Diseases of the oral cavity are common in rabbits and small herbivorous mammals with completely elodont dentition. Different forms of congenital, developmental or acquired dental disease induce signs of hypersalivation, anorexia, chewing disturbances, changes in food preferences and poor body condition. Dental disease can also be accompanied by the development of facial abscesses, wet dermatitis, epiphora, exophthalmia and damage to the temporomandibular joint.

Rabbits seem to be more affected by periapical infection and associated facial abscesses than other herbivorous rodents with elodont dentition, such as guinea pigs, chinchillas or degus. Due to late diagnosis or improper treatment, periapical abscesses (odontogenic, dentoalveolar abscesses) in rabbits often lead to severe osteomyelitis development with subsequent anorexia leading to animal death. Bacterial pathogens commonly involved in periapical lesions are Fusobacterium nucleatum, Prevotella heparinolytica, Prevotella spp., Peptostreptococcus micros, Streptococcus milleri group, Actinomyces israelii and Arcanobacterium haemolyticum.

Based on clinical status and concurrent diseases, the rabbit must be stabilised before further diagnostics and surgical treatment. The clinical work-up includes haematological and plasma chemistry analyses and urinalysis. A very good knowledge of skull anatomy is necessary for radiography, computed tomography (CT) or magnetic resonance evaluation and further selection of proper surgical approach. Skull radiographs and/or CT under anaesthesia are essential to evaluate the presence and extent of infection associated with tooth root abscess and osteomyelitis. Oral cavity endoscopy is a very useful method for thorough oral cavity inspection.

The thick consistency of rabbit pus makes aspiration and drainage of these abscesses very difficult and sole antibiotic therapy problematic and ineffective. Appropriate treatment of osteomyelitis includes surgical intervention in combination with antibiotic therapy.

A number of surgical techniques and options have been proposed for treating rabbits including surgical and conservative approaches. Based on author experience, lancing the skin and pus evaluation together with any antibiotic treatment is ineffective. Therefore, a surgical approach with excision or extraction of affected soft and hard tissues is the only effective method for treatment of odontogenic abscesses. Marsupialisation, thorough debridement, affected tooth extraction and affected bone removal are critical in the primary control of the source of infection. Another possibility is the insertion of antibiotic-impregnated polymethylmethacrylate (AIPMMA) beads into the wound at closure. Additional treatments include a combination of surgical debridement and tooth extraction with local use of AIPMMA beads, long-lasting doxycycline gel or manuka honey. The surgical approach to infraorbital or maxillary abscesses is challenging and may require an intraoral (tooth extraction, wound debridement through the extraction site) or extraoral approach. Systemic antibiotic treatment for a minimum of 2–4 weeks after surgery is also recommended.

All the procedures should be explained precisely to the client at all points of the therapy. Clients must know the prognosis and must be aware of the need for long-term treatment and of the animal's appearance after the surgery. In severe cases, two surgeries are necessary to reach the optimal treatment point.

Choice of antimicrobial agents for the treatment of osteomyelitis is based on cytological and microbiological findings and antimicrobial susceptibilities. Antimicrobial agents demonstrate variable penetration into bone. However, agents with poor bone penetration can achieve bone tissue concentration above minimum inhibitory concentration for target pathogens. Experimental studies performed in rabbits generally demonstrate excellent to good bone penetration by fluoroquinolones and satisfactory bone concentrations achieved by beta-lactams. Based on laboratory results, the author recommends parenteral administration of a combination of fluoroquinolones (enrofloxacin, marbofloxacin) and beta-lactams (penicillin G) on a daily basis. Metronidazole is most active against gram-negative anaerobes, such as Bacteroidesand Fusobacterium, whereas its activity against gram-positive anaerobes, such as Peptostreptococcus and Clostridium is more variable. It seems that in the case of marsupialisation, the use of antibiotics seems to be less important due to suppression of growth of anaerobes in the aerobic environment. However, when severe soft tissue inflammation is present, fluoroquinolones in combination with metronidazole or betalactam (parenteral administration) antibiotics are recommended. When using AIPMMA beads, clindamycin, metronidazole or beta-lactam are the first antibiotic choices.

In cases where operative treatment of osteomyelitis is not feasible, suppressive oral antibiotic therapy has been described to control the disease. There is a potential benefit from chronic antibiotic suppressive therapy but it is not an effective alternative to surgical treatment of bone infection.

Step-By-Step Recommended Treatment for Facial Abscesses in Rabbits

1.  Thorough history, including previous medication

2.  Clinical examination

3.  Conscious oral cavity examination:

a.  Paediatric laryngoscope

b.  Vaginoscope

c.  Otoscope

4.  Blood tests (haematology, plasma biochemistry - sampling from middle ear artery or from cephalic vein)

a.  At this point, ensure intravenous catheter placement + intravenous fluid administration

5.  Skull radiography - five views (dorsoventral, lateral, two lateral oblique, rostrocaudal)

6.  And/or computed tomography

7.  Oral cavity endoscopy/oral cavity examination under sedation/anaesthesia

a.  Teeth palpation

b.  Probing of the gingival sulci

c.  Recording all the abnormalities

8.  Prognosis

9.  Stabilisation

a.  Intravenous fluid administration

b.  Analgesia

i.  Non-steroidal anti-inflammatory drugs: meloxicam (0.5–1 mg/kg q12h orally, s.c.; carprofen 2–4 mg/kg s.c.

