Auris (pl. Aures)
The equine pinna (auricle) is a highly mobile structure controlled by roughly 16 muscles, allowing nearly 180° of independent rotation. This mobility helps horses orient toward sounds, although horses localize brief sounds less precisely than many other large mammals. Horses hear a broader frequency range than humans (roughly 55 Hz to 33,500 Hz) and can detect sounds from considerable distances. The external ear canal is L-shaped and about 5–7 cm deep. The inner ear contains the cochlea (hearing) and vestibular apparatus (balance). Ear position is a primary communication tool: ears pricked forward signal attention or interest, pinned-back ears often indicate irritation, pain, or aggression, and rapidly swiveling ears show alertness or anxiety. The skin on the inner pinna is thin and contains protective hair that helps keep out debris and insects. The guttural pouches (diverticula of the auditory tubes) communicate with the middle ear and can be a source of related pathology.
Aural plaques (ear papillomas) are common, associated with equine papillomaviruses and thought to be transmitted by black flies; they appear as white, crusty, coalescing patches on the concave pinna. They are often asymptomatic but can cause head-shaking or ear sensitivity. Spinose ear ticks (Otobius megnini) in endemic areas (especially the southwestern U.S.) live in the ear canal and cause head shaking, rubbing, and irritation. Ear-shy behavior is common and may reflect current or past painful ear conditions. Sedation is often needed for thorough examination. Avoid completely clipping the protective hair inside the ear.
## Overview Aural plaques, also known as ear papillomas or papillary acanthoma, are benign, virus-induced lesions on the inner surface of the pinna. They appear as depigmented, hyperkeratotic papules
## Overview The spinose ear tick (Otobius megnini) infests the external ear canal of horses, particularly in dry regions of the western United States and Mexico. Larvae and nymphs feed for weeks to m
## Overview Ear melanomas are melanocytic tumors that develop at the base of the ear, within the ear canal, or on the pinna of gray horses. They are part of the progressive melanoma syndrome common i
## Overview A dentigerous cyst (also called ear tooth or heterotopic polydontia) is a congenital anomaly in which dental tissue develops in an abnormal location, most often at the base of the ear. It
## Overview Ear shyness is resistance to having the ears touched or handled. It ranges from mild avoidance to striking or aggression. Causes include medical problems (aural plaques, ticks, infection,
Use fly masks with ear covers or ear bonnets to protect against black flies and other insects. Never “ear twitch” a horse; twisting the ear for restraint causes pain and lasting shyness. If a normally tolerant horse suddenly becomes head-shy or starts shaking its head, investigate (ticks, plaques, dental pain, poll pain, or bridle issues) rather than training through it. In endemic areas, periodically check deep in the ear canal for ticks. Do not clip all the hair inside the ear; it is protective. Trimming excess hair beyond the tip is cosmetic and acceptable.
## Overview Aural plaques, also known as ear papillomas or papillary acanthoma, are benign, virus-induced lesions on the inner surface of the pinna. They appear as depigmented, hyperkeratotic papules and plaques and are caused by equine papillomaviruses, most likely transmitted by black flies (Simulium species). The condition is common, primarily cosmetic, and usually asymptomatic, although fly bites themselves can cause irritation and head shyness. ## Causes Equus caballus papillomavirus types 1, 3, 4, 5, and 6 have been associated with the lesions. Black flies serve as mechanical vectors, feeding on the relatively hairless inner ear at dawn and dusk. ## Diagnosis Diagnosis is clinical based on the characteristic white, crusty plaques on the concave pinna. Biopsy is rarely needed but confirms papillated epidermal hyperplasia and hyperkeratosis with viral cytopathic effects. ## Treatment Most cases require no treatment. When plaques cause significant irritation, topical 5 percent imiquimod cream applied two to three times weekly has been shown to resolve lesions, although the intense inflammatory response usually necessitates sedation. Fly control reduces discomfort and may limit spread. ## Recovery and Prognosis Prognosis is excellent. Lesions are benign and do not affect general health. Recurrence is possible if fly exposure continues. ## Prevention Fly masks or ear covers, stabling during peak fly activity, and topical repellents reduce transmission and irritation. Signs include: white, raised, crusty plaques on the inner surface of one or both ears; occasional head shyness or sensitivity related to fly irritation; no systemic illness
## Overview The spinose ear tick (Otobius megnini) infests the external ear canal of horses, particularly in dry regions of the western United States and Mexico. Larvae and nymphs feed for weeks to months, causing intense irritation, head shaking, and secondary infection. ## Causes