• An abscess forms when infection, inflammation, and damaged cells cannot be cleared by the body.
  • Abscesses can occur when bacteria are deposited under the skin (as with bite wounds or other wounds).
  • Abscesses can cause pain, fever, and lethargy (tiredness) until the infection is cleared up.
  • Abscesses are treated with antibiotics and possibly surgery, depending on the size and severity of the infection.
  • Keeping cats indoors is a good way to prevent abscesses caused by bite wounds.
  • Rabies is passed through bite wounds, and prevention/quarantine should be considered when treating an abscess associated with a bite wound.

What Is an Abscess?

An abscess is a pocket of pus that is formed when the body’s immune system is unable to quickly clear a site of infection. Pus is a liquid collection of inflammatory cells, bacteria, and damaged tissue. Abscesses can form in any part of the body and often result from bacterial infections in bite wounds, tooth roots, and anal glands. Abscesses just under the skin are quite common in indoor/outdoor cats. This article focuses on abscesses that form when a cat is bitten by another cat or a wild animal.

Cats that are allowed outdoors are the most likely to have bite-wound abscesses because these cats have the opportunity to fight other animals. During a fight, the skin can be punctured by a tooth or a claw.  Bacteria on the tooth or claw are deposited under the skin, and the immune system activates to fight off a possible infection and promote healing. Unfortunately, if the body’s initial attempt is unsuccessful, the skin may heal over the wound and trap the bacteria, damaged tissue, and inflammatory cells under it. At this point, there is no easy way for this material to leave the body and a pocket of liquid pus forms.

What Are the Signs of an Abscess?

An abscess usually presents as a painful, fluid-filled lump under the skin. You may see a small scab over a puncture wound near the lump, but sometimes abscesses aren’t even noticed until they break through the skin and pus oozes from the site. Sometimes cats develop a fever before the abscess is obvious and the only change noticed is that their appetite and activity level may have decreased.

How Are Abscesses Diagnosed and Treated?

If you believe your cat has an abscess, it is important to go to your veterinarian as soon as possible.  Once an abscess forms, it is very difficult for the body to remove the material and fight the infection by itself. An untreated abscess can lead to deeper or more widespread infection. Antibiotics are needed to help fight the infection. However, the abscess commonly needs to be drained in order for healing to occur. In some cases, a sample of the fluid may be sent to a diagnostic laboratory to identify the bacteria and the most appropriate antibiotic. If an abscess is allowed to progress, permanent damage could result.

Since it is difficult for the body to clear the buildup of pus, it is often necessary to open an abscess and flush it with solution to allow the pus to drain. If the abscess pocket is large and there is concern that another abscess may form before the antibiotics take effect, your veterinarian may choose to place a surgical drain to promote removal of fluid for a few days. Then, once the antibiotics have controlled the production of pus, the drain can be removed and the wound can heal completely.

One of the biggest concerns with bite wounds is the spread of infectious diseases like feline immunodeficiency virus (FIV, also known as feline AIDS) and rabies. Only cats can get FIV, but the rabies virus is fatal and can be transmitted to people. Even if your cat’s rabies vaccination is up-to-date, state regulations may require your veterinarian to administer a booster vaccine if your cat is bitten. If your cat is overdue for or has not received a rabies vaccination, it is possible that your cat will have to be quarantined for a period of time. Each region has its own regulations regarding rabies exposure and quarantine procedures. Your veterinarian will advise you about the law in your location.

How Can I Prevent Abscesses?

The best way to prevent bite wound abscesses is to keep your cat indoors.  Even though fights sometimes occur among housemates, transmission of infectious diseases like rabies is less likely among a group of vaccinated indoor cats.  If you do choose to allow your cat outdoors, you should be sure to do the following:

  • Spay or neuter your cat—this will make your cat less likely to become territorial and get involved in fights.
  • Keep your cat’s rabies vaccinations up-to-date—rabies is a deadly virus that can be prevented from  causing disease with regular vaccinations.
  • Check your cat frequently for bite wounds, lumps, or other injuries.