ii.  Opioids: butorphanol 0.3–0.5 mg/kg i.m. q6h; buprenorphine 0.03–0.05 q12h i.m., s.c.; tramadol 4–12 mg/kg q12h orally

c.  Antibiotics:

i.  Fluoroquinolones: enrofloxacin 10–15 mg/kg q12h i.m., s.c., orally; marbofloxacin 5–10 mg/kg q24h i.m., orally

ii.  Beta-lactams (parenterally): penicillin G 40,000–60,000 IU/kg q24h i.m.; bicillin 75,000 IU/kg q48h i.m.; amoxicillin–clavulanate 7.5 mg/kg q24h s.c.

d.  Prokinetics:

i.  Cisapride 1.0–1.5 mg/kg q12h orally

ii.  Itopride 10 mg/kg q12h orally

iii.  Metoclopramide 0.5–1.5 mg/kg q12h i.m., orally

iv.  Ranitidine 3–5 mg/kg q12h i.m., orally

v.  Trimebutine 1.5 mg/kg q12h orally

e.  Appetite stimulation:

i.  Vitamin B as in specific drug leaflet

ii.  Butafosfanum as in specific drug leaflet

f.  Surgical adjustment of clinical crowns

g.  Treat concurrent disease

h.  Force-feeding if necessary: Oxbow critical care®, Rodicare®, Supreme Recovery®

10.  Planning the surgery

11.  Anaesthesia:

a.  Premedication, analgesia (see above). Combination of:

i.  Ketamine 0.5–3 mg/kg i.m.

ii.  Midazolam 0.1–0.3 mg/kg i.m.

iii.  Butorphanol 0.3 mg/kg i.m.

iv.  Medetomidine 0.02–0.04 mg/kg i.m.

b.  Local anaesthesia:

i.  Particular nerve block (infraorbital, mental or inferior alveolar nerve block)

ii.  Lidocaine 2.0% 1 mg/kg

iii.  Bupivacaine 0.5 % 1 mg/kg

c.  Propofol to effect (usually 0.2–1 ml)

d.  Intubation. Preferably over-the-endoscope technique. Endotracheal tube with proper diameter or endotracheal tube with smaller diameter with pharyngeal packing

e.  Isoflurane for maintenance (1.5–3%)

12.  Perioperative care

a.  Patient monitoring: electrocardiogram (ECG), pulse oximetry, auscultation, capnography

b.  Continual warm fluid administration isotonic, 5–10 ml/kg/hr

c.  Heating pad 37–39°C

13.  Surgery:

a.  Capsule blunt preparation (avoid extensive dissection from the skin)

b.  Capsule excision and pus removal

c.  Surgical curettage

d.  Identification of affected bone and its removal. Sometimes need to drill holes into the bone and then remove, safe at least medial or lateral part of mandible. Do not break jaw or nasal bone

e.  Identification of affected teeth and their retrograde or normograde extraction. Use luxators; incise gingiva if necessary. If there is ankylosis split affected tooth in two parts and then remove

f.  Surgical curettage

g.  Sampling for bacteriology and cytology - part of the affected bone and tooth and capsule

h.  Marsupialisation - leave the wound open even if a bone is exposed

i.  Try to avoid ligating or incising major vessel supply and facial nerves

j.  Thorough saline flushing

k.  Use of collagen together with antibiotic (GENTA-COLL® resorb) in cases of diffuse bleeding or to plug small bone cavities

l.  Suture the gingiva if necessary

m.  Remove pharyngeal packing if used

14.  Postoperative care:

a.  Atipamezole administration

b.  Oxygen cage

c.  Remove endotracheal tube

d.  Continue stabilisation

e.  Syringe force-feeding if necessary

f.  Anaesthetise animal again in 2–3 days. Recheck the oral cavity, wound debridement

g.  Home care - continue antibiotics and analgesic treatment

h.  Evaluate results of bacteriological culture and change or add antibiotics

i.  Follow-up 8–10 days after surgery:

i.  Recheck the oral cavity

ii.  Remove stitches, clean the wound, curettage

iii.  Kalium-hypermanganicum solution into the wound

15.  Follow-up:

a.  14–20 days after surgery

b.  30–40 days after surgery

c.  Regular follow-up in 2–6 months

Note: Not all medications are authorised for veterinary use, some may need to be 'imported'.

References

1.  Capello V, Gracis M, et al. Rabbit and Rodent Dentistry Handbook. Lake Worth: Zoological Education Network, Inc, 2005.

2.  Harcourt-Brown F. Textbook of Rabbit Medicine. Oxford: Reed Educational and Professional Publishing Ltd, 2002.

3.  Jekl V, Hauptman K, et al. Quantitative and qualitative assessments of intraoral lesions in 180 small herbivorous mammals. Veterinary Record 2008;162:442–449.

4.  Taylor WM, Beaufrère H, et al. Long-term outcome of treatment of dental abscesses with a wound-packing technique in pet rabbits: 13 cases (1998–2007). Journal of the American Veterinary Medical Association 2010;237:1444–1449.

5.  Tyrrell KL, Citron DM, et al. Periodontal bacteria in rabbit mandibular and maxillary abscesses. Journal of Clinical Microbiology 2002;40:1044–1047.