Exposure to environments where the tick is present. Nymphs attach deep in the canal. ## Diagnosis Otoscopic visualization of blue-gray nymphs in the ear canal, plus clinical signs of irritation. ## Treatment Manual removal when possible, acaricides labeled for equine use, and treatment of secondary bacterial otitis. Environmental control reduces reinfestation. ## Recovery and Prognosis Excellent once ticks are eliminated and secondary infection resolves. ## Prevention Regular ear inspection in endemic areas and appropriate environmental management. Signs include: head shaking; ear rubbing; ear-shy behavior; dropping feed; visible nymphs in the canal; secondary discharge
## Overview Ear melanomas are melanocytic tumors that develop at the base of the ear, within the ear canal, or on the pinna of gray horses. They are part of the progressive melanoma syndrome common in aging grays. Most grow slowly, but larger masses can obstruct the ear canal, interfere with tack, or ulcerate. ## Causes Genetic predisposition in gray horses linked to the same mutation that causes progressive graying. Melanocytes proliferate over time. ## Diagnosis Visual and otoscopic examination. Biopsy confirms the diagnosis when needed. Staging evaluates for internal melanomas. ## Treatment Monitoring for small, non-obstructive lesions. Surgical excision, laser ablation, or cisplatin beads for problematic masses. Systemic therapies are under investigation for widespread disease. ## Recovery and Prognosis Good for local control of accessible lesions. The overall melanoma burden in gray horses is progressive. ## Prevention None. Regular monitoring of gray horses allows early intervention. Signs include: dark firm nodules at the ear base or in the canal; possible obstruction causing head tilt or discharge; interference with bridle fit; may ulcerate
## Overview A dentigerous cyst (also called ear tooth or heterotopic polydontia) is a congenital anomaly in which dental tissue develops in an abnormal location, most often at the base of the ear. It typically presents in young horses as a swelling with a draining tract that does not respond to antibiotics. Complete surgical excision is curative. ## Causes Misplacement of dental epithelium during embryonic development from the first branchial arch. ## Diagnosis Clinical appearance of a draining tract near the ear base plus radiographs or computed tomography showing tooth-like structures. Computed tomography aids surgical planning. ## Treatment Surgical excision of the cyst and associated dental material. Prognosis is excellent when removal is complete. ## Recovery and Prognosis Excellent. Recurrence is rare after thorough excision. ## Prevention None (congenital). Signs include: chronic draining tract at the base of the ear in a young horse; intermittent discharge; non-responsive to antibiotics; tooth-like structure on imaging
## Overview Ear shyness is resistance to having the ears touched or handled. It ranges from mild avoidance to striking or aggression. Causes include medical problems (aural plaques, ticks, infection, melanoma) and learned behavior from previous rough handling or ear twitching. ## Causes Painful ear conditions or prior negative experiences. Sudden onset suggests a new medical issue; gradual onset may be behavioral or progressive disease. ## Diagnosis Careful otoscopic examination to rule out plaques, ticks, or masses, plus history of handling. ## Treatment Treat any medical cause. Behavioral rehabilitation with gradual, positive desensitization once pain is eliminated. ## Recovery and Prognosis Good when medical issues are resolved and handling is patient and consistent. ## Prevention Gentle ear handling from a young age and prompt treatment of ear problems. Signs include: head raising or pulling away when ears are touched; resistance to bridling; striking; head tossing; may be unilateral
Aural plaques (ear papillomas) are common, associated with equine papillomaviruses and thought to be transmitted by black flies; they appear as white, crusty, coalescing patches on the concave pinna. They are often asymptomatic but can cause head-shaking or ear sensitivity. Spinose ear ticks (Otobius megnini) in endemic areas (especially the southwestern U.S.) live in the ear canal and cause head shaking, rubbing, and irritation. Ear-shy behavior is common and may reflect current or past painful ear conditions. Sedation is often needed for thorough examination. Avoid completely clipping the protective hair inside the ear.
Use fly masks with ear covers or ear bonnets to protect against black flies and other insects. Never “ear twitch” a horse; twisting the ear for restraint causes pain and lasting shyness. If a normally tolerant horse suddenly becomes head-shy or starts shaking its head, investigate (ticks, plaques, dental pain, poll pain, or bridle issues) rather than training through it. In endemic areas, periodically check deep in the ear canal for ticks. Do not clip all the hair inside the ear; it is protective. Trimming excess hair beyond the tip is cosmetic and acceptable.
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