Streptococcus equi Infections in Horses: Guidelines for Treatment, Control, and Prevention of Strangles-Revised Consensus Statement

Immune-mediated Equine Vasculopathies

Immune-mediated vasculopathies occur secondary to infection or another noninfectious stimulus. Potential triggers include heterologous antigens including viruses, injected proteins and drugs; or auto-antigens including immunoglobulins or other endogenous proteins. Although these conditions are rare in horses, immune-mediated vasculopathies can cause considerable morbidity, with variable clinical signs depending on severity and organ system affected. Examples include purpura hemorrhagica, systemic lupus erythematosus, drug-induced vasculitis, paraneoplastic vasculitis, and idiopathic immune-mediated vasculitis. Diagnosis is presumptive or based on histopathology of skin biopsies if cutaneous signs are present. Treatment relies on removing the inciting cause, immunosuppression, and supportive care.

Untangling the stranglehold through mathematical modelling of Streptococcus equi subspecies equi transmission

Strangles, a disease caused by infection with Streptococccus equi subspecies equi (S. equi), is endemic worldwide and one of the most frequently diagnosed infectious diseases of horses. Recent work has improved our knowledge of key parameters of transmission dynamics, but important knowledge gaps remain. Our aim was to apply mathematical modelling of S. equi transmission dynamics to prioritise future research areas, and add precision to estimates of transmission parameters thereby improving understanding of S. equi epidemiology and quantifying the control effort required. A compartmental deterministic model was constructed. Parameter values were estimated from current literature wherever possible. We assessed the sensitivity of estimates for the basic reproduction number on the population scale to varying assumptions for the unknown or uncertain parameters of: (mean) duration of carriership (1∕γC), relative infectiousness of carriers (f), proportion of infections that result in carriership (p), and (mean) duration of immunity after natural infection (1∕γR). Available incidence and (sero-)prevalence data were compared to model outputs to improve point estimates and ranges for these currently unknown or uncertain transmission-related parameters. The required vaccination coverage of an ideal vaccine to prevent major outbreaks under a range of control scenarios was estimated, and compared available data on existing vaccines. The relative infectiousness of carriers (as compared to acutely ill horses) and the duration of carriership were identified as key knowledge gaps. Deterministic compartmental simulations, combined with seroprevalence data, suggest that 0.05 Collapse

Key Words

• Epidemiology
• Infectious disease modelling
• Streptococcus equi

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MESH Headings

• Animals
• Horses
• Streptococcal Infections/veterinary
• Streptococcal Infections/epidemiology
• Streptococcal Infections/transmission
• Horse Diseases/transmission
• Horse Diseases/epidemiology
• Horse Diseases/microbiology
• Models, Theoretical
• Prevalence
• Incidence
• Streptococcus equi
• Models, Biological
• Streptococcus

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Affiliation(s)

R M A C Houben Department of Clinical Sciences, faculty of Veterinary medicine, Utrecht University, the Netherlands.
J R Newton Equine Infectious Disease Surveillance (EIDS), Department of Veterinary Medicine, Cambridge, UK
C van Maanen Royal GD, Deventer, the Netherlands
A S Waller Intervacc AB, Stockholm, Sweden; Department of Biomedical Science and Veterinary Public Health, Swedish University of Agricultural Sciences, Uppsala, Sweden
M M Sloet van Oldruitenborgh-Oosterbaan Department of Clinical Sciences, faculty of Veterinary medicine, Utrecht University, the Netherlands
J A P Heesterbeek Department of Population Health Sciences, faculty of Veterinary Medicine, Utrecht University, the Netherlands

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First Molecular Detection and Epidemiological Analysis of Equine Influenza Virus in Two Regions of Colombia, 2020-2023

Equine influenza is a viral disease caused by the equine influenza virus (EIV), and according to the WOAH, it is mandatory to report these infections. In Latin America and Colombia, EIV risk factors have not been analyzed. The objective of this research is to perform an epidemiological and molecular analysis of the EIV in horses with respiratory symptoms from 2020 to 2023 in Colombia. Molecular EIV detection was performed using RT-qPCR and nanopore sequencing. A risk analysis was also performed via the GEE method. A total of 188 equines with EIV respiratory symptoms were recruited. The positivity rate was 33.5%. The descriptive analysis showed that only 12.8% of the horses were vaccinated, and measures such as the quarantine and isolation of symptomatic animals accounted for 91.5% and 88.8%, respectively. The variables associated with the EIV were the non-isolation of positive individuals (OR = 8.16, 95% CI (1.52-43.67), p = 0.014) and sharing space with poultry (OR = 2.16, 95% CI (1.09-4.26), p = 0.027). In conclusion, this is the first EIV investigation in symptomatic horses in Colombia, highlighting the presence of the virus in the country and the need to improve preventive and control measures.

Development of novel Streptococcus equi vaccines with an assessment of their immunizing potentials and protective efficacies

Strangles is a highly contagious disease of the equine upper respiratory tract caused by Streptococcus equi subspecies. Streptococcus equi subsp. equi (S. equi) and Streptococcus equi subsp. zooepidemicus (S. zooepidemicus) was isolated, as local, hot, and field strains, from horses clinically suffering from respiratory distress. The isolated Streptococci were identified using bacteriological and molecular techniques. Four formulations of inactivated S. equi vaccines were developed and evaluated. The first formulation was prepared using the S. equi isolates, adjuvanted with MONTANIDE GEL adjuvant, while the second formulation was adjuvanted with MONTANIDE ISA-70 adjuvant. The other 2 formulations were inactivated combined vaccines prepared from both S. equi and S. zooepidemicus isolates. The 3rd formulation was the combined isolates adjuvanted with MONTANIDE GEL while the 4th formulation was the combined isolates adjuvanted with MONTANIDE ISA-70. The developed vaccines' physical properties, purity, sterility, safety, and potency were ensured. The immunizing efficacy was determined in isogenic BALB/c mice and white New Zealand rabbits using the passive hemagglutination test. Also, the antibodies' titer of the combined S. equi and S. zooepidemicus vaccine adjuvanted with MONTANIDE ISA-70 in foals was tracked using an indirect enzyme-linked immunosorbent assay. The protective efficacy of the developed vaccines was determined using a challenge test in both laboratory and field animal models, where a 75% protection rate was achieved. The combined vaccine proved to be more efficacious than the monovalent vaccine. Also, the MONTANIDE ISA-70 adjuvant provided significant protective efficacy than the MONTANIDE GEL. The current work is introducing a very promising mitigative and strategic controlling solution for strangles.

Development of a Real-Time Recombinase-Aided Amplification Method for the Rapid Detection of Streptococcus equi subsp. equi

Streptococcus equi subspecies equi (S. equi) is the causative pathogen of strangles in horses, donkeys, and other equine animals. Strangles has spread globally and causes significant losses to the horse industry. In response to the urgent need for effective disease control, this study introduces a novel nucleic acid diagnostic method known as a real-time recombinase-assisted amplification (RAA) assay, developed based on the eqbE gene, for the rapid detection of S. equi nucleic acid. The real-time RAA method employs specifically designed probes and primers targeting the eqbE gene, enhancing the overall specificity and sensitivity of the detection. After efficiency optimization, this real-time RAA method can detect 10 or more copies of nucleic acid within 20 min. The method demonstrates high specificity for S. equi and does not cross-react with other clinically relevant pathogens. Real-time RAA diagnostic performance was evaluated using 98 nasal swab samples collected from horses and compared with the real-time PCR detection method. Results revealed that 64 and 65 samples tested positive for S. equi using real-time RAA and real-time PCR, respectively. The overall agreement between the two assays was 96.94% (95/98), with a kappa value of 0.931 (p < 0.001). Further linear regression analysis indicated a significant correlation in the detection results between the two methods (R2 = 0.9012, p < 0.0001), suggesting that the real-time RAA assay exhibits a detection performance comparable to that of real-time PCR. In conclusion, the real-time RAA assay developed here serves as a highly specific and reliable diagnostic tool for the detection of S. equi in equine samples, offering a potential alternative to real-time PCR methods. In conclusion, the real-time RAA nucleic acid diagnostic method, based on the eqbE gene, offers rapid and accurate diagnosis of S. equi, with the added advantage of minimal equipment requirements, thus contributing to the efficient detection of strangles in horses.

