Prevalence of headshaking within the equine population in the UK

Effect of repetitive transcranial magnetic stimulation on trigeminal-mediated headshaking in 17 horses

BACKGROUND

Trigeminal-mediated headshaking is a neuropathic facial pain condition in horses. No treatment has been entirely successful. Repetitive transcranial magnetic stimulation (rTMS) is used in human medicine as a treatment for various neuropathic pain conditions, and good results have been achieved in cases of trigeminal neuralgia.

OBJECTIVES

Apply rTMS to horses with trigeminal-mediated headshaking (TMHS) and to evaluate tolerability, application of the setting, and success rate.

ANIMALS

Seventeen horses with nonseasonal signs of TMHS.

METHODS

Other underlying causes of headshaking were ruled out. The rTMS was performed under standing sedation on 5 consecutive days applying 3 sets of 500 stimulations each, with a stimulation strength of 5 Hz. Horses were evaluated on Day 1 (t0) and Day 5 (t1) of the treatment and 2 (t2) and 4 weeks (t3) afterwards using a special scoring system.

RESULTS

The rTMS was well tolerated. Headshaking signs during exercise were decreased by 70% (Day 5; t1). Four weeks after rTMS, signs were still decreased (mean reduction of 50%) during exercise. Improvement of mean resting and exercise scores was significant (P < .05) and effect sizes between pretreatment and all time points after treatment (t1, t2, t3) were large (>±0.8).

CONCLUSIONS AND CLINICAL IMPORTANCE

Repetitive transcranial magnetic stimulation may be a promising treatment for neuropathic pain and headshaking in affected horses. Pain-free periods after treatment differ individually, and repeated treatment may be necessary. More studies should be performed to determine ideal settings for horses.

Use of a poll-mounted accelerometer for quantification and characterisation of equine trigeminal-mediated headshaking

BACKGROUND

Equine trigeminal-mediated (TGM) headshaking (HS) is a neuropathic facial pain syndrome characterised by varying intensity and frequencies of head movements and signs of nasal irritation. An accurate method for quantification and/or characterisation of HS severity is lacking.

OBJECTIVES

To develop and validate an objective measure of TGMHS.

STUDY DESIGN

Prospective case control study.

METHODS

Horses presenting for investigation of HS were recruited alongside those presenting for forelimb lameness (LAME) and pre-purchase examination as well as healthy controls (CONTROL). Head movement data were collected for 5 min whilst trotting on the lunge using a tri-axial accelerometer, with a range of ±16 g and sampling rate of 800 Hz, attached to the bridle headpiece. Recordings were exported for processing. Peak detection was performed using minimum and maximum thresholds of -1 g and +1 g (corrected for gravity) and a minimum peak width of 10 samples.

RESULTS

Fifty-six horses were included in the study; 18 TGMHS, 10 non-TGMHS, 12 LAME and 16 CONTROL. Characteristics and frequency of vertical (Z axis) head movements of TGMHS horses differed significantly from other horses. TGMHS horses had peaks with greater mean and maximum positive g-force (P < 0.005) and lower mean and minimum negative g-force (P < 0.001), greater frequency of peaks/min (P < 0.001) and over 12 times greater percentage of peaks >+2 g compared with other horses (P < 0.001). Receiver operator curve characteristics of percentage of peaks >+2 g (CI 0.72-0.95), percentage of peaks <-2 g (CI 0.66-0.92) and percentage of peaks <-2 g and >+2 g (CI 0.72-0.96) showed excellent discrimination of TGMHS horses from LAME, CONTROL and non-TGMHS horses.

MAIN LIMITATIONS

Referral population of horses, small sample size and control horses were not evaluated for orthopaedic disease.

CONCLUSIONS

Accelerometer data from trotting exercise on the lunge provides an objective measure of HS and can differentiate between TGMHS, non-TGMHS, normal head movements and those associated with forelimb lameness. Accelerometer use may aid HS diagnosis and monitoring of management strategies.

