Equine Veterinary Journal最新文献

Background: Rhodococcus equi causes pneumonia in young foals, but disease susceptibility and severity vary. Cortisol and vitamin D modulate immune responses and cytokine production during bacterial infection, and altered concentrations are associated with sepsis in neonatal foals. We hypothesised an age and disease effect on circulating steroid hormone concentrations in foals, and that differences in cytokines and steroid hormone concentrations would predict disease severity in pneumonic foals.

Objectives: To investigate circulating concentrations of various cytokines, cortisol and vitamin D as predictors of individual disease severity in R. equi foals.

Study design: Prospective cohort.

Methods: Blood samples were collected from 200 initially healthy foals on a pneumonia-endemic breeding farm after birth and at 1, 2, 4, 8, 12 and 20 weeks of age. Health status was tracked weekly. At weaning (20 weeks), foals were divided into three health groups: (1) foals that remained healthy, (2) foals that developed subclinical, self-resolving pneumonia and (3) foals that developed clinically apparent pneumonia necessitating antimicrobial treatment. Foals were randomly selected (n = 30/group) for cortisol, vitamin D and cytokine (TNFα, IL-4, IL-10, IL-17 and interferon-gamma [IFN-γ]) analysis using validated assays.

Results: We observed disease-associated differences for IFN-γ at 4 weeks (χ² = 13.91; df = 2; p = 0.001) and 20 weeks (χ² = 10.0; df = 2; p = 0.007) and age-associated differences for cortisol, vitamin D and other cytokines (p < 0.001).

Main limitations: Causative agent not identified, frequency and timing of sample collection may have impacted results, and systemic cytokine concentrations may not accurately reflect cytokine availability and activity at the tissue level.

Conclusions: Periodic measurement of circulating steroid hormones and cytokines from birth to weaning was not predictive of pneumonia susceptibility and severity in foals on a farm with endemic pneumonia. Disease-associated IFN-γ differences warrant further investigation.

Background: Equine trypanosomiasis is a neglected protozoal disease.

Objectives: To answer the study question: In equines what are the effects of disease management of trypanosomiasis on disease severity (individual level) and disease prevalence (population level) compared to no intervention?

Study design: Systematic review.

Methods: Studies were identified that described management of naturally occurring equine trypanosomiasis in any country following 'Preferred Reporting Items for Systematic Reviews and Meta-analyses' using eight international databases (1980-2022). Risk of bias was assessed using ROBINS-I. Data synthesis was descriptive.

Results: Thirty studies were included (9 case reports, 5 case series, 15 cohorts, 1 randomised non-inferiority trial). Risk of bias was 'serious' (22/30), 'moderate' (7/30), 'low' (1/30). Heterogeneity was high. Disease severity (individual): Trypanosoma evansi: all evaluated trypanocides were effective in blood parasitaemia clearance (weak evidence). Clinical relapses were common (n = 60/241 equines treated; 25%) (strong evidence). Efficacy was poor once neurological signs were present (n = 12/19 equines; 63% mortality) (strong evidence). Trypanosoma equiperdum: a combination protocol could be curative before CNS invasion (weak evidence). Tsetse transmitted trypanosomiasis: Treatment of haemolymphatic disease with isometamidium or diminazene resulted in a positive clinical response (strong evidence). New/recrudescing infections were common in some regions (strong evidence). Trypanosoma vivax: treatment with high-dose diminazene had a poor clinical outcome (weak evidence). Disease prevalence (population): a multifaceted control programme was effective in reducing disease prevalence (weak evidence). Early (<2 days post-infection) treatment was more effective (weak evidence). Reported side effects were uncommon (n = 70/7888 equines; 1%) (strong evidence). Isometamidium chloride (0.5 mg/kg i.v.) can cause a shock response (13%; range 10-14; n = 14/105) (strong evidence).

Main limitations: Publication bias, heterogeneity, descriptive data.

Conclusions: Short-term trypanocide response for haemolymphatic disease was positive but optimisation of treatment protocols is required to reduce relapse and combat neurotrypanosomiasis. Reliance on trypanocidal treatment alone is common. Side effects are rare but can be severe.

Background: Based on human studies, surgical antimicrobial (AMD) prophylaxis (SAP) beyond 24 h is unnecessary and potentially detrimental.

