Fungal Diseases in Dogs
Coccidioidomycosis (Valley Fever) continued...
Infection occurs by inhaling spores. Most cases are subclinical or
inapparent. A severe form affects the lungs and produces acute pneumonia. If the disease becomes systemic, it may
involve the long bones (most common), liver, spleen, lymph nodes, brain, and
skin. Affected dogs will often have a chronic
cough, weight loss, lameness, and fever.
The diagnosis is made by identifying the organism (Coccidioides immitis)in
cytology, biopsy, or culture specimens.
Treatment: Coccidioidomycosis can be treated effectively using one of the
imidazole group of antifungal agents (as described for Histoplasmosis).
Prolonged treatment for up to a year is required to try to prevent recurrence.
However, relapses are common.
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.
This systemic fungal disease occurs along the eastern seaboard, in the Great
Lakes region, and the Mississippi, Ohio, and Missouri River valleys. The fungus
is associated with moist, rotting organic debris protected from sunlight and
enriched with bird droppings, particularly those of pigeons. The disease is
acquired by inhaling infected spores. Dogs are considerably more susceptible to
blastomycosis than are humans.
Most cases of acute canine blastomycosis involve the respiratory system and
cause bronchopneumonia. About 40 percent of cases involve the eyes and skin,
producing signs similar to those of cryptococcosis (see above). Weight loss and
lameness may also be noted.