Cryptococcosis in Cats


Overview of Cryptococcosis in Cats

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.

Below is an overview of Cryptococcosis in Cats followed by detailed information on the diagnosis and treatment of this serious infection. 

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

In affected cats, 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 Cats

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

  • A complete medical history and physical examination. The diagnosis of cryptococcosis is based on history, clinical symptoms, microscopic examination of exudates, serologic tests and biopsy if necessary.
  • Serology. Blood samples or samples of cerebrospinal fluid in animals with nervous system symptoms may be tested for antibodies. The most commonly used serology test is the latex agglutination test, designed to detect antigens from the capsule of the fungus. The test is very specific and sensitive. False negative results may occur in localized infections and false positive results may result from contamination of the specimen by talc from latex gloves worn during fluid collection.
  • Microscopic examination of exudate from cutaneous nodules or the nose. The organism also can be identified by microscopic examination of tissue biopsy specimens (histopathology). Special stains may be needed.

    Treatment of Cryptococcosis in Cats

    Treatment for cryptococcosis may include: 

  • Surgery to de-bulk lesions in the nasal cavity. The prognosis for recovery is poor when infected cats have widespread nervous system involvement.
  • Anti-fungal drugs such as amphotericin B, flucytosine, ketoconazole, itraconazole, and fluconazole.

    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 Feline Cryptococcosis

    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. It has worldwide distribution. It is the most common systemic mycosis in cats.

    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.

    Animals that are compromised immunologically, such as by feline immunodeficiency virus, feline leukemia virus, corticosteroid therapy or malnutrition are most susceptible.

    Spreading of infection depends on the host’s immunity however not all affected animals have concurrent immunosuppressive disease to justify the development of cryptococcosis. Cell-mediated immunity is vital to recover from Cryptococcosis. More specifically, it seems that T helper type 1 cells (the ones producing interleukin-12 and gamma interferon) are the ones involved in the defense mechanisms against this type of infection.


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