section name header

Basics ⬇

Outline

BASICS

Definition!!navigator!!

An emotion of alarm and agitation caused by real or perceived danger and manifested by physiologic and behavioral responses.

Pathophysiology!!navigator!!

  • Medical explanations of fearful behavior must be considered, particularly in horses showing an acute change in their behavior or those that exhibit concomitant neurologic abnormalities. Pain, toxin exposure, infectious conditions (e.g. rabies, tetanus, equine protozoal myelitis), and some ophthalmic conditions can cause animals to exhibit hyperreactive responses that may mimic fear
  • Chronic conditions, such as pain, may affect responses to stimuli as horses attempt to avoid conditions previously associated with pain

Systems Affected!!navigator!!

  • Nervous—restlessness, pacing, attempts to escape restraint or confinement, inattentiveness during training, inadequate performance, or aggression to handlers
  • Neuromuscular—trembling
  • Gastrointestinal—inappetence or altered eating habits and increased defecation rate when fearful/reactive; gastric ulceration may be associated with chronic fearful states
  • Cardiovascular—horses rated as reactive (fearful) in behavioral tests exhibited high mean heart rate and low heart rate variability
  • Respiratory—tachypnea or frequent snorting when exposed to fearful stimulus
  • Endocrine/metabolic—chronic fear may increase metabolic rate and elevate endogenous cortisol levels
  • Hemic/lymphatic/immune—conditions of chronic fear may reduce immune competence
  • Musculoskeletal—traumatic injuries may occur during escape attempts or restraint
  • Ophthalmic—rule out visual abnormalities, especially in cases of adult-onset fear responses
  • Skin/exocrine—sweating may occur due to autonomic arousal
  • Reproductive—fear may affect breeding performance and tractability by stallions and mares

Genetics!!navigator!!

  • There is a genetic component to fearful responses. Although selective breeding for attenuated fear responses is part of the domestication process, some ancestral characteristics remain, including heritable tendencies to monitor the environment and react to novel stimuli
  • In adult horses, fearfulness, as measured on personality tests, tends to be stable over years

Incidence/Prevalence!!navigator!!

  • Common
  • Aversion to veterinary and handling procedures may be a manifestation of fear

Geographic Distribution!!navigator!!

Regional conventions for horse handling may affect the prevalence of fearful responses.

Signalment!!navigator!!

Breed Predilections

May be breed-specific differences in fear response to novel stimuli and attempts to flee.

Mean Age and Range

Common in young animals lacking positive experiences with humans or novel situations.

Signs!!navigator!!

Historical Findings

  • Horses raised without exposure to humans may have a large flight distance compared with handled horses
  • Lack of systematic, positive training is associated with more reactive responses, especially in novel environments
  • Affected horses described as “spooky” or “flighty”

Physical Examination Findings

  • Usually unremarkable, may sweat, defecate excessively
  • Acute—orientation toward the stimulus, head-up alert/immobility stance, spin, retreat
  • Chronic—poor body condition, postural effects, often the opposite of acute reactions, such as droopy head position
  • Self-inflicted trauma, secondary to attempts to escape
  • May be difficult to examine, attempting escape or engaging in reactive/defensive/aggressive behavior when approached or restrained

Causes!!navigator!!

  • Strongly influenced by individual temperament, experiences, and expertise of handler/trainer
  • Neonatal handling has not been shown to reduce adult reactions to novel situations any more than systemic exposure to novel stimuli and positive training

Risk Factors!!navigator!!

  • Horses with minimal exposure to humans and their activities
  • Excessive arousal or frustration
  • Previous or current mismanagement, abuse, and/or harsh, inadequate, or incompetent training

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

Identify associated pathologic conditions before seeking a purely behavioral diagnosis.

CBC/Biochemistry/Urinalysis!!navigator!!

  • Usually normal; possible stress leukogram
  • Abnormalities may suggest metabolic or endocrine explanations

Other Laboratory Tests!!navigator!!

May be indicated to rule out medical explanations.

Imaging!!navigator!!

May be indicated to identify sources of pain, congenital abnormalities, or cerebral neoplasia.

Other Diagnostic Procedures!!navigator!!

  • Risk analysis involves historical information, observation of the horse, and supporting medical and legal data. Goals are to prevent injury, reduce client's and veterinarian's liability risk, and establish a rational management/rehabilitation plan
  • “Flighty” horses that unpredictably exhibit fearful behavior (e.g. bolting) and horses that exhibit fear-motivated aggression are dangerous and should be handled only by experienced personnel

Treatment ⬆ ⬇

Outline

TREATMENT

Aims!!navigator!!

Reduce fear responses in order to safely manage and improve the horse's usefulness and welfare.

