Nocardiosis is a bacterial infection. The Nocardia bacteria behind it live in soil all over the world and feed on dead plant matter [1]. A wound that picks up soil can let them into the body [1].
If your cat has a wound or abscess that does not heal or keeps draining, see your vet. If your cat has trouble breathing, see your vet now.
How cats get it
The bacteria usually get in through a dirty wound. Less often a cat breathes them in or swallows them [1]. For how fight wounds start and why they need a vet, see bite wounds in dogs and cats.
Animals with a weak immune system are more at risk [1]. In one published case, a cat whose belly wound would not heal turned out to carry feline immunodeficiency virus (FIV) [2]. The same group of bacteria can also infect people [2].
Skin signs
In cats and dogs, the infection shows up as swollen, inflamed skin, lumps that break open into sores, and abscesses that often form draining tracts [1]. An abscess is a pocket of pus. A draining tract is a small channel that keeps leaking fluid onto the skin.
The sores tend to appear where the skin was hurt, most often on the legs and paws [1]. Cats also often get sores on the underside of the belly [1]. The leaking fluid can be pus mixed with blood [1].
The lymph nodes near the sores are often swollen [1]. Lymph nodes are small glands that can swell when the body is fighting infection.
Signs beyond the skin
Sometimes the infection spreads inside the body. A cat may then have a fever, seem dull and low, struggle to breathe, or show nervous system signs [1]. Pus can also collect in the chest [1].
How vets diagnose it
Your vet will look at your cat’s history and signs, then test a sample. That can mean looking at fluid from a sore under a microscope, growing the bacteria in a lab (a culture), or taking a small piece of tissue (a biopsy) [1]. Labs can also identify the exact bacteria with DNA tests [1].
Finding the cause can take more than one try. In the published cat case, the first lab result pointed to a different bacterium, and Nocardia was only found after surgery and more tests [2].
Treatment
Your vet will advise on treatment for your cat. Treatment is usually long [1].
At home, as directed by a vet:
- do not give your cat human or leftover medicines unless your vet says so;
- do not stop or change any medicine without talking to your vet;
- give any treatment exactly as your vet prescribes, for as long as your vet says;
- go back for any recheck your vet books.
Outlook
When the infection stays in the skin, the outlook is usually good [1]. When it has spread inside the body, the outlook is much less certain [1].
These are statements about groups of cats. They cannot predict how one cat will do. Your vet can explain what this means for your cat.
When to see your vet
See your vet if your cat has:
- a wound that keeps draining or will not heal [1];
- lumps, sores or abscesses on the legs, paws or belly [1];
- swollen glands, fever or low energy [1];
- any wound or skin change you are unsure about.
See your vet now if your cat has trouble breathing [1].
The bottom line
Nocardiosis is a long-lasting bacterial infection from the soil that can follow a wound and cause abscesses and draining sores in a cat’s skin. Only a vet can find the cause with lab tests.
This article is for general information only and does not replace advice from your veterinarian. If your cat has a wound that will not heal, see your vet.
Sources
- Torres SMF. 1.7 Actinomycetic Infections: Small and Large Animals. In: Small and Large Animal Dermatology Handbook, Vol. 1. University of Minnesota, 2025. CC BY 4.0. https://open.lib.umn.edu/animaldermatology/chapter/actinomycetic-infections-small-and-large-animals-2/
- Silkworth A, Cavanaugh R, Bolfa P, Becker AAMJ. Cutaneous Pyogranulomas Associated with Nocardia jiangxiensis in a Cat from the Eastern Caribbean. Tropical Medicine and Infectious Disease, 2019. CC BY 4.0. https://pmc.ncbi.nlm.nih.gov/articles/PMC6958412/