In silico approaches for predicting natural compounds with therapeutic potential and vaccine candidates against Streptococcus equi

Equine strangles is a prevalent disease that affects the upper respiratory in horses and is caused by the Gram-positive bacterium Streptococcus equi. In addition to strangles, other clinical conditions are caused by the two S. equi subspecies, equi and zooepidemicus, which present relevant zoonotic potential. Treatment of infections caused by S. equi has become challenging due to the worldwide spreading of infected horses and the unavailability of effective therapeutics and vaccines. Penicillin treatment is often recommended, but multidrug resistance issues arised. We explored the whole genome sequence of 18 S. equi isolates to identify candidate proteins to be targeted by natural drug-like compounds or explored as immunogens. We considered only proteins shared among the sequenced strains of subspecies equi and zooepidemicus, absent in the equine host and predicted to be essential and involved in virulence. Of these, 4 proteins with cytoplasmic subcellular location were selected for molecular docking with a library of 5008 compounds, while 6 proteins were proposed as prominent immunogens against S. equi due to their probabilities of behaving as adhesins. The molecular docking analyses revealed the best ten ligands for each of the 4 drug target candidates, and they were ranked according to their binding affinities and the number of hydrogen bonds for complex stability. Finally, the natural 5-ring compound C25H20F3N5O3 excelled in molecular dynamics simulations for the increased stability in the interaction with UDP-N-acetylenolpyruvoylglucosamine reductase (MurB). This research paves the way to developing new therapeutics to minimize the impacts caused by S. equi infections.Communicated by Ramaswamy H. Sarma.

Complete genome sequencing and comparative genomic analysis of three donkey Streptococcus equi subsp. equi isolates

Introduction

Streptococcus equi subspecies equi (S. equi) is the causative agent of strangles, which is one of the most common and highly contagious respiratory infectious illnesses in horses. Streptococcus equi (S. equi) is a horse-specific pathogen that originated from the closely related zoonotic pathogen Streptococcus equi subspecies zooepidemicus (S. zooepidemicus). Despite decades of research, the movement of genetic material across host-restricted diseases remains a mystery.

Methods

Three S. equi donkey isolates (HTP133, HTP232, and HT1112) were recently isolated from a strangles epidemic on donkey farms in China's Xinjiang Province. In this study, we performed a comprehensive comparative analysis of these isolates using whole genome sequencing and compared them to the published genomic sequences of equine strain S. equi 4047 to uncover evidence of genetic events that shaped the evolution of these donkey S. equi isolates' genomes.

Results

Whole genome sequencing indicated that both strains were closely related, with comparable gene compositions and a high rate of shared core genomes (1788-2004). Our comparative genomic study indicated that the genome structure is substantially conserved across three donkey strains; however, there are several rearrangements and inversions when compared to the horse isolate S. equi 4047. The virulence factors conveyed by genomic islands and prophages, in particular, played a key role in shaping the pathogenic capacity and genetic diversity of these S. equi strains. Furthermore, we discovered that the HT133 isolate had a strong colonization ability and increased motility; the HT1112 isolates had a significantly higher ability for antimicrobial resistance and biofilm formation, and the HT232 isolate gained pathogenic specialization by acquiring a bacteriophage encoding hyaluronate lyase.

Discussion

In summary, our findings show that genetic exchange across S. equi strains influences the development of the donkey S. equi genome, offering important genetic insights for future epidemiological studies of S. equi infection.

Dynamics analysis of strangles with asymptomatic infected horses and long-term subclinical carriers

Strangles is one of the most prevalent horse diseases globally. The infected horses may be asymptomatic and can still carry the infectious pathogen after it recovers, which are named asymptomatic infected horses and long-term subclinical carriers, respectively. Based on these horses, this paper establishes a dynamical model to screen, measure, and model the spread of strangles. The basic reproduction number $ \mathcal{R}_0 $ is computed through a next generation matrix method. By constructing Lyapunov functions, we concluded that the disease-free equilibrium is globally asymptotically stable if $ \mathcal{R}_0 < 1 $, and the endemic equilibrium exits uniquely and is globally asymptotically stable if $ \mathcal{R}_0 > 1 $. For example, while studying a strangles outbreak of a horse farm in England in 2012, we computed an $ \mathcal{R}_0 = 0.8416 $ of this outbreak by data fitting. We further conducted a parameter sensitivity analysis of $ \mathcal{R}_0 $ and the final size by numerical simulations. The results show that the asymptomatic horses mainly influence the final size of this outbreak and that long-term carriers are connected to an increased recurrence of strangles. Moreover, in terms of the three control measures implemented to control strangles(i.e., vaccination, implementing screening regularly and isolating symptomatic horses), the result shows that screening is the most effective measurement, followed by vaccination and isolation, which can provide effective guidance for horse management.

Development of a novel real-time PCR multiplex assay for detection of Streptococcus equi subspecies equi and Streptococcus equi subspecies zooepidemicus

Strangles is a contagious bacterial disease of horses caused by Streptococcus equi subspecies equi (SEE) that occurs globally. Rapid and accurate identification of infected horses is essential for controlling strangles. Because of limitations of existing PCR assays for SEE, we sought to identify novel primers and probes that enable simultaneous detection and differentiation of infection with SEE and S. equi subsp. zooepidemicus (SEZ). Comparative genomics of U.S. strains of SEE and SEZ (n = 50 each) identified SE00768 from SEE and comB from SEZ as target genes. Primers and probes for real-time PCR (rtPCR) were designed for these genes and then aligned in silico with the genomes of strains of SEE (n = 725) and SEZ (n = 343). Additionally, the sensitivity and specificity relative to microbiologic culture were compared between 85 samples submitted to an accredited veterinary medical diagnostic laboratory. The respective primer and probe sets aligned with 99.7 % (723/725) isolates of SEE and 97.1 % (333/343) of SEZ. Of 85 diagnostic samples, 20 of 21 (95.2 %) SEE and 22 of 23 SEZ (95.6 %) culture-positive samples were positive by rtPCR for SEE and SEZ, respectively. Both SEE (n = 2) and SEZ (n = 3) were identified by rtPCR among 32 culture-negative samples. Results were rtPCR-positive for both SEE and SEZ in 21 of 44 (47.7 %) samples that were culture-positive for SEE or SEZ. The primers and probe sets reported here reliably detect SEE and SEZ from Europe and the U.S., and permit detection of concurrent infection with both subspecies.

Detection of Viable Streptococcus equi equi Using Propidium Monoazide Polymerase Chain Reaction

There is debate around the clinical significance of Streptococcus equi subsp. equi detection in low numbers using quantitative real-time PCR (qPCR). Propidium monoazide (PMA) qPCR has been used to differentiate DNA from viable and nonviable bacterial cells. The aim of this study was to evaluate the ability of PMA eqbE SEQ2190 triplex qPCR to differentiate DNA from viable and nonviable S. equi in positive and suspect positive clinical specimens. Fifty-seven stored (frozen and refrigerated) positive (36) or suspect positive (21) clinical specimens (determined via SeeI qPCR as the gold standard) were tested using eqbE SEQ2190 triplex qPCR with (+) and without (-) PMA pretreatment. Cycle thresholds were higher when using PMA indicating a mixture of heat killed and viable cells. Number of S. equi positive specimens were as follows: 6/57 eqbE + PMA, 13/57 eqbE -PMA (Chi- squared 3.1, p = .079); 10/57 SEQ2190 +PMA, 53/57 SEQ2190 -PMA (Chi- squared 65.6, p < .0001). The mean cycle thresholds were as follows: 23.88 eqbE -PMA, 29.89 eqbE + PMA (p = .04); 24.9 SEQ2190 -PMA, 31.9 SEQ2190 +PMA (p < .0001). PMA qPCR can be used to determine S. equi viability, but testing should be performed on fresh specimens.