Time-Budget and Welfare Indicators of Stabled Horses in Three Different Stall Architectures: A Cross-Sectional Study

Keeping horses in single stalls can lead to the development of abnormal and stereotypic behaviors (ASB). Opportunities for social interactions and stall architecture can influence behavior. The current study aimed to identify how three different stall architectures influenced time-budget and physiological parameters in horses. Stall types included: (1) 3.2 × 3.7 m with tactile contact between horses (B1); (2) 2.6 × 3.5 m with visual contact between horses and outside view (B2); (3) 2.3 × 3.4 m with visual contact and outside view (B3). Ten horses from B1 and B3, and nine from B2 were randomly selected, filmed for 24 hours and the video was analyzed with continuous behavioral sampling. Nine horses from B1, 8 from B2 and 7 from B3 were randomly selected for blood sampling used to determine cortisol levels, cortisol circadian rhythm (CCR), white blood cells (WBC) and neutrophil/lymphocyte ratio. The effects of different stall architectures were analyzed by ANOVA and post hoc Tukey test. B1 had higher social interaction time (2.77% of the time-budget) (P = .020), with no other differences. Time spent eating represented a low proportion of horses' time-budget (14.31%) and all horses demonstrated ASB behaviors (21.10% of the time-budget). Twenty-five percent of the horses presented low WBC, 38% of the horses had high cortisol levels, and 29% of the horses had an altered CCR. Those alterations along with high prevalence of ASB indicate that horses were in a state of chronic stress. The stalls' architecture did not affect the presence of abnormal behaviors or indicators of stress.

Expression of Cannabinoid Receptors in the Trigeminal Ganglion of the Horse

Cannabinoid receptors are expressed in human and animal trigeminal sensory neurons; however, the expression in the equine trigeminal ganglion is unknown. Ten trigeminal ganglia from five horses were collected post-mortem from an abattoir. The expression of cannabinoid receptors type 1 (CB1R) and type 2 (CB2R), and the cannabinoid-related receptors like transient receptor potential vanilloid type 1 (TRPV1), peroxisome proliferator-activated receptor gamma (PPARɣ), and G protein-related receptor 55 (GPR55) in the trigeminal ganglia (TG) of the horse were studied, using immunofluorescence on cryosections and formalin-fixed paraffin-embedded (FFPE) sections. Neurons and glial cells were identified using fluorescent Nissl staining NeuroTrace® and an antibody directed against the glial marker glial fibrillary acidic protein (GFAP), respectively. Macrophages were identified by means of an antibody directed against the macrophages/microglia marker ionized calcium-binding adapter molecule 1 (IBA1). The protein expression of CB1R, CB2R, TRPV1, and PPARɣ was found in the majority of TG neurons in both cryosections and FFPE sections. The expression of GPR55 immunoreactivity was mainly detectable in FFPE sections, with expression in the majority of sensory neurons. Some receptors were also observed in glial cells (CB2R, TRPV1, PPARγ, and GPR55) and inflammatory cells (PPARγ and GPR55). These results support further investigation of such receptors in disorders of equine trigeminal neuronal excitability.

Impact of Different Diagnostic Procedures on Diagnosis, Therapy, and Outcome in Horses with Headshaking: Recommendations for Fast-Track Advanced Diagnostic and Therapeutic Protocols

Most horses affected by headshaking (HS) are diagnosed with idiopathic trigeminal-mediated headshaking (i-TMHS) when no underlying disease is found. Diagnosis is made by the exclusion of differentials considering history, clinical signs, and diagnostic investigations. Therefore, in horses presented with headshaking, many diagnostic procedures and therapies are conducted. Retrospectively, the digital patient records of 240 horses with HS were analysed regarding the impact of diagnostic procedures on diagnosis, therapy, and outcome. Horses were extensively examined using a standardised protocol including clinical (ophthalmologic, orthopaedic, neurologic, dental) examination, blood analysis, and imaging techniques (endoscopy, radiographs, computed tomography (CT), and magnetic resonance imaging). Many findings were revealed but were of clinical relevance in only 6% of the horses. These horses were, therefore, diagnosed with secondary headshaking (s-HS). In addition, all of these horses demonstrated a positive outcome. The CT of the head revealed 9/10 of the clinically relevant findings. Other diagnostic procedures had no major additional impact. Conclusively, the diagnostic investigation of horses with HS should aim at differentiating i-TMHS from s-HS. The clinical relevance of findings should be verified through diagnostic anaesthesia or targeted therapy depending on risks, invasiveness, and expected benefits. To reduce the multitude of examinations, diagnostic investigations should focus on the CT of the head in those horses with suspicion of i-TMHS based on typical history, clinical signs, and physical examination.

