Alessandra Ramseyer

Effects of genetic and environmental factors on chronic lower airway disease in horses

BACKGROUND Environment and genetics influence the manifestation of recurrent airway obstruction (RAO), but the associations of specific factors with mild, moderate, and severe clinical signs are unknown. HYPOTHESIS We hypothesized that sire, feed, bedding, time outdoors, sex, and age are associated with clinical manifestations of mild, moderate, and severe lower airway disease. ANIMALS Direct offspring of 2 RAO-affected Warmblood stallions (F1S1, n = 172; F1S2, n = 135); maternal half-siblings of F1S1 (mHSS1, n = 66); and an age-matched, randomly chosen control group (CG, n = 33). METHODS A standardized questionnaire was used to assess potential risk factors and to establish a horse owner assessed respiratory signs index (HOARSI 1-4, from healthy to severe) according to clinical signs of lower airway disease. RESULTS More F1S1 and F1S2 horses showed moderate to severe clinical signs (HOARSI 3 and HOARSI 4 combined, 29.6 and 27.3%, respectively) compared with CG and mHSS1 horses (9.1 and 6.2%, respectively; contingency table overall test, P < .001). Sire, hay feeding, and age (in decreasing order of strength) were associated with more severe clinical signs (higher HOARSI), more frequent coughing, and nasal discharge. CONCLUSIONS AND CLINICAL RELEVANCE There is a genetic predisposition and lesser but also marked effects of hay feeding and age on the manifestation of moderate to severe clinical signs, most markedly on coughing frequency. In contrast, mild clinical signs were not associated with sire or hay feeding in our populations.

A region on equine chromosome 13 is linked to recurrent airway obstruction in horses

UNLABELLED REASONS FOR STUDY: Equine recurrent airway obstruction (RAO) is probably dependent on a complex interaction of genetic and environmental factors and shares many characteristic features with human asthma. Interleukin 4 receptor a chain (IL4RA) is a candidate gene because of its role in the development of human asthma, confirmation of this association is therefore required. METHODS The equine BAC clone containing the IL4RA gene was localised to ECA13q13 by the FISH method. Microsatellite markers in this region were investigated for possible association and linkage with RAO in 2 large Warmblood halfsib families. Based on a history of clinical signs (coughing, nasal discharge, abnormal breathing and poor performance), horses were classified in a horse owner assessed respiratory signs index (HOARSI 1-4: from healthy, mild, moderate to severe signs). Four microsatellite markers (AHT133, LEX041, VHL47, ASB037) were analysed in the offspring of Sire 1 (48 unaffected HOARSI 1 vs. 59 affected HOARSI 2-4) and Sire 2 (35 HOARSI 1 vs. 50 HOARSI 2-4), age 07 years. RESULTS For both sires haplotypes could be established in the order AHT133-LEXO47-VHL47-ASB37. The distances in this order were estimated to be 2.9, 0.9 and 2.3 centiMorgans, respectively. Haplotype association with mild to severe clinical signs of chronic lower airway disease (HOARSI 2-4) was significant in the offspring of Sire 1 (P = 0.026) but not significant for the offspring of Sire 2 (P = 0.32). Linkage analysis showed the ECA13q13 region containing IL4RA to be linked to equine chronic lower airway disease in one family (P<0.01), but not in the second family. CONCLUSIONS This supports a genetic background for equine RAO and indicates that IL4RA is a candidate gene with possible locus heterogeneity for this disease. POTENTIAL RELEVANCE Identification of major genes for RAO may provide a basis for breeding and individual prevention for this important disease.

Endoscopic scoring of the tracheal septum in horses and its clinical relevance for the evaluation of lower airway health in horses.

