Abscessation in Lagomorphs 

General Information on Investigation / Diagnosis

Aspiration and direct smears

• Use a 22 gauge or larger needle. 
• A thick, caseous or creamy, white exudate. 
• Pyogenic bacteria may be identified in cells or more frequently, in the wall of the abscess
  • A Gram's stain is useful for directing the antibiotic treatment. 
• A high nucleated cell count primarily consisting of of degenerative neutrophils and then smaller numbers of lymphocytes and macrophages. 

(B602.18.w18, B609.2.w2)

Biopsy and histopathology

• Useful in ruling out granuloma, neoplasia, and other causes of masses. (B609.2.w2)
• The sample should contain both abnormal and normal tissue in the same specimen. (B609.2.w2)

Culture and sensitivity testing

• Unusual bacteria may be involved. (B600.8.w8)
• Always submit samples even after antibiotic therapy of recurrent abscesses, because bacteria can develop resistance to antibiotics. (B602.18.w18)
• Useful in directing the antibiotic therapy. (B609.2.w2)
• Exudate and/or affected tissue should be cultured for both aerobic and anaerobic bacteria. (B602.18.w18, B609.2.w2)
  • Ideally, wall or capsule should be sampled because bacteria that are deep within the exudate are frequently nonviable. (B606.4.w4, B609.2.w2)
• It is common to get lack of growth, particularly with anaerobic infections or a fastidious bacterial infection. (B602.18.w18, B609.2.w2)
• "If anaerobic culture is not possible, diagnosis is often presumed". (B609.2.w2)

Blood work and urinalysis

• These should be carried out. (B602.18.w18, B609.2.w2)
• CBC is often normal. Total white blood cell elevations generally do not occur. What does tend to happen is the neutrophil to lymphocyte ratio may shift to a relative neutrophilia, lymphopenia. (B609.2.w2)
• Biochemical changes depend on the system affected, e.g. if the liver is involved then there may be slight to moderate in the liver enzymes. (B609.2.w2)

• Useful in determining the extent of the bone involvement and essential in guiding the expected prognosis and treatment plan. (B601.13.w13, B602.18.w18, B609.2.w2)
  • Osteomyelitis will have a poorer prognosis and prolonged treatment. (B609.2.w2)
• Thoracic and abdominal: 
  • Useful in identifying and determining the extent of any internal abscesses. (B609.2.w2)
  • If a rabbit has a head abscess then take thoracic radiographs as well as skull radiographs to check for pulmonary abscesses or pneumonia. (B602.18.w18)
• Skull: essential in identifying the type and the extent of the dental disease in patients with facial abscesses. Radiographs must be carried out under general anaesthesia with five views for a thorough assessment (B602.18.w18):
  • ventral-dorsal 
  • lateral 
  • two lateral obliques
  • rostral-caudal 
    (B609.2.w2)
• See: Imaging in Lagomorph Diagnosis and Treatment - Radiography

• Useful in determining the organ system that is affected and the extent of the disease. (B609.2.w2)
• Helpful in delineating the margins of the abscess particularly of retrobulbar abscesses. (B602.18.w18)
• See: Imaging in Lagomorph Diagnosis and Treatment - Ultrasonography

• Useful in diagnosing a pericardial abscess. (B609.2.w2)

• These are more accurate than radiography for assessing facial or brain abscesses, or bullae involvement. (B609.2.w2)
• CT can be helpful in delineating the margins of the abscess particularly retrobulbar abscesses. (B602.18.w18)
• See: 
  • Imaging in Lagomorph Diagnosis and Treatment - Computed Tomography (CT)
  • Imaging in Lagomorph Diagnosis and Treatment - Magnetic Resonance Imaging (MRI)

• Unfortunately, the usefulness of this test is severely limited and often not helpful in diagnosing pasteurellosis in the pet rabbit. 
• An ELISA is available and will report results as high positive, low positive, or negative:
  • Positive result: even if the result is high, it only indicates a prior exposure to the bacteria and then the development of antibodies. It does not confirm active infection. Low positive results can occur due to a cross-reaction with another nonpathogenic bacteria giving a false-positive result.
  • Negative result: false negative results are common if it is early infection or if there is immunosuppression. 
• There is currently no evidence to support the correlation of titres to the abscence of presence of disease. 

