REASONS FOR PERFORMING THE STUDY: Red complex bacteria, i.e. Porphyromonas gingivalis, Treponema denticola and Tannerella forsythia, are involved in the onset and progression of human periodontal disease, yet seldom inhabit the oral cavity of healthy individuals. Periodontal disease is also encountered in horses, with equine odontoclastic tooth resorption and hypercementosis (EOTRH) constituting a particular form of disease. However, only little is known about the oral microbiome of healthy and periodontitis-affected equids.

OBJECTIVE:

We aimed to test the hypothesis that red complex bacteria are also associated with EOTRH related periodontal disease.

STUDY DESIGN:

Controlled cross-sectional study.

METHODS:

We screened DNA purified from crevicular fluid derived from 23 EOTRH-affected and 21 disease-free horses for the presence of Treponema ssp., Tannerella ssp. and Porphyromonas gingivalis DNA by PCR. Subsequently, amplified DNA was bi-directionally sequenced and identified via BLAST analysis.

RESULTS:

Treponema and/or Tannerella DNA were detected in 100% of periodontitis-related samples and in 52.2% of DNA derived from healthy horses. Twenty-six amplicon sequences were 98 to 100% homologous to published bacterial sequences, which mostly corresponded to Treponema pectinovorum, oral Treponema clones JU025 and OMZ 840, and Tannerella forsythia. P. gingivalis DNA was only found in 3 EOTRH-related samples. Forty-three amplicon sequences revealed weaker homologies ranging between 80 and 97% to known Treponema or Tannerella strains, partly because of their heterogeneity, partly because they obviously represented so far unknown types.

CONCLUSIONS:

This is the first report in which known and novel Treponema and Tannerella ssp. were isolated in association with EOTRH related periodontal disease.

REASONS FOR PERFORMING STUDY: There is little published information on whether measurement of plasma ACTH concentration at a single time point is a repeatable indicator of pituitary pars intermedia dysfunction (PPID).

OBJECTIVES:

To determine whether ultradian or circadian fluctuations in ACTH production influence plasma ACTH concentration in normal horses and horses with PPID.

STUDY DESIGN:

Prospective observational study.

METHODS:

Plasma ACTH concentration in 8 non-PPID horses and 8 horses with PPID was measured at 08.00, 11.00, 14.00 and 17.00 on 5 non-consecutive days within a 3 week period. In addition at 08.30 on one day, 6 samples were collected from each horse at precisely 5 min intervals over a period of 25 min. Descriptive and graphical analysis was performed and a linear mixed effects model was fitted to assess the effect of time of day on ACTH concentration in non-PPID and PPID horses.

RESULTS:

Evidence of ultradian fluctuation in ACTH production was not identified in either non-PPID or PPID horses. Evidence for circadian fluctuation was identified in non-PPID horses; plasma ACTH concentrations were highest at 08.00 am and decreased through the day. There was no evidence of circadian fluctuation in PPID horses. In non-PPID horses, the magnitude of circadian changes in ACTH concentration was smaller than variations in concentration that occurred at random. Intra-horse variability of ACTH concentration was greater in PPID horses than in non-PPID horses.

CONCLUSIONS:

Ultradian and circadian fluctuations in ACTH concentration are unlikely to influence clinical decision making; however, variations of potential clinical relevance do occur in individual horses, for reasons that remain to be determined, and increase in magnitude with progression of PPID. Results of the current study indicate that when an ACTH concentration between 19 and 40 pg/ml is measured, further testing should be considered to increase the accuracy of PPID diagnosis.

REASONS FOR PERFORMING STUDY: The effect of racetrack surface (dirt or synthetic) on distal hindlimb kinematics of racehorses running at competition speeds is not known.

OBJECTIVES:

To compare distal hindlimb and hoof kinematics during stance of breezing racehorses between dirt and synthetic surfaces.

STUDY DESIGN:

Two-dimensional kinematic video analysis of 5 Thoroughbred racehorses galloping at high speeds (12-17 m/s) on a dirt racetrack and a synthetic racetrack.