Comparison of the Current Situation of Equine Headshaking Syndrome in France and Switzerland Based on an Online Survey

Simple Summary

Headshaking syndrome is a frustrating health problem in horses whose aetiopathogenesis is poorly understood. This study was dedicated to investigating signalment and therapeutic interventions in headshakers in France and Switzerland. To do this, an online survey was developed and distributed via the Internet. This showed that mainly middle-aged geldings were affected. The breeding distribution matched the breeding distribution of the relevant country. Furthermore, alternative healing methods were used by the horse owners, which have not yet been scientifically examined. Overall, it was possible to formulate conclusions regarding signalment and therapies used in practice.

Abstract

Equine headshaking syndrome (EHS) is characterised as non-physical and involuntary movement of the horse’s head and neck. Although EHS is clinically simple to diagnose, its aetiopathogenesis often remains unclear. The aim of this study was to gain an overview of signalment and therapy possibilities used in France and Switzerland. To do this, an online survey was developed and distributed via newsletters. A total of 933 complete, answered surveys from France (n = 804) and Switzerland (n = 129) were evaluated. The median age in France was 12.4 years (CH = 14.3). Mostly geldings were affected (58.5%_FRA, 57.4%_CH). There was an association with Warmbloods in Switzerland (55.8%_CH), but in France, in addition to Warmbloods (34.4%_FRA), Thoroughbreds (27.2%_FRA) were also affected. Moreover, horses affected by EHS often show stereotypical behaviour (15.7%_FRA, 14.7%_CH). A total of 38.4%_FRA and 67.4%_CH of horse owners utilised therapy measures, with nose covers being most commonly used (19.9%_FRA, 30.2%_CH). Horse owners resorted to alternative treatments that had not previously been studied in context with EHS (15%_FRA, 20.9%_CH). Conservative treatments, such as medication, were used by 5.4%_CH and 1.9%_FRA. This study provides an overview of the status of horses affected by EHS in France and Switzerland and thus offers a fundamental step to understanding the consequences of welfare issues associated with EHS.

Caecal microbiota in horses with trigeminal‐mediated headshaking

Background

Trigeminal‐mediated headshaking (TMHS) in horses is a form of neuropathic pain of undetermined cause that often results in euthanasia. The role of microbiota in TMHS has not been investigated in diseased horses.

Objective

To investigate if gastrointestinal microbiota in the cecum is different in horses with TMHS compared to a control population, during a summer season with clinical manifestations of disease.

Animals

Ten castrated horses: five with TMHS and five neurologically normal controls.

Methods

All horses were sourced from our institution and kept under the same husbandry and dietary conditions. All horses were fed orchard grass hay for 30 days and then were euthanized due to chronic untreatable conditions including TMHS and orthopedic disease (control group). Caecal samples for microbiota analysis were collected within 20 min after euthanasia. Sequencing was performed using an Illumina MiSeq platform and the microbiome was analyzed.

Results

The caecal microbiota of horses with TMHS was similar to control horses in terms of diversity but differed significantly with Methanocorpusculum spp. having higher abundance in horses with TMHS. 

Conclusions and clinical importance

Methanocorpusculum spp. was more abundant in the cecum of horses with TMHS. However, its role in disease is unknown. Furthermore, it could also represent an incidental finding due to our small population size.