(B609.2.w2)

• Environmental Assessment
• History & Documentation
• Physical Examination of Mammals
• Necropsy of Mammals
• Imaging in Lagomorph Diagnosis and Treatment
• Clinical Pathology of Lagomorphs
• Chapter 2 - B36 Field Manual of Wildlife Diseases - Specimen Collection and Preservation
• Chapter 3 - B36 Field Manual of Wildlife Diseases - Specimen shipment
• Appendix A - B36 Field Manual of Wildlife Diseases - Sample specimen history form

Similar Diseases (Differential Diagnosis)

• Granuloma
  • This is generally firmer than an abscess without the fluctuant centre. (B609.2.w2)
• Neoplasia, see Cutaneous Neoplasia
  • This will have variable growth and be associated with variable pain. (B609.2.w2)
• Cyst: This will lack the white caseous exudate of an abscess. (B609.2.w2)
• Haematoma/seroma
  • This will be nonencapsulated and unattached to the surrounding tissues. (B609.2.w2)
  • Fluctuant and fluid-filled initially and then will become more firm with organisation. (B609.2.w2)
• Fibrous scar tissue
  • Firm and non painful and does not enlarge. (B609.2.w2)
• Cuterebra (B609.2.w2)
  • See Cuterebra (Warble) Infection in Lagomorphs
• Some viral diseases may grossly appear to be similar to abscesses, e.g.
  • Myxomatosis
  • Shope papilloma Virus  
    (J213.7.w2)

Specific Medical Treatment

• Rabbit abscesses will not be resolved with simple lancing, flushing, and draining. The thick exudate does not drain very well and antibiotics do not penetrate the thick capsule of the abscess. Recurrence of the abscess is likely. (B602.18.w18, B608.21.w21, B609.2.w2)
• Treatment of choice is surgical excision with a minimum of two weeks of antibiotic treatment. (B601.13.w13, B606.4.w4, B608.21.w21, J213.7.w2)
• Often both local and systemic antibiotic treatment are required. (V.w128)
• For long term success, it is crucial to correct any underlying cause of the abscess. (B609.2.w2)

Systemic Antibiotics

• Long term antimicrobial therapy is often necessary, especially if there is bone involvement. (B609.2.w2)
• As a general rule in the treatment of bacterial skin conditions in rabbits, marbofloxacin, Enrofloxacin, or Trimethoprim sulfa are useful for non-suppurative infections and may be given orally. However, purulent infections respond better to the penicillin related compounds. Amoxycillin, Penicillin G, and Cephalexin are safe as long as they are not used orally. These antibiotics must always be administered parenterally. (P601.1.w1)
• Choice of antibiotic should ideally be based on the results of culture and sensitivity tests. (B609.2.w2)
• Duration of therapy depends on severity of infection: 
  • Four to six weeks minimum to several months / years. (B609.2.w2)
• Use broad spectrum antibiotics, e.g.,
  • Enrofloxacin
    • 5-20 mg/kg orally or by subcutaneous or intramuscular injection every 12-24 hours. (B609.2.w2)
    • 10 mg/kg daily orally. (B606.4.w4)
    • Alternatively use in the drinking water (dilute 100mg/kg). (B606.4.w4)
  • Trimethoprim sulfa
    • 30 mg/kg orally every 12 hours
  • Chloramphenicol
    • 50 mg/kg orally every 8 hours. (B64.22.w8, B609.2.w2)
    • Avoid human contact with this drug due to potential blood dyscrasia. (B609.2.w2)
  • Oxytetracycline
    • 30 mg/kg every 3 days. (B606.4.w4)
• Note: If a rabbit is on long term antibiotic therapy, it is important that it receives a probiotic and a healthy diet based on hay and plant fibre. (B606.4.w4)

If anaerobic infection is suspected as in most dental or facial abscesses, use:

• Metronidazole
  • 20 mg/kg orally every 12-24 hours. (B609.2.w2)
• Azithromycin
  • 30 mg/kg orally every 24 hours. (B609.2.w2)
  • Can use this drug alone or in combination with metronidazole, 20 mg/kg orally every 12 hours. (B609.2.w2)
• Penicillin G benzathine / penicillin G procaine 
  • 40000-60000 IU/kg by subcutaneous injection every two to seven days. (B609.2.w2)
  • Success has been achieved with this antibiotic in the treatment of jaw abscesses. (B602.18.w18)
    • Rabbits <  2.5 kg: 75000 units by subcutaneous injection every other day. (B602.18.w18)
    • Rabbits > 2.5 kg: 150000 units by subcutaneous injection every other day. (B602.18.w18)

Contraindications

• Oral antibiotics that select primarily against the Gram-positive bacteria:
  • Penicillins, macrolides, lincosamides and cephalosporins. (B609.2.w2)
  • These may cause a fatal enteric dysbiosis and enterotoxaemia. (B609.2.w2)

