Dangerous Behavior and Intractable Axial Skeletal Pain in Performance Horses: A Possible Role for Ganglioneuritis (14 Cases; 2014-2019)

Primary phenotypic features associated with caudal neck pathology in warmblood horses

BACKGROUND

Detailed descriptions of clinical signs associated with radiological findings of the caudal cervical vertebral column are not available.

OBJECTIVES/HYPOTHESES

Describe the clinical features associated with neck pain or stiffness, neck-related thoracic limb lameness, proprioceptive ataxia consistent with a cervicothoracic spinal cord or nerve lesion, and their frequency of occurrence compared with control horses.

ANIMALS

A total of 223 Warmblood horses.

METHODS

Case-control study. Controls and cases were recruited prospectively. All horses underwent predetermined lameness and neurologic examinations. The frequency of occurrence of each clinical feature was compared between cases and controls and relative risk (RR) were calculated.

RESULTS

Ninety-six cases and 127 controls were included. Forty-seven (49%) of the cases were classified as neurologic, 31 (32.3%) had thoracic limb lameness, and 18 (18.7%) had neck stiffness or pain or both. Focal caudal cervical muscle atrophy (46, 47.9%), hypoesthesia (38, 39.6%), patchy sweating (16, 16.7%), hyperesthesia (11, 11.5%), and pain upon firm pressure applied over the caudal cervical articular process joints and transverse processes (58, 60.4%) were only observed in cases (P < .001). Sideways flexion of the neck was restricted in a higher proportion of cases (47/96, 49%) compared with controls (40/127, 31.8%; P = .009, RR 1.5). Hopping-type thoracic limb lameness was only observed in cases, (30, 31.6%). Deterioration in lameness after diagnostic anesthesia occurred in 13/31 (41.9%) cases.

CONCLUSIONS AND CLINICAL IMPORTANCE

Systematic clinical evaluation using the methods described should enable clinical differentiation between horses with caudal cervical lesions and horses with other causes of gait abnormalities.

Reported Agonistic Behaviours in Domestic Horses Cluster According to Context

Agonistic behaviours are often directed at other animals for self-defence or to increase distance from valued resources, such as food. Examples include aggression and counter-predator behaviours. Contemporary diets may boost the value of food as a resource and create unanticipated associations with the humans who deliver it. At the same time the domestic horse is asked to carry the weight of riders and perform manoeuvres that, ethologically, are out-of-context and may be associated with instances of pain, confusion, or fear. Agonistic responses can endanger personnel and conspecifics. They are traditionally grouped along with so-called vices as being undesirable and worthy of punishment; a response that can often make horses more dangerous. The current study used data from the validated online Equine Behavioural and Research Questionnaire (E-BARQ) to explore the agonistic behaviours (as reported by the owners) of 2734 horses. With a focus on ridden horses, the behaviours of interest in the current study ranged from biting and bite threats and kicking and kick threats to tail swishing as an accompaniment to signs of escalating irritation when horses are approached, prepared for ridden work, ridden, and hosed down (e.g., after work). Analysis of the responses according to the context in which they arise included a dendrographic analysis that identified five clusters of agonistic behaviours among certain groups of horses and a principal component analysis that revealed six components, strongly related to the five clusters. Taken together, these results highlight the prospect that the motivation to show these responses differs with context. The clusters with common characteristics were those observed in the context of: locomotion under saddle; saddling; reactions in a familiar environment, inter-specific threats, and intra-specific threats. These findings highlight the potential roles of fear and pain in such unwelcome responses and challenge the simplistic view that the problems lie with the nature of the horses themselves rather than historic or current management practices. Improved understanding of agonistic responses in horses will reduce the inclination of owners to label horses that show such context-specific responses as being generally aggressive.

Clinical and histopathological features in horses with neuroaxonal degeneration: 100 cases (2017-2021)

BACKGROUND

Adult horses with proprioceptive ataxia and behavior changes that have histologic lesions consistent with neurodegenerative disease have been increasingly recognized.

