Antimicrobial prescribing and antimicrobial resistance surveillance in equine practice

Understanding antimicrobial use by equine owners in Wales: Using cross-sectional survey and semi-structured interviews

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.

Influence of antimicrobial prophylaxis in horses undergoing sutured castrations

OBJECTIVE

To investigate the influence of surgical antimicrobial prophylaxis (SAP) on complication rates and surgical site infections (SSI) in horses undergoing sutured castration in a hospital setting.

STUDY DESIGN

Retrospective chart review of a convenience sample.

ANIMALS

A total of 220 colts and stallions admitted for sutured castration.

METHODS

Medical records of sutured castration were assessed for patient characteristics, perioperative and postoperative medications, and postoperative complications within 6 weeks after surgery. The effect of these variables on the occurrence of complications was analyzed using χ2 tests, and the association between SAP use and SSI probability was evaluated.

RESULTS

The median age of horses included in the study was 3 years (range 1-14 years), and the overall complication rate was 10.0% (22/220). Surgical antimicrobial prophylaxis was administered to 62% of the patients (136/220). There were no differences in the overall complication rates, with a 7.1% (6/84) complication rate among horses without SAP (SAP-) and an 11.8% (16/136) rate in those receiving SAP (SAP+) (p = .36). There was no association between the use of SAP and the probability of SSI, with an incidence of 3.6% in SAP- and 4.4% in SAP+ (3/84 and 6/136 respectively) (p = 1.0).

CONCLUSION

Administering SAP did not influence the overall complication rate or the SSI rate following sutured castrations in a hospital setting.

CLINICAL SIGNIFICANCE

These findings prompt a reconsideration of the use of SAP for sutured castrations under aseptic conditions. The results may also serve as a basis for future randomized controlled trials.

Ex Vivo Pharmacokinetic/Pharmacodynamic Integration Model of Cefquinome Against Escherichia coli in Foals

Cefquinome is used to treat septicemia caused by Escherichia coli (E. coli) and respiratory infections caused by Streptococcus equi subsp. zooepidemicus in foals. However, studies reporting the use of cefquinome to target E. coli as pathogens of sepsis are lacking. Therefore, this study aimed to determine the optimal dosage regimen for cefquinome against E. coli using a PK/PD model. After the administration of 1 mg/kg cefquinome (intramuscularly or intravenously), blood samples were collected at different time points to determine the serum concentration of cefquinome via HPLC. The pharmacokinetic parameters were evaluated via NCA (WinNonlin 5.2.1 software). The main pharmacokinetic parameters of cefquinome in foals were as follows: after intravenous administration, the elimination half-life (T1/2β) was 2.35 h, the area under the curve (AUC0-last) was 12.33 μg·h/mL, the mean residence time (MRT0-last) was 2.67 h, and the clearance rate (CL) was 0.09 L/h/kg. After intramuscular administration, the peak concentration (Cmax) was 0.89 μg/mL, the time to reach the maximum serum concentration (Tmax) was 2.16 h, T1/2β was 4.16 h, AUC0-last was 5.41 μg·h/mL, MRT0-last was 4.92 h, CL was 0.15 L/h/kg, and the absolute bioavailability (F) was 43.86%. An inhibitory sigmoid Emax model was used to integrate the PK/PD indices with ex vivo antimicrobial effects to identify pharmacodynamic targets (PDTs). According to the dose calculation formula, the doses of intramuscularly administered cefquinome required to achieve bacteriostatic effects, bactericidal effects, and bactericidal elimination were 1.10, 1.66, and 2.28 mg/kg, respectively. However, further studies are warranted to verify the therapeutic efficacy of cefquinome in clinical settings.

A scoping review on intraoperative and postoperative surgical castration complications in domesticated equids

BACKGROUND

Castration is the most common surgical procedure in domesticated equids; surgical techniques used and perioperative management vary considerably.

OBJECTIVES

To identify and chart the current evidence on perioperative complications associated with different methods of surgical castration in domesticated equids.

STUDY DESIGN

Joanna Briggs Institute systematic scoping review.

