This disease, caused by the yeastlike fungus Cryptococcus neoformans, is acquired by inhaling spores found in soil contaminated by bird droppings, especially those of pigeons. In dogs, cryptococcosis involves the brain, eyes, lymph nodes, and skin. About 50 percent of the dogs with this fungus will also show respiratory signs. Signs of brain involvement are an unsteady gait, pressing the head against a hard surface or standing with the head up against a wall, circling, seizures, blindness, and dementia. Involvement of the inner structures of the eyes leads to blindness.
In the less common form that infects the skin, cryptococcosis produces firm nodules, primarily in the head area, that ulcerate and drain pus.
The diagnosis is made by fungal culture and/or tissue biopsy. A cryptococcus latex agglutination test is available.
Treatment: Oral antifungal drugs of the imidazole group (as described for Histoplasmosis) are partially effective when started early in the course of the disease. The response is uncertain and treatment is prolonged. Overall, the prognosis for dogs is guarded to poor.