Evaluating Trends in Strangles Outbreaks Using Temperature and Precipitation Data in the United States of America for 2018-2022

Strangles is a highly contagious upper respiratory infection of equids that is globally distributed. The causative agent of strangles, Streptococcus equi subspecies equi, can be spread through indirect contact with infected fomites, and studies have shown this microbe to live well in varying environmental conditions. The purpose of this study was to analyze strangles case numbers across the United States of America from 2018 to 2022 to investigate potential temporal or weather patterns associated with outbreaks. Diagnosed case records were obtained from the Equine Disease Communication Center, university databases, government agencies, or veterinary diagnostic labs, and geographic information systems (GISs) were used to map cases and to acquire relevant meteorological data from outbreak areas. These data were analyzed using logistic regression to explore trends that occur between outbreaks and changes in temperature and precipitation. Initial review of weather data suggested monthly changes in strangles case numbers corresponded with changing seasons. Logistic regression indicated that changes in monthly average temperature and minimum temperature were significantly associated with increased or decreased odds of strangles outbreaks, respectively. Future analyses should focus on weather data isolated within a smaller region or state to better resolve trends in strangles outbreaks throughout the continental USA.

Endoscopic Anatomy of the Equine Guttural Pouch: An Anatomic Observational Study

Guttural pouch endoscopy allows for both the visualization and treatment of many clinical problems in the equine retropharyngeal region. This area is extremely complex, and its description remains a real challenge for veterinary anatomists and practitioners. Six clinically normal equine cadavers were employed. Conventional dissections of guttural pouches without penetrating the guttural pouch membrane were first performed, and each adjacent structure was identified. Then, a guttural pouch endoscopic exam of the dissected heads was performed in order to correctly map each visible underlying anatomic structure identified in the previous dissection. This allowed us to: 1-identify each structure visible on endoscopic examination of the guttural pouch; 2-create a representative map of all the structures accurately identified via endoscopy; and 3-describe a systematic guttural pouch endoscopic examination with practical keys to help identification of the underlying vital structures. Our investigation provides new practical information on guttural pouch endoscopic anatomy and has allowed us to identify structures that were not previously described. We believe that this information may help with an accurate diagnosis in some cases and also potentially reduce iatrogenic trauma to important structures.

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.

Usage of Antimicrobials in Equine Veterinary Practice in Denmark - A Case-Based Survey

Horses may be carriers of important resistant bacteria like methicillin-resistant staphylococci. Such bacteria can potentially threaten both equine and public health, but little is known about predisposing factors like antimicrobial usage patterns in equines. Objectives of this study were to investigate the antimicrobial usage practices by Danish equine practitioners as well as factors impacting usage. A total of 103 equine practitioners filled in an online questionnaire. When asked to explain their typical treatment of six clinical case scenarios, only 1% and 7% of respondents prescribed systemic antimicrobials for a cough and pastern dermatitis, respectively. More frequent usage was reported for diarrhoea (43%), extraction of a cracked tooth (44%), strangles (56%), and superficial wound near a joint (72%). Among the antibiotics indicated for treatment, enrofloxacin was the only critically important antimicrobial agent reported by two respondents. Thirty-eight (36%) respondents worked in practices with antimicrobial protocols. When asked to prioritize the most important factor influencing prescribing habits, bacterial culture (47%) and antimicrobial protocols (45%) were selected far more often than the owner´s economy (5%) and expectations (4%). Veterinarians reported limitations such as the availability of only one oral antibiotic (sulphadiazine/trimethoprim), and a need for clearer treatment guidelines. In conclusion, the study highlighted important aspects regarding antimicrobial usage among equine practitioners. Antimicrobial protocols and pre- and post-graduate education on prudent antimicrobial usage are recommended.

Efficacy of high-level disinfection of endoscopes contaminated with Streptococcus equi subspecies equi with 2 different disinfectants

BACKGROUND

Prevention of spread of Streptococcus equi subspecies equi (S. equi) after an outbreak is best accomplished by endoscopic lavage of the guttural pouch, with samples tested by culture and real time, quantitative polymerase chain reaction (qPCR). Disinfection of endoscopes must eliminate bacteria and DNA to avoid false diagnosis of carrier horses of S. equi.

HYPOTHESIS/OBJECTIVES

Compare failure rates of disinfection of endoscopes contaminated with S. equi using 2 disinfectants (accelerated hydrogen peroxide [AHP] or ortho-phthalaldehyde [OPA]). The null hypothesis was that there would be no difference between the AHP and OPA products (based on culture and qPCR results) after disinfection.

METHODS

Endoscopes contaminated with S. equi were disinfected using AHP, OPA or water (control). Samples were collected before and after disinfection and submitted for detection of S. equi by culture and qPCR. Using a multivariable logistic regression model-adjusted probability, with endoscope and day as controlled variables, the probability of an endoscope being qPCR-positive was determined.

RESULTS

After disinfection, all endoscopes were culture-negative (0%). However, the raw unadjusted qPCR data were positive for 33% AHP, 73% OPA, and 71% control samples. The model-adjusted probability of being qPCR-positive after AHP disinfection was lower (0.31; 95% confidence interval [CI], -0.03-0.64) compared to OPA (0.81; 95% CI, 0.55-1.06), and control (0.72; 95% CI, 0.41-1.04).

CONCLUSION AND CLINICAL IMPORTANCE

Disinfection using the AHP product resulted in significantly lower probability of endoscopes being qPCR-positive compared to the OPA product and control.

Relationship between quantitative real-time PCR cycle threshold and culture for detection of Streptococcus equi subspecies equi

Objective

To compare PCR and culture results for the detection of Streptococcus equi subspecies equi (S. equi).

Animals

Respiratory tract samples (N = 158) from horses being tested for S. equi.

Procedure

Bacterial culture was carried out on samples from which S. equi was detected by quantitative real-time PCR.

Results

S. equi was isolated from 12 (7.6%) samples: 4/9 (44%) samples when the PCR cycle threshold (CT) was ≤ 30, 7/30 (23%) when the CT was 30.1 to 35, and 1/119 (0.8%) when the CT was 35.1 to 40. The highest CT sample from a sample that yielded a positive culture was 36.9. The optimal Youden's J value was at a CT of 34.2, the same value as determined by number needed to misdiagnose when the cost of a false negative is deemed to be either 5 or 10 × that of a false positive.

Conclusions

Viable S. equi was only detected in a minority of quantitative PCR (qPCR) positive samples. A qPCR CT of 34.2 was a reasonable breakpoint for likelihood of the presence of culturable S. equi.

Clinical relevance

Evaluation of CT values may be useful as a proxy to indicate the likelihood of cultivable S. equi being present and could be useful as part of risk assessments.

Streptococcus equi Subspecies equi

Strangles, caused by the bacteria Streptococcus equi subsp equi, is a highly contagious disease of equids classically characterized by a high fever and enlarged lymph nodes of the head. Diagnostic sampling depends on the stage of the disease. The goal of treating strangles is to control transmission and to eliminate infection while providing future host immunity. Daily temperature checking and isolation of febrile horses is the key to controlling outbreaks. Eradication of this disease will not be possible until S equi carriers are eliminated from the equine population.

A Horse of a Different Color: A Case Report of Streptococcus Equi Meningitis in a Kidney Transplant Recipient

Streptococcus equi is an opportunistic pathogen in horses that has rarely been transmitted to humans. Here we present a zoonotic S. equi meningitis case in a kidney transplant recipient with exposure to infected horses. We discuss the patient's risk factors, clinical presentation, and management in the context of the limited literature on S. equi meningitis.

SUPERFICIAL CERVICAL LYMPHADENITIS ASSOCIATED WITH STREPTOCOCCUS PHOCAE IN FIVE COMMON BOTTLENOSE DOLPHINS (TURSIOPS TRUNCATUS): A CASE SERIES

Between 2009 and 2018, five common bottlenose dolphins (Tursiops truncatus) at the US Navy Marine Mammal Program presented with superficial cervical lymphadenitis. Clinical findings included ultrasonographic evidence of cervical lymph node enlargement, severe leukocytosis, elevated erythrocyte sedimentation rates, and reduced serum iron. Three of the dolphins presented with clinicopathologic changes without presence of clinical signs, and the other two cases additionally presented with partial to complete anorexia, lethargy, and refusal to participate in training sessions. Ultrasound-guided fine needle aspiration or biopsy of the affected lymph nodes yielded Streptococcus phocae by PCR in all cases, and the organism was cultured in one of five cases. Animals were treated with a combination of enteral, parenteral, intralesional antimicrobial, or a combination of those therapies and supportive care. Time to resolution of clinical disease ranged between 62 and 188 days. To the authors' knowledge, this is the first report of Streptococcus phocae cervical lymphadenitis in cetaceans. Streptococcus phocae lymphadenitis should be a differential for cervical lymphadenopathy in this species, especially when associated with pronounced systemic inflammation and a history of potential exposure.

