Sporotrichosis is a rare but potentially serious fungal infection that can infect dogs, cats, or people. Because of the risk of people contracting this disease from infected cats, the seriousness of this disease should never be underestimated. Because this disease is not very common, veterinarians or owners may often overlook sporotrichosis as a potential cause of the symptoms.
What is sporotrichosis and how does an animal acquire it?
Sporotrichosis is an infection caused by the fungus Sporothrix schenckii. This fungus is found in soil and organic debris and is widespread in the U.S. Sporotrichosis is more commonly seen in outdoor dogs, particularly hunting dogs, and in outdoor cats (especially males) that are prone to fighting. In dogs, it is believed that the fungus enters through a puncture wound from a stick or thorn. In cats, it is thought to be transmitted from a scratch or bite from a cat that has contaminated claws or teeth. Humans have become infected through coming in contact with the open, draining sores on infected cats.
What are the symptoms of sporotrichosis? In dogs, the most common symptoms are small raised nodules on the head, ears, and body. The nodules may become ulcerated and drain clear or cloudy fluid. The dog is usually healthy otherwise and the lesions do not appear to be painful, nor do they itch. Lesions on the feet with involvement of local lymph nodes can also occur.
In humans, sporotrichosis is more common on the fingers, hands, or face - locations where the person may have had an open wound and come into contact with an infected cat. The nodule may open and drain and the surrounding lymph nodes may become swollen as well.
How is sporotrichosis diagnosed?
In the dog, unlike the cat, the organism is hard to find and if the infection is suspected but no organisms can be found, then a fluorescent antibody test can often confirm a diagnosis. A culture of the fluid may also aid in the diagnosis.
What is the treatment for sporotrichosis?
Infected dogs are treated with oral potassium iodide. Treatment usually lasts 4 to 8 weeks. Ketoconazole, and the more expensive itraconazole, are sometimes used as an alternative therapy.
Since Sporothrix is a fungus and not a bacteria, antibiotics are ineffective. Animals with sporotrichosis should not be given steroids.
How is sporotrichosis prevented?
Prevention consists of prompt treatment of all puncture wounds and having dogs avoid densely wooded or thorn infested areas.
Sporotrichosis is fortunately very rare in dogs, cats, and people. It is just common enough that we should keep it in mind if our pets develop nodules or non-healing sores.