Clindamycin

• In some cases of head abscesses, a 25 mg clindamycin capsule can be pricked using a needle, and then sutured into the cavity of the abscess to provide a slow release antibiotic. Simultaneous probiotic use in the rabbit's diet is recommended. (B606.4.w4)

Antibiotic impregnated poly-methyl methacrylate (AIPMMA) beads

• The beads are made of a synthetic polymer bone cement. (B602.18.w18)
• Useful in areas where it is not possible to completely excise the abscess. (J213.4.w4)
• Used to fill the defect in severely diseased wounds. The wound must be surgically debrided and flushed prior to insertion of beads. (B603.3.w3, B609.2.w2)
• Selection of the antibiotic should be based on the results of culture and sensitivity tests and is limited to those antibiotics that are known to elute appropriately from the bead to the tissues. (B609.2.w2)
• See: Production of Antibiotic-Impregnated Beads (Techniques)

Advantages

• These beads can release a high concentration of the antibiotic into the local tissues for several months. (B609.2.w2, J213.4.w4)
• The antibiotic will only have low systemic levels and so few systemic side effects. (B602.18.w18, J213.4.w4)
• Useful when systemic use of the antibiotic of choice (after culture results) is contraindicated or when the patient is particularly difficult to treat. (J213.4.w4)
• The surgical wound is closed and no further flushing or topical treatment or administration of oral or injectable antibiotics are necessary. (J213.4.w4)
• This method is also useful in cases where the antibiotic of choice is expensive. (J213.4.w4)

Successfully used antibiotics include:

• Cephalothin, cefazolin, or Ceftiofur at 2 g/20 g PMMA 
• Tobramycin or Gentamicin at 1 g/2 g PMMA 
• Amikacin at 1.25 g/2 g PMMA 

(B609.2.w2)

Method:

• Treat the abscess surgically (see surgical techniques below) by removing pus and as much as possible of the infected tissue. After debridement, place the beads into the surgical site and then close the wound. (J213.4.w4)
• Beads must be inserted aseptically with any unused beads being gas sterilised prior to their future use. (B609.2.w2)
• Leave the beads in the incision site for a minimum of two months or they can be left in indefinitely. (B609.2.w2)

Antibiotic impregnated synthetic surface-active ceramic alloplast

• (Consil, Nutramax, Baltimore, Maryland)
• Used as an alternative to to AIPPMA beads to fill defects in debrided bone. 
• Induces production of osteocalcin and the formation of new bone. 
• Antibiotics added to this substance don't need to be heat stable. 

(J213.7.w2)

Impregnated Gauze

• Penicillin G
  • 80000 IU/kg 
• Ampicillin
  • 20 mg/kg 
• Cefazolin
  • 25 mg/kg 
• Metronidazole
  • 50 mg/kg 
• Oral antibiotic treatment is used concurrently throughout the entire treatment period. 
• The wounds should be evaluated and the gauze removed and repacked every seven days under general anaesthesia until there is complete resolution. 
• Efficacy is determined by the severity of the disease and owner compliance. 

(B609.2.w2)

ALTERNATIVE METHODS

50% dextrose or honey

• Used successfully as a topical abscess treatment after surgical debridement. 
• Dextrose or honey have bactericidal properties and promote formation of a granulation bed. 
• Method:
  • Fill the abscess cavity with gauze soaked in honey or dextrose. 
  • Replace daily until a healthy granulation bed forms. 
  • Remove the old gauze from the cavity before instilling a fresh gauze. 
• The treatment often needs to be continued for weeks. 
• Effectiveness varies and will depend on disease severity and owner compliance. 

(B600.9.w9, B609.2.w2)

Doxycycline gel

• Use following surgical debridenent, to fill the abscess cavity. (V.w128)
• The gel is marketed for use in treatment of human periodontal disease. (V.w128)

Amorphous hydrogel dressing

• This type of dressing which contains glycol and a modified CHC polymer (Intrasite, Smith and Nephew), encourages the dissolution of any necrotic tissue and also promotes healing. (B606.4.w4)

Calcium hydroxide paste

• This has been used historically because the high pH leads to an unsuitable environment for bacteria. However, it can cause severe soft tissue necrosis and must be used with caution. 