Objective: To compare clinical and microbiological outcomes in patients receiving 24- or 72-h of SAP for colic surgery.

Study design: Prospective randomised clinical trial.

Methods: Horses that recovered from colic surgery were considered. Exclusion criteria were (1) age <2 years; (2) Miniature Horses, pony, and draught breeds; (3) azotaemia; (4) recent hospitalisation, colic surgery, or AMDs; (5) local AMD administration. Eligible horses were randomly assigned to receive SAP with potassium penicillin and gentamicin for 24- or 72-h. Clinical data and complications were compared between SAP groups. Admission and discharge faecal samples from a subset of horses (N = 49) underwent shotgun metagenomic sequencing on an Illumina platform. Host reads were filtered by aligning to reference genomes using the Burrows-Wheeler Aligner, and taxonomic classification was performed with kraken2. Sequencing reads were aligned to the Comprehensive Antimicrobial Resistance Database (CARD)5 and characterised using the AMR++ pipeline. The microbiome/resistome was characterised and compared between SAP groups over time.

Results: One hundred and forty horses completed the study (24-h N = 71 and 72-h N = 69). The only clinical variable that was different between SAP groups was age (24-h median age 16 [IQR 9, 20] and 72-h 12 [6, 18] years, p = 0.03). There was no significant difference between groups for any complications including incisional infection (24-h 17 [95% CI 10-27]% and 72-h 16 [9-26]%, p = 0.9). Time was the main driver of changes in the microbiome/resistome: alpha diversity decreased while AMD resistance genes associated with administered AMD increased between admission and discharge. Discharge beta-lactam resistance genes were significantly higher in the 72-h than the 24-h group.

Main limitations: Single hospital, small numbers for complications, clinicians not blinded to SAP group.

Conclusions: SAP for 24-h is recommended for horses undergoing colic surgery.

Background: To date, relationships between pre-covering endometrial swab cytology and bacteriology and fertility outcomes in Thoroughbred broodmares in the United Kingdom are unknown and could aid clinical decision making.

Objectives: To investigate associations between cytology and bacteriology findings from the last endometrial swab taken in the breeding season (15 February to 15 July) and live-foal rates (predicted mean probability of producing a live foal) in UK Thoroughbred broodmares.

Study design: Retrospective cohort study.

Methods: Endometrial cytology and bacteriology findings were extracted from laboratory records for all last-swabs submitted between 2014 and 2020. Mares' status, age and foaling outcome were collected from publicly available data sources. Live-foal rates were estimated for reported categories of cytology and bacteriology findings using a multivariable logistic regression model with mare and farm fitted as random effects, while adjusting for mares' age, status, number of previous swabs submitted in that season and any interactions. Pairwise comparisons with Bonferroni correction evaluated between-category live-foal rate differences.

Results: Data were available from 7691 last swabs from 3579 mares on 196 farms. In contrast to other categories of isolate, mares with a profuse growth of Escherichia coli had significantly lower (p = 0.005) live-foal rates (59.1%; 95% confidence interval (CI) 43.7-74.5) compared to those with no growth (80.9%; 95% CI 79.2-82.6). There was interaction between mares' age and cytology. In mares >12 years, significant reductions in live-foal rates (p < 0.05 in pairwise comparisons) were observed between mares with >30% polymorphonuclear: endometrial cells/high power field at cytological examination and mares with ≤0.5% PMN, a finding absent in mares ≤12 years.

Main limitations: The use of unguarded swabs and absence of clinical information.

Conclusions: Results highlight complexities to consider when interpreting endometrial swab cytology findings and a subset of mares with a profuse growth of E. coli in which knowledge gaps exist around the aetiologies underlying their poorer fertility outcomes.

Background: Antimicrobial resistance (AMR) is increasingly recognised in equine medicine. Antimicrobial use (AMU) is a key driver of AMR.

Objectives: To pilot a point prevalence survey (PPS), based on the Global-PPS used in human hospitals, to obtain data on antibiotic prescribing and AMR in equine hospitals and to identify targets for improvement in AMU.

Study design: Point prevalence survey.

Methods: Eight equine hospitals located in Australia, Belgium, South Africa, the United Kingdom and the United States were recruited. Data on AMU were collected from all in-patients on antibiotic treatment at 08h00 on four selected study days throughout the study year (2022).