REASONS FOR PERFORMING STUDY Although endoscopic scoring of the tracheal septum thickness is used as a diagnostic tool for evaluation of lower airway disease, its clinical relevance and reliability have never been critically assessed in the horse. OBJECTIVES To investigate if septum thickness scores (STS) are reliable and serve as a clinically useful indicator of lower airway disease status and/or inflammation. METHODS The variance of STS attributable to the horse, observer and changes over time was determined. The distribution of STS in a population of clinically normal horses and correlations of STS with age, gender, as well as mucus accumulation and cell differentials of tracheobronchial secretions and bronchoalveolar lavage fluid were investigated. Effects of altered pulmonary ventilation, induced by different drugs, on STS were assessed. Finally, STS of horses affected with recurrent airway obstruction (RAO) were compared to those of clinically normal horses. RESULTS Recorded STS showed excellent intra- and satisfactory interobserver agreement Established clinical, endoscopic and cytological measures of lower airway inflammation, i.e. mucus accumulation scores and airway neutrophilia, did not correlate with STS. In horses age > or = 10 years, septum scores were significantly higher (P = 0.022) than in younger horses. Septum thickness scores did not differ significantly between clinically normal and RAO-affected horses both in exacerbation and in remission. Horses with markedly increased breathing effort (i.e. with metacholine- or lobeline hydrochloride-challenge), often differed markedly (up to 1.9 scores), but the average of end-inspiratory and end-expiratory STS did not differ from baseline STS. CONCLUSIONS AND CLINICAL RELEVANCE Endoscopic STS are a reproducible measure, but STS did not correlate with clinical, endoscopic and cytological findings indicative of RAO or inflammatory airway disease.

The physiological consequences of crib-biting in horses in response to an ACTH challenge test.

Stereotypies are repetitive and relatively invariant patterns of behavior, which are observed in a wide range of species in captivity. Stereotypic behavior occurs when environmental demands produce a physiological response that, if sustained for an extended period, exceeds the natural physiological regulatory capacity of the organism, particularly in situations that include unpredictability and uncontrollability. One hypothesis is that stereotypic behavior functions to cope with stressful environments, but the existing evidence is contradictory. To address the coping hypothesis of stereotypies, we triggered physiological reactions in 22 horses affected by stereotypic behavior (crib-biters) and 21 non-crib-biters (controls), using an ACTH challenge test. Following administration of an ACTH injection, we measured saliva cortisol every 30 min and heart rate (HR) continuously for a period of 3h. We did not find any differences in HR or HR variability between the two groups, but crib-biters (Group CB) had significantly higher cortisol responses than controls (Group C; mean ± SD: CB, 5.84 ± 2.62 ng/ml, C, 4.76 ± 3.04 ng/ml). Moreover, crib-biters that did not perform the stereotypic behavior during the 3-hour test period (Group B) had significantly higher cortisol levels than controls, which was not the case of crib-biters showing stereotypic behavior (Group A) (B, 6.44 ± 2.38 ng/ml A, 5.58 ± 2.69 ng/ml). Our results suggest that crib-biting is a coping strategy that helps stereotypic individuals to reduce cortisol levels caused by stressful situations. We conclude that preventing stereotypic horses from crib-biting could be an inappropriate strategy to control this abnormal behavior, as it prevents individuals from coping with situations that they perceive as stressful.

Genetics of recurrent airway obstruction (RAO)

Recurrent airway obstruction (RAO) is a multifactorial and polygenic disease. Affected horses are typically 7 years of age or older and show exercise intolerance, increased breathing effort, coughing, airway neutrophilia, mucus accumulation and hyperreactivity as well as cholinergic bronchospasm. The environmental factors responsible are predominantly allergens and irritants in haydust, but the immunological mechanisms underlying RAO are still unclear. Several studies have demonstrated a familiar predisposition for RAO and it is now proven that the disease has a genetic basis. In offspring, the risk of developing RAO is 3-fold increased when one parent is affected and increases to almost 5-fold when both parents have RAO. Segregation analysis in two high-prevalence families demonstrated a high heritability and a complex inheritance with several major genes. A whole genomescan showed chromosome-wide significant linkage of seven chromosomal regions with RAO. Of the microsatellites, which were located near atopy candidate genes, those in a region of chromosome 13 harboring the IL4R gene were strongly associated with the RAO phenotype in the offspring of one RAO-affected stallion. Furthermore, IgE-levels are influenced by hereditary factors in the horse, and we have evidence that RAO-affected offspring of the same stallion have increased levels of specific IgE against moldspore allergens. The identification of genetic markers and ultimately of the responsible genes will not only allow for an improved prophylaxis, i.e. early identification of susceptible individuals and avoidance of high-risk matings, but also improve our ability to find new therapeutic targets and to optimize existing treatments.

Increased adrenocortical response to adrenocorticotropic hormone (ACTH) in sport horses with equine glandular gastric disease (EGGD).

