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A 1.5-year-old, 37.7 kg, female alpaca was evaluated for a 2-week history of weight loss, left ear droop, and deviation of the rostral mandible to the right. Antemortem radiography and postmortem examination revealed otitis interna, media, and externa, destruction of the left tympanic bulla, and subluxation and septic arthritis of the left temporomandibular joint.
Otite interne, moyenne et externe avec destruction de la bulle tympanique gauche et subluxation et arthrite septique de l’articulation temporomandibulaire gauche chez un alpaga(Vicugna pacos). Une femelle alpaga âgée de 1,5 an, pesant 37,7 kg, a été évaluée pour une anamnèse de 2 semaines de perte de poids, d’oreille gauche pendante et de déviation de la mandibule rostrale à la droite. Une radiographie avant le décès et une nécropsie ont révélé une otite interne, moyenne et externe, la destruction de la bulle tympanique gauche ainsi qu’une subluxation et l’arthrite septique de l’articulation temporomandibulaire gauche.
(Traduit par Isabelle Vallières)
A 1.5-year-old, 37.7 kg, female, Huacaya breed alpaca was evaluated for a 2-week history of weight loss, drooping of the left ear, and deviation of the rostral mandible to the right. The owner reported the animal was having difficulty prehending and masticating feed. The owner obtained the alpaca with an unknown medical history 2 mo prior to presentation. The intended purpose of this animal was as a breeding female. Heart rate [48 beats/min; reference range (RR): 60 to 90 beats per min (1)], respiratory rate [26 breaths/min; RR: 10 to 30 breaths per min (1)], and rectal temperature [39°C (101.9°F); RR: 37.5 to 38.9°C (99.5 to 102.0°F) (1)] were not appreciably different from reference ranges. Physical examination revealed a body condition score of 2 out of 9 and the animal appeared small for its age. Examination of the head revealed ptosis of the left upper eyelid, absence of a menace and palpebral reflex on the left, and decreased facial sensation on the left side. The left external ear canal was inflamed, contained white exudate, and was painful on palpation. No otoscopic examination could be performed due to severe inflammation and debris occluding the ear canal. Palpation of the left mandible revealed soft tissue swelling ventral to the left pinna involving the ramus of the mandible and extending to the region of the temporomandibular joint (TMJ). There was palpable laxity in the region of the left TMJ. No other abnormalities were found on physical examination.
Based on physical examination, the primary differential diagnoses included otitis externa, media, and interna, primary mandibular osteomyelitis, dislocation of the TMJ due to infection or trauma, or traumatic or pathologic fracture of the ramus of the mandible. Skull radiographs were performed to determine whether there was a fracture of the mandible or dislocation of the TMJ and to better define the otitis.
Skull radiographs showed a soft-tissue mass ventral to the left tympanic bulla on the lateral view, which was partially obscuring the nasopharynx and causing mild ventral displacement of the soft palate. Emphysematous soft tissues were seen dorsal to the trachea to the level of C2, likely representing gas in the esophagus. There was increased opacity with ill-defined margins superimposed over the region of the left TMJ. On the ventrodorsal view, there was amorphous bone proliferation, irregular margins, and lysis of the left osseous bulla. There was an adjacent lateral soft tissue mass containing multifocal areas of gas, and the left horizontal ear canal could not be visualized. The TMJ articulation was grossly abnormal and there was lateral rotation of the mandible relative to the maxilla and remaining skull compatible with a TMJ subluxation. The right TMJ was unremarkable. The radiographic diagnoses were left TMJ subluxation, chronic otitis media and externa with abscessation, and nasopharyngeal narrowing. The subluxation of the TMJ was likely secondary to a dissecting infection originating from the ear canal into the tympanic bulla and finally the TMJ. Due to the poor prognosis, the owners elected to have the alpaca humanely euthanized.