HYPOTHESIS/OBJECTIVES

Describe the history, clinical findings and histopathologic features of horses presented to a referral institution with neuroaxonal degeneration.

ANIMALS

One hundred horses with a necropsy diagnosis of neuroaxonal degeneration compatible with neuroaxonal dystrophy/degenerative myeloencephalopathy (eNAD/EDM).

METHODS

Retrospective study of horses presented to the University of Pennsylvania, New Bolton Center, between 2017 and 2021 with a necropsy diagnosis of eNAD/EDM.

RESULTS

Affected horses had a median age of 8 years (range, 1-22), and the majority were Warmbloods (72). Sixty-eight horses had behavioral changes, and all 100 had proprioceptive ataxia (median grade, 2/5). Fifty-seven horses had abnormal findings on cervical vertebral radiographs, and 14 had myelographic findings consistent with compressive myelopathy. No antemortem diagnostic test results were consistently associated with necropsy diagnosis of neurodegenerative disease. All 100 horses had degenerative lesions characteristic of eNAD in the brainstem gray matter, and 24 had concurrent degenerative features of EDM in the spinal cord white matter.

CONCLUSIONS AND CLINICAL IMPORTANCE

Clinical and histopathologic findings in this large group of horses with neurodegenerative disease were most consistent with eNAD/EDM, but with a different signalment and clinical presentation from earlier descriptions. The increasing occurrence of neurodegenerative disease in horses and the safety risk posed emphasize the importance of focused research in affected horses.

How equestrians conceptualise horse welfare: Does it facilitate or hinder change?

More than ever the welfare of horses in equestrian sport is in the spotlight. In response to this scrutiny, one peak body, the Federation Equestre Internationale (FEI) has created an Equine Ethics and Wellbeing Commission to protect their sport's longevity. However, for welfare-based strategies to be successful, the conceptualisation of horse welfare must align across various stakeholders, including the general public. The value-laden nature of welfare makes agreement on its definition, even among scientists, difficult. Given little is known about how equestrians conceptualise horse welfare, we interviewed 19 Australian amateur equestrians using a semi-structured format. Systems thinking and the Five Domains Model provided the theoretical framework and informed our methods. Using reflexive thematic analysis, three themes were identified: (1) good horse welfare is tangible; (2) owners misinterpret unwanted horse behaviour; and (3) equestrians publicly minimise horse welfare issues but are privately concerned. Our results highlight participants' conceptualisations of horse welfare do not align with the Five Domains Model; participants' ideal of prioritising horse welfare does not align with their practice; and there is inconsistency between what participants share publicly and what they think privately about horse welfare. These findings can inform the development of programmes to improve ridden horse welfare throughout the horse industry. As a starting point, programmes that provide a safe space for equestrians to explore their private horse welfare concerns, and programmes that build a partnership mindset to facilitate knowledge exchange between all stakeholders are needed.

Understanding and treating equine behavioural problems

Behaviour-related issues are common in horses. Many 'undesirable behaviours' pose important safety concerns for the human handlers / riders / carers, as well as welfare concerns for the horse. Undesirable behaviours can also devalue a horse, or result in the horse being re-homed, relinquished, or euthanased. Undesirable behaviours occur for a range of reasons. These include physiological causes, poor management, and the use of inappropriate or poorly applied handling and training techniques. The potential contribution of each of these aspects must be considered when attempting to reduce or eliminate undesirable behaviours. Effectively modifying the existing behaviour includes investigation and treatment of potential physiological causes, assessing and adjusting existing handling, husbandry and management, and undertaking behaviour modifying training. Unlike in the treatment of dogs and cats, the use of psychotropic agents is uncommon in equine behaviour medicine but the benefits of using these agents in appropriate cases is gaining recognition. This review discusses potential causes for the development and maintenance of undesirable behaviours in horses and highlights the various considerations involved in determining the most appropriate course for reducing or eliminating these behaviours. There is also a brief discussion about the potential role of psychotropic agents as an additional component of an overall behaviour modification plan to reduce or eliminate undesirable behaviours in horses.

