Facial
abscesses
Michel Gruaz, with Esther van Praag, Ph.D.
Warning:
this page may contain pictures that may be distressing for some persons.
|
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
Animal Clinic, Houston,
TX, US), to Bonnie Salt (USA), to Tal Saarony (USA) and her rabbit
Motek, to Dr. Gil Stanzione (Dakota Veterinary Clinic,
White Plains, NY, US), to Jen Smuck (USA), and to Akira Yamanouchi
(Veterinary Exotic Information Network,
Japan) for the permission to use their pictures. Further
information
Harcourt-Brown
F. Textbook of Rabbit Medicine. Oxford, UK: Butterworth-Heinemann; 2001. 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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