| Abscesses in Rabbits
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Jason Hutcheson, DVM
For Pet’s Sake: The Avian and Exotic Animal Hospital of Atlanta
Abscesses occurring in rabbits can have many different causes. Some of these
causes can be prevented while others are not known until the abscess has
occurred. Once formed, the treatment for these abscesses can be both time
consuming and costly for the owner as well as uncomfortable for the bunny. The
most common bacteria found in rabbit abscesses are Pasteurella spp. but a
bacterial culture may be necessary to confirm or guide treatment. The purpose of
this article is to inform the bunny owner of the different types of rabbit
abscesses, the prevention of some (where applicable), and the length of
treatment that may be involved in clearing up an abscess once it has formed.
This listing is not all inclusive but does discuss the types most often seen in
this practice.
Superficial abscesses can occur on any part of the body and are found just under
or in between the layers of the skin. The rabbits typically do not show signs of
a problem such as pain, lethargy, or anorexia. The owner will commonly notice a
swelling in or scab on the skin and bring the bunny into the clinic, where the
final diagnosis is made. The underlying cause is generally from a penetrating
wound such as a bite from a cage mate, sharp objects (such as wire, hay stems,
or sewing needles), or projectiles (such as BB’s or pellets from a kid’s air
rifle!). Treatment usually involves lancing and flushing the abscess, placing
the bunny on systemic antibiotics, as well as scheduling follow-up appointments
to make sure the lanced area stays open long enough for the infection to clear.
The healing process from a superficial abscess may take as little as ten days or
as long as three months. One case in particular comes to mind: “Frans” was
presented for assessment of a recent bite wound on his side. Initially the wound
did not look too bad but I mentioned to the owners the potential of it becoming
a severe abscess. As predicted, the wound became very serious despite preemptive
treatment. Three surgeries, many flushings and bandage changes, two long-term
antibiotic treatments, and three months later…the abscess healed with no other
ill effects.
Joint abscesses are very painful and can occur in any joint of the body but are
most typically found in the hock joint of the hind leg or the wrist joint of the
fore leg. The owner may notice the bunny being reluctant to move or a tendency
to “shuffle” instead of hop. In addition, the bunny may go off feed and become
very lethargic. Upon presentation the rabbit will have severely swollen limb
joints and often have scabs and pus on their hocks and wrists. The most common
underlying cause of a joint abscess is frequently a result of being housed on a
wire surface, although some joint abscesses are a result of bacteria getting
into the blood stream and then settling out in one or more of the aforementioned
joints. The cause of the bacterial infection of the blood is a result of a
compromised immune system that stress, poor nutrition, and bad husbandry
practices often induce. Treatment for this type of abscess is very lengthy and
may include, but is not limited to systemic antibiotics, topical antiseptic
treatment of the affected joints, pain control, and, most importantly,
correction of the poor husbandry techniques. A bunny recovering from a leg joint
abscess will usually have severe joint damage which results in irreversible
arthritis and may need to be placed on lifelong anti-arthritis medications. The
case of “Mr. Ben” comes to mind: He was presented to the hospital in very bad
shape; calling his husbandry sub-standard was a compliment! He suffered from
severe malnutrition in addition to joint abscesses of BOTH hocks and BOTH
wrists. He was adopted by HRS and for three months was treated with systemic
antibiotics, chlorhexadine soaks of all four feet, repeated lancing of all four
affected joints, and pain medication. After this period of treatment and
correcting his diet (he almost doubled his weight) and providing proper living
conditions; “Mr. Ben’s” joints were so deteriorated that he still cannot walk
normally and is given anti-arthritis medication regularly.
Abscesses that occur around the base of the ear are called periaural abscesses.
These are typically not painful and often an owner will note a grape-sized
swelling in the area where the ear meets the head. Some bunnies alert their
owners to investigate the affected ear by scratching at it furiously or repeated
head shaking. Sometimes a periaural abscess is caused by the same things that
would cause a superficial abscess. Other times, they may be the result of an ear
infection. Regardless of the cause, they usually rupture on the inside of the
ear resulting in drainage of some of the pus down the ear canal. This tendency
to rupture and partially drain may account for the abscess’ small size upon
presentation. In any case, they should be treated with both systemic antibiotics
and topical ear medications after the initial lancing and flushing. Rechecks are
just as important with this type as they are with the superficial abscesses to
prevent premature closure of the lanced area and subsequent reformation of the
abscess. In my experience this type of abscess tends to reoccur; often months
after the initial treatment and apparent healing. An example is “Skittles”: I
have treated her for this type of abscess approximately once every ten to twelve
months for the past three years. Never has she appeared to be bothered by this
reoccurring problem (except when I lance and flush it!). Every year the area
appears to heal up and has no further swelling for months. Her owners have
become very astute to this problem and bring her back in at the first sign of
reoccurrence.