Environmental Management

  • Use adequate barriers and sufficient restraint to prevent injuries and horse's escape
  • Use well-fitting, sturdy halters with leads and other necessary restraint devices; competent, patient handler
  • In some situations, a calm companion horse may attenuate physiological and fear responses of a frightened horse
  • Establish safe, quiet environment to practice behavior modification techniques. Start in a familiar environment; then with success, progress to unfamiliar environments

Behavior Modification

  • Training methods. “Sympathetic (positive) horsemanship”
  • Desensitization/counterconditioning—list all situations in which the horse is fearful and align them along a continuum from least to most fearful. Initially, avoid all these situations. Teach the horse basic exercises in nonfearful, familiar conditions. Reward the horse for being calm and obedient. Then, practice these exercises in a range of environmental conditions and situations. Escape behavior must be avoided since it is strongly reinforced by the diminished fear that results from greater distance from the stimulus
  • Next, when practicing control exercises, expose the horse, while in a calm state, to the least fearful stimulus on the fear continuum. Reward the horse for calm, tractable behavior. If necessary reduce the intensity of the fearful stimulus and more gradually move it closer as the horse acclimates to it
  • A “target,” such as a tennis ball affixed to a wooden dowel, can be used in a counterconditioning process. Initially, the target is associated with something of value to the horse. Position the target so that the horse voluntarily touches it. Immediately, this response is paired with a sound such as praise or a handheld clicker followed by a coveted reward, such as a small food treat. Repeat this sequence until the horse learns that when it touches the target, a reward is delivered. With time, the target can be used to teach the horse to move forward under potentially fearful conditions, such as walking into a transport trailer

Appropriate Health Care!!navigator!!

Positive-based, species-appropriate handling should be part of routine health care of all horses.

Activity!!navigator!!

Regular exercise.

Diet!!navigator!!

Vitamin B complex supplementation is allegedly helpful.

Client Education!!navigator!!

  • Recommend handling of the affected horse by experienced persons
  • Recommend safe, quiet housing. Extreme fear reactions can result in self-trauma during escape attempts
  • Chronic fear responses constitute a welfare issue. Horses in a chronic, high-fear state may eat or drink poorly, exhibit stereotypic behaviors, or develop gastric ulcers. Wild mustangs transported for long distances have died from acidosis and dehydration associated with such a state

Surgical Considerations!!navigator!!

Possibly castration to prevent reproduction.

Medications ⬆ ⬇

Outline

MEDICATIONS

Drug(s) of Choice!!navigator!!

Generally, drugs are not used for treatment. However, when used with a behavioral management program, may decrease arousal or anxiety and facilitate learning and safe handling.

Contraindications!!navigator!!

For ethical, legal, and safety reasons, the drugs listed below are not recommended for use in performance animals, e.g. while racing, showing, or sporting activities.

Precautions!!navigator!!

No drugs are approved by the FDA for treatment of fearful behaviors in horses. No clinical trials have been performed on these extralabel drugs; our knowledge is based on evidence from other species and anecdotal information from a few, individual cases. Inform the client regarding the experimental nature of these treatments and the risk involved; document the discussion in the medical record.

Possible Interactions!!navigator!!

To avoid risk of serotonin syndrome, SSRIs generally should not be used concurrently with tricyclic antidepressants or monoamine oxidase inhibitors.

Alternative Drugs!!navigator!!

  • Acepromazine, a phenothiazine tranquilizer, is used widely, and is valuable to reduce the effect of environmental stimuli, if acute fear-inducing situations are anticipated. Side effects include priapism and paraphimosis in stallions
  • Fluoxetine, an SSRI with anxiolytic effects, may require 1–4 weeks of daily administration. Fluoxetine may decrease libido; high doses of fluoxetine may result in serotonin effects in the gastrointestinal tract
  • Fluphenazine decanoate, a phenothiazine dopamine antagonist, has been used to reduce reactivity. Serious extrapyramidal side effects (motor restlessness, altered mentation) have been reported. Diphenhydramine has been used successfully as an antidote
  • Tricyclic antidepressants, such as amitriptyline or imipramine, have serotonin and norepinephrine reuptake inhibitor effects; may enhance behavioral calming; side effects can include mild sedation and anticholinergic effects. Imipramine is associated with masturbation and erection in males. At high doses, imipramine (2–4 mg/kg PO every 24 h) can cause muscle fasciculations, tachycardia, and hyperresponsiveness to sound, likely due to norepinephrine effects
  • A synthetic equine appeasing pheromone (Modipher EQ, VPL), commercially available and administered via intranasal spray, prior to exposure to an anxiety-producing situation has been reported to reduce fear responses and tachypnea in a test situation
  • Sublingual detomidine hydrochloride (Dormosedan Gel, Zoetis) has anxiolytic and sedative effects; may be helpful prior to examination or handling fearful animals. Consult package insert for contraindications
  • NSAIDs may be used for 2 weeks to help assess pain as an etiologic factor

Follow-up ⬆ ⬇

Outline

FOLLOW-UP

Patient Monitoring!!navigator!!

  • Weekly to biweekly contact during the initial phases
  • Clients frequently need feedback and assistance with behavior modification plans and medication management

Prevention/Avoidance!!navigator!!