METHODS:

The positions of kinematic markers applied to the left hindlimb were recorded at 500 Hz. Position, velocity and acceleration of joint angles and hoof translation during stance were calculated in the sagittal plane. Peak translational and angular kinematic values were compared between the dirt and synthetic race surfaces using mixed model analyses of covariance.

RESULTS:

Maximum and heel-strike metatarsophalangeal (fetlock) angles were greater (P<0.05) on the dirt surface than the synthetic surface. Maximum fetlock angle occurred earlier during stance on the dirt surface (P<0.05). Greater horizontal displacement of the heel during slide occurred on the dirt surface (P<0.05).

CONCLUSIONS:

During high-speed gallop, hindlimb fetlock hyperextension and horizontal hoof slide are greater on a dirt surface compared to a synthetic surface. Synthetic race surfaces may mitigate risk of injury to hindlimb fetlock structures by reducing fetlock hyperextension and associated strains in fetlock support structures. Differences in hoof slide may contribute to different distal hindlimb kinematics between surfaces.

REASON FOR PERFORMING STUDY: Although arthropathy of the cervical articular process joints is common, descriptions of the arthroscopic technique of the cervical articular process joint (APJs) have not been reported previously.

OBJECTIVES:

To develop an arthroscopic approach to the APJs and to describe the arthroscopic anatomy of the APJs.

STUDY DESIGN:

Descriptive cadaver study and clinical case report.

METHODS:

The regional anatomy was reviewed and the technique developed on fresh cadaver necks. A series of cadaveric APJs arthroscopies from C2-C3 to C6-C7 were performed to evaluate the procedure, which was then used in 3 clinical patients. A description of the procedure and the potential complications encountered were recorded.

RESULTS:

The equine APJs consist of cranioventral and caudodorsal recesses; a single entry point at one of these recesses enables almost complete evaluation of cartilage surfaces and the synovial membrane and its villi. Successful entry into both APJ recesses was achieved in 22 cadaveric APJs and 5 APJs in the 3 clinical cases operated upon. An instrument portal was created to assess the feasibility of surgical arthroscopy. Complications were minor and dissection of the APJs following the arthroscopic exploration revealed that the cartilage and periarticular neurovascular structures were not damaged during the procedure.

CONCLUSIONS:

This study shows that arthroscopic examination of the APJs of equine cervical vertebra is feasible and can be performed in adult horses. Arthroscopy of the APJs may provide additional diagnostic information compared to conventional diagnostic techniques.

REASONS FOR PERFORMING STUDY: Hereditary Equine Regional Dermal Asthenia (HERDA) is an autosomal recessive disorder of Quarter Horses characterised by skin fragility. HERDA horses have a missense mutation in peptidyl-prolyl cis-trans isomerase B (PPIB) which encodes Cyclophilin B (CYPB) and alters folding and post-translational modifications of fibrillar collagen.

Objectives:

The study aimed to test the hypothesis that tendon, ligament, and great vessels, which like skin are rich in fibrillar collagen, will also have abnormal biomechanical properties in HERDA horses.

Study design:

Ex-vivo biomechanical study comparing horses with and without a diagnosis of HERDA.

METHODS:

Forelimb suspensory ligament, superficial and deep digital flexor tendons; withers, forelimb, and abdominal skin; main pulmonary artery and the aortic arch were harvested from 6 HERDA and 6 control horses without the HERDA allele. Tissues were distracted to failure. Tensile strength (TS), elastic modulus (EM), and energy to failure (ETF) were compared.

RESULTS:

HERDA horses had significantly lower TS and EM in tendinoligamentous tissues and great vessels, respectively. TS, EM and ETF were significantly lower in HERDA skin. Differences in TS and ETF were more extreme at the withers than the forelimb or abdomen.

CONCLUSIONS:

Tendinoligamentous tissue, great vessels, and skin are significantly weaker in horses with HERDA than horses lacking the PPIB mutation, substantiating that diverse tissues with high fibrillar collagen content are abnormal in HERDA and the HERDA phenotype is not limited to the integument.