Voluntary Biosurveillance of Streptococcus equi Subsp. equi in Nasal Secretions of 9409 Equids with Upper Airway Infection in the USA

This study aimed to describe selected epidemiological aspects of horses with acute onset of fever and respiratory signs testing qPCR-positive for S. equi and to determine the effect of vaccination against S. equi on qPCR status. Horses with acute onset of fever and respiratory signs from all regions of the United States were included in a voluntary biosurveillance program from 2008 to 2020 and nasal secretions were tested via qPCR for S. equi and common respiratory viruses. A total of 715/9409 equids (7.6%) tested qPCR-positive for S. equi, with 226 horses showing coinfections with EIV, EHV-1, EHV-4, and ERBV. The median age for the S. equi qPCR-positive horses was 8 ± 4 years and there was significant difference when compared to the median age of the S. equi qPCR-negative horses (6 ± 2 years; p = 0.004). Quarter Horse, Warmblood, and Thoroughbred were the more frequent breed in this horse population, and these breeds were more likely to test qPCR-positive for S. equi compared to other breeds. There was not statistical difference for sex between S. equi qPCR-positive and qPCR-negative horses. Horses used for competition and ranch/farm use were more likely to test qPCR-positive for S. equi (p = 0.006). Horses that tested S. equi qPCR-positive were more likely to display nasal discharge, fever, lethargy, anorexia, and ocular discharge compared to horses that tested S. equi qPCR-negative (p = 0.001). Vaccination against S. equi was associated with a lower frequency of S. equi qPCR-positive status.

Molecular Features and Antimicrobial Susceptibilities of Streptococcus equi ssp. equi Isolates from Strangles Cases in Indonesia

Strangles, caused by Streptococcus equi ssp. equi (S. equi equi), is a highly infectious and frequent disease of equines worldwide. No data are available regarding the molecular epidemiology of strangles in Indonesia. This study aimed to characterize S. equi equi isolates obtained from suspected strangles cases in Indonesia in 2018. Isolates originated from seven diseased horses on four different farms located in three provinces of Indonesia. Whole genome sequences of these isolates were determined and used for seM typing, multilocus sequence typing (MLST), and core genome MLS typing (cgMLST). Genomes were also screened for known antimicrobial resistance genes and genes encoding for the recombinant antigens used in the commercial Strangvac^® subunit vaccine. All seven S. equi equi isolates from Indonesia belonged to ST179 and carried seM allele 166. Isolates differed from each other by only 2 to 14 cgSNPs and built an exclusive sub-cluster within the Bayesian Analysis of Population Structure (BAPS) cluster 2 (BAPS-2) of the S. equi equi cgMLST scheme. All isolates revealed predicted amino acid sequence identity to seven and high similarity to one of the eight antigen fragments contained in Strangvac^®. Furthermore, all isolates were susceptible to beta-lactam antibiotics penicillin G, ampicillin, and ceftiofur. Our data suggest that the horses from this study were affected by strains of the same novel sublineage within globally distributed BAPS-2 of S. equi equi. Nevertheless, penicillin G can be used as a first-choice antibiotic against these strains and Strangvac^® may also be protective against Indonesian strains.

Conservation of vaccine antigen sequences encoded by sequenced strains of Streptococcus equi subsp. equi

BACKGROUND

Streptococcus equi subspecies equi (S equi) is the cause of Strangles, one of the most prevalent diseases of horses worldwide. Variation within the immunodominant SeM protein has been documented, but a new eight-component fusion protein vaccine, Strangvac, does not contain live S equi or SeM and conservation of the antigens it contains have not been reported.

OBJECTIVE

To define the diversity of the eight Strangvac antigens across a diverse S equi population.

STUDY DESIGN

Genomic description.

METHODS

Antigen sequences from the genomes of 759 S equi isolates from 19 countries, recovered between 1955 and 2018, were analysed. Predicted amino acid sequences in the antigen fragments of SEQ0256(Eq5), SEQ0402(Eq8), SEQ0721(EAG), SEQ0855(SclF), SEQ0935(CNE), SEQ0999(IdeE), SEQ1817(SclI) and SEQ2101(SclC) in Strangvac and SeM were extracted from the 759 assembled genomes and compared.

RESULTS

The predicted amino acid sequences of SclC, SclI and IdeE were identical across all 759 genomes. CNE was truncated in the genome of five (0.7%) isolates. SclF was absent from one genome and another encoded a single amino acid substitution. EAG was truncated in two genomes. Eq5 was truncated in four genomes and 123 genomes encoded a single amino acid substitution. Eq8 was truncated in three genomes, one genome encoded four amino acid substitutions and 398 genomes encoded a single amino acid substitution at the final amino acid of the Eq8 antigen fragment. Therefore, at least 1579 (99.9%) of 1580 amino acids in Strangvac were identical in 743 (97.9%) genomes, and all genomes encoded identical amino acid sequences for at least six of the eight Strangvac antigens.

MAIN LIMITATIONS

Three hundred and seven (40.4%) isolates in this study were recovered from horses in the UK.

CONCLUSIONS

The predicted amino acid sequences of antigens in Strangvac were highly conserved across this collection of S equi.

Review of the Foundational Knowledge Required for Assessing Horse Welfare

A detailed understanding of what is usual for a species under optimal conditions is critical for identifying and interpreting different features of body function that have known impacts on animal welfare and its assessment. When applying the Five Domains Model to assess animal welfare, the key starting point is therefore to acquire extensive species-specific knowledge relevant to each of the four physical/functional Domains of the Model. These Domains, 1 to 4, address areas where objective information is evaluated and collated. They are: (1) Nutrition; (2) Physical environment; (3) Health; and (4) Behavioural interactions. It is on the basis of this detailed knowledge that cautious inferences can then be made about welfare-relevant mental experiences animals may have, aligned with Domain 5, Mental State. However, this review is focused entirely on the first four Domains in order to provide a novel holistic framework to collate the multidisciplinary knowledge of horses required for undertaking comprehensive welfare assessments. Thus, inferring the potential mental experiences aligned with Domain 5, the final step in model-based welfare assessments, is not considered here. Finally, providing extensive information on free-roaming horses enables a better understanding of the impacts of human interventions on the welfare of horses in both free-roaming and domestic situations.

Prospective bacterial and fungal sources of hyaluronic acid: A review

The unique biological and rheological properties make hyaluronic acid a sought-after material for medicine and cosmetology. Due to very high purity requirements for hyaluronic acid in medical applications, the profitability of streptococcal fermentation is reduced. Production of hyaluronic acid by recombinant systems is considered a promising alternative. Variations in combinations of expressed genes and fermentation conditions alter the yield and molecular weight of produced hyaluronic acid. This review is devoted to the current state of hyaluronic acid production by recombinant bacterial and fungal organisms.

A review of horses as a source of spreading livestock-associated methicillin-resistant Staphylococcus aureus to human health

Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) was first discovered in horses in 1989. Since then, LA-MRSA has begun to be considered an important strain of pathogenic bacteria in horses, which can cause LA-MRSA infection and colonization in humans with public health impacts. The anterior nares are the primary site of LA-MRSA colonization in horses, although LA-MRSA colonization may also occur in the gastrointestinal tract in horses. LA-MRSA-infected horses typically exhibit clinical infection or may not exhibit clinical infection. There are two potential risks associated with LA-MRSA colonization in horses: The possibility of disease development in horses infected with LA-MRSA and the possibility of LA-MRSA transfer to humans and other horses. The diagnosis of LA-MRSA in horses can be made by conducting in vitro sensitivity testing for oxacillin and cefoxitin, and then followed by a molecular test using polymerase chain reaction. LA-MRSA transmission in animal hospitals and on farms is most likely due to contact with horses infected or colonized by LA-MRSA. The history of prior antibiotic administration, history of prior LA-MRSA colonization, and length of equine hospitalization were described as risk factors in cases of infection and colonization of LA-MRSA in horses. Nebulized antibiotics may be a viable alternative to use in horses, but nebulized antibiotics are only used in horses that are persistently colonized with LA-MRSA. Controlling the spread of LA-MRSA in horses can be done by regularly washing horses, eradicating vectors in horse stalls such as rats, and maintaining the cleanliness of the stable and animal hospital environment. Meanwhile, cleaning hands, using gloves, and donning protective clothes are ways that humans can prevent the transmission of LA-MRSA when handling horses. This review will explain the definition of LA-MRSA in general, LA-MRSA in horses, the epi­demiology of LA-MRSA in horses, the diagnosis of LA-MRSA in horses, the transmission of LA-MRSA in horses, risk factors for spreading LA-MRSA in horses, public health impact, treatment of LA-MRSA infection in horses, and control of the spread of LA-MRSA in horses.

