Fungal Disease (Sporotrichosis) of the Skin in Dogs

Sporotrichosis is a zoonotic condition, which can be passed to humans through handling an infected animal. As such strict hygiene measures must be followed to prevent animal-to-human transmission.

Sporotrichosis is a rare condition in dogs, but it can cause severe life-threatening disease and, as such, must be treated as an emergency. If the condition is left untreated, it can progress to a potentially fatal systemic infection.

If the condition is diagnosed early, the majority of dogs are able to recover completely after antifungal therapy.

Sporotrichosis is divided into three forms depending on the stage of the infection.

Cutaneous sporotrichosis The cutaneous form is the most common kind of sporotrichosis. It is characterized by small (1-3 cm) subcutaneous or dermal nodules.

Lymphocutaneous sporotrichosis If the infection is not treated, it enters into the second phase, characterized by the formation of new nodules and the appearance of skin lesions, especially on the bridge of the nose and the ear flaps (pinna). Dogs commonly develop swollen or enlarged lymph nodes throughout their body.

Disseminated sporotrichosis If the condition continues to be left untreated, the infection can progress and become disseminated throughout the organ systems. While rarely reaching this phase, disseminated sporotrichosis is life-threatening as the infection can spread to the lungs, bones, spleen, central nervous system, and gastrointestinal tract.

Sporotrichosis is caused by the Sporothrix schenckii fungus. The fungus is abundant in nature and can be found in soil, vegetation and timber worldwide. The infection occurs when the fungal spores are inoculated into the animal's skin. The most common causes of infection occur as the result of puncture wounds.

Most cases of canine sporotrichosis are cutaneous, but if the condition is left untreated, it can progress and become systemic. Dogs that are immunosuppressed are more likely to develop systemic disease.

The main symptoms of sporotrichosis are papules, nodules or ulcers that drain fluid or crust over. These lesions are typically located on the animal's nose and ears, but can also occur on the chest and limbs.

Diagnosis of sporotrichosis is difficult as it is a rare condition in dogs. Dogs presenting symptoms of sporotrichosis infection generally undergo the following diagnostics:

• Physical examination
• Fungal culture
• Microscopic examination
• Biopsy
• Specific testing to confirm the type of fungus

Once diagnosed, treatment for sporotrichosis is straightforward and involves a long course of antifungal medication. Treatment continues until 3 to 4 weeks after clinical signs disappear

If the sporotrichosis is left untreated, skin lesions can persist indefinitely. In rare occasions, untreated sporotrichosis can cause the fungus to invade other parts of the animal's system (bones, internal organs, brain, and lungs), endangering the animal's life.

With prompt and proper treatment, most animals are able to recover, but it may take up to several months for the lesions to clear up completely.

During treatment, the animal must be monitored every two weeks to evaluate its overall health and ensure that the treatment is working correctly.

Sporotrichosis is a contagious condition.

There is no completely effective way to prevent sporotrichosis in animals, as it is impossible to eradicate the S. schenckii fungus from the environment. Prevention strategies include:

• Removing sharp organic objects (such as broken sticks) from the animal's environment
• Isolating affected animals
• In endemic areas, keeping animals indoors, particularly when there is a high risk of exposure
• If skin lesions are present, prompt medical attention is the best way to prevent the development of severe symptoms

Sporotrichosis is a rare condition in dogs. The majority of canine sporotrichosis cases are cutaneous, and only rarely does the infection progress and become systemic.

Antifungal medication