Age and sex correlate with bony changes and anatomic variations of the lumbosacroiliac region of the vertebral column in a mixed population of horses

OBJECTIVE

To provide a postmortem description of anatomic variations and changes of the lumbosacroiliac region in horses. The authors hypothesized that lesion severity would increase with age and body weight and correlate to anatomic variations.

SAMPLES

Lumbosacroiliac vertebral specimens from 38 horses (mean age, 16 years; range, 5 to 30 years) that died or were euthanized for reasons unrelated to the study between November 2019 and October 2021.

PROCEDURES

The lumbosacroiliac region of the vertebral column was removed from each cadaver. After dissection, disarticulation, and boiling, the anatomic specimens were examined for anatomic variations and osseous changes of the articular process joints (APJs), intertransverse joints (ITJs), and sacroiliac joints (SIJs). The lengths of L6-S1 intertransverse articular surfaces were measured and their ratios calculated. Descriptive statistics were obtained, and the χ2 test was used to assess differences in anatomic variations and abnormal changes of the APJs, ITJs, and SIJs.

RESULTS

The most common anatomic variation was a sacrum-like shape of the transverse processes of L6 (29/38 [76%]) and converging orientation of dorsal spinous process of L6 (33/38 [87%]). The highest prevalence of bony changes was detected at L5-L6 (right, 34/38 [89%]; left, 33/38 [87%]) and L6-S1 APJs (right, 38/38 [100%]; left, 37/38 [97%]) and at SIJs (right, 32/38 [86%]; left, 31/38 [82%]). The shape of L6 transverse processes differed between breed (P = .01) and was associated with presence of L4-L5 ITJs (P < .01).

CLINICAL RELEVANCE

Age and sex were associated with changes of the sacral dorsal spinous processes, ITJs, and APJs. The clinical significance of these findings could not be confirmed based on the study limitations.

The Effect of Chiropractic Treatment on Limb Lameness and Concurrent Axial Skeleton Pain and Dysfunction in Horses

Chiropractic care is a common treatment modality used in equine practice to manage back pain and stiffness but has limited evidence for treating lameness. The objective of this blinded, controlled clinical trial was to evaluate the effect of chiropractic treatment on chronic lameness and concurrent axial skeleton pain and dysfunction. Two groups of horses with multiple limb lameness (polo) or isolated hind limb lameness (Quarter Horses) were enrolled. Outcome measures included subjective and objective measures of lameness, spinal pain and stiffness, epaxial muscle hypertonicity, and mechanical nociceptive thresholds collected on days 0, 14, and 28. Chiropractic treatment was applied on days 0, 7, 14, and 21. No treatment was applied to control horses. Data was analyzed by a mixed model fit separately for each response variable (p < 0.05) and was examined within each group of horses individually. Significant treatment effects were noted in subjective measures of hind limb and whole-body lameness scores and vertebral stiffness. Limited or inconsistent therapeutic effects were noted in objective lameness scores and other measures of axial skeleton pain and dysfunction. The lack of pathoanatomical diagnoses, multilimb lameness, and lack of validated outcome measures likely had negative impacts on the results.

A systematic review of clinical signs associated with degenerative conditions and morphological variations of the equine caudal neck

Conditions of the equine caudal neck (C5-C7) are thought to be associated with various clinical signs. However, little investigation has been undertaken to isolate clinical indicators associated with specific conditions of the equine caudal cervical spine. This systematic review aimed to evaluate associations of clinical signs with anatomical malformation of caudal cervical vertebrae, spinal cord compression of the caudal cervical spine, and arthropathy of the caudal cervical articular process joints (APJs). A literature search was carried out using Google Scholar in accordance with PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) guidelines. Studies were selected for inclusion in this systematic review according to a set of inclusion criteria, resulting in a small group of eligible studies (n=12) that addressed clinical signs associated with caudal cervical spine conditions in horses. The results of the included studies indicate that there are grounds for further investigation of clinical presentations of specific conditions of the equine caudal neck such as anatomical variations, myelopathy, and alteration to the APJs.