Cryptococcosis in Dogs

Overview of Cryptococcosis in Dogs

Cryptococcosis is an infectious disease caused by the fungus Cryptococcosis neoformans. The disease affects human beings and animals and is contracted by inhaling infectious spores. The excrement of birds, especially pigeons, is the main environmental reservoir for the spores, although birds rarely become infected with this organism due to the higher body temperature, which does not allow the growth of the organism. After the spores are inhaled, the organism spreads to other organs. Cryptococcus has a tendency to invade the nervous system.

Immunosuppressed humans and animals are at increased risk for developing cryptococcosis. Cryptococcosis has a worldwide distribution.

In affected dogs, non-specific symptoms of systemic illness are most common, such as weight loss and lethargy. Central nervous system problems may also occur such as head tilt, back-and-forth eye movements called nystagmus, paralysis of the facial nerve leading to inability to blink, incoordination, circling and seizures. Eye problems, such as hemorrhage in the retina and inflammatory disorders of the eye called chorioretinitis and anterior uveitis, also are common.

Contact with infected animals is not a concern because the yeast form of the organism grows in infected tissues and does not become aerosolized.

Diagnosis of Cryptococcosis in Dogs

Diagnostic tests are needed to recognize cryptococcosis and confirm the diagnosis. Tests may include:

Treatment of Cryptococcosis in Dogs

Treatment for cryptococcosis may include

Home Care and Prevention

Administer as directed any medications prescribed by your veterinarian and follow recommendations for dietary modification. Long term treatment up to 6 months or more may be required. Observe your pet’s general condition: Watch for worsening of symptoms and bring any changes to the attention of your veterinarian.

Some anti-fungal medications (e.g. ketoconazole, itraconazole) have the potential to cause liver damage. The animal should have periodic blood tests performed to evaluate for the presence of liver damage. These medications should be administered with food and they may cause vomiting or diarrhea.
Amphotericin B has the potential to cause kidney damage and must be given by intravenous infusion after being diluted in a 5 percent dextrose solution. The animal should have periodic blood tests performed to evaluate for the presence of kidney damage.

The possible sources of infection for affected animals should be evaluated because these areas represent potential sources of exposure and infection for human beings as well, especially children, immunosuppressed patients, and the elderly.

Restrict animals from areas that contain large amounts of pigeon droppings, especially shady, damp buildings. Areas where pigeons reside should be cleaned with hydrated lime diluted in water and sodium hydroxide solution.

In-depth Information on Cryptococcosis in Dogs

Cryptococcosis is a systemic fungal disease caused by Cryptococcus neoformans. Cryptococcus is a yeast-like fungus found most often in association with pigeon droppings. Cryptococcus does not cause disease in pigeons due to the high body temperature of these birds (107.6 degrees Fahrenheit or 42 degrees Celsius), which inhibits growth of the organism. Optimal growth occurs at 98.6 degrees F (37 C), which is the average temperature of mammals.

Cryptococcus neoformans has a worldwide distribution and is the most common systemic fungal infection of cats, although it also affects dogs. Doberman pinschers and Great Danes appear to be at increased risk in Australia, whereas cocker spaniels seem to be at higher risk in North America. However, dogs of any breed, as well as mixed breed dogs, can develop cryptococcosis. Young dogs less than four years of age seem to be predisposed. No gender predilection has been recognized.

Cryptococcus has a thick capsule surrounding it, which contributes to its virulence and resistance to treatment. Infection occurs after inhalation of the organism, when cryptococcus produces a thick capsule that interferes with the ability of the immune system to eliminate it. Immunosuppressed animals, such as animals suffering from malnutrition or receiving treatment with cortisone-like drugs are most susceptible.

Clinical Symptoms of Cryptococcosis in Dogs

Other diseases of the nasal cavity and nervous system may produce similar signs and must be eliminated as diagnostic possibilities:

In-depth Information on Diagnosis of Cryptococcosis in Dogs

Veterinary care should include diagnostic tests and subsequent treatment recommendations. Diagnostic tests are needed to identify cryptococcosis and exclude other diseases that may cause similar symptoms. Tests may include:

The need for additional diagnostic tests will be determined based on the results of the medical history, physical examination and initial laboratory tests:

Your veterinarian may recommend additional diagnostic tests based on the results of initial examinations. These tests may help diagnose other concurrent medical problems or allow your veterinarian to understand the impact of the underlying disease on your pet. Such tests insure optimal medical care and are selected on a case-by-case basis.

Treatment In-depth of Cryptococcosis in Dogs

Various anti-fungal drugs can be used for the treatment of cryptococcosis but most affected pets require prolonged therapy, often six months or more depending on the severity and extent of the disease. Treatments include:

Follow-up Care for Dogs with Cryptococcosis

Optimal treatment for your dog requires a combination of home and professional veterinary care. Treatment may be necessary for 6 months to one year. Follow-up may include frequent re-evaluation until the pet’s condition stabilizes

A decrease in the cryptococcal titer over time suggests effective treatment and a hopeful prognosis. Affected animals should be treated for one month after resolution of clinical signs and preferably until their cryptococcal titer becomes undetectable.

Treated animals should be monitored closely for drug toxicity. Periodic liver function tests should be performed in pets treated with ketoconazole or itraconazole and kidney function tests should be monitored in pets treated with amphotericin B.

The animal should be monitored closely for recurrence of symptoms after a decision has been made to stop treatment as a result of apparent recovery.

Therapy can be monitored repeating antigen titers. A decrease in the titers is indication of a positive response to the therapy.

No vaccine is available. Contact with pigeon droppings should be avoided.