Facial abscesses
Michel Gruaz, with Esther van Praag, Ph.D.
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In past times,
when a rabbit developed a large sized abscess on the cheek, the cause was
believed to be bovine hypodermosis or warbles caused by the larva of the ox
warble-fly Hypoderma bovis. Lumps (sterile abscesses) on the back of
cattle or deer contain young warbles/larva. The presence of a facial abscess
should, however, be taken seriously. Main causes are dental problems and
bacterial infections like staphylococcosis and pasteurellosis. An abscess is a
pocket of fluids and pus that results from an attack by pyogenic organisms
(bacteria that produce pus), followed by cell destruction. The content
consists of pus, dead phagocytic white blood cells, necrotic cells and dead
or living bacteria. The pocket grows in size when the amount of pus
increases. During the encapsulation phase, the abscess gets isolated from the
surrounding tissues and blood circulation. If the abscess is not treated, it
can burst to the inside or at the surface of the skin. Bacteria and their
toxins will be released in the blood, which is life-threatening (septicemia,
which is difficult to treat in rabbits) and painful. Many rabbits
suffering from abscesses have a history of pasteurellosis or infections
caused by other bacteria, e.g., Streptococcus sp., Pseudomonas
sp. and/or fusiform – spindle shaped bacteria. The development of jaw
abscesses may have a genetic origin (malocclusion, abnormal elongation of a
molar), but can also relate to apical (tooth root) problems due to dental
trauma (fracture) or to the presence of a foreign body such as a piece of hay
stuck between molars. Bacteria can enter the space between the gum tissue and
the tooth and reach the dental root. Often Staphylococcus sp. or Pasteurella
sp. bacteria are isolated, but Fusobacterium sp., Actinomyces
sp. or Streptococcus sp. (which can infect humans teeth) may be the
cause as well. No specific
clinical signs are linked to the presence of an abscess. In a primary stage,
it is possible to feel a lump or a bump along the bone of the mandibular jaw.
Abscesses can feel hard or as a soft paste like lump that can be moved. Their
presence does not appear to cause pain in rabbits, unlike observed in other
animals. Growth of abscesses is usually fast, and their size can double
within a few days.
This stage is
often overlooked the rabbit continues to eat normally. Then, gradually, an
unusual limp appears, accompanied by a reduced appetite, increased drinking
and sometimes fever.
Identification of the problem - diagnosis
If
the visual examination and palpation of head conclude to the presence of a
maxillary or mandibular abscess, the oral cavity of the rabbit must be
carefully examined. This is best done on a sedated or anesthesized rabbit.
The anesthesized rabbit is immobilized to avoid any movement
that could blur the images. Ideally, radiographs are taken from different
angles (ventrodorsal, lateral et oblique). Images must be of irreproachable
quality, high resolution when available. In order to provide information of
the dental problem such as e.g., bone deformation, root-related problems,
presence of abscesses, and spread of the infection to the jaw bone. Computed
tomography (CT scan) can help refine diagnosis, e.g., by locating the dental
problem precisely and image its extent, evaluate prognosis and predict
therapeutic outcomes.
The jaw bone can
get infected. A sample can be aspirated in a syringe with a needle of smaller
gauge and sent to a specialized laboratory. Unfortunately, it happens that
diagnosis comes back with an incorrect diagnosis such as osteosarcoma (tumor
of the bone, rare in rabbits) instead of dental abscess with bone infection
(osteomyelitis). This mistake can have disastrous consequences, delaying
proper treatment and administration of antibiotics.
Treatment
Treatment of a
facial abscess is difficult and long, and requires cooperation and dedication
of the owner for post-surgical care. Recurrence is frequent. If the lump can be
felt, but is small in size, an antibiotic treatment can be attempted. In one
case, the rabbit had lost a tooth, and the cavity was filled with pus. The
combined administration of daily marbofloxacin and weekly injection of
long-acting penicillin cured the problem. If the rabbit presents sensitivity
to penicillin, this antibiotic can be replaced by e.g., metronidazole. The
use of systemic antibiotics is, however, not always efficacious and a more
aggressive approach is necessary. The safest approach is full excision of
the abscess capsule and of surrounding infected and/or necrotic tissues.
During the surgery, it is important to verify that all fibrous channels
leading to abscess cavities located deeper in the tissue are removed. If
those pockets cannot be removed, they should be flushed with an antiseptic
solution (chlohexiderme or povidone iodine) by means of a catheter. The
debrided cavity can be filled with products impregnated with antibiotics.
Another option is to place a drain to facilitate post-surgical care and help
healing.
If
surgical excision is not possible, the abscess pocket should be carefully
debrided. Every trace of pus, of tooth or bone fragments, or of necrotic
tissue should be removed to promote a good healing. The pocket can be filled
with PMMA beads impregnated with antibiotics, with cellulose-based sponges or
calcium hydroxide, before the incision is sutured. Details about fillings can
be found here: Skin abscess in rabbits. Another option
is to keep the wound open by suturing the edges of the incision to the skin
(marsupialisation). This enables an “easy” daily care, such as flushing with
chlohexiderme or povidone iodine or filling with products that dry out the
cavity (e.g., dextrose, medical honey, manuka honey). During the healing
process, the cavity will progressively fill with scar tissue and heal. If osteomyelitis,
its extension in the jaw bone must be assessed. If the infection spreads over
a few molars, prognosis is guarded and the option of humanely putting the
rabbit to sleep should be considered. Treatment includes the administration
of systemic antibiotics that penetrate the bone, chosen according to the
results obtained from the bacterial culture and antibiotic sensitivity tests.
The choice of antibiotics safe to use in rabbits is limited. The treatment
must be aggressive and long, between 4 to 6 weeks. If the antibiotics fails
to reduce the infection, or bone has been destroyed, surgical debridement
should be considered. After the surgery
and during recovery, analgesics should be given to the rabbit. Several products
such as e.g., creams/gel with d’Echinacea or HEALx Soother Plus have
properties that promote healing. It must be taken
into consideration that abscesses are often difficult to treat and healing
cannot be 100% guaranteed. Post-surgical follow-up are, therefore,
recommended. Acknowledgement
A big thank you to (alphabetic order)
Caroline Charland (www.BunnyBunch.org),
to Michel Gruaz (Suisse), to Debbie Hanson (USA) and her
rabbit Stella, to Dr. Cheryl Morales (Prestonwood Further
information
Capello V. Case
Report: Use of HEALx Soother Plus in Postoperative Treatment of a
Dental-related Abscess in a Pet Rabbit. http://www.exoticdvm.com/mammal Capello V, Gracis
M, Lennox A. Rabbit and Rodent Dentistry Handbook. Lake Worth - FL, USA:
Zoological Education Network; 2005. Harcourt-Brown F.
Textbook of Rabbit Medicine. Oxford, UK: Butterworth-Heinemann; 2001. Meredith A,
Flecknell P. BSAVA Manual of Rabbit Medicine and Surgery. Cheltenham, UK:
British Small Animal Veterinary Association; 2006. Quesenberry KE,
Carpenter J. Ferrets, Rabbits, and Rodents. St-Louis-MO, USA: Saunders; 2004. Van Praag E, Maurer A, Saarony T. Skin Diseases of Rabbits. Geneva, CH: MediRabbit.com; 2010. |
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