Results: In total, 742 patients, 310 (41.8%) surgical and 432 (58.2%) nonsurgical cases, were evaluated and 58.7% (182/310) surgical and 25.9% (112/432) nonsurgical patients were on antibiotics. The most prescribed antibiotics were penicillin, gentamicin and trimethoprim sulfonamides. In 45.2% (215/476) of prescriptions, use was prophylactic. Therapeutic use was based on a biomarker in 48.8% (127/260) of treatments. A sample was submitted for culture in 56.9% (148/260) of therapeutic treatments. A positive culture result was reported from 49.3% (73/148) of samples, with an antibiogram available for 90.4% (66/73) of the positive cultures. An antibiotic use stop/review date was not recorded in 59.5% (283/476) of uses.

Main limitations: This PPS was a pilot study with a relatively small sample size and likely does not reflect AMU in all types of equine hospitals in all geographic locations.

Conclusions and clinical relevance: The PPS identified multiple ways in which antibiotic prescribing could be improved. Targets identified for stewardship interventions included empiric use of European Medicines Agency Category A and B antibiotics, the high prevalence of prophylaxis and the lack of use of a stop/review date. The survey could be used as a repeatable tool to assess stewardship interventions in equine hospitals.

Background: Antimicrobial resistance (AMR) is an increasingly serious threat to human and animal health. Antimicrobial use (AMU) in horses is gathering research interest, although there remain significant evidence gaps. Currently, there is scant qualitative research into equine owners' use of antimicrobials, specifically antibiotics, hindering the design of evidence-based stewardship interventions and policies.

Objectives: To understand Welsh equine owners' views and behaviours relating to antimicrobial usage.

Study design: Cross sectional survey and qualitative data collection and analysis.

Methods: An online survey (n = 319) and semi-structured interviews (n = 21) were conducted with Welsh equine owners. The survey examined participant knowledge of and relationship with their horse(s), sourcing of antibiotics, owner-vet interactions on antibiotic prescribing, antibiotic usage, and their understanding of AMR. Semi-structured in-depth interviews further explored horse owner perspectives, experiences, and decision-making relating to these areas, to add nuance and depth to quantitative data. Survey data were descriptively analysed, and interview data were coded and qualitatively analysed using a thematic approach.

Results: Welsh equine owners regarded their horses as members of the family (84.8%). Most sourced antibiotics from their vet (68.9%) with a minority (5.1%) never having done so or having used antibiotics left over (16.6%) and 13.6% would consider changing veterinary practice if they did not receive antibiotics when they requested them. Interview data suggest that antibiotic use was shaped by (i) key relationships of care (human-animal and owner-vet); (ii) competing priorities (treatment need versus ease of administration); and (iii) imperfect comprehension (education, information, AMU/AMR knowledge).

Main limitations: Potential self-selection bias of respondents due to the voluntary nature of participation.

Conclusions: This study highlights variations in the horse-owner relationship, conflicting priorities involved in horse ownership, and the quality of vet-client relationships which may influence treatment decision-making. It raises some concerns about the sourcing of antibiotics and variable understanding of AMR, with important implications for antimicrobial stewardship and educational priorities.

Background: Strangles, caused by Streptococcus equi subspecies equi (S. equi), is a prevalent infectious disease of horses. This is the first report on the use of a new vaccine, Strangvac, in a natural outbreak of strangles.

Objectives: To measure the effects of Strangvac vaccination during an outbreak of strangles at a Swedish farm.

Study design: Longitudinal cohort study.

Methods: Healthy horses (n = 17) were vaccinated on day 0, which occurred 23 days after strangles was first confirmed in three unvaccinated horses on the same farm. Blood serum samples were collected on day 0, day 28 and day 489. A combined iELISA was used to measure total antibody titres towards the components of the vaccine. Specific antibody levels in blood sera to S. equi were also quantified using the antigen A/C iELISAs, which can differentiate infected from vaccinated animals. Clinical signs were monitored.