Identifying Sources of Potential Bias When Using Online Survey Data to Explore Horse Training, Management, and Behaviour: A Systematic Literature Review

Owner-reported behavioural observations form an essential part of the veterinarians’ diagnosis and treatment plan. The way we train and manage horses affects their behaviour and, in turn, their health and welfare. Current horse training and management practices are largely driven by traditional techniques and longstanding methodologies. These approaches generally lack an evidence base for evaluation purposes. The absence of evidence and evaluation contributes to the persistent use of risky practices and this, in turn, increases risk of potential harms for both horse and rider, and fuels questioning of the equine industry’s current social license to operate. Objective evidence is required to make training and management decisions based on demonstrable best practice. Large-scale experimental or intervention studies using horses are generally not practical because of the associated costs and logistics of gaining ethical approval. Small studies generally lack statistical power and are subject to the effects of many forms of bias that demand caution in the interpretation of any observed effects. An alternative to collecting large amounts of empirical data is the use of owner-reported observations via online survey. Horse owners are ideally placed to report on the domestic equine triad of training, management, and behaviour. The current article highlights three sources of potential bias in a systematic review of literature on large-scale online studies of horse owners’ observational reports that met the following selection criteria: English-language, published, peer-reviewed articles reporting on studies with over 1000 respondents and open access to the survey instrument. The online surveys were evaluated for three common forms of bias: recall, confirmation, and sampling bias. This review reveals that online surveys are useful for gathering data on the triad of horse training, management, and behaviour. However, current use of online surveys to collect data on equitation science (including horse training, management, and behaviour) could be improved by using a standardised and validated tool. Such a tool would facilitate comparisons among equine and equitation science studies, thus advancing our understanding of the impacts of training and management on horse behaviour. The authors of the current review suggest the use of a standardised behavioural and management assessment tool for horses. Such a tool would help define what constitutes normal behaviour within geographically disparate populations of horses, leading to improvements in rider safety and horse welfare.

Overview of the Current Situation in a Sample of Headshakers and Owner Assessment of Effective Therapeutic Measures Used in Germany

Equine headshaking syndrome is a problematic behavior that has been described in literature for more than 100 years. The signs of headshaking syndrome appear frequently and violently so that riding the horse can be dangerous. The aim of this research was to gain an overview of the underlying causes of equine headshaking syndrome to identify effective treatment options, reduce the distress of horses and, in a second step, potentially improve therapeutic possibilities for horse owners and veterinarians. Most studies on prevalence originate from Anglo-American countries, so this research was to provide an overview of German horses; therefore, an online survey was designed by experts in the field (researchers and veterinarians) and answered by German horse owners. Questionnaires were pretested by a small group of horse owners (n = 5) and redesigned accordingly. The final questionnaire consisted of 27 questions, which were divided into seven open questions with an associated text field and 20 multiple-choice questions (Supplementary Material 1). For some of the multiple-choice questions, multiple answers were permitted. In total, 163 completed questionnaires were obtained from owners of headshaking horses (n_total = 163). Gender distribution of the horses resulted in 64.4% geldings, 33.7% mares, and 1.8% stallions. Most horses were German warmbloods (55.4%). The average age was 12.7 years (with a wide range of 5 to 34 years). The vertical movement of the head was the most frequently mentioned symptom in 75.5% of the evaluated horses. In 18.4% of the cases, the horse owners identified stress as the main trigger for headshaking. Furthermore, 18.4% claimed that their horses suffered from additional stereotypical behavior. The percentages do not refer to the same horses here. 11.0% of the participants in this study tried scientifically evaluated therapies such as surgical therapy (1.2%) or medical treatment (9.8%). In addition, 54.0% of the owners utilized a nose cover to reduce the symptoms of the headshaking syndrome. A high percentage of 84.0% used alternative therapies such as physiotherapy (31.9%), change of equipment (22.7%), or change of riding style (29.4%). Overall, this study provides a useful overview of causes and effective therapies.