Estimation of the basic reproduction number for Streptococcus equi spp equi outbreaks by meta-analysis of strangles outbreak reports

BACKGROUND

Streptococcus equi spp equi (S. equi), the cause of strangles in horses, is considered a highly contagious pathogen affecting equines and the equine industry worldwide. Fundamental epidemiological characteristics of outbreaks, such as the basic reproduction number (R₀ ), are not well described.

OBJECTIVES

Estimate R₀ for S. equi in equine populations from outbreak data.

STUDY DESIGN

Systematic review and meta-analysis of published and unpublished data.

METHODS

A literature search for outbreak reports was carried out. Depending on data available in the reports, the early epidemic growth rate or final attack rate (AR) approach was used to estimate the basic reproduction number for that outbreak. Other recorded outbreak characteristics were the type of housing (group vs individual). An overall estimate for R₀ was computed by meta-analysis.

RESULTS

Data from 8 outbreaks were extracted from peer-reviewed publications. Data from two additional, non-published outbreaks was also included in the meta-analysis. A conservative estimate for R₀ was 2.2 (95% CI 1.9- 2.5). A less conservative estimate, including outbreaks with a 100% AR for which a lower limit R₀ was estimated, was 2.7 (95% CI 2.1- 3.3).

MAIN LIMITATIONS

Few papers describing longitudinal incidence data were found so most estimates were based on the outbreaks' final size. Several outbreaks had a 100% attack rate and could therefore only be included as a lower limit estimate in the meta-analysis. The reported result therefore may be an underestimation.

CONCLUSIONS

This estimate for R₀ for S. equi informs parameters for future mathematical modelling, quantifies desired preventive vaccine coverage and helps evaluate the effect of prevention strategies through future modelling studies.

Frequency of Detection and Prevalence Factors Associated with Common Respiratory Pathogens in Equids with Acute Onset of Fever and/or Respiratory Signs (2008–2021)

A voluntary biosurveillance program was established in 2008 in order to determine the shedding frequency and prevalence factors for common respiratory pathogens associated with acute onset of fever and/or respiratory signs in equids from the USA. Over a period of 13 years, a total of 10,296 equids were enrolled in the program and nasal secretions were analyzed for the qPCR detection of equine influenza virus (EIV), equine herpesvirus-1 (EHV-1), EHV-4, equine rhinitis A and B virus (ERVs), and Streptococcus equi subspecies equi (S. equi). Single infections with respiratory pathogens were detected in 21.1% of the submissions with EIV (6.8%) and EHV-4 (6.6%) as the two most prevalent viruses, followed by S. equi (4.7%), ERVs (2.3%), and EHV-1 (0.7%). Multiple pathogens were detected in 274 horses (2.7%) and no respiratory pathogens in 7836 horses (76.2%). Specific prevalence factors were determined for each of the six respiratory pathogen groups; most differences were associated with age, breed, and use of the horses, while the clinical signs were fairly consistent between viral and bacterial respiratory infections. Monitoring the frequency of detection of common respiratory pathogens is important in order to gain a better understanding of their epidemiology and to implement management practices aimed at controlling disease spread.

[Management and hygiene measures during an outbreak of herpes, influenza, strangles or infections with multidrug resistant bacteria]

The aim of this review is to describe general guidelines of hygiene measures in the horse stable as well as to provide current recommendations for an outbreak of a common infectious disease. General cleanliness, hand hygiene, avoidance of stress, regular deworming, and vaccinations belong to the basic hygiene measures in a horse herd. All new or returning equids should be submitted to a quarantine period as an important prevention measure. Repeated washing and disinfection of hands may prevent spreading of infectious agents to people and horses.The conception of a hygiene plan, including general biosecurity procedures and standard operating procedures in a case of an outbreak of an infectious disease, zoonosis, or colonization with multi-resistant bacteria is strongly recommended. As soon as the disease is suspected, extended hygiene measures including protective clothing, cleaning, disinfection, and isolation of potentially infected animals should be implemented. Prompt confirmation of the causative agent by examination of appropriate samples is crucial. It is important to adjust all safety measures based on the contagious nature of the respective pathogen and its major transmission routes. Apart from a lock-down of the stable, clinic or show grounds, the segregation of horses plays an important role. Implementation of the "traffic light system" is recommended. In this, the red group ("infected") include animals with clinical signs of the disease or that have been tested positive. All horses with possible pathogen contact should be allocated to a yellow group ("suspected") and regularly controlled for the signs of infection and fever. Clinically normal horses without contact to the infected animals belong to the green group ("healthy"). A change of protective clothing and an extensive disinfection should be performed when moving between the groups.The extended hygiene measures are to be maintained until all animals have been tested negative or fail to exhibit clinical signs of the disease for a certain time period.

Metabolic Alternations During Gestation in Dezhou Donkeys and the Link to the Gut Microbiota

The maternal intestinal microbial community changes dramatically during pregnancy and plays an important role in animal growth, metabolism, immunity and reproduction. However, our understanding of microbiota compositional dynamics during the whole pregnancy period in donkey is incomplete. This study was carried out to evaluate gut microbiota alterations as well as the correlation with serum biochemical indices, comparing pregnant donkeys to non-pregnant donkeys. A total of 18 pregnant (including EP, early-stage pregnancy; MP, middle-stage pregnancy and LP, late-stage pregnancy) and six non-pregnant (C as a control) donkey blood samples and rectum contents were collected. The results showed that pregnant donkeys had higher microbial richness than non-pregnant donkeys and that the lowest microbial diversity occurred at the EP period. Moreover, the relative abundances of the families Clostridiaceae and Streptococcaceae were significantly higher in the EP group (p < 0.05) than that in the C and MP groups, while the relative abundances of the families Lachnospiraceae and Rikenellaceae were significantly lower in the EP group (p < 0.05) than that in the C group. The predicted microbial gene functions related to the inflammatory response and apoptosis, such as Staphylococcus aureus infection, the RIG-1-like receptor signaling pathway and apoptosis, were mainly enriched in EP. Furthermore, pregnant donkeys had higher glucose levels than non-pregnant donkeys, especially at EP period. EP donkeys had lower triglyceride, total protein and albumin levels but higher malondialdehyde, interleukin 1β, interleukin 6 and tumor necrosis factor-α levels than those in the C and MP groups. Additionally, there were strong correlations between inflammatory cytokine levels and the relative abundances of genera belonging to the Clostridiaceae and Streptococcaceae families. This is the first comparative study performed in donkeys that indicates that pregnancy status (especially in the early pregnancy period) alters the gut microbiota composition, which was correlated with serum biochemical parameters. These results could provide useful information for improving the reproductive management in Dezhou donkeys.

Equids’ Core Vaccines Guidelines in North America: Considerations and Prospective

Vaccination against infectious diseases is a cornerstone of veterinary medicine in the prevention of disease transmission, illness severity, and often death in animals. In North American equine medicine, equine vaccines protecting against tetanus, rabies, Eastern and Western equine encephalomyelitis, and West Nile are core vaccines as these have been classified as having a heightened risk of mortality, infectiousness, and endemic status. Some guidelines differ from the label of vaccines, to improve the protection of patients or to decrease the unnecessary administration to reduce potential side effects. In North America, resources for the equine practitioners are available on the American Association of Equine Practitioners (AAEP) website. Conversely, in small companion animals, peer review materials are regularly published in open access journals to guide the vaccination of dogs and cats. The aims of this review are to present how the vaccine guidelines have been established for small companion animals and horses in North America, to review the equine literature to solidify or contrast the current AAEP guidelines of core vaccines, and to suggest future research directions in the equine vaccine field considering small companion animal strategies and the current available resources in equine literature.

