Cryptococcus gattii

Cryptococcus gattii is a fungus that lives in the environment in primarily tropical and sub-tropical areas of the world but also in some temperate regions such as British Columbia and some parts of the United States. C. gattii cryptococcosis is a rare infection that people can get after breathing in the microscopic fungus. The infection can affect the lungs, central nervous system, or other parts of the body.

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Symptoms

C. gattii usually infects the lungs or the central nervous system (the brain and spinal cord), but it can also affect other parts of the body. The symptoms of the infection depend on the parts of the body that are affected.

Lung infection

A C. gattii infection in the lungs can cause a pneumonia-like illness. The symptoms are often similar to those of many other illnesses, and can include:

• Cough
• Shortness of breath
• Chest pain
• Fever

Cryptococcus gattii selection

Cryptococcal meningitis

Cryptococcal meningitis is an infection caused by C. gattii and other types of Cryptococcus after it spreads from the lungs to the brain, but patients can have a brain infection without a lung infection. The symptoms of cryptococcal meningitis include:

• Headache
• Fever
• Confusion or changes in behavior
• Neck pain
• Nausea and vomiting
• Sensitivity to light

C. gattii infection can also cause cryptococcomas (fungal growths) to develop in the lungs, skin, brain or other organs, causing symptoms in the affected parts of the body.

Incubation period

The incubation period of C. gattii infection is not well-established. Symptoms of C. gattii infection can appear between two and 13 months after breathing in the fungus, with an average of approximately six to seven months.4,5 However, people can develop an infection as soon as two7 weeks or as late as three years after breathing in the fungus

Risk factors

Anyone can be infected with C. gattii if they’ve been in an area where the fungus lives in the environment. However, in different parts of the world, different characteristics may make some people more likely to get C. gattii infections than others.1 For example, in Australia and New Zealand, C. gattii infections are thought to be more common among:

• People who are otherwise healthy,
• Males, and
• Aboriginal peoples

In British Columbia, Canada,3 the disease is more likely to occur in people who:

Have weakened immune systems, for example, because of:

• HIV/AIDS
• Cancer treatment
• Medications that weaken the immune system such as corticosteroids
• Have other lung conditions
• Are 50 years of age or older
• Smoke tobacco

Source of infection and transmission

• C. gattii lives in the environment, usually on trees, in tree hollows, and in the soil around trees.
• The fungus primarily lives in tropical and subtropical areas of the world.
• It also lives in mainland British Columbia, Vancouver Island, the U.S. Pacific Northwest (Oregon and Washington), and California. Some people from other parts of the United States have gotten C. gattii infections without traveling to the West Coast, suggesting that C. gattii may also live in other areas of the United States, such as the Southeast.

Life cycle of C. gattii

• C. gattii infections are not contagious. Humans and animals can become infected with C. gattii after inhaling dried yeast cells or spores in air.
• C. gattii travels through the airway and enters the lungs.
• The body’s temperature allows C. gattii to transform into its yeast form, and the cells grow thick outer layers to protect themselves.
• The yeasts then divide and multiply by budding.
• After infecting the lungs, C. gattii can travel through the bloodstream to infect other areas of the body, such as the central nervous system.

Diagnosis

• Diagnosis is with a combination medical and travel history, symptoms, physical examinations, and laboratory tests to diagnose a C. gattii infection.
• Take a sample of tissue or body fluid (such as blood, cerebrospinal fluid, or sputum) and send the sample to a laboratory to be examined under a microscope, tested with an antigen test, or cultured (see Testing for C. gattii infection vs. C. neoformans infection).
• Chest x-ray or CT scan of your lungs, brain, or other parts of the body.

Lab tests

• Testing for C. gattii infection vs. C. neoformans infection
• Testing serum (a component of blood) or cerebrospinal fluid for cryptococcal antigen is useful as a first test for cryptococcal infection, but the test doesn’t tell the difference between Cryptococcus neoformans and Cryptococcus gattii.
• Culture is traditionally used to tell if a cryptococcal infection is due to C. neoformans species complex or C. gattii species complex.
• On canavanine-glycine-bromthymol blue (CGB) agar, C. gattii will turn the culture medium blue, but C. neoformans will leave the color of the medium unaffected (yellow to green).
• Recent advances in identification systems such as Matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) can also distinguish between C. gattii and C. neoformans but might not be able to distinguish between the species.

Treatment

• People who have C. gattii infection need to take prescription antifungal medication for at least 6 months, often longer.
• The type of treatment usually depends on the severity of the infection and the parts of the body that are affected.
• For people who have asymptomatic infections or mild-to-moderate pulmonary infections, the treatment is usually fluconazole.
• For people who have severe lung infections or infections in the central nervous system (brain and spinal cord), the recommended initial treatment is liposomal amphotericin B in combination with flucytosine.
• After initial antifungal therapy, patients usually need to take fluconazole for an extended time to clear the infection.
• Some people will need lumbar punctures to get rid of increased pressure in the brain.
• Some people will also need corticosteroids.
• The type, dose, and duration of antifungal treatment may differ for certain groups of people, such as pregnant women, children, and people in resource-limited settings.
• Some people may also need surgery to remove fungal growths (cryptococcomas).