Introduction

• Cause: causation in rabbits usually unknown. Varied in other species – depends on specific disease process.
• Signs: early stages may be asymptomatic. Pain, swelling around the mandible, ptyalism, anorexia, ileus, masticatory difficulties and dental malocclusion.
• Diagnosis: history and clinical examination, radiography, cytology, histopathology, bacteriology, virology, computed tomography.
• Treatment: medical management of inflammation/infection. Surgical resection in some cases. Supportive care.
• Prognosis: good to guarded depending on cause.

Normal anatomical features

• Rabbits possess several major salivary glands which include paired parotid, submandibular and sublingual glands.
• Rabbit submandibular gland contain many types of cell surface neurotransmitter receptors such as muscarinic receptors (m1 and m3).
• Secretion varies between glands:
  • Most glands require a humoral (such as food intake) or nervous stimulus.
  • Submandibular glands secrete saliva components spontaneously and continuously but will increase secretion rate in response to stimuli.
• Submandibular glands are a seromucous gland.
• Salivary gland disease is very rare in rabbits.

Pathogenesis

Predisposing factors

General

• Infectious or inflammatory processes of the oral cavity may extend to the salivary glands and ducts.

Specific

• Necrotizing sialometaplasia has only been reported secondary to facial trauma in a rabbit.

Pathophysiology

• Salivary gland abscessation: possible, but no reports in literature.
• Necrotizing sialometaplasia is a rare inflammatory process affecting the submandibular salivary glands:
  • Cause not well understood but likely due to ischemic infarct of the gland.
  • Viral and autoimmune causation has been proposed in dogs.
  • Experimentally induced in rabbits following photodynamic therapy of the mandible.
  • Single report in a 7-month old male laboratory rabbit: facial trauma of unknown cause → comminuted fracture of the mandibular body, ramus and symphysis → secondary trauma to submandibular gland and vasculature → thrombosis of gland → salivary gland infarction → coagulative necrosis and swelling of affected gland.
  • Must be differentiated from neoplastic processes to prevent inappropriate treatment.
• Adenocarcinoma:
  • Uncommon in domestic animals.
  • No reports of neoplasia specific to submandibular gland.
  • Adenocarcinoma of the parotid gland involving the submandibular gland has been reported:
    • Single report in 7-year old female pet rabbit.
    • Aggressive neoplastic mass of the parotid gland → expansile with compression and replacement of surrounding musculature and facial nerves → Infiltration and destruction of adjacent submandibular gland → invasion of mandibular ramus and tympanic bulla.
• Sialocele:
  • No reports of disease specific to submandibular glands.
  • Single report of a sublingual gland ranula in a laboratory rabbit:
    • Cystic structure noted under the tongue at necropsy.
    • Gross morphology similar to oral papilloma.
    • Incidental finding.
  • Infectious, inflammation, trauma, sialoliths → obstruct salivary ducts → Failure to drain saliva from gland → duct dilation with pseudocyst → secondary dilation of internal gland ducts → gland swelling.
• Sialadenitis:
  • Experimental induction in rabbits using autologous lymphocytes targeting lacrimal antigens.
  • Spontaneous infectious or autoimmune causes possible but no reports in literature.
• Sialectasis:
  • Dilation of the salivary duct.
  • Single report in a 10-year old female pet rabbit.
  • Congenital abnormalities, sialolith formation and infectious processes → stricture of the salivary duct → failure to drain saliva from gland → duct dilation and swelling.
  • Cocci and Candida albicans have been implicated as possible etiological agents in this case.
• Sialolithiasis: possible but no reports in literature.

Diagnosis

Treatment

Prevention

Outcomes