Repeated nasopharyngeal lavage predicts freedom from silent carriage of Streptococcus equi after a strangles outbreak

Background

The value of repeated nasopharyngeal lavage (NPL) to detect silent carriers of Streptococcus equi has not been investigated.

Hypothesis/Objectives

Determine if results of serial testing for S. equi by NPL predicts subsequent true carrier status as determined by both NPL and guttural pouch lavage.

Animals

An outbreak of strangles with 100% morbidity in 41 mature Icelandic horses was followed prospectively to investigate development of silent carriers. All were initially positive to S. equi on NPL. The farm was closed to horse movement during the entire study.

Methods

Prospective observational study. Testing for S. equi was performed by NPL at weeks 18, 28, 29, and 30 postindex case and subsequently at week 45 by both NPL and guttural pouch lavage. Carrier status at week 45 was compared to results obtained at weeks 18, 28, 29, and 30. Descriptive statistics were calculated. Comparisons were made using Fisher's exact test or the Freeman‐Halton extension with a P < .05 level of significance.

Results

Of 24 noncarriers at week 45, only 4 horses were negative on all 3 consecutive weekly NPL samples at weeks 28 to 30. However, 10 of the 11 horses with at least 3 negative NPL obtained from weeks 18, 28, 29, and 30 were S. equi‐free at week 45 (P = .03).

Conclusions and Clinical Importance

Repeated NPL on at least 3 separate occasions can assist in predicting S. equi carrier‐free status in horses after recovery from a strangles outbreak.

Differences in the Accessory Genomes and Methylomes of Strains of Streptococcus equi subsp. equi and of Streptococcus equi subsp. zooepidemicus Obtained from the Respiratory Tract of Horses from Texas

Streptococcus equi subsp. equi (SEE) is a host-restricted equine pathogen considered to have evolved from Streptococcus equi subsp. zooepidemicus (SEZ). SEZ is promiscuous in host range and is commonly recovered from horses as a commensal. Comparison of a single strain each of SEE and SEZ using whole-genome sequencing, supplemented by PCR of selected genes in additional SEE and SEZ strains, was used to characterize the evolution of SEE. But the known genetic variability of SEZ warrants comparison of the whole genomes of multiple SEE and SEZ strains. To fill this knowledge gap, we utilized whole-genome sequencing to characterize the accessory genome elements (AGEs; i.e., elements present in some SEE strains but absent in SEZ or vice versa) and methylomes of 50 SEE and 50 SEZ isolates from Texas. Consistent with previous findings, AGEs consistently found in all SEE isolates were primarily from mobile genetic elements that might contribute to host restriction or pathogenesis of SEE. Fewer AGEs were identified in SEZ because of the greater genomic variability among these isolates. The global methylation patterns of SEE isolates were more consistent than those of the SEZ isolates. Among homologous genes of SEE and SEZ, differential methylation was identified only in genes of SEE encoding proteins with functions of quorum sensing, exopeptidase activity, and transitional metal ion binding. Our results indicate that effects of genetic mobile elements in SEE and differential methylation of genes shared by SEE and SEZ might contribute to the host specificity of SEE.

IMPORTANCE Strangles, caused by the host-specific bacterium Streptococcus equi subsp. equi (SEE), is the most commonly diagnosed infectious disease of horses worldwide. Its ancestor, Streptococcus equi subsp. zooepidemicus (SEZ), is frequently isolated from a wide array of hosts, including horses and humans. A comparison of the genomes of a single strain of SEE and SEZ has been reported, but sequencing of further isolates has revealed variability among SEZ strains. Thus, the importance of this study is that it characterizes genomic and methylomic differences of multiple SEE and SEZ isolates from a common geographic region (viz., Texas). Our results affirm many of the previously described differences between the genomes of SEE and SEZ, including the role of mobile genetic elements in contributing to host restriction. We also provide the first characterization of the global methylome of Streptococcus equi and evidence that differential methylation might contribute to the host restriction of SEE.

CLINICAL AND MICROBIOLOGICAL CHARACTERIZATION OF LYMPH NODE ABSCESSATION IN PUP AND YEARLING CALIFORNIA SEA LIONS (ZALOPHUS CALIFORNIANUS) UNDERGOING REHABILITATION IN A MARINE MAMMAL CENTER

Severe focal to multifocal abscessation of the axillary and inguinal lymph nodes is an important cause of morbidity and mortality in stranded pup and yearling California sea lions (Zalophus californianus; CSLs) at The Marine Mammal Center (TMMC). A retrospective case review was conducted of all pup and yearling CSLs with axillary and/or inguinal lymph node abscesses admitted to this California rehabilitation center between January 2015 and December 2019 (n = 162). Clinical data and cultured isolates were evaluated to (1) characterize the clinical syndrome, (2) report isolated pathogens, and (3) investigate factors associated with clinical outcome (survival to release versus death). Of the 162 CSLs admitted with at least one axillary or inguinal lymph node abscess, almost all were in poor body condition, and overall mortality rate was 63% (102 of 165). Mortality rate was lower for animals presenting with a single abscess and abscess(es) in the inguinal location only; odds of death were significantly lower for animals that had their abscesses surgically drained (P = 0.029) and those that received antimicrobials (P = 0.037). Hematology and serum chemistry parameters at the time of abscess diagnosis reflected inflammation and malnutrition. Radiographic findings associated with abscesses from 45 cases included soft tissue swelling (n = 40), intralesional gas (n = 19), and osteomyelitis (n = 3). Ninety bacterial isolates were recovered from aerobic (n = 48) and anaerobic cultures (n = 17), 48.9% of which were gram negative. The most common gram-negative organisms were Escherichia coli (n = 15), Proteus spp. (n = 8), and Bacteroides ureolyticus (n = 7), and the most common gram-positive organisms were Streptococcus phocae (n = 10) and Staphylococcus spp. (n = 9). Management of lymph node abscesses via surgical drainage and multimodal systemic antimicrobial therapy with a broad-spectrum of activity may be considered to improve survival of these cases.

Occurrence and Antimicrobial Susceptibility Profiles of Streptococcus equi subsp. zooepidemicus Strains Isolated from Mares with Fertility Problems

Streptococcus equi subsp. zooepidemicus (S. zooepidemicus), is a β-hemolytic Streptococcus belonging to the Lancefield group C; it is a rare human pathogen, but in horses, it is frequently associated with endometritis. This study aimed to isolate S. zooepidemicus strains, associated with bacterial endometritis in mares, and to define their antimicrobial resistance profile. Twenty-three isolates were recovered from one hundred ninety-six equine uterine swabs (11.7%). Bacterial identification was carried out by Api 20 Strep and confirmed by matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS), while antimicrobial susceptibility testing was performed by disk diffusion method on Muller Hinton agar plates. The antibiotic resistance profiles of the isolates revealed a high percentage of resistance to amikacin (95.6%), ampicillin (73.9%) and tetracycline (69.6%), while ceftiofur and ceftriaxone were highly effective with 82.6% and 78.3% of the isolates inhibited, respectively. An intriguing value of resistance to penicillin (34.8%), which represents the first-choice antibiotic in equine S. zooepidemicus infections, was observed. Furthermore, a high prevalence of multidrug-resistant strains (82.6%) was recorded. Continuous surveillance of this potential zoonotic pathogen and an appropriate antimicrobial stewardship program with the promotion of correct use of antimicrobials, after a proper diagnosis, are needed to allow an effective therapy.

Surveillance of strangles in UK horses between 2015 and 2019 based on laboratory detection of Streptococcus equi

BACKGROUND

Previously national surveillance data for monitoring strangles (Streptococcus equi infection) in UK horses was limited. Improved awareness and knowledge of positive diagnoses would permit the optimisation of biosecurity protocols, decreasing the prevalence of strangles.

METHODS

Seven UK laboratories reported positive strangles diagnoses between 1 January 2015 and 31 December 2019 based on identifying Streptococcus equi via agent detection assays from field-based practitioner-submitted samples. Associated clinical history and animal signalment were collected where provided, and descriptive analysis undertaken.

