Cryptococcosis

Notification requirement for cryptococcosis

Notification is not required.

Primary school and children’s services centre exclusion for cryptococcosis

School exclusion is not required.

Infectious agent of cryptococcosis

Cryptococcus is a fungus that is found in soil and is usually associated with bird droppings. Infection occurs after inhalation of spores that are present in the environment. The major species of Cryptococcus include C. neoformans (var. neoformans and var. grubii) and C. gattii.

C. gattii has been associated with some tree species (eucalyptus); its natural habitat is soil and plant debris.

Identification of cryptococcosis

Clinical features

Cryptococcal infection usually presents as subacute or chronic meningitis or meningoencephalitis with headache and altered mental state. Lung involvement may cause symptoms of lower respiratory tract infection or may be asymptomatic. Skin, bone and other organs are less frequently infected.

Pulmonary cryptococcosis in immunocompetent people usually manifests as a nodule, which must be distinguished from a malignancy; however, malignancies may co-exist.

Immunocompromised people (including those with HIV infection or cancer) often present with meningitis (subacute or chronic) and may have disseminated infection at other sites, including kidneys, prostate, bone and skin, in the form of pustules, papules, plaques and ulcers. Untreated meningitis can be fatal in weeks to months.

C. neoformans is more commonly seen in immunocompromised people; C. gattii is more commonly seen in immunocompetent people.

Diagnosis

Encapsulated budding forms of the fungus may be seen in the cerebrospinal fluid (CSF), urine or pus using Indian ink staining. Cryptococcal antigens may also be detected in the CSF and serum.

The diagnosis is confirmed by culture (CSF, blood, sputum or urine) or by histopathology (Mayer’s mucicarmine staining).

Point-of-care antigen testing via dipstick is becoming increasingly available in resource-limited settings. Molecular diagnostic methods are also emerging.

Incubation period of cryptococcus

The incubation period is unknown. Pulmonary infection may precede infection in other sites by months or years.

Public health significance and occurrence of