Investigation of the Shedding of Selected Respiratory Pathogens in Healthy Horses Presented for Routine Dental Care

Prevalence and Sequence Analysis of Equine Rhinitis Viruses among Horses in Poland

Equine rhinitis A (ERAV) and B (ERBV) viruses are respiratory pathogens with worldwide distribution. The current study aimed to determine the frequency of infection of ERAV and ERBV among horses and foals at Polish national studs, and to determine genetic variability within the viruses obtained. Virus-specific quantitative RT-PCR assays targeting a 5' untranslated region were used to screen nasal swabs collected from 621 horses at 16 national horse studs from throughout Poland, including 553 healthy horses and 68 horses with respiratory disease. A partial DNA polymerase gene was amplified and sequenced from the qRT-PCR-positive samples. The obtained sequences were analysed using phylogeny and genetic network analysis. None of the nasal swabs were positive for ERAV, whereas ERBV was found in 11/621 (1.78%) samples collected from 10 healthy horses and one foal affected by respiratory disease. Partial DNA polymerase gene sequence variability was correlated with individual horses and studs from which samples were collected when only Polish sequences were analysed, but there was no correlation between country of origin and ERBV sequence when Polish and international sequences were included in the network. The report presents the first detection of ERBV in Poland.

Outbreak of equine herpesvirus 4 (EHV-4) in Denmark: tracing patient zero and viral characterization

BACKGROUND

Equine herpesvirus 4 (EHV-4) causes respiratory disease in horses, and the virus is considered endemic in the global equine population. However, outbreaks can occur when several horses are gathered in relation to shows, competitions, breeding units and at hospitals. In the spring year 2022, an EHV-4 outbreak occurred at the Large Animal Teaching Hospital, University of Copenhagen, Denmark. Nine horses were tested EHV-4 positive during the outbreak, which lasted approx. seven weeks. In addition, a tenth horse "Eq10" tested EHV-4 positive almost three weeks after the last of the outbreak horses tested positive. Detailed clinical registrations were obtained from all ten horses as well as their location and movement during hospitalization. Nasal swabs were obtained throughout the outbreak and tested by qPCR for EHV-4. Additionally, pre- and post-infection sera were tested for the presence of EHV-4 antibodies. Selected samples were characterized by partial and full genome sequencing.

RESULTS

The most common clinical signs of the EHV-4 infected horses during this outbreak were pyrexia, nasal discharge, mandibular lymphadenopathy and increased lung sounds upon auscultation. Based on the locations of the horses, EHV-4 detection and antibody responses the most likely "patient zero" was identified as being "Eq1". Partial genome sequencing revealed that Eq10 was infected by another wild type EHV-4 strain, suggesting that the hospital was able to eliminate the outbreak by testing and reinforcing biosecurity measures. The complete genome sequence of the outbreak strain was obtained and revealed a closer relation to Australian and Japanese EHV-4 strains rather than to other European EHV-4 strains, however, very limited sequence data are available from Europe.

CONCLUSION

The study illustrated the transmission of EHV-4 within an equine facility/hospital and provided new insights into the viral shedding, antibody responses and clinical signs related to EHV-4 infections. Finally, sequencing proved a useful tool in understanding the transmission within the hospital, and in characterizing of the outbreak strain.

In vitro virucidal activity of nebulized citrate-complexed silver nanoparticles against equine herpesvirus-1 and murine norovirus

Viruses can be involved in respiratory disorders in horses, with limited therapeutic options. Citrate-complexed silver nanoparticles (C-AgNP) have shown bactericidal properties after in vitro nebulization. The aim of the present study was to assess the virucidal activity of C-AgNP after in vitro instillation or nebulization on equine herpesvirus-1 (EHV-1) and murine norovirus (MNV), the latter used as surrogate for small non-enveloped viruses. Both viruses were instilled or nebulized with C-AgNP of increasing concentrations, and titres were determined via TCID₅₀ method. We demonstrated efficient inactivation of enveloped EHV-1 following instillation and nebulization of C-AgNP (infectivity losses of ≥ three orders of magnitude). While tenacious MNV was inactivated via 2000 ppm C-AgNP instillation, nebulized C-AgNP did not lead to reduction in MNV titres. Nebulization of C-AgNP may represent a novel virucidal therapeutic approach in horses. Further investigations are needed to assess its safety and effective concentrations for in vivo use.