RESULTS

Within the study period, 1617 laboratory-confirmed diagnoses occurred from samples submitted by 315 veterinary practices. Of these, 51.6% were swabs and 44.0% guttural pouch lavages. Diagnoses were primarily based on qPCR alone (59.6%), qPCR and culture (35.8%), or culture alone (4.6%). A total of 1791 clinical signs were reported for 713 diagnoses, where nasal discharge (31.3%) and pyrexia (20.5%) were most frequently reported. Regions with the highest number of diagnoses included North Yorkshire (n = 75, 4.6%), Staffordshire (n = 71, 4.4%) and West Sussex (North East) (n = 63, 3.9%).

CONCLUSION

This study presents important insights into the diagnosis and clinical features of strangles in UK horses, even though limited and/or missing clinical history and signalment on laboratory submission forms restricts the completeness of the data.

Home Sweet Home: New Insights Into the Location of Equine Premises in France and Keeping Habits to Inform Health Prevention and Disease Surveillance

Identifying and tracking equines are key activities in equine health prevention. France is one of the few European countries with an operational centralized database that records information on equines, owners, and keepers but not on the location and keeping conditions of equines. The objective of our study was to collect information on keeping habits of equines and the relative location of a wide range of equines, owners, and keepers and discuss their implication for surveillance and control of outbreak improvement. A national email survey was conducted among the 1.9% of people registered as owners and 8.2% of people registered as keepers in the French national equine identification database having given their agreement to be contacted by email. It led to the collection of information from 728 owners, 121 keepers, and 2,669 owner-keepers. Most of them housed their equines in a single commune (smallest geographic administrative unit in France) at their home as private individuals. The distance between the communes of residence and of holding was, in most cases (including 79% of owners in the owner survey, 89.5% of the keepers in the keeper survey, and about 94% of the owner-keepers in both surveys), less than 30 km. More than half of the keepers kept a maximum of five equines and the majority with two different uses/destinations together, mostly leisure-retirement, leisure-breeding, leisure-sport, and sport-breeding. The main limitation of the study was that a relatively limited number of people (n = 3518) were reachable due to the low availability of an email address and contact agreement. Nonetheless, the findings provide an overview of how equines are kept by non-professional owners and keepers and complements information usually collected by the French riding institute. Additionally, information collected is very helpful to determine a realistic estimate of the spatial distribution of equines in France. This information is very important for the equine sector, for demographic knowledge and also improvement of surveillance plans and control measures and for the management and monitoring of health events to limit the spread of diseases.

Challenges in navigating molecular diagnostics for common equine respiratory viruses

Equine respiratory viruses remain a leading cause of equine morbidity and mortality, with the resurgence of certain infections, an increasing population of elderly, more susceptible horses, the growth of international equine commerce, and an expansion in geographic distribution of pathogens. The focus of rapid diagnosis of infectious diseases has also shifted recently, with the appearance and increasing importance of nucleic acid amplification-based techniques, primarily polymerase chain reaction (PCR), at the expense of traditional methods such as clinical microbiology. While PCR is fast, reliable, cost-effective, and more sensitive than conventional detection methods, careful interpretation of diagnostic test results is required, taking into account the clinical status of the patient, sample type, assay used and biological relevance of the detected viruses. The interpretation of common equine respiratory viruses such as influenza virus (EIV), alpha herpesviruses (EHV-1, EHV-4), arteritis virus (EAV) and rhinoviruses (ERAV, ERBV) is straight forward as causality can generally be established. However, the testing of less-characterized viruses, such as the gamma herpesviruses (EHV-2, EHV-5), may be confusing, considering their well-established host relationship and frequent detection in both diseased and healthy horses. For selected viruses, absolute quantitation (EHV-1 and EHV-4) and genotyping (EIV and EHV-1) has allowed additional information to be gained regarding viral state and virulence, respectively. This information is relevant when managing outbreaks so that adequate biosecurity measures can be instituted and medical interventions can be considered. The goal of this review is to help the equine practitioner navigate through the rapidly expanding field of molecular diagnostics for respiratory viruses and facilitate the interpretation of results.

Vancomycin resistant Streptococcus equi subsp. equi isolated from equines suffering from respiratory manifestation in Egypt

Background and Aim:

Upper respiratory tract infections are common in horses and can be caused by a variety of pathogens, mainly Streptococcus equi subsp. equi, which are a significant equine pathogen causing major health issues as well as financial losses to the equine industry. This study aimed to determine the prevalence of Streptococcal bacteria in equines in Egypt, and characterize vancomycin-resistant S. equi subsp. equi phenotypically and genotypically.

Materials and Methods:

S. equi subsp. equi was isolated from internal nares of horses. All strains were confirmed by polymerase chain reaction-based detection of Streptococcus genus-specific 16S rRNA, sodA and seeI genes. Antibiotic susceptibility was determined phenotypically using the disk diffusion method. Genotypic detection of antibiotic resistance genes was performed by analyzing as b-lactamase resistance (blaZ), tetracycline resistance (tetK), vancomycin resistance (vanA), and chloramphenicol resistance (fexA).

Results:

Eight streptococcal isolates were confirmed as S. equi subsp. equi. The genotypic characterization of antibiotic resistance showed resistance to vanA and tetK, with a frequency of 87.5% and 12.5%, respectively, while the frequency of sensitivity was 100% for blaz gene and fexA gene.

Conclusion:

In this study, we assessed vancomycin-resistant S. equi subsp. equi from equines suffering from respiratory manifestation in Egypt.

THREE CASES OF ACUTE BACTERIAL SEPSIS IN PYGMY HIPPOPOTAMUS (CHOEROPSIS LIBERIENSIS) CALVE SIBLINGS

A multiparous pygmy hippopotamus (Choeropsis liberiensis) dam produced three consecutive calves that died acutely at 13-15 wk of age from bacterial sepsis, for which diagnostic and therapeutic intervention was not possible. Streptococcus iniae (Cases 1 and 3), Escherichia coli (Case 2), and an unidentified member of the family Pasteurellaceae (Case 1) were identified in postmortem tissues through bacterial culture followed by standard and molecular identification methods. After the loss of two calves, a series of vaccinations were administered to the dam during the third pregnancy to enhance transplacental and colostral transfer of antibodies to the calf. The third calf did not survive, and the source of the bacterial infection in these three calves was undetermined. Prior to and after the birth of the fourth calf, nutritional and nutraceutical supplements were provided to the dam and calf. Additionally, pest control around the barn was enhanced. The fourth calf survived. Pygmy hippopotamus calves at the age of 13-15 wk may have increased susceptibility to bacterial infection, possibly due to waning maternally derived immunity. The findings in these cases, combined with a previous association of S. iniae in pygmy hippopotamus deaths, suggest that this bacterium is an especially important pathogen of the endangered pygmy hippopotamus.

Streptococcus equi-derived extracellular vesicles as a vaccine candidate against Streptococcus equi infection

Streptococcus equi subspecies equi is a pathogenic bacterium that causes strangles, a highly contagious respiratory infection in horses and other equines. The limitations of current vaccines against S. equi infection warrants the development of an affordable, safe, and effective vaccine. Because gram-positive extracellular vesicles (EVs) transport various immunogenic antigens, they are attractive vaccine candidates. Here, we purified the EVs of S. equi ATCC 39506 and evaluated them as a vaccine candidate against S. equi infection in mice. As an initial step, comparative proteomic analysis was performed to characterize the functional features of the EVs. Reverse vaccinology and knowledge-based annotations were then used to screen potential vaccine candidates (PVCs) for S. equi ATCC 39506. Finally, 32 PVCs were found to be enriched in the EV fraction, suggesting the usefulness of this fraction as a vaccine. Importantly, a significantly higher survival rate after S. equi infection was detected in mice immunized with S. equi-derived EVs via the intraperitoneal route than in mice immunized with heat-killed bacteria. Of note, immunoprecipitation-mass spectrometry results validated various immunogenic antigens within the EV proteome. In conclusion, our results suggest that S. equi-derived EVs can serve as a vaccine candidate against S. equi infection.