This study tested the hypothesis that adrenocortical function would be altered in horses with equine gastric ulcer syndrome (EGUS). Twenty-six sport horses competing at national or international levels in eventing (n=15) or endurance (n=11) were subjected to a gastroscopic examination and an adrenocorticotropic hormone (ACTH) stimulation test. Salivary cortisol concentrations were measured before (baseline) and after (30, 60, 90, 120 and 150min) IV ACTH injection (1μg/kg bodyweight). Within EGUS, two distinct diseases, equine squamous gastric disease (ESGD) and equine glandular gastric disease (EGGD), can be distinguished. ESGD was diagnosed in 8/11 (73%; 95% confidence intervals [95%CI], 43-92%) endurance horses and 5/15 (33%; 95% CI, 14-58%) eventing horses. EGGD was observed in 9/11 (82%; 95% CI, 53-96%) endurance horses and 9/15 (60%; 95% CI, 35-81%) eventing horses. The presence or severity of ESGD was unrelated to the presence or severity of EGGD. ACTH stimulation induced a larger increase in cortisol concentration in horses with moderate EGGD than in horses with mild EGGD. Cortisol concentration during the entire sampling period (total increase in cortisol concentration during the entire sampling period [dAUC], 31.1±6.4ng/mL) and the highest measured concentration at a single time point (maximal increase in cortisol concentration [dMAX], 10.3±2.3ng/mL) were increased (P=0.005 and P=0.038, respectively), indicating that horses with glandular gastric disease exhibited increased adrenocortical responses to ACTH stimulation. These results suggest that EGGD might be associated with an enhanced adrenocortical sensitivity. Further investigations are warranted to confirm the association between adrenocortical sensitivity and EGGD and to elucidate the pathophysiological mechanisms involved.

Safety of Intra-Articular Gold Microimplants in Horses–A Randomized, Blinded, Controlled Experimental Study

Abstract Arthrogenic pain is a common problem in equids. Frequently used treatments such as systemic non‐steroidal anti‐inflammatory drugs or intra‐articular steroids can lead to severe side effects if used repeatedly. Gold has been used since ancient times to treat a variety of conditions and has anti‐inflammatory and immunomodulating properties. Results from clinical and in vitro studies suggest that local gold might provide a safe and effective alternative to alleviate articular pain. In particular, gold microimplants have been proposed to this end, but it is unknown if and how healthy joints react to this treatment. The aim of this study was to evaluate the safety of gold microimplants (Berlock‐Micro‐Implants) mixed with hyaluronic acid and injected into the middle carpal joint of nine healthy horses. Each horse was treated in one carpus and sham‐treated on the contralateral. Lameness, carpal temperature increase, swelling, and reactions to joint palpation were observed in both treated and sham‐treated carpi in the first week after needle arthroscopy and treatment. Significant differences between treated and sham‐treated carpi were found only for mechanical nociceptive thresholds 4 days after treatment. Higher thresholds were found in treated joints compared with sham‐treated joints. None of the outcome measures selected in the present study indicated systemic or local adverse effects specifically attributed to gold microimplants. In the absence of systemic and local adverse reactions to gold microimplants, the results of the present study support future clinical trials to test the pain‐relieving efficacy of this treatment modality in subacute or chronic articular inflammatory processes in equine patients. HighlightsThe safety of intra‐articular gold microimplants was evaluated in healthy horses.No systemic or local adverse effects specifically attributed to gold microimplants were found.The pain‐relieving efficacy of gold microimplants can now be evaluated in equine patients.

Repeated Measurements of Markers of Autonomic Tone Over a Training Season in Eventing Horses

