Cathrine T. Fjordbakk

REASON FOR PERFORMING STUDY: Dynamic laryngeal collapse (DLC) associated with poll flexion is a newly diagnosed upper respiratory tract obstructive disorder that causes poor racing performance. OBJECTIVES: To determine if Norwegian Coldblooded Trotters (NCTs) affected with DLC associated with poll flexion differ from normal, elite NCTs based on simple airway mechanics measurements. METHODS: Five normal elite NCTs and 6 NCTs diagnosed previously with DLC underwent treadmill videoendoscopy while tracheal pressures were measured continuously. Alternating head positions were used such that horses were exercised with free head carriage and induced poll flexion at heart rates >200 beats/min. RESULTS: Peak inspiratory tracheal pressures were significantly more negative for horses with DLC compared to the elite horses. This difference was only significant during the exercise phases when the poll region was flexed, P = 0.0015. Head position significantly affected peak inspiratory pressure for both elite and affected horses, P < 0.0001. CONCLUSIONS AND CLINICAL RELEVANCE: Induced poll flexion significantly affected peak inspiratory pressure (PIP) in all horses; however, PIPs were significantly more negative in those affected with DLC. Based upon the tracheal pressure measurements recorded in this study, DLC in NCTs is a severe obstructive upper respiratory tract disorder that is induced by poll flexion.

Significance Bioelectronic modulation of the autonomic nervous system innervating the spleen represents a new therapeutic avenue. Studies in rodents suffer from the limitation that stimulation parameters and anatomy are not directly applicable to humans. This work demonstrates the translation of biological mechanisms in a large animal model with similar anatomical, histological, and functional characteristics for derivation of human-relevant parameters. Here, we show the scientific process for translating a bioelectronic medicine to clinical readiness. The results presented can be used in three ways: 1) as a system to demonstrate the species translation of neuroimmune modulation, 2) as an exemplar of how translational models can reveal additional potential mechanisms, and 3) as a general methodology to determine human-relevant stimulation parameters.

REASONS FOR PERFORMING STUDY: Two genetically and phenotypically distinct horse breeds are used for harness racing in Scandinavia: the Standardbred (SB) and Coldblooded Trotter. These racehorses have identical environmental, management and racing conditions. Therefore, this study was undertaken to identify and compare the relative prevalence of upper respiratory tract (URT) obstructive disorders in these 2 breeds. OBJECTIVES: To determine whether these 2 phenotypically different breeds of harness racehorses have different predispositions for URT disorders. METHODS: Retrospective study of 88 Norwegian Coldblooded Trotters (NCT) and 97 SBs referred to this hospital for URT evaluation between 1998 and 2006. Case records of all horses diagnosed with an URT disorder during resting endoscopy, and all horses undergoing high-speed treadmill videoendoscopy (HSTV) with one or more periods of induced poll flexion were evaluated. The relative prevalence of URT disorders between the 2 breeds was analysed using a Fisher's exact test. RESULTS: There was a significant (P<0.05) breed predisposition regarding 6 URT disorders. Bilateral dynamic laryngeal collapse associated with poll flexion and flaccid epiglottis was significantly more frequent in the NCT. Alar fold collapse and nasopharyngeal collapse were significantly more frequent in SBs. Epiglottic entrapment and nasal flutter were only diagnosed in the SBs. Dynamic disorders were more common than resting disorders in both breeds. CONCLUSION: URT obstructive disorders (dynamic laryngeal collapse associated with poll flexion, flaccid epiglottis, pharyngeal collapse, alar fold collapse, nasal flutter and epiglottic entrapment) are breed related, indicating an anatomic or functional cause. Periods of induced poll flexion during HSTV was essential to declare harness racehorses free of URT disorders. POTENTIAL RELEVANCE: Further anatomic or physiological studies comparing these breeds could potentially provide insight into the pathogenesis of certain URT obstructive disorders. Induced poll flexion should be included in routine HSTV examinations of all harness racehorses.

A retrospective study of 63 horses diagnosed with limb cellulitis between 1994 and 2005 was conducted. They all had an acute onset of painful, generalised limb swelling, and a clinical diagnosis of limb cellulitis was made by the attending clinician. None of the horses had more than one limb affected. Hindlimbs were significantly more often affected than the forelimbs (P<0.05). Thoroughbreds were significantly over-represented compared with the general distribution of breeds examined at the hospital. Blunt limb trauma, limb surgery and limb injections were associated with the cellulitis in most of the horses, but no plausible cause could be determined in 27 (43 per cent) of the cases. Staphylococcus aureus and Streptococcus species were frequently isolated, although mixed bacterial infections were also common. All the horses were treated with broad spectrum antimicrobials and non-steroidal anti-inflammatory agents, and ultrasound-guided surgical drainage was also applied in 14 cases. Fifty-six of the 63 horses (89 per cent) were discharged from the hospital. Laminitis affecting the contralateral limb was the most common reason for the euthanasia of the other seven horses.