylorellae. The survival of taylorellae inside the potential environmental reservoir A. castellanii brings new insight, fostering a broader understanding of taylorellae biology and its potential natural ecological niche.

Genomic characterization of the Taylorella genus

The Taylorella genus comprises two species: Taylorella equigenitalis, which causes contagious equine metritis, and Taylorella asinigenitalis, a closely-related species mainly found in donkeys. We herein report on the first genome sequence of T. asinigenitalis, analyzing and comparing it with the recently-sequenced T. equigenitalis genome. The T. asinigenitalis genome contains a single circular chromosome of 1,638,559 bp with a 38.3% GC content and 1,534 coding sequences (CDS). While 212 CDSs were T. asinigenitalis-specific, 1,322 had orthologs in T. equigenitalis. Two hundred and thirty-four T. equigenitalis CDSs had no orthologs in T. asinigenitalis. Analysis of the basic nutrition metabolism of both Taylorella species showed that malate, glutamate and alpha-ketoglutarate may be their main carbon and energy sources. For both species, we identified four different secretion systems and several proteins potentially involved in binding and colonization of host cells, suggesting a strong potential for interaction with their host. T. equigenitalis seems better-equipped than T. asinigenitalis in terms of virulence since we identified numerous proteins potentially involved in pathogenicity, including hemagluttinin-related proteins, a type IV secretion system, TonB-dependent lactoferrin and transferrin receptors, and YadA and Hep_Hag domains containing proteins. This is the first molecular characterization of Taylorella genus members, and the first molecular identification of factors potentially involved in T. asinigenitalis and T. equigenitalis pathogenicity and host colonization. This study facilitates a genetic understanding of growth phenotypes, animal host preference and pathogenic capacity, paving the way for future functional investigations into this largely unknown genus.