&NA; Autonomic nervous system tone varies with fitness, training, and conditions such as cardiac disease, hypertension, or overtraining. Normal values of autonomic tone markers and changes over a competition season are incompletely described in eventing horses. The objectives of this study were to describe normal values and changes over a competition season of markers of autonomic tone in competing eventing horses. These values were measured in conjunction with previously reported variables to monitor training and compared with non‐competing breed‐matched controls. Heart rate variability (HRV), non‐invasive blood pressure, splenic volume, pre‐ and post‐exercise hematocrit and cortisol, standardized exercise tests (SETs), and muscle enzyme activities were measured preseason (T1), midseason (T2), and at the peak and/or end of the competition season (T3) in eventing and control horses. Heart rate variability was lower (P < .05) at all times and post‐exercise cortisol lower at T2 and T3 in eventing horses compared with controls. Heart rate variability and post‐exercise cortisol did not change over the season in any group. Eventers had higher fitness levels during SETs than controls. Non‐invasive blood pressure, splenic volume, hematocrit, pre‐exercise cortisol, muscle enzyme activities, and weight were not significantly different between groups and did not change over the season. The lower HRV in competing eventers suggests a lower parasympathetic and/or higher sympathetic tone in this group. A lower post‐exercise cortisol suggests a decreased stress response in eventers to the SET. Non‐invasive blood pressure, splenic volume, and resting or post‐exercise hematocrit did not detect differences or changes in autonomic tone in this population. HighlightsMarkers of autonomic tone were repeatedly measured in eventers.Eventing horses had significantly lower heart rate variability than control horses.Eventing horses had a lower postexercise cortisol.

Complications associated with closed castration using the Henderson equine castration instrument in 300 standing equids: RACINE ET AL.

OBJECTIVE To describe a closed castration technique in standing equids, report associated complications, and identify potential risk factors. STUDY DESIGN Prospective cohort study of 300 standing equids that were castrated with the Henderson Equine Castrating Instrument. METHODS Thirteen participating veterinarians recorded intraoperative difficulties and postoperative complications. Descriptive statistics, univariate analyses with Fishers exact tests, and logistic regressions were used to evaluate intraoperative difficulties and postoperative complications and to assess risk factors for postoperative complications. RESULTS Data were collected on 300 equids (269 horses, 23 ponies, and 8 donkeys). Intraoperative difficulties were experienced in 39 of 300 (13%) procedures. Postoperative complications were reported in 69 of 300 (23%) equids, including excessive swelling (29, 9.67%), surgical site infection (SSI; 27, 9%), severe hemorrhage (3, 1%), and prolapse of the omentum (2, 0.64%). Donkeys were at increased risk of severe hemorrhage (2/8, 25%, P = .0019). Equids that were castrated in a hospital setting (83/300, 27.66%) more frequently developed excessive swelling (P = .0034, odds ratio [OR] = 3.20) and SSI (P = .0047, OR = 3.18) compared with equids that were castrated in a field setting (217/300, 72.33%). Prolonging antimicrobial prophylaxis or age of the equid at the time of castration had no effect on the prevalence of excessive swelling or SSI. CONCLUSION The method of castration evaluated here resulted in a similar prevalence of postoperative complications to that previously reported for castrations in standing horses but fewer SSI. CLINICAL SIGNIFICANCE The described method provides a viable option for castrating horses and ponies, but is not recommended in donkeys.

Effect of three types of horseshoes and unshod feet on selected non-podal forelimb kinematic variables measured by an extremity mounted inertial measurement unit sensor system in sound horses at the trot under conditions of treadmill and soft geotextile surface exercise

Therapeutic farriery is part of the management of certain orthopaedic conditions. Non-podal parameters are important as most horses shod with therapeutic shoes are expected to perform again and the choice of shoe type may be influenced by the effects they may have on gait. The aim of this prospective study was to evaluate the effects of three different shoe designs and unshod front feet on forelimb non-podal kinematic variables using an extremity mounted inertial measurement unit (IMU) system under conditions of treadmill and overground exercise on a soft geotextile surface at the trot. Ten sound horses with no underlying orthopaedic problem were instrumented with eight IMUs at distal radii, tibia and third metacarpal/tarsal regions. Measurements were performed during four consecutive days. During the first three days, the three shoe types were randomly selected per horse and day. On the fourth day, all horses were tested unshod. Data were collected at the trot on a treadmill, and on a soft geotextile surface. Specifically designed software and a proprietary algorithm processed the accelerometer and gyroscope signals to obtain orientation and temporal data to describe selected kinematic variables predetermined by the system. Repeated-measures analysis of variance (ANOVA) was used to assess differences between shoe type and surface. The presence of shoes produced significant changes in spatiotemporal variables which seemed to be related to shoe mass rather than shoe design as there were no significant differences found between different shoe types. Shod horses showed a gait characterised by an increased range of motion (ROM) of the fore limbs. Previously reported effects of the investigated shoes on podal kinematics do not seem to affect the investigated kinematic variables indicating perhaps a compensatory effect occurring at some level in the extremity.