Postmortem computed tomography (CT) scan of the head was performed to further define the extent of the animal’s disease. There was a large soft tissue attenuating mass surrounding the ventromedial aspect of the left tympanic bulla with multifocal air attenuating foci throughout. This soft tissue mass was impinging on the dorsolateral aspect of the nasopharynx causing significant narrowing (Figure 1A). There was exuberant periosteal reaction engulfing the left tympanic bulla and TMJ causing lateral displacement of the mandible. This bony proliferation extended to the base of the skull and the retroarticular process of the temporal bone dorsal to the ear canal (Figures 1A, B). There was obliteration of the left horizontal ear canal with soft tissue and mineral-attenuating material, and thickening of the soft tissues with multifocal gas attenuating regions medial and lateral to the left mandible (Figure 1B). The CT diagnosis was severe otitis media and externa with osteomyelitis of the osseous bulla and abscessation of the adjacent soft tissues. The lateral displacement of the mandible and asymmetry of the left and right mandibles in Figure 1A support a diagnosis of left TMJ subluxation. Computed tomography significantly added to our understanding of the extent of the soft tissue and bony lesions in the patient, including the degree of occlusion of the nasopharynx, obliteration of the left external ear canal, severity of the osteomyelitis, and displacement of the left TMJ.
A complete necropsy examination was also performed. Necropsy examination revealed abundant caseous yellow exudate within the left external ear and auditory meatus. The ventral skull around the left tympanic bulla was bulging and distorted and the TMJ was subluxed. The articular surface of the left TMJ was roughened and eroded. The lysis of the articular surface of the left TMJ was not identified on the CT, most likely due to the 5 mm slice thickness and partial volume averaging artifact. The left tympanic bulla was not intact and there was abundant caseous exudate present. Similar caseous exudate extended into the soft tissues and submucosa adjacent to the pharynx. Microscopically, the honeycombed spaces of the tympanic bulla were often filled with degenerate neutrophils and cellular debris. The normal tissue architecture of the left osseous ear canal was multifocally distorted by the proliferation of the loose fibrous tissue stroma with a mixed population of inflammatory cells including neutrophils, macrophages, and lymphocytes. There was active bone remodeling with osteoclastic osteolysis and bony proliferation. The collagenous stroma and adipose tissue of the soft tissue adjacent to the left auditory meatus were multifocally infiltrated with large numbers of neutrophils and macrophages admixed with fibroblasts. Bacteriologic culture of an ear swab from the left ear yielded a heavy, pure growth of Propionibacterium spp. Antimicrobial susceptibility was not determined. Final diagnosis was severe suppurative otitis interna, media, and externa with destruction of the left tympanic bulla and subluxation and septic arthritis of the left TMJ.
The ear canal of the South American camelid is sigmoid-shaped, making otoscopic examination difficult and complicating treatment of otitis externa (1). Clinical signs associated with otitis externa include head shaking, pruritis, head tilt, abnormal positioning of the pinna, and visible exudate in the ear canal (1). Otitis media, interna is often associated with facial nerve paralysis, Horner’s syndrome, disorientation, ataxia, and circling (1). The alpaca in this case exhibited left facial nerve paralysis and ptosis of the left upper eyelid, but did not exhibit other symptoms associated with Horner’s syndrome including miosis, retraction of the globe, or protrusion of the nictitating membrane. Epidemiologic studies regarding the incidence of otitis in South American camelids are lacking. There are a few published case reports, but the etiologic agents causing the infection vary by report with no consistent causative bacteria being reported (2–4). Listeria moncytogenes was implicated in 1 report (4), while in another report Actinomyces spp. and group D Streptococcus spp. were isolated from ear canal exudate (2). In the final report (3), bacteria were not isolated from tissue collected from the tympanic bulla, but histologic examination revealed Gram-positive, branching filamentous forms consistent with Actinomyces spp. or Nocardia spp. Propionibacterium spp., isolated in the present case, does not appear to have been previously reported in cases of otitis in South American camelids.
Treatment of otitis externa in South American includes ear canal irrigation and topical antimicrobials (1). However, the shape of the canal can hamper drainage and thus treatment success. Treatment of otitis media, interna has included systemic antimicrobials, anti-inflammatories and supportive care (1–4). There is 1 report of a total ear canal ablation and lateral bulla osteotomy in an alpaca with chronic otitis externa, media. Surgery was reported to be successful for at least 9 mo after surgery (4). Due to the poor prognosis dictated by the extent of the infection and the involvement and subluxation of the TMJ, therapy was not pursued in the present case. This case is unique in that the chronic otitis and infection of the tympanic bulla dissected into the adjacent TMJ, causing arthritis and subluxation. Additionally, computed tomography images detailing the extent of the disease process are presented. CVJ
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