Investigation of the Frequency of Detection of Common Respiratory Pathogens in Nasal Secretions and Environment of Healthy Sport Horses Attending a Multi-Week Show Event during the Summer Months

Little information is presently available regarding the frequency of the silent shedders of respiratory viruses in healthy sport horses and their impact on environmental contamination. Therefore, the aim of this study was to investigate the detection frequency of selected respiratory pathogens in nasal secretions and environmental stall samples of sport horses attending a multi-week equestrian event during the summer months. Six out of fifteen tents were randomly selected for the study with approximately 20 horse/stall pairs being sampled on a weekly basis. Following weekly collection for a total of 11 weeks, all samples were tested for the presence of common respiratory pathogens (EIV, EHV-1, EHV-4, ERAV, ERBV, and Streptococcus equi ss equi (S. equi)) using qPCR. A total of 19/682 nasal swabs (2.8%) and 28/1288 environmental stall sponges (2.2%) tested qPCR-positive for common respiratory pathogens. ERBV was the most common respiratory virus (17 nasal swabs, 28 stall sponges) detected, followed by EHV-4 (1 nasal swab) and S. equi (1 nasal swab). EIV, EHV-1, EHV-4 and ERAV were not detected in any of the study horses or stalls. Only one horse and one stall tested qPCR-positive for ERBV on two consecutive weeks. All the other qPCR-positive sample results were related to individual time points. Furthermore, only one horse/stall pair tested qPCR-positive for ERBV at a single time point. The study results showed that in a selected population of sport horses attending a multi-week equestrian event in the summer, the frequency of the shedding of respiratory viruses was low and primarily restricted to ERBV with little evidence of active transmission and environmental contamination.

Frequency of Detection of Respiratory Pathogens in Clinically Healthy Show Horses Following a Multi-County Outbreak of Equine Herpesvirus-1 Myeloencephalopathy in California

Actively shedding healthy horses have been indicated as a possible source of respiratory pathogen outbreak, transmission, and spread. Using nasal swabs from clinically healthy sport horses submitted for qPCR testing after an outbreak of equine herpesvirus-1 (EHV-1) myeloencephalopathy (EHM) in the spring of 2022, this study aimed to identify the rate of clinically healthy horses shedding common and less characterized respiratory pathogens within the sport horse population to better understand their role in outbreaks. Swabs were collected during a required quarantine and testing period, according to the United States Equestrian Federation (USEF), and showed return-to-competition requirements. Common respiratory pathogens, such as equine influenza virus (EIV), EHV-4, and equine rhinitis B virus (ERBV), were found at low but stable frequencies within previously reported ranges, whereas EHV-1 and Streptococcus equi subspecies equi (S. equi) were found at or above previously reported frequencies. Less characterized respiratory pathogens, such as EHV-2, EHV-5, and S. equi subspecies zooepidemicus (S. zooepidemicus), were found within previously reported ranges. Common respiratory pathogens, especially EHV-1 following the multiple EHM outbreaks, were found to be circulating in clinically healthy sport horse populations, reflecting their silent transmission. The strategy of quarantine and EHV-1 qPCR testing of clinically healthy horses was successful at eliminating additional EHM outbreaks and facilitating safe return to competition with no reported respiratory disease outbreaks following the subsequent shows in California.

Frequency of detection of respiratory pathogens in nasal secretions from healthy sport horses attending a spring show in California

The objective of this study was to determine detection frequency of respiratory viruses (equine influenza virus (EIV), equine herpesvirus-1 (EHV-1), EHV-2, EHV-4, EHV-5, equine rhinitis A virus (ERAV), ERBV) and bacteria (Streptococcus equi ss. equi (S. equi), S. equi ss. zooepidemicus (S. zooepidemicus)) in 162 nasal secretions and 149 stall swabs from healthy sport horses attending a spring show in California. Nasal and stall swabs were collected at a single time point and analyzed using qPCR. The detection frequency of respiratory pathogens in nasal secretions was 38.9% for EHV-2, 36.4% for EHV-5, 19.7% for S. zooepidemicus, 1.2% for ERBV, 0.6% for S. equi and 0% for EIV, EHV-1, EHV-4 and ERAV. The detection frequency of respiratory pathogens in stall swabs was 65.8% for S. zooepidemicus, 33.5% for EHV-2, 27.5% for EHV-5, 3.3% for EHV-1, 1.3% for EHV-4 and 0% for EIV, ERAV, ERBV and S. equi. Commensal viruses and bacteria were frequently detected in nasal secretions and stall swabs from healthy sport horses. This was in sharp contrast to the subclinical shedding of well-characterized respiratory pathogens. Of interest was the clustering of five EHV-1 qPCR-positive stalls from apparently healthy horses with no evidence of clinical spread. The results highlight the role of subclinical shedders in introducing respiratory pathogens to shows and their role in environmental contamination. The results also highlight the need to improve cleanliness and disinfection of stalls utilized by performance horses during show events.