REASONS FOR PERFORMING STUDY: Many studies of respiratory disease in racehorses have focused on a combination of increased tracheal mucus and airway neutrophilia. Examination of each component separately should provide further insight into this condition.

OBJECTIVES:

To identify infectious risk factors for endoscopically-visible tracheal mucus in National Hunt racehorses.

STUDY DESIGN:

A 2-year prospective longitudinal study.

METHODS:

Monthly quantitative bacteriological examinations of tracheal wash samples and viral serological examinations were conducted. Risk factors for 'small amounts of mucus' (mucus score = 1/3) and 'increased mucus' (score >2/3) were identified.

RESULTS:

There were increased odds of small amounts of mucus when both S.zooepidemicus and non-haemolytic streptococci (NHS) were isolated (OR 2.6; 95%CI: 1.5-4.6; p<0.001) but not when either species was isolated in the absence of the other. Increased odds of increased mucus were associated with the isolation of either S.zooepidemicus (OR 5.6; 95% CI: 1.2-25.9; p = 0.03) or NHS (OR 3.7; 95% CI: 1.2-11.6; p = 0.02), with an increased effect when both were isolated together (OR 12.5; 95% CI: 3.7-41.6; p<0.001). Approximately 6-fold increased odds of small amounts of mucus were associated with the first 3 months in training (OR 6.3; 95% CI: 2.0-19.4; p<0.001) and 3-fold increased odds of increased mucus associated with the first 6 months in training (OR 2.9; 95% CI: 1.3-6.4; p = 0.01). Coughing at exercise and increased serous nasal discharge were specific but insensitive indicators of increased mucus.

CONCLUSIONS:

Associations with S.zooepidemicus corroborate previous research, but an independent effect of NHS has not been reported previously. The possibility that there are individual pathogenic species within this group should be considered. Further work is required to identify S.zooepidemicus subtypes and NHS species associated with disease. Closer monitoring of the respiratory health of horses entering training for the first time is likely to be valuable.

REASONS FOR PERFORMING STUDY: Atrial fibrillation cycle length (AFCL) is an indicator of atrial electrical remodeling during atrial fibrillation (AF).

OBJECTIVES:

To compare invasively measured AFCL from an intra-atrial electrogram (AFCLEGM ) to non-invasively measured AFCL by atrial colour tissue Doppler imaging (AFCLTDI ).

STUDY DESIGN:

Prospective descriptive clinical study.

METHODS:

Measurements were performed in 31 episodes of AF or flutter in 29 horses (588 ± 61 kg, 9 ± 3 years) admitted for transvenous electrical cardioversion. AFCLEGM was measured from an intra-cardiac electrogram using a bipolar sensing/pacing electrode inserted in the right atrium. AFCLTDI was measured from atrial colour tissue velocity curves in 5 regions: (1) left atrial free wall from a right parasternal 4-chamber view, (2) left atrial free wall from a short-axis view, (3) left atrial free wall from a left parasternal long-axis view, (4) interatrial septum and (5) right atrial dorsal wall near the tuberculum intervenosum. AFCLEGM and AFCLTDI from the 5 regions were compared using a one-way repeated measures analysis of variance with Bonferroni correction for multiple comparisons and calculation of the Bland-Altman mean bias and limits of agreement of AFCLEGM and AFCLTDI .

RESULTS:

AFCLEGM was 161 ± 18 ms in 29 AF episodes. Two horses showed atrial flutter and had an AFCLEGM of 244 and 324 ms. The mean bias between AFCLTDI and AFCLEGM ranged from -18 ms to +9 ms depending on the atrial wall region. AFCLTDI was significantly shorter in the left atrial free wall from the right parasternal 4-chamber view and short-axis view compared to the other regions (P<0.001).

CONCLUSIONS:

TDI allows non-invasive measurement of AFCL in horses with AF and is able to identify spatial differences within the equine atria. AFCL may be an important variable to study AF pathophysiology or the effect of anti-arrhythmic drugs.