The next group of abscesses occurs less frequently, but due to their underlying
causes are worth mentioning. Internal abscess may form in either the abdomen or
the chest. They can be associated with any organ found therein. In most cases,
they are the result of bacteria in the bloodstream due to a decreased immune
system. As previously mentioned, a rabbit’s immune system can be compromised
from increased stress, i.e. poor nutrition, improper housing, and inappropriate
living conditions. The bacteria responsible for the abscesses is not taken care
of by the bunnies own defenses and can settle out in various organs of the body.
In addition to joints (previously mentioned), organs such as the liver, kidneys,
lungs, or intestinal lymph nodes may be involved. The uterus can also be the
site of internal abscess formation. Obviously, spaying a female bunny at an
early age can prevent this type. Signs of an internal abscess are much vaguer
than any signs mentioned previously. More often, these rabbits are presented for
anorexia, lethargy, or “ADRD” syndrome (Ain’t Doin’ Right, Doc!) Diagnosis is
made with X-ray films or ultrasound and treatment is surgical with outcomes
being very guarded.
The most common site for jaw abscesses in rabbits occurs in the lower jaw. The
most common breeds tend to be dwarf males. Often, the rabbit is brought into the
hospital for such vague signs as not eating, not defecating, lethargy, or
drooling. Sometimes owners notice a large, sometimes golf ball-sized hard lump
on the affected jaw. The physical exam typically reveals the large lump which
may be hard, soft, or a combination of the two as well as a malocclusion of the
back or “cheek” teeth. X-ray films then confirm the presence of a jaw abscess
with proliferation of the jaw bone.
The cause of these abscesses and accompanying malocclusions are usually
multifactor and may never be definitively determined. As mentioned, rabbits with
jaw abscesses usually have malocclusions and the two problems are definitely
linked. So which problem came first: the abscess or the malocclusion? The answer
is either could have come first with the other being the result.
Infection of the tooth roots or gums could spread to the bone surrounding the
teeth. The infection could have been introduced by foreign objects such as
hayseeds wedging between the teeth and gums or splinters from wood chewing. I
have even seen one bunny that got into the sewing basket and got a sewing needle
lodged in his gums. Regardless of entryway, the bacteria can proliferate and
invade the surrounding bone causing the bone to weaken. The teeth then become
loose in their sockets and shift their position. A malocclusion is the result.
Additionally, physiologic stressors such as poor diet, bad husbandry, and
inappropriate living conditions can weaken a bunny’s immune system facilitating
the above process.
The above paragraph describes how infection precedes malocclusion with the end
result being an abscess of the jaw. The same resulting abscess can also be
obtained when the chain of events are reversed. More commonly, a malocclusion is
the initiating cause and the infected abscess comes along secondarily. Tooth
root elongation is one type of acquired malocclusion linked to jaw abscess
formation. The theory is that rabbits without proper wear-down of their cheek
teeth end up with their jaws held slightly open due to the tooth crowns being
too long above the gum line. Over time the jaws cannot be held open any wider
and the pressure exerted on the teeth caused by their continuous growth
essentially pushed the tooth roots in the opposite direction. The tooth roots
basically are pushed out of their sockets and into the deeper layers of the jaw
bone. The bunny’s body perceives this as a foreign invasion (tooth roots are not
supposed to be out of their sockets and in the deeper layers of jaw bone) and a
major inflammatory response occurs with a hard bony abscess resulting. Metabolic
bone disease is another theory as to how some abscesses form. Basically bone
needs calcium, phosphorus, and vitamin D to remain solid and strong. A
deficiency of or problem utilizing any of the three ingredients can lead to thin
and week bones all over the body. In addition to bone fractures, malocclusion is
a common manifestation of metabolic bone disease. This occurs because the body
starts to reabsorb the minerals from its own stores in the bones. The tooth
sockets become too big to hold the teeth adequately. The teeth are loose and are
easily shifted into a misalignment. The resulting gaps and loose fitting teeth
allow foodstuffs and bacteria from the mouth to become wedged into the space
between tooth root and boney socket creating a perfect environment for the
bacteria to grow and invade the surrounding bone. The result, once again, is a
bony jaw abscess.
Once diagnosed, treatment for jaw abscesses should be aggressive! Each bunny and
situation is different and this list of treatments may not apply to every bunny.
At for Pet’s Sake we typically place these bunnies on antibiotics and
anti-inflammatory medication immediately and schedule there first surgery to
lance, flush, and remove parts of the infected jaw bone. I say first surgery
because rarely will one single surgery and one simple round of antibiotics cure
this problem. During this first surgery we also trim and file the overgrown
misaligned back teeth. The lanced abscesses are usually left open and flushed
with an antimicrobial solution daily. Subsequent surgeries are usually required
to remove more of the infected bone, flush out more pockets of pus, instill
antibiotic impregnated beads or gel, or remove infected teeth. Treatments can go
on for months and despite any combination of above treatments, may never “cure”
the problem. I consider treatment successful if the jaw does not form any more
abscesses for two years. These “cured” bunnies will require periodic back teeth
trims and files for the rest of their lives as the malocclusion never corrects
itself after treatment of the abscess.
Copyright 2005 For Pet’s Sake and Jason Hutcheson, DVM.
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