METHOD

CAB Abstracts, Medline and Embase databases were searched using terms related to equine castration complications. Two authors independently and blindly screened publications against eligibility criteria. Data on study methods, perioperative management, surgical techniques, and perioperative complications were extracted. Surgical techniques were grouped into categories depending on technique; open, closed or half-closed, and whether the parietal tunic was open or closed at the end of surgery.

RESULTS

The search identified 1871 publications; 71 studies met the final inclusion criteria. The data reported 76 734 castrations, most of which were open or closed, with the vaginal tunic remaining open at the end of surgery. Twenty-five studies reported information regarding surgical techniques and perioperative management, allowing detailed charting and comparisons, of which analgesia and antimicrobial usage varied notably. Eighteen different complications were reported, with swelling or oedema being the most common. Evisceration was most commonly reported in draught breeds and Standardbreds, and the risk appeared low if the parietal tunic was closed at the end of surgery.

MAIN LIMITATIONS

Grey literature and studies not available in English were not included. Existing studies varied greatly in perioperative management, surgical techniques and reporting of outcomes, making evidence consolidation problematic.

CONCLUSION

A lack of consensus regarding complication definitions creates uncertainty and discrepancies between complication rates associated with different surgical techniques and perioperative management. The implementation of standardised systems for describing surgical techniques and complications is recommended for future studies. A number of studies did not follow current recommendations for perioperative analgesia and use of antimicrobials.

An updated description of bacterial pneumonia in adult horses and factors associated with death

BACKGROUND

Available descriptive studies on equine pneumonia are outdated or focus on specific horse or bacterial populations.

OBJECTIVES

To describe the clinical presentation and bacterial isolates of adult horses with bacterial pneumonia and identify factors associated with death.

ANIMALS

One hundred sixteen horses >2 years old with bacterial pneumonia.

METHODS

Retrospective case series. Data regarding history, physical examination, clinicopathologic features, treatment, bacterial culture and sensitivity, and outcome were collected and analyzed retrospectively.

RESULTS

Historical risk factors were present for 60% of cases, whereas abnormal vital signs on intake were present for <50%. Most horses (58%) underwent at least 1 change of antimicrobial treatment, and 67% received the highest-priority critically important antimicrobials. Streptococcus zooepidemicus was the most isolated bacteria (44%), followed by Escherichia coli (19%), Klebsiella spp. (18%), other Streptococcus species (17%), and Bacillus spp. (13%). Fusobacterium spp. were the most common anaerobic isolates (11%). Antimicrobial susceptibility varied widely. Survival to discharge was 73%. Heart rate at presentation (odds ratio [OR] 1.08, 95% confidence interval [CI] 1.008-1.17, P = .03) and higher creatinine (OR 14.1, 95% CI 1.56-127.6, P = .02) increased the risk of death. Higher lymphocyte count (OR 0.27, 95% CI 0.08-0.94, P = .04) reduced risk.

CONCLUSIONS AND CLINICAL IMPORTANCE

Contrasting older literature, Fusobacterium spp. were the most common anaerobes. Streptococcus zooepidemicus remained the most common isolate and was predictably susceptible to penicillin. Antimicrobial susceptibility was otherwise variable and broad applicability is limited as this was a single-center study. Increased risk of death associated with tachycardia and abnormally high serum creatinine concentration is consistent with previous studies.

Antibiotic usage in 14 equine practices over a 10-year period (2012-2021)

BACKGROUND

Monitoring antibiotic usage is an important part of tackling antimicrobial resistance. The use of computerised records for monitoring has been previously described in the equine sector but there is currently no consensus on metrics used to report usage.

OBJECTIVES

To document antibiotic use in equine practices in the United Kingdom over a 10-year period using commercially available practice management software.

STUDY DESIGN

Retrospective survey.

METHODS

A custom antibiotic usage report was created using Eclipse® practice management software. Participating practices were given instructions on how to generate the usage report. Annual reports were requested for a 10-year period (2012-2021 inclusive). Each report provided sales of each class of antibiotic in total mg and in mg/kg, based on the number of equids treated (for any transaction) and their average weight. The defined daily dose for animals (DDDvet) and the DDD/1000 (used in people) were also calculated to correct for variation in dosage rates between antibiotics.

RESULTS

Fourteen practices submitted data for an annual maximum of 107 977 horses. Overall, median annual antibiotic usage was 54.25 mg/kg (range 45.34-60.27 mg/kg), 1.52 defined daily doses/animal/year (range 1.39-1.70) and 4.17 defined daily dose/1000 animals (range 3.82-4.66). Overall median highest priority critically important antimicrobial usage was 0.67 mg/kg (range 0.56-1.71), 0.12 defined daily doses/animal/year (range 0.10-0.14) and 0.33 defined daily dose/1000 animals (range 0.29-0.39).

MAIN LIMITATIONS

The software relied on the accurate identification of antibiotic preparations. The calculation of DDDvet was complicated by the varying dose rates of antimicrobials used in equine practice.

CONCLUSIONS

A reliable technique to measure antibiotic usage is presented. Defined daily dosage calculations may be more helpful in equine practice due to the preponderance of potentiated sulphonamides usage. These data and methods may provide the basis for future clinical audits aiming to enhance antimicrobial stewardship.

Pharmacokinetics of Enrofloxacin in Plasma, Urine, and Feces of Donkey (Equus asinus) after a Single Intragastric Administration

Enrofloxacin is a broad-spectrum antimicrobial agent, but the study of its pharmacokinetics/pharmacodynamics (PKs/PDs) in donkeys is rarely reported. The present study aimed to investigate the pharmacokinetics of enrofloxacin administered intragastrically, and to study the pharmacokinetics of enrofloxacin and its metabolite ciprofloxacin in plasma, urine, and feces, and the PK/PD parameters were investigated to provide a rationale for enrofloxacin treatment in donkeys. A total of five healthy donkeys were selected for intragastric administration of 7.5 mg·kg-1 BW of enrofloxacin by gavage, and blood, urine, and fecal samples were collected. The results showed that the elimination half-life of plasma enrofloxacin was 11.40 ± 6.40 h, Tmax was 0.55 ± 0.12 h, Cmax was 2.46 ± 0.14 mg·L-1, AUC0-∞ was 10.30 ± 3.37 mg·L-1·h, and mean residence time (MRT) was 7.88 ± 1.26 h. The Tmax of plasma ciprofloxacin was 0.52 ± 0.08 h, Cmax was 0.14 ± 0.03 mg·L-1, and AUC0-∞ was 0.24 ± 0.16 mg·L-1·h. Urinary Cmax was 38.18 ± 8.56 mg·L-1 for enrofloxacin and 15.94 ± 4.15 mg·L-1 for ciprofloxacin. The total enrofloxacin and ciprofloxacin recovered amount in urine was 7.09 ± 2.55% of the dose for 144 h after dosing. The total enrofloxacin and ciprofloxacin recovered amount in feces was 25.73 ± 10.34% of the dose for 144 h after dosing. PK/PD parameters were also examined in this study, based on published MICs. In conclusion, 7.5 mg/kg BW of enrofloxacin administered intragastrically to donkeys was rapidly absorbed, widely distributed, and slowly eliminated in their bodies, and was predicted to be effective against bacteria with MICs < 0.25 mg·L-1.

Pattern of prescriptions and prudent use of antimicrobial in horse practice at a Veterinary Teaching Hospital

Antimicrobial prescriptions of the University of Pisa and their compliance with prudent use recommendations were investigated over 11 years (2011-2021). At least one antimicrobial was always prescribed in surgical prophylaxis for the suture of wounds and in 33% of horses with signs of disease of a body system. Antimicrobials were administered in monotherapy (48%) in fixed dose combinations (21%) and empirical combinations (31%). Antimicrobials were mostly (63%) administered by parenteral route, while oral and topical antimicrobials accounted for 14% and 23% of prescriptions, respectively. Gentamicin, benzylpenicillin and ceftiofur were the most prescribed antimicrobials; aminoglycosides, penicillins and cephalosporins were the most common class of antimicrobial prescribed. Protected antimicrobials (WHO HPCIA and rifampicin) represented 24% of antimicrobial dispensations. The pattern of classes of antimicrobial used by body system was broad and included up to eight different pharmaceutical classes. The heterogeneity of antimicrobial use was confirmed by the estimate of the prescription diversity index. Antimicrobial prescriptions were in compliance with prudent use recommendations in terms of availability of diagnosis, respect of the dose range and duration of treatment On the contrary, principles of appropriate antimicrobial use have only been partially observed in relation to off-label use, use of antimicrobials in empirical combination, use of antimicrobial susceptibility tests and use of protected antimicrobials, suggesting that additional interventions are required to improve the responsible use of antimicrobials use in our equine practice.

Antimicrobial Prescription Behavior in Equine Asthma Cases: An International Survey

Equine asthma is considered a non-infectious respiratory disease characterized by inflammation and hypersensitivity. Given the importance of antimicrobial stewardship, an international survey was designed to investigate the use of antimicrobials in asthmatic horses and the factors influencing prescription behavior. An online survey was distributed in six languages by international mailing lists and social media from December 2020 to January 2022. Of the 434 responses recorded, 249 veterinarians working in 25 countries finished the survey. These included 79 ECEIM/ACVIM diplomats. A total of 204 respondents confirmed national regulations concerning antimicrobial use in their country. Knowledge of the asthma definitions as presented in the revised ACVIM consensus statement was greater in veterinarians treating over 95% of equine patients compared to veterinarians treating more species, based on 10 questions (answers consistent with the consensus statement in 7 (IQR 5-9) and 4 (IQR 3-6) questions, respectively, (p < 0.001)). A total of 131 respondents stated to use antimicrobials (at least 'sometimes') in at least one of the three presented cases consistent with equine asthma. Trimethoprim-Sulfa combinations, penicillin(s), and tetracyclines were prescribed most (by 105, 53 and 38 veterinarians, respectively). Aminoglycosides, cephalosporins and fluoroquinolones were also selected (22, 15, 9 veterinarians respectively). Tetracyclines and cephalosporins are prescribed more often by veterinarians working without national regulations (p 0.019 and p 0.035, respectively). The most selected factors influencing prescription behavior were: 'tracheal wash culture' (62% of 131 veterinarians using antimicrobials in these cases), 'whether other horses in the barn have similar complaints' (60%), and 'response to other forms of therapy' (53%). In conclusion, insight into prescription behavior is the first step towards minimizing and optimizing antimicrobial use.

The Effects of Antimicrobial Protocols and Other Perioperative Factors on Postoperative Complications in Horses Undergoing Celiotomy: A Retrospective Analysis, 2008-2021

Recognition of antimicrobial resistance in equine practice has increased over the past decade. The objective of this study was to provide an updated retrospective review of antimicrobial regimens in one tertiary referral hospital and to evaluate the association with postoperative complications. A secondary objective was to evaluate other perioperative factors including surgical procedure, anesthetic and recovery parameters, and the effect of perioperative medications on complications and outcomes. A computerized search of medical records was performed to identify horses undergoing exploratory celiotomy from 1 January 2008 to 31 December 2021. A total of 742 celiotomies were performed (608 completed, 134 terminated intraoperatively). Factors recorded were evaluated using logistic regression for the presence of either incisional infection, postoperative ileus, or other complications postoperatively. Antimicrobial type or timing (pre-, intra-, or postoperative) were not associated with decreased risk of incisional infection or postoperative ileus; however, the duration of NSAID use was positively associated with incisional infection (OR 1.14 per day). Lidocaine and alpha-2-agonist administration postoperatively were also associated with increased incidence of postoperative ileus (OR 21.5 and 1.56, respectively). Poor recovery quality (OR 4.69), the addition of other antimicrobials besides penicillin/gentamicin postoperatively (OR 3.63), and an increased number of different NSAID classes used (OR 1.46 per additional) were associated with other complications. Implementation of enterotomy was associated with decreased risk of other complications (OR 0.64). These findings provide an updated summary of factors associated with postoperative complications in horses undergoing celiotomy.