Results: All vaccinated horses had increased total antibody titres to CCE, Eq85 and/or IdeE from day 0 (2.50 ± 0.28) to day 28 (3.63 ± 0.31; p < 0.0001). Seropositivity in the antigen A/C iELISA was noted in 8/17 healthy horses on day 0 (prior to vaccination), in 9/16 vaccinates on day 28, and in 3/3 unvaccinated clinical cases on day 28. None of the vaccinated horses developed strangles, but 5/7 of the original vaccinated horses tested seropositive in the A/C iELISA on day 489, which was 377 days after their third vaccination.

Main limitations: Aside from the three unvaccinated clinical cases, no unvaccinated control group was available.

Conclusions: Despite adherence to recommended biosecurity measures, serological evidence of exposure to S. equi was demonstrated in half of the vaccinated horses. Notably, all horses vaccinated during the outbreak responded to the vaccine components and remained healthy, suggesting a protective effect of vaccination of healthy horses with Strangvac in outbreak situations.

Background: Equid alphaherpesvirus 1 (EHV-1) remains a major concern for the equine industry, with recent outbreaks at international equestrian events highlighting the need for improved surveillance during competitions.

Objectives: To investigate EHV-1 and -4 presence in shared airspaces and environmental surfaces in direct contact with horses at international equestrian events; and to evaluate air sampling as a surveillance alternative to individual horse testing.

Study design: Cross-sectional field study.

Methods: Air (37) and surface samples (205) were collected from temporary stabling facilities across six events in Spain and 2 in the United States at different seasons over 10 months. Viral DNA (genomic copies) was measured and quantified by quantitative and digital PCR. During all the Spanish events, we sampled the air twice, early evening and night.

Results: EHV-1 was frequently detected in the air in 20/28 samples in Spain, in all 3 samples from Florida and in 3/6 samples from Kentucky. Surface samples were positive 15.6% in Spain, 26.3% in Florida and 0.0% in Kentucky. EHV-4 was found in air samples at rates of 12/28 in Spain, 5/6 in Kentucky and 0/3 in Florida, with surface detection of 1.6% in Spain and 7% in Kentucky. No significant differences were observed between daytime (high activity) and nighttime (low activity) airborne viral loads, suggesting that daytime horse movement and management practices had minimal impact on detection levels in our study. A positive correlation (Cohen's K = 0.401) and moderate agreement between surface and air positivity for EHV-1 emphasised the potential of air sampling as a non-invasive, cohort-based surveillance tool.

Main limitations: Virus isolation was not used; only molecular detection was employed, which limits conclusions about transmission risk.

Conclusions: These findings underscore the utility of air sampling for early EHV-1 detection at mass gatherings; although further validation is needed to connect genomic detection to active shedding and viral infectivity.

Background: Despite routine vaccination, equine influenza outbreaks occur due to disparities of virus strains between vaccine and field, and immunity gaps between vaccinations.

Objectives: To evaluate whether a combination of adjuvants can enhance immune responses to equine influenza virus (EIV) vaccines.

Study design: In vivo experimental study.

Methods: Eight mixed-breed horses were immunised intramuscularly with a recombinant canarypox-based EIV vaccine, either alone or in combination with monophosphoryl lipid A (MPL) and polyinosinic-polycytidylic acid (poly I:C). A single vaccine dose was administered, and serum samples were collected before immunisation and at 2, 8, and 24 weeks post-immunisation to assess the humoral immune response. Peripheral blood mononuclear cells (PBMCs) were isolated to evaluate immunomodulatory cytokine expression and characterise recall cellular immune responses. Additionally, bone marrow and lymph node cells were analysed to assess memory cell responses.

Results: The combination of MPL and poly I:C significantly enhanced serum IgG antibody concentrations and haemagglutination inhibition (HI) titres against H3N8 A/equine/Kyonggi/SA01/2011 (Florida sub-lineage clade 1) and maintained these for up to 24 weeks post-immunisation. This combination led to increased cytokine mRNA expression and interferon-gamma (IFN-γ) responses in PBMCs. Enhanced memory B cell responses were also observed in the bone marrow and lymph nodes at 8 weeks post-immunisation. MPL and poly I:C induced higher frequencies of CD4⁺ and CD8⁺ T cells following in vitro restimulation with H3N8 EIV.

Main limitations: A viral challenge experiment was not included.

Conclusions: The use of MPL and poly I:C as adjuvants in EIV vaccines significantly improved immune responses by enhancing humoral immunity, memory cell responses, and antigen-specific cellular immunity.