Fungal Disease (Sporotrichosis) of the Skin in Cats

The cause of sporotrichosis is infection by the fungus Sporothrix. The Sporothrix fungi tend to thrive on organic material such as soil, wood, and vegetation.

Sporotrichosis is uncommon, and is typically not a life threatening condition. It usually affects the skin or the lymphatic system of infected cats. Only in rare cases does the fungus spread to other systems, making the infection more dangerous. Cats with symptoms of sporotrichosis require prompt veterinary attention.

Sporotrichosis affects both indoor and free-roaming cats, although outdoor cats in close contact with other cats have a higher chance of becoming infected. Males are slightly more susceptible, as are young (2 to 3 year old) cats. Cats who are often involved in fights with other cats are also more at risk.

Sporotrichosis is more common in warmer climates. Cats living in tropical and semi-tropical locations are more at risk.

In more severe cases, sporotrichosis infects tissues deeper in the body, particularly the lymphatic system.

Symptoms include:

• Swelling of the lymph nodes, particularly near the original site of infection on the skin
• Skin nodules or crusts along the pathway between nearby lymph nodes

In rare cases, the cat develops disseminated sporotrichosis which affects the lungs, bones, joints, or internal organs. This form of sporotrichosis is sometimes fatal. The lungs are the most commonly affected.

The cause of sporotrichosis is infection by the fungus Sporothrix. The Sporothrix fungi tend to thrive on organic material such as soil, wood, and vegetation.

Cats become infected by coming into contact with the fungus, but only in the case where the skin of the cat is damaged. Possible circumstances in which the cat is infected by Sporothrix include:

• The cat’s skin is penetrated by a splinter, thorn, or other contaminated material
• The cat has previously damaged skin that comes in contact with the fungus
• A cat who is already infected with the fungus or is carrying the fungus on its claws scratches another cat and transmits the fungus

The main symptoms of sporotrichosis are:

• Crusty or weeping sores over a firm nodule
• Hair loss in the area of the nodules

The nodules of sporotrichosis are most commonly found on the head, ears and front limbs.

Diagnosis of sporotrichosis involves identifying the fungal pathogen. Diagnostic tools include:

• Physical examination
• Cytologic examination of skin impressions or oozing material
• Biopsy of the skin
• Fungal cultures

Treatment is antifungal medication. It is recommended that treatment continue for at least a month after symptoms resolve.

Cats undergoing treatment for sporotrichosis often require hospitalization under strict biosecurity protocols, to prevent the fungus from spreading to other animals or humans. Cats on antifungal medications also require routine blood work during the treatment period, to monitor for side effects of the antifungal medications.

Left untreated, sporotrichosis can last for months to years. Treatment takes several months to clear the infection and should continue for at least a month after symptoms resolve. The prognosis with treatment is good. In cases where disseminated sporotrichosis has developed, the prognosis is guarded.

There are no known preventative measures for sporotrichosis. Infected cats should be isolated to prevent spread of infection to other pets and humans. Reporting cases to concerned organizations helps to track outbreaks. Keeping cats indoors is recommended to reduce their potential exposure to the fungus.

Sporotrichosis is uncommon in cats, but is more common in tropical and semi-tropical climates.

Antifungal medications