(B601.13.w13, B609.2.w2, J213.7.w2)

CONTRAINDICATIONS

Corticosteroids

• Systemic or topical corticosteroid preparations may severely exacerbate an infection. (B609.2.w2)

• Treatment and Care

General Nursing and Surgical Techniques

SURGICAL TREATMENT

Treatment of choice is surgical excision with a minimum of two weeks of antibiotic treatment. (B601.13.w13, B608.21.w21, J213.7.w2)

• It is necessary to remove the abscess, foreign object, or nidus of infection, for example, teeth. (B609.2.w2)
• Penrose, or a similar drain, placement is not recommended because the exudate is too thick. (B602.18.w18, B609.2.w2)

Carbon dioxide laser sterilisation

• One study reported this procedure followed by skin closure to be more effective than iodine surgical scrub followed by closure of the skin, in the treatment of rabbits with infected Pseudomonas abscesses. (J213.7.w2)

Superficial abscesses that do not involve teeth or bone

• The ideal treatment for subcutaneous abscesses is excision of the abscess together with its capsule, followed by systemic antibiotic treatment. (B600.8.w8)
• En bloc excision of the entire abscess with wide margins. Take care not to rupture the capsule. (B609.2.w2)
  • If this is not possible, then lance, remove the exterior wall and any nidus of infection, curette all the exudates and let the wound heal by secondary intention. (B602.18.w18, B608.21.w21, B609.2.w2)
  • Irrigate the wound two to three times a day until a healthy granulation bed forms. (B602.18.w18, B609.2.w2) Once the granulation bed has formed use antibiotic cream until reepithelialisation occurs. (B609.2.w2)
  • Irrigation solutions:
    • Dilute antiseptic solution (iodine (Iodophors) or Chlorhexidine). (B336.42.w42, B601.13.w13, B606.4.w4, B609.2.w2)
    • Sterile saline solution. (B602.18.w18)
  • Long term antibiotic therapy is needed after excision. (B609.2.w2)
    • If the abscess is excised en bloc, it should be followed by a minimum of two weeks of antibiotic therapy. (B602.18.w18, B608.21.w21)
    • If the complete surgical excision is not possible then antibiotics will be needed for several weeks. (B608.21.w21)
• Penrose drain placement is contraindicated because it does not facilitate the drainage and it may just act as an avenue for further infection. (B608.21.w21, B609.2.w2)

Facial abscesses

• Jaw abscesses:
  • These are particularly difficult to treat. (B601.13.w13, B602.18.w18)
  • There is often a fistula that connects the pocket of the abscess to the teeth roots. (B602.18.w18)
  • The abscess may be due to periapical disease that causes abnormal tooth growth and the destruction of the surrounding bone. (B602.18.w18) 
  • Remove, in entirety, all the teeth involved in the abscess. (B601.13.w13, B609.2.w2)
  • Remove the abscess and its capsule, and the affected bone, in entirety, whenever this is possible. (B609.2.w2)
    • If it is not possible to do this then remove the abscess at the bone level and then curette or debride all the grossly abnormal soft tissue, teeth, bone. Flush the wound copiously to remove all the exudates. (B602.18.w18, B609.2.w2)
  • Depending on the location of the abscess, either marsupialise it and leave it open to heal by secondary intention as described above, or use AIPMMA (antibiotic-impregnated polymethyl methacrylate) beads to fill the defect. (B601.13.w13, B602.18.w18, B609.2.w2, V.w128)
    • Alternatively, a synthetic bone graft particulate can be used to pack the defect (Consil, Nutramax Laboratories, Baltimore, MD). (B602.18.w18)
  • In a patient with an extensive head abscess, aggressive bone debridement is frequently indicated and so referral is recommended if AIPMMA beads or surgical expertise is not available. (B609.2.w2)
  • Long term systemic antibiotic therapy and pain management are needed. (B609.2.w2)
    • Systemic antibiotics are needed for a minimum of two weeks after surgery and possibly up to six weeks or longer. (B602.18.w18)
• Retrobulbar abscess:
  • If an abscess extends into the retrobulbar space then enucleation may be necessary. (B602.18.w18)

Abscesses involving feet or joints

• See Ulcerative Pododermatitis 
• As for facial abscesses, remove as much of the abscess en bloc as possible, taking care not to cause abscess rupture and further contamination of the incision site. 
• Debride or curette all the visible abnormal tissue and then flush copiously. 
• Treat as an open wound by flushing and debriding the wound daily at first, followed by twice a week to once a week debridement as healing occurs. Apply soft bandages after debridement. If the bandage becomes wet, it must be changed immediately. 
• When feasible, AIPPMA beads (Production of Antibiotic-Impregnated Beads) can be used to fill a defect as described above. If they are place in a joint space, they must be removed after four to six weeks. 
• If there is severe osteomyelitis, then amputation may be required. 
• It is necessary to correct the underlying cause, e.g, improve the husbandry; provide soft bedding; weight loss. 
• Long term antibiotic therapy and pain management are needed. 

