Valley fever, also called coccidioidomycosis, is an infection caused by a fungus named Coccidioides. The fungus lives in the soil of dry regions, and animals and people catch it by breathing in its spores [1][2]. Spores are tiny seeds that the fungus spreads by. In people, the infection does not pass from one person to another [2].
If your cat has a draining sore, a lump under the skin or an abscess, see your vet, and tell them where your cat has lived or travelled. If your cat has trouble breathing, see your vet now.
Where it occurs
The fungus is found in the southwestern United States (including California, Arizona, Texas, New Mexico, Nevada and Utah), in northern Mexico, and in parts of Central and South America [1]. Dogs get valley fever more often than cats, and in cats the disease is uncommon [1].
Where the fungus lives
The fungus does best in sandy, alkaline soil in hot, low-lying places that get little rain [1]. In the soil it grows as fine threads. When an animal breathes in its spores, the fungus changes form inside the body [1].
Infections tend to follow a damp spell that lets the fungus grow, then a dry spell when the soil is stirred up, for example by building work or an earthquake [1]. Breathing in spores is by far the most common route. Infection straight through a skin wound can happen but is rare [1].
Skin signs
In many animals, valley fever starts in the lungs. In cats, though, skin problems are one of the most common reasons owners notice something is wrong: about half of the cats described in reports had skin lesions [1]. These include:
- lumps under the skin;
- abscesses, which are pockets of pus;
- sores that leak fluid (draining sores) [1].
In dogs, skin sores often sit over an infected bone. In cats, that link is less common [1].
Signs beyond the skin
Other signs reported in cats include fever (in about 3 in 10 cats), fast or hard breathing (about 1 in 4), lameness (fewer than 1 in 5) and eye problems (about 1 in 8) [1]. A few cats have had neurologic signs, which means signs from the brain and nerves [1]. The infection can reach organs in the belly, and many cats already have it in several parts of the body by the time it is diagnosed [1].
How vets diagnose it
Your cat’s history, including where it has lived, and its signs matter a great deal [1]. A vet may look at fluid from a draining sore or a sample from a lump under the microscope, or send a tissue sample (biopsy) to a lab. The fungus can be hard to find in these samples, so a negative result does not always rule it out [1]. Blood tests that look for antibodies against the fungus are also used [1].
Treatment
Your vet will advise on treatment for your cat.
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 or blood test your vet books.
Outlook
The University of Minnesota handbook describes the outlook with treatment as generally good, with roughly 6 in 10 animals recovering. The outlook is less certain, or poor, when the brain or spinal cord is involved [1].
These are statements about groups of animals. 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:
- draining skin sores, lumps under the skin or abscesses [1];
- fever, lameness or eye changes [1];
- any lump or sore you are unsure about, especially if your cat has lived in or travelled to an affected region.
See your vet now if your cat has difficulty breathing [1].
The bottom line
Valley fever is a fungal infection from dry, dusty regions of the Americas that in cats can show up as draining sores, lumps and abscesses in the skin. Only a vet can confirm it with the right tests.
This article is for general information only and does not replace advice from your veterinarian. If your cat has a draining sore or a lump under the skin, see your vet.
Sources
- Torres S. 4.7 Systemic Mycosis: Coccidioidomycosis, Small Animals. Small and Large Animal Dermatology Handbook, Vol. 1. University of Minnesota Libraries Publishing. CC BY 4.0. https://open.lib.umn.edu/animaldermatology/chapter/systemic-mycosis-coccidioidomycosis-small-and-large-animals/
- Valley Fever. MedlinePlus, U.S. National Library of Medicine. https://medlineplus.gov/valleyfever.html