Helpful examination strategies:

  • Rapid recognition of fearful/phobic behavior by the examiner
  • Suitable restraint equipment and environment
  • A familiar, tractable horse within visual range
  • Familiar, experienced handler using rewards for acceptable responses
  • Familiar location, with nonslippery floor, that prevents escape or injury
  • Avoid erratic movements and speech
  • Allow the horse visual and olfactory inspection
  • Chemical restraint, if necessary, to prevent injury and negative associations with the veterinarian

Possible Complications!!navigator!!

  • Injuries caused by a horse exhibiting fearful behavior
  • Consider euthanasia for high-risk cases in which all other treatment options have failed or are not an option

Expected Course and Prognosis!!navigator!!

  • The knowledge and patience of the handler greatly influence treatment success
  • Individual temperament of horses may limit treatment success

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

Associated Conditions!!navigator!!

Pain may exacerbate fear responses.

Age-Related Factors!!navigator!!

  • Fear-motivated behavior problems are common in young horses with little training
  • Adult- or acute-onset fear-motivated behavior, particularly in previously well-handled animals, suggests a medical etiology or a severe emotional experience

Zoonotic Potential!!navigator!!

Rabies is a potential cause of fearful behavior or aggression.

Pregnancy/Fertility/Breeding!!navigator!!

Chronic use of behavioral medications is not recommended in pregnant animals.

Abbreviations!!navigator!!

  • USFDA = United States Food and Drug Administration
  • NSAID = nonsteroidal anti-inflammatory drug
  • SSRI = selective serotonin reuptake inhibitor

Suggested Reading ⬆ ⬇

Beaver BV. Equine Behavioral Medicine. Cambridge, MA: Academic Press, 2019.

Christensen JW, Keeling LJ, Nielsen BL. Responses of horses to novel visual, olfactory and auditory stimuli. Applied Animal Behaviour Science 2005;93(1–2):53–65.

Christensen JW, Malmkvist J, Nielsen BL, Keeling LJ. Effects of a calm companion on fear reactions in naive test horses. Equine Veterinary Journal 2010;40(1):46–50.

DeAraugo J, McLean A, McLaren S, et al. Training methodologies differ with the attachment of humans to horses. J Vet Behav 2014;9(5):235–241.

Falewee C, Gaultier E, Lafont C, et al. Effect of a synthetic equine maternal pheromone during a controlled fear-eliciting situation. Appl Anim Behav Sci 2006;101:144–153.

Gorecka-Bruzda A, Jastrzebska E, Sosnowska Z, et al. Reactivity to humans and fearfulness tests: field validation in Polish cold blood horses. Appl Anim Behav Sci 2011;133(3-4):207–215.

Heleski C, Wickens C, Minero M, et al. Do soothing vocal cues enhance horses’ ability to learn a frightening task? J Vet Behav 2015;10:41–47.

Hintze S, Smith S, Patt A, et al. Are eyes a mirror of the soul? What eye wrinkles reveal about a horse's emotional state. PLoS One 2016;11(10):e0164017.

Karrasch S, Karrasch V, Newman A. You Can Train Your Horse to Do Anything: Target Training, Clicker Training, and Beyond. North Pomfret, VT: Trafalgar Square Publishing, 2000.

Lansade L, Bouissou M-F, Erhard HW. Fearfulness in horses: a temperament trait stable across time and situations. Applied Animal Behaviour Science 2008;115(3–4):182–200.

Lansade L, Pilippon P, Herve L, Vidament M. Development of personality tests to use in the field, stable over time and across situations, and linked to horses’ show jumping performance. Appl Anim Behav Sci 2016;176:43–51.

Leiner L, Fendt M. Behavioural fear and heart rate responses of horses after exposure to novel objects: Effects of habituation. Science Direct 2011;131(3–4):104–109.

Mansmann RA, Currie MC, Correa MT, et al. Equine behavior problem around farriery: foot pain in 11 horses. J Equine Vet Sci 2011;31:44–48.

McDonnell SM. Oral imipramine and intravenous xylazine for pharmacologically-induced ex copula ejaculation in stallions. Anim Reprod Sci 2001;68(3–4):153–159.

Momozawa Y, Ono T, Sata F, et al. Assessment of equine temperament by a questionnaire survey to caretakers and evaluation of its reliability by simultaneous behavior test. Appl Anim Behav Sci 2003;84:127–138.

Voith VL. Fears and phobias. In: Voith V, Borchelt P, eds. Readings in Companion Animal Behavior. Trenton, NJ: Veterinary Learning Systems, 1996:140–152.

Wathan J, Burrows AM, Waller BM, McComb K. EquiFACS: The Equine Facial Action Coding System. PLoS One 2015:10(8);e0131738.

Author(s) ⬆

Authors: Victoria I. Voith and Barbara L. Sherman

Consulting Editor: Victoria L Voith

Acknowledgment: The authors acknowledge the prior contribution of Richard A. Mansmann.