(B609.2.w2)

Internal abscesses

• Thoracic: 
  • These can be occasionally amenable to surgical excision by thoracotomy. (B609.2.w2)
  • If excision is not possible, then treat with long term antibiotics and supportive care including analgesia (B600.8.w8, B609.2.w2)
• Abdominal: 
  • Ideally, surgical removal if possible and then followed by long term antibiotic therapy. (B609.2.w2, B600.8.w8)
  • Removal can be difficult to impossible due to adhesions to surrounding organs. (B600.8.w8)

NURSING CARE

See also: Treatment and Care

Acute pain management 

• Butorphanol
  • 0.1-1.0 mg/kg by subcutaneous, intramuscular or intravenous injection every 4-6 hours. 
  • May cause profound sedation. 
  • This is a short-acting drug. 
• Buprenorphine
  • 0.01-0.05 mg/kg by subcutaneous, intramuscular or intravenous injection every eight to twelve hours. 
  • This is a less sedating and longer acting drug than butorphanol.
• Morphine
  • 2-5 mg/kg by subcutaneous or intramuscular injection every two to four hours. 
  • More than one to two doses can cause gastrointestinal stasis. 
• Oxymorphone
  • 0.05-0.2 mg/kg by subcutaneous or intramuscular injection every eight to twelve hours. 
  • More than one to two doses can cause gastrointestinal stasis. 
• Meloxicam
  • 0.2 mg/kg by subcutaneous or intramuscular injection every 24 hours. 
  • Use with care in rabbits that have compromised renal function. 
• Carprofen
  • 1-4 mg/kg by subcutaneous injection every twelve hours. 

(B609.2.w2)

Long term pain management

• NSAIDs 
  • These drugs have been used for short or long term treatment in rabbits to reduce inflammation and pain:
    • Meloxicam
      • 0.2-0.5 mg/kg orally every 24 hours. [Note: higher doses are now recommended]
    • Carprofen
      • 2.2 mg/kg orally every 12 to 24 hours. 

(B609.2.w2)

Fluid therapy

• Aggressive fluid therapy is necessary if there is sepsis or peritonitis. (B609.2.w2)
• See: Treatment and Care - Fluid Therapy

Sedation

• Light sedation:
  • Midazolam
    • 0.5-2 mg/kg by intramuscular injection. 
  • Diazepam
    • 1-3 mg/kg by intramuscular injection.  
• For deeper sedation and longer procedures:
  • Ketamine (15-20 mg/kg by intramuscular injection) and Midazolam (0.5 mg/kg by intramuscular injection). 

(B609.2.w2)

• See: Treatment and Care - Anaesthesia and Chemical Restraint

Diet

• It is very important that the patient continues to eat throughout treatment.
• If the rabbit is unable or unwilling to eat, or resists syringe feeding, use of tube feeding is recommended. (V.w128)
• See: 
  • Treatment and Care - Supportive Care and Nursing
  • Nasogastric and Naso-oesophageal Tube Placement in Rabbits
  • Oesophagostomy Tube Placement in Rabbits
  • Pharyngostomy Tube Placement in Rabbits

Protection of the wound

• Use an Elizabethan collar or protective bandage as necessary. 
  • Note: Elizabethan collars are often stressful to rabbits, and prevent normal coprophagy; they should be avoided where possible. (J213.7.w2, J83.29.w2, V.w128)

(B609.2.w2)

• Production of Antibiotic-Impregnated Beads
• Treatment and Care - Supportive Care and Nursing
• Nasogastric and Naso-oesophageal Tube Placement in Rabbits
• Oesophagostomy Tube Placement in Rabbits
• Pharyngostomy Tube Placement in Rabbits

Preventative Measures

--

• Prevent otitis media and subsequent brain abscesses by:
  • Treatment of upper respiratory infection or otitis in the early stages. 

(B609.2.w2)

• Preventative Medicine for Mammals

Environmental and Population Control Measures

Lagomorphs

• Prevent feet or joint abscesses by:
  • Provision of solid, clean surfaces and appropriate surface substrates. 
  • Prevention of obesity.
• Prevent otitis media and subsequent brain abscesses by:
  • Treatment of upper respiratory infection or otitis in the early stages. 

(B609.2.w2)

• Prevent progressive dental disease by:
  • Selection of pets without a congenital predisposition to dental disease. 
  • Provision of high fibre food and good quality hay.
  • Periodically trimming any overgrown crowns. 

  (B609.2.w2)

• Prevent superficial abscesses by:
  • Prevention of fighting between rabbits. 

  (B609.2.w2)

• In the colony situation, the affected animal should be eliminated from the colony to prevent spread of the infection and contamination of facilities and equipment. (B611.9.w9)

• Environmental and Population Management - General