Differential Defecation of Solid and Liquid Phases in Horses-A Descriptive Survey

Simple Summary

Free faecal liquid is a condition in horses where faeces are voided in one solid and one liquid phase. The presence of free faecal liquid may cause management problems in equine husbandry and is potentially contributing to impaired equine welfare. Causes of free faecal liquid are not known, but nutritional factors such as the feeding of specific forages have been suggested to be of importance. Characterization of horses showing free faecal liquid and their feeding and management was, therefore, performed via an internet-based survey in order to map the condition further. Results showed that horses with free faecal liquid included a large variety of different breeds, ages, disciplines, coat colours, housing systems and feeding strategies, meaning that almost any type of horse could be affected. Horses that were reported to show free faecal liquid did so with all types of feeding strategies, but changes from wrapped forage to hay, to pasture, or to another batch of wrapped forage often resulted in diminished signs of free faecal liquid. Horses were also reported to have a comparably high incidence of colic in relation to published data for other horse populations. The results indicated that more detailed studies are required for a further understanding of the underlying cause of free faecal liquid.

Abstract

Free faecal liquid (FFL) is a condition in horses where faeces are voided in one solid and one liquid phase. The liquid phase contaminates the tail, hindlegs and area around the anus of the horse, resulting in management problems and potentially contributing to impaired equine welfare. The underlying causes are not known, but anecdotal suggestions include feeding wrapped forages or other feed- or management-related factors. Individual horse factors may also be associated with the presence of FFL. This study, therefore, aimed to characterize horses showing FFL particularly when fed wrapped forages, and to map the management and feeding strategies of these horses. Data were retrieved by a web-based survey, including 339 horses with FFL. A large variety of different breeds, ages, disciplines, coat colours, housing systems and feeding strategies were represented among the horses in the study, meaning that any type of horse could be affected. Respondents were asked to indicate if their horse had diminished signs of FFL with different changes in forage feeding. Fifty-eight percent (n = 197) of the horse owners reported diminished signs of FFL in their horses when changing from wrapped forages to hay; 46 (n = 156) of the horse owners reported diminished signs of FFL in their horses when changing from wrapped forages to pasture; 17% (n = 58) reported diminished signs of FFL when changing from any type of forage batch to any other forage. This indicated that feeding strategy may be of importance, but cannot solely explain the presence of FFL. The results also showed that the horses in this study had a comparably high incidence of previous colic (23%, n = 78) compared to published data from other horse populations. In conclusion, the results showed that FFL may affect a large variety of horse types and that further studies should include detailed data on individual horse factors including gastrointestinal diseases as well as feeding strategies, in order to increase the chance of finding causes of FFL.

Is Electrical Nerve Stimulation the Answer for Management of Equine Headshaking?

Horses with trigeminal mediated headshaking (TMHS) have a decreased activation threshold of the trigeminal nerve and clinical signs are suspected to be a manifestation of trigeminal neuralgia. Electrical nerve stimulation (ENS) is used for management of neuralgia in humans and appears to work via gate control theory. Use of an equine specific percutaneous ENS program in over 130 TMHS horses has resulted in approximately 50% success return to previous work. Electroacupuncture may also be useful in the management TMHS. Optimization of ENS procedures for TMHS is likely to require a greater understanding of the etiopathogenesis of the aberrant neurophysiology.

Trigeminal-mediated headshaking in horses: prevalence, impact, and management strategies

Trigeminal-mediated headshaking is a little-understood neuropathic facial pain condition of the horse. The condition may affect around 1% of the equine population to a degree of severity sufficient to require veterinary attention. As a pain condition, this represents a significant welfare issue. Horses are usually more severely affected at exercise which can leave them unable to perform, or even dangerous to ride and handle. With little known about the condition and variable response to treatments, severely affected horses are often euthanized. This review article considers the literature on trigeminal-mediated headshaking, focusing on what is known, and indeed not known, about the prevalence of the condition and its impact. The current published management options are considered, along with their challenges and limitations.