Differences in the genome, methylome, and transcriptome do not differentiate isolates of Streptococcus equi subsp. equi from horses with acute clinical signs from isolates of inapparent carriers

Streptococcus equi subsp. equi (SEE) is a host-restricted bacterium that causes the common infectious upper respiratory disease known as strangles in horses. Perpetuation of SEE infection appears attributable to inapparent carrier horses because it neither persists long-term in the environment nor infects other host mammals or vectors, and infection results in short-lived immunity. Whether pathogen factors enable SEE to remain in horses without causing clinical signs remains poorly understood. Thus, our objective was to use next-generation sequencing technologies to characterize the genome, methylome, and transcriptome of isolates of SEE from horses with acute clinical strangles and inapparent carrier horses—including isolates recovered from individual horses sampled repeatedly—to assess pathogen-associated changes that might reflect specific adaptions of SEE to the host that contribute to inapparent carriage. The accessory genome elements and methylome of SEE isolates from Sweden and Pennsylvania revealed no significant or consistent differences between acute clinical and inapparent carrier isolates of SEE. RNA sequencing of SEE isolates from Pennsylvania demonstrated no genes that were differentially expressed between acute clinical and inapparent carrier isolates of SEE. The absence of specific, consistent changes in the accessory genomes, methylomes, and transcriptomes of acute clinical and inapparent carrier isolates of SEE indicates that adaptations of SEE to the host are unlikely to explain the carrier state of SEE. Efforts to understand the carrier state of SEE should instead focus on host factors.

Antimicrobial prescribing patterns in equine ambulatory practice

Antimicrobial resistance is one of the most important public health risks facing our world today. Antimicrobials are commonly prescribed in equine veterinary medicine, but limited information exists documenting their use in practice. The goal of this study was to investigate antimicrobial prescription patterns in regards to prescription frequency, duration, drug class, clinician and affected body system in an equine ambulatory setting via retrospective analysis of billing and electronic medical records. Risk factors associated with antimicrobial prescription including the nature of the visit, submission of a culture, body system affected and clinician were assessed using multivariable regression. We found that antimicrobials were prescribed in 8.5 % of visits with a median number of 3.5 (IQR 0.8-12.2) animal-defined daily doses (ADD), defined as the number of daily doses of all antimicrobials prescribed to a patient at a single visit. Aminoglycosides were the most common class of antimicrobials prescribed and trimethoprim sulfamethoxazole was the most common drug prescribed overall. Amikacin was primarily used for patients presenting with musculoskeletal signs, and the median number of ADDs for visits where amikacin was prescribed was 1 (IQR 0.9-1.9), while the median number of antimicrobial ADDs for all other visits was 4.4 (IQR 0-14.1). Statistically significant differences in antimicrobial use patterns existed across clinicians, months, years and affected body systems. Horses presenting with ocular (OR 1199; 95 % CI 204-7,037; p < 0.001) and integumentary (OR 365; 95 % CI 87.2-1532; p < 0.001) signs were most likely to be prescribed an antimicrobial. Emergency visits (OR 5.61; 95 % CI 3.19-9.89; p < 0.001) and submission of a bacterial culture (OR 3.58; 95 % CI 2.11-6.09; p < 0.001) were associated with an increased likelihood of an antimicrobial prescription. This observational study was the first to quantitatively characterize antimicrobial use patterns in equine ambulatory practice in the United States, which is an important step needed to determine appropriateness of use and develop and evaluate antimicrobial stewardship guidelines.

Respiratory Distress in the Adult and Foal

Respiratory distress in the horse and foal is an emergency. Managing equine respiratory distress in the field starts with appropriate assessment of the patient to determine whether the breathing obstruction stems from the upper or lower respiratory tract or is nonrespiratory in origin. From a thorough, but efficient, physical examination to point-of-care ultrasound and endoscopy, the veterinarian has many tools in the field to help diagnose the patient.

Diagnostic testing patterns for Streptococcus equi subsp. equi in Ontario horses during the years 2008 to 2018

This retrospective study describes testing patterns and the incidence of Streptococcus equi subsp. equi in Ontario to assess the utility of laboratory data for surveillance purposes. Laboratory records for equine infectious disease test submissions were extracted from the Animal Health Laboratory (AHL) at the University of Guelph for the years 2008 to 2018. Yearly and seasonal trends in S. equi testing and the proportion of tests that returned positive results were assessed. The number of samples submitted for S. equi testing decreased over the 11-year period (odds ratio = 0.96, 95% confidence interval: 0.92 to 0.999; P = 0.04). A generalized linear model identified a significant seasonal effect for animals recognized as clinically ill, with the highest test positivity noted in the winter. Although this study identified important trends in the incidence of S. equi in Ontario, the variability in information accompanying test submissions made the data challenging to interpret, highlighting the need for more complete diagnostic submission data for S. equi.

The clinical and histopathologic effects of potentiated chlorhexidine in the upper respiratory tract of horses

OBJECTIVE

To describe the bactericidal and fungicidal properties of a 0.0005% chlorhexidine (CHD) solution potentiated with EDTA-Tris buffers (CHD-EDTA-Tris) and evaluate the safety of 0.0005% CHD-EDTA-Tris in the upper respiratory tract (URT) of normal horses.

STUDY DESIGN

Clinical, prospective study.

ANIMALS

Eight healthy, skeletally mature horses.

METHODS

In vitro-serial dilutions of CHD-EDTA-Tris and EDTA-Tris alone were evaluated for bactericidal and fungicidal activity against Aspergillus fumigatus, Escherichia coli, Staphylococcus aureus, Streptococcus equi subspecies ssp. equi, Streptococcus equi ssp. zooepidemicus, and Pseudomonas aeruginosa. In vivo-eight healthy horses were topically treated twice with 30 ml of 0.0005% CHD-EDTA-Tris. Mucosal samples from each location were evaluated for the presence of inflammation or pathologic lesions.

RESULTS

Solutions containing CHD were superior in fungal and bacterial killing to those without. In vitro-a 0.005% CHD-EDTA-Tris was 100% effective against all bacterial and fungal species evaluated, while a 0.0005% CHD-EDTA-Tris was less efficacious against A. fumigatus and S. equi ssp. equi. In vivo-a 0.0005% CHD-EDTA-Tris did not cause any clinical, gross, or histologic abnormalities when topically applied to the equine URT.

CONCLUSIONS

A 0.0005% CHD-EDTA-Tris was highly effective for killing of common bacterial and fungal isolates in the equine upper respiratory tract. Short-term topical treatment of the equine URT with dilute CHD did not cause gross or histological inflammation in the tissue.

CLINICAL SIGNIFICANCE

A 0.0005% CHD solution with EDTA-Tris should be considered for treatment of clinically relevant inflammatory or infectious conditions or in the URT of the horse.

Nicoletella semolina in the airways of healthy horses and horses with severe asthma

Background

Nicoletella semolina was identified in the airways of horses and its low prevalence could be because of its difficult differentiation from other Pasteurellaceae.

Objectives

To develop a molecular method for the identification of N. semolina and to evaluate its prevalence in the mouth and the airways of healthy and severe asthmatic horses.

Animals

Six healthy and 6 severely asthmatic horses in phase I, 10 severely asthmatic horses in phase II, and 10 healthy horses in phase III.

Methods

Cohort (phases I and II) and cross‐sectional (phase III) studies. Quantitative polymerase chain reaction primers targeting the sodA gene were optimized. N. semolina was quantified in oral and nasal washes and in bronchoalveolar lavage fluid (BALF; phase I, sampled twice), in nasal washes and BALF (phase II, sampled twice), and in nasal washes (phase III).

Results

N. semolina was found in the nose of 5, 10, and 9 horses in phases I, II, and III, respectively (first sampling for phases I and II). Six BALF from 5 different horses were positive for N. semolina in phase II. In phase I, there was no significant difference in the nasal loads of healthy horses (median (range): 2.04 × 10⁴ copies/mL (0‐2.44 × 10⁵)) and asthmatic horses in exacerbation (3.75 × 10² (0‐4.84 × 10⁶); Wilcoxon's rank sum test, P = .57).

Conclusions and Clinical Importance

N. semolina is commonly found in the airways of horses. The potential pathogenicity of N. semolina remains to be elucidated, but the molecular technique we developed will facilitate future studies.