Molecular Monitoring of EHV-1 in Silently Infected Performance Horses through Nasal and Environmental Sample Testing

While the main goal in the management of an EHM outbreak focuses on identifying early clinical disease in order to physically separate infected horses, little effort is placed towards monitoring healthy horses. The assumption that EHV-1 shedding parallels clinical disease is erroneous, as subclinical shedders have been shown to be actively involved in viral spread. In an attempt to document the frequency of EHV-1 shedders and their impact on environmental contamination, we collected nasal swabs from 231 healthy horses and 203 environmental samples for the testing of EHV-1 by qPCR. Six horses and 28 stalls tested qPCR-positive for EHV-1. There was no association in the EHV-1 qPCR-positive status between nasal and stall swabs. While testing nasal secretions of healthy at-risk horses can detect active shedding at a specific time point, the testing of stall swabs allows to assess the temporal EHV-1 shedding status of a horse. The study results highlight the risk of subclinical EHV-1 shedders and stalls occupied by these horses as sources of infection for susceptible horses. The testing of individual stalls for the presence of EHV-1 may be a more practical approach than the collection of individual nasal swabs for the monitoring and early detection of the circulating virus. The results also highlight the need to improve the cleanliness and disinfection of stalls utilized by performance horses during show events.

Recent advancements in our understanding of equid gammaherpesvirus infections

Equid gammaherpesviruses are ubiquitous and widespread in the equine population. Despite their frequent detection, their contribution to immune system modulation and the pathogenesis of several diseases remains unclear. Genetic variability and the combination of equid gammaherpesvirus strains a horse is infected with might be clinically significant. Initial gammaherpesvirus infection occurs in foals peripartum with latency then established in peripheral blood mononuclear cells. A novel EHV-5 study suggests that following inhalation equid gammaherpesviruses might obtain direct access to T and B lymphocytes via the tonsillar crypts to establish latency. EHV-5 is associated with equine multinodular pulmonary fibrosis, however, unlike with EHV-2 there is currently minimal evidence for its role in milder cases of respiratory disease and poor performance. Transmission is presumed to be via the upper respiratory tract with periodic reactivation of the latent virus in adult horses. Stress of transport has been identified as a risk factor for reactivation and shedding of equine gammaherpesviruses. There is currently a lack of evidence for the effectiveness of antiviral drugs in the treatment of equine gammaherpesvirus infections.

Bacterial Contamination of Equine Dentistry Equipment-Effect of Cleaning and Disinfection

Simple Summary

Some of the equipment used in equine dentistry is difficult to clean and disinfect. Since it is vital to avoid the spread of infections in equine healthcare it is important to develop practical and easy-to-follow methods for cleaning and disinfecting dental equipment. The aim of this study was to investigate hygiene in equine dentistry. Dental equipment and the head support, where horses rest their head during dental care, were sampled for the amount of bacteria between each patient before and after dental care as well as after cleaning and/or disinfecting. The amount of bacteria was, in general, high on dental equipment and the head support after dental procedures. Bacteria were found in different amounts on most of the dental equipment after cleaning or disinfecting, which indicates a risk for spreading infections when using the equipment. For the head support, cleaning and/or disinfecting generally resulted in a reduced amount of bacteria, indicating a lowered risk for spreading infections. There is a great need for evidence-based guidelines on hygiene in equine dentistry to decrease the risk of transmitting infections between patients, facilities, and stables.

Abstract

Equine dentistry has developed immensely and human dental equipment, such as handpieces, are often used. Measures to avoid the spread of infectious microorganisms are important, but this is challenging since handpieces are difficult to decontaminate. Thus, it is necessary to develop effective IPC measures in equine dentistry. The aim of this study was to contribute to the evidence needed for future evidence-based guidelines on IPC by investigating hygiene in equine dentistry. Used handpieces and dummies (i.e., handpieces not used during dental procedure, reflecting environmental bacterial contamination) and the head support were sampled each day before the first patient, for each patient after treatment, and after decontamination. All equipment was sampled with 3M ^TM Swab Samplers and the head support additionally sampled with dip slides. After dental procedures, the detected bacterial load was often high on used handpieces, dummies, and the head support. After decontamination, handpieces did not meet the criteria for high-level disinfected equipment. In all but one case decontamination of the head support resulted in a lowered bacterial load. There is a great need for evidence-based guidelines on hygiene in equine dentistry, including IPC measures, to decrease the risk of spreading infectious microorganisms between patients, facilities, and stables.

Equine antimicrobial therapy: Current and past issues facing practitioners

Equine antimicrobial therapy has advanced over time with the availability of increasing pharmacokinetic and pharmacodynamic studies in horses, allowing for greater evidence-based clinical decision-making. However, many challenges to optimal antimicrobial therapy remain and further research is needed to address these areas. There are a limited number of approved antimicrobials for use in horses, which creates a need for compounded preparations for clinicians. Extra-label drug use is commonplace in equine practice, which warrants continual education of veterinarians about policies and updates. Performance and competitive horses have their own unique concerns when it comes to antimicrobial use and drug testing. In keeping with the use of a broader range of antimicrobials over time, antimicrobial resistance is emerging as an important issue facing veterinary medicine, including equine practice. Another challenge is that of drug interactions and adverse drug events for which there are little scientific data available for horses, especially for critically important diseases such as Rhodococcus equi infection. Finally, much progress has been made in the availability of equine-specific antimicrobial susceptibility break points. These aid clinicians in interpreting culture and susceptibility results and antimicrobial selection. Even with these advances, continuing education and further research are needed in this area.