A fluid-filled swelling

A cat's abscess from a bite wound. Photo courtesy of MarVistaVet

An abscess forms when an infected bite wound heals over on its surface, thus sealing the deeper infection inside. Fever is generated as the infection incubates. Diseased tissue and the inflammatory cells liquefy into pus. The pus breaks through the overlying surface skin and drains, leading to foul odor, pain, and discharge. The area may or may not heal on its own.

What to Look for at Home

If the abscess has not yet ruptured, your cat will likely be feverish, which means you will see listlessness and appetite loss. Depending on how long the area has been swollen, the skin involved may be very tender or fragile. If you look closely, a small scab from the tooth mark that caused the abscess may still be visible on the surface of the swollen area.

A smelly, draining sore

The bite mark is hard to see but a fluid-filled lump could be easily felt. Photo courtesy of MarVistaVet

The fluid pocket will eventually rupture and release foul-smelling pus. The fever may break once the rotten tissue is able to drain. You may not see the sore, but you will probably smell it.

Some cats will lick the fur away from the wound, making the area more visible. At this point, it is likely to look raw and may no longer be actively draining pus. Sometimes, the overlying skin is especially fragile and tears away, leaving a large raw area.

A wound that is not healing

The abscess was hidden in this cat's armpit area but the smell of the infection was obvious. Photo courtey of MarVistaVet

Sometimes, the wound is buried so deeply in the fur that it is not apparent. You may only find a tender area and possibly notice the odor characteristic of deep infection. 

A tender area

This abscess had been there so long that the overlying tissue was sloughing off, leaving a large open area. Photo courtesy of MarVistaVet

Common areas for bite wound abscesses include the facial cheeks, the legs, and the base of the tail. Fighting cats tend to bite one another in these areas.

Common area for cats to bite

This patient’s bite wound abscess (the small red puncture wound on its hip) would not be visible without shaving the fur away from the area. Photo courtesy of MarVistaVet

Treatment

• If the abscess has not ruptured, it will need to be lanced. Once the abscess is open, it will need to be flushed clean of infected debris. If the abscess is large or especially painful, sedation may be required to accomplish this.
  
  
• Older abscesses may have enough devitalized overlying tissue to require surgical trimming and stitches. Some abscesses are large enough to require an indwelling rubber drain to remove the pus. You may have to flush the drain with disinfectant at home.
  
  
• The cat will likely need antibiotics at home. If so, you will need to give either pills or liquid medication (tell your veterinarian if you have a preference). Alternatively, there is an injectable antibiotic (Convenia®) that lasts two weeks and may be given in the clinic, eliminating the need for oral medication at home. Your veterinarian will likely recommend one of these treatments in addition to cleaning and flushing out the wound.
  
  
• Warm compresses are helpful for the first few days following discharge. The heat helps liquefy diseased tissues so that they can drain. To hot pack the area, use a warm (not hot) washcloth applied to the wound for 5 to 10 minutes once or twice a day as directed by your pet's doctor.

Other Important Things

Feline leukemia (FeLV) and feline immunodeficiency (FIV) viruses represent serious contagious infections spread by bite wounds. The American Association of Feline Practitioners has guidelines for viral testing. Testing, accomplished by a simple kit that can be done in your veterinarian’s office, ideally should be done 60 days or more from the time of the bite. Outdoor cats should be tested annually for these viruses regardless of vaccination status. Testing is recommended at the time of the abscess treatment if a test has not been performed in the last year. This test will not rule out any infection initiated by this bite but will test for any infection from past bites. A positive test could alter your cat's ability to heal. Additionally, positive cats should best become indoor cats to minimize exposure to hazards and reduce disease transmission to other cats.

If your cat has not been vaccinated for rabies, it is especially important to ensure this vaccine is current. Bite wounds transmit rabies, and since there is no effective treatment for either animals or humans, it is important to consider this simple prevention.

Be sure you understand how to give medication, perform hot packing, and manage rubber drains if your pet has them.  Most abscesses heal over the course of a week, though larger abscesses can take longer. If your cat’s abscess is not healed in one week, be sure to notify your veterinarian.