REASONS FOR PERFORMING STUDY: Infection with Streptococcus equi subspecies equi (S. equi) is endemic in the United Kingdom. A proportion of horses serve as long term carriers and act as a reservoir of infection. Detection of these persistently infected horses is difficult using standard culture techniques due to a lack of sensitivity and overgrowth by contaminating bacteria. In addition, differentiation of this causative bacterium from the closely related S. equi zooepidemicus has made the development of reliable and accurate diagnostic tests difficult.

OBJECTIVE:

To develop and validate a sensitive and specific real time PCR assay to detect S. equi and to compare the results with traditional culture techniques.

STUDY DESIGN:

Retrospective cross-sectional study.

METHODS:

The assay was validated using a panel of 92 samples from suspected clinical cases of strangles. These were cultured using microbial techniques and tested using the S. equi real time PCR. The results of the 2 methods were compared and the diagnostic sensitivity and specificity of the real time PCR were calculated. The real time PCR was tested for cross-reactivity with horse commensal bacteria and the efficiencies and limits of detection were established.

RESULTS:

The assay had a diagnostic sensitivity of 95% and specificity of 86%. No cross-reactivity was observed with any of the bacterial species tested, including S. equi zooepidemicus. The assay detected as few as 3 gene copies.

CONCLUSION

AND

CLINICAL RELEVANCE:

The assay is fast, sensitive, specific and will detect S. equi DNA directly from a crude extraction of clinical material on a swab. POTENTIAL RELEVANCE: This assay could aid in the rapid detection of sub-clinical shedders of S. equi, enabling quicker treatment and helping to limit the spread of strangles in equine populations.

REASONS FOR PERFORMING STUDY: Resistance to the somatotropic axis and increases in ghrelin concentrations have been documented in critically ill humans, but limited information exists in healthy or sick foals.

OBJECTIVES:

To investigate components of the somatotropic axis (ghrelin, growth hormone and insulin-like growth factor-1 [IGF-1]) in regard to energy metabolism (glucose and triglycerides), severity of disease and survival in critically ill equine neonates. We hypothesised that ghrelin and growth hormone would increase and IGF-1 would decrease in proportion to severity of disease, supporting somatotropic axis resistance, which would be associated with severity of disease and mortality in sick foals.

STUDY DESIGN:

Prospective multi-centre cross-sectional study.

METHODS:

Blood samples were collected at admission from 44 septic, 62 sick non-septic (SNS), and from 19 healthy foals, all <7 days of age. Foals with positive blood cultures or sepsis scores ≥12 were considered septic, foals with sepsis scores between 5 and 11 were classified as SNS. Data was analysed by nonparametric methods and multivariate logistic regression.

RESULTS:

Septic foals had higher ghrelin, growth hormone and triglyceride and lower IGF-1 and glucose concentrations than healthy foals (P<0.01). SNS foals had higher growth hormone and triglycerides and lower IGF-1 concentrations than healthy foals (P<0.05). Growth hormone:IGF-1 ratio was higher in septic and SNS foals than healthy foals (P<0.05). Hormone concentrations were not different between septic non-survivors (n = 14) and survivors (n = 30), but the growth hormone:IGF-1 ratio was lower in non-survivors (P = 0.043).

CONCLUSIONS:

Somatotropic axis resistance, characterised by a high growth hormone:IGF-1 ratio, was frequent in sick foals, associated with the energy status (hypoglycaemia, hypertriglyceridemia) and with mortality in septic foals. POTENTIAL RELEVANCE: A functional somatotropic axis appears to be important for foal survival during sepsis. Somatotropic resistance is likely to contribute to severity of disease, a catabolic state and likelihood of recovery.

REASON FOR PERFORMING STUDY: Cheek teeth diastemata are a common cause of painful periodontal disease in horses, but there is limited objective information on their treatment.

OBJECTIVE:

To assess the long-term response to diastema widening in clinically affected horses.

STUDY DESIGN:

Retrospective study.

METHOD:

Medical records from cases of cheek teeth diastemata treated by diastema widening referred to the University of Edinburgh Equine Hospital between 2008-2011 were analysed.

RESULTS:

During this period, 302 horses were diagnosed with clinically significant cheek teeth diastemata of which 202 cases, median age 11 years, with severe associated periodontitis were treated by widening of 674 problematic diastemata; 89.8% between mandibular cheek teeth and 10.2% between maxillary cheek teeth, with a mean of 1.5 treatments performed per case. These 202 cases showed quidding in 76.2%; weight loss in 33.2%; bitting problems in 20.1% and halitosis in 10.9%, with 5.4% being asymptomatic. Follow-up information 92% of treated cases, a mean of 20.8 months after their initial treatment showed 72.6% of cases had complete remission of clinical signs that was permanent (for the duration of this study) in 50.5% and temporary in 22%. A partial response was obtained in 17.2%; no response was obtained in 4.3%, and owners were unsure of response in 5.9%. Clinical improvement was sometimes delayed, with 19% taking >4 weeks following treatment for improvement. Inappropriate sites were burred in individual teeth of 6 horses, causing iatrogenic pulpar exposure in 2 cases, but following treatment, none developed clinical signs of apical infection.

CONCLUSIONS:

Diastemata widening is an effective but potentially invasive treatment for horses with cheek teeth diastemata with severe periodontitis. POTENTIAL RELEVANCE: Diastema widening by trained personnel is suitable for advanced cases of cheek teeth diastema but many cases require repeated treatments.

REASONS FOR PERFORMING STUDY: Lameness is a common problem in the horse. Despite this, information on the incidence of lameness in horses in the UK is restricted to studies of lameness in performance horses, racehorses, or referral hospital populations.

OBJECTIVES:

To determine the overall incidence, and common causes of lameness in a working horse population, and the incidence, duration and outcome of the conditions observed.

STUDY DESIGN:

Prospective questionnaire study

METHODS:

Questionnaires were used to record lameness episodes in 294 horses in an equine military establishment. Information recorded included age, years of service, type of work, causal lesion, time taken to return to work and outcome. Lameness problems could be reported by any staff involved in the horses' care and were diagnosed by a veterinary surgeon or qualified farrier. Trends between lame and non-lame populations were compared using chi-square analysis. Lameness diagnoses were grouped and analysed by disease category.

RESULTS:

Completed questionnaires for 273 horses were analysed. The mean monthly incidence of lameness was 2.1%, equivalent to an annual rate of 25.4 cases per 100 horses per annum, with a mean of 1.2 lameness episodes per horse in the lame population. Horse age and duration of service were not significantly different between the lame and non-lame populations. The most common diagnoses were cellulitis (18.6%), skin wounds (16.3%) and foot/shoeing problems (11.6%) and 88% of cases had returned to previous levels of work by the conclusion of the study.

CONCLUSIONS:

This initial field study showed that lameness is a common occurrence in this working military horse population, and the majority of cases make a full return to work. The most common causes of lameness identified in this study and the outcomes of these conditions differ from existing literature. POTENTIAL RELEVANCE: This study highlights the need for further studies of lameness in the wider horse population.

REASONS FOR PERFORMING STUDY: Computed tomography (CT) is increasingly accessible in equine referral hospitals.

OBJECTIVES:

To document the level of agreement within and between radiography and CT in characterising equine distal limb fractures.

STUDY DESIGN:

Retrospective descriptive study

METHODS:

Images from horses that underwent radiographic and CT evaluation for suspected distal limb fractures were reviewed, including 27 horses and 3 negative controls. Using Cohen's kappa and weighted kappa analysis, the level of agreement among 4 observers for a predefined set of diagnostic characteristics for radiography and CT separately and for the level of agreement between the 2 imaging modalities were documented.

RESULTS AND CONCLUSIONS:

Both CT and radiography had very good intra-modality agreement in identifying fractures, but inter-modality agreement was lower. There was good inter-modality and intra-modality agreement for anatomical localisation and the identification of fracture displacement. Agreement for articular involvement, fracture comminution and fracture fragment number was towards the lower limit of good agreement. There was poor to fair inter-modality agreement regarding fracture orientation, fracture width and coalescing cracks; intra-modality agreement was higher for CT than for radiography for these features. POTENTIAL RELEVANCE: Further studies, including comparisons with surgical and/or post-mortem findings, are required to determine the sensitivity and specificity of CT and radiography in the diagnosis and characterisation of equine distal limb fractures.

OBJECTIVES:

Dorsal displacement of the soft palate (DDSP) in the horse has been previously described as intermittent, typically occurring at fast exercise; or persistent, seen at rest. DDSP has recently been reported following laryngoplasty (LP) and can be associated with continued poor performance and respiratory noise. The current study aimed to characterise the DDSP diagnosed post-LP.

STUDY DESIGN:

Cross-sectional study.

METHODS:

The owners/trainers of horses undergoing LP at one institution over 6 years were contacted to determine the horse's progress, and the willingness for re-examination. The horses were examined at the rest, walk, trot and canter with an over-ground exercising endoscope. A GPS-equipped watch was carried to obtain maximal exercising speeds. Videos of horses with DDSP were reviewed to determine the frequency and duration of DDSP and swallowing events at the various gaits.

RESULTS:

Exercising endoscopy was performed in 41 of the 89 horses that had undergone laryngoplasty. Nineteen of the 41 horses were diagnosed with DDSP at exercise, of which 7/41 also had DDSP at rest. No difference was detected in the percentage of total time spent displaced at each gaits (p = 0.67); or in the frequency of new DDSP events per minute between each gait (p = 0.10), or in the frequency of swallowing events per minute between each gait (p = 0.52). The majority of horses displaced at various times throughout each gait. DDSP was most commonly solely induced spontaneously, and was always corrected with a swallow. The maximum speed achieved was 8.3 ms(-1) .

CONCLUSIONS:

DDSP was common following LP, and it appears to be induced at slower gaits than DDSP that has previously been described, it also occurred at various times throughout each gait, and did not always occur persistently at rest. POTENTIAL RELEVANCE: These findings suggest horses undergoing LP may be more prone to DDSP and further investigations into the aetiology of post LP palatal dysfunction are warranted.

REASON FOR PERFORMING STUDY: Diagnostic techniques for oviductal obstruction in the mare are limited and development of a more reliable and direct method to assess oviductal patency is needed.

OBJECTIVE:

Evaluate the feasibility of hysteroscopic selective hydrotubation of the equine oviduct via videoendoscopy in standing mares.

METHODS:

Using a catheter inserted under endoscopic guidance into the uterotubal junctions of 10 mares, 5 ml of indigo carmine solution (4 mg/ml) was flushed into the oviduct. After introduction of the dye, peritoneal fluid was obtained via abdominocentesis. A colpotomy was also performed to allow introduction of a videoendoscope into the abdominal cavity to visually assess the presence of dye at the ovarian end of the oviduct.

RESULTS AND CONCLUSIONS:

In 15 of 20 (75.0%) attempts, the catheter was successfully inserted into the uterotubal junction, and dye was observed at the ampulla, fimbria, overlying the ovary or surrounding tissue. In 2 mares, the videoendoscope could not be manipulated to identify the uterotubal junction. Only one of 2 oviducts was flushed in an additional mare because insufflation of the uterus could not be maintained. The colour of the dye was evident macroscopically and spectrophotometrically in 4 of 8 mares from which peritoneal fluid was successfully collected. POTENTIAL RELEVANCE: The equine oviduct can be evaluated by hysteroscopic selective hydrotubation.

REASONS FOR PERFORMING STUDY: Cyathostomins comprise 50 helminth species, considered the most problematic equine endoparasites. Three classes of anthelmintic are currently licensed for their control, namely the benzimidazoles (fenbendazole), tetrahydropyrimidines (pyrantel) and macrocyclic lactones (ivermectin and moxidectin). Anthelmintic resistance in cyathostomins is common. With no new classes expected in the near future, it is essential to determine the efficacy of the available anthelmintics to inform future control programmes.

OBJECTIVES:

To determine the efficacy of all 3 anthelmintic classes against strongyles in equids on livery yards in east and central Scotland.

STUDY DESIGN:

Anthelmintic efficacy testing using the faecal egg count reduction test (FECRT).

METHODS:

FECRTs were performed on equids with initial strongyle faecal egg counts (FECs) of ≥50 eggs per gram. Efficacy was determined by comparing pretreatment (Day 0) and 14 days post treatment (Day 14) FECs. The following chemicals were tested: fenbendazole, pyrantel, ivermectin and moxidectin. Group arithmetic mean FECR of >90% for fenbendazole and pyrantel, and >95% for ivermectin and moxidectin, represented efficacy, whereas lower mean FECR indicated potential resistance.

RESULTS:

A total of 447 FECRTs were performed on 15 yards, as follows (the numbers in parentheses represent the number of yards each anthelmintic was tested on): 55 equids (7 yards) fenbendazole, 111 (8 yards) pyrantel, 163 (13 yards) ivermectin and 118 (10 yards) moxidectin. Fenbendazole resistance was documented on all yards (range of mean FECR, 15.8-83.4%), whereas pyrantel (90.4-99.6%), ivermectin (99.5-100%) and moxidectin (99.4-100%) treatment had acceptable efficacy.

CONCLUSIONS:

Reduced efficacy of fenbendazole was widespread, whereas >90% efficacy was found after pyrantel, and >95% efficacy after ivermectin and moxidectin. Overall, efficacies were higher than reported previously in Europe and the USA, potentially reflecting differences in management and anthelmintic use on the yards surveyed. POTENTIAL RELEVANCE: The use of fenbendazole for strongyle control in Scotland should be questioned. Targeted use of pyrantel should be encouraged to reduce reliance on macrocyclic lactones. Further work to correlate management practices with the presence of anthelmintic resistance is warranted. The Summary is available in Chinese - see Supporting information.

REASONS FOR PERFORMING STUDY: Research in Thoroughbred racehorses is often specific to horses from a given racing population or region. In order to investigate trends in racehorse careers across populations accurately, population-specific benchmarks for performance outcomes must be established.

OBJECTIVES:

To provide summary statistics for performance outcomes for Thoroughbreds racing in Hong Kong between 2000 and 2010 and to document and provide evidence on the current differences in racing careers across sexes and regions of origin for horses racing in Hong Kong.

STUDY DESIGN:

Performance data on the population of Thoroughbreds racing in Hong Kong between 3 September 2000 and 12 March 2011 (n = 4950) were acquired and used to describe and compare the careers of Thoroughbred racehorses in Hong Kong.

METHODS:

Career length, number of career starts and number of spells from racing per year were evaluated. Kaplan-Meier survival curves, stratified by sex, age group, country of origin and region of origin were produced for career length. A Cox's proportional hazards model was fitted to assess factors influencing the risk of retirement from racing in Hong Kong.

RESULTS:

Log-rank tests for equality of career length survivor functions showed significant differences (P<0.001) across sexes, age groups, countries of origin and regions of origin. An increased age at first start in Hong Kong tended to increase the hazard rate for retirement from racing in Hong Kong, whereas greater earnings per race and originating from Europe tended to reduce the hazard rate for racing retirement.

CONCLUSIONS

AND POTENTIAL RELEVANCE: Differences in career outcomes within a racing population appear to be influenced partly by the region from which a horse originates, with specific effects on each performance outcome also varying between regions. Future research should take into account these potential differences when comparing results across populations. The Summary is available in Chinese - see Supporting information.

REASONS FOR PERFORMING STUDY: Equine grass sickness (EGS) remains a frequently fatal disease of equids in Britain. Since previous investigations of signalment- and meteorology- related risk factors for EGS have yielded some conflicting data, further investigation is warranted.

OBJECTIVES:

To identify signalment- and meteorology- related risk factors for EGS in Scotland.

METHODS:

A retrospective time-matched case-control study was undertaken using data for 455 EGS cases and 910 time-matched controls that were referred to the Royal Dick School of Veterinary Studies (R(D)SVS), and average UK Meteorological Office weather station meteorological values from the month of admission of the animal, from the 3, 6 and 12 months prior to admission, and for the entire 1990 to 2006 period.

RESULTS

AND

CONCLUSION:

Signalment-related risk factors associated with an increased risk of EGS were native Scottish compared to cross-breeds (Odds ratio (OR) = 3.56, 95% Confidence Interval (CI) = 2.43-5.43) and animals living on premises located further north within the study region (OR = 1.08, CI = 1.06-1.10). There was a decreased risk of EGS in animals aged 11-20 years old compared to animals 2-10 years old (OR = 0.32, CI = 0.22-0.45), non-native Scottish pure breeds compared to cross-breeds (OR = 0.71, CI = 0.54-0-94), and stallions compared to mares (OR = 0.43, CI = 0.22-0.86). Meteorology-related risk factors associated with an increased risk of EGS were (if Ordnance Survey northing excluded) more sun hours (OR>1.43) and more frost days (OR>1.13), while there was a decreased risk of EGS with higher average maximum temperature (OR<0.83). POTENTIAL RELEVANCE: The signalment-related risk factors will help owners identify high-risk animals, thereby allowing them to prioritise management strategies. The identification of meteorological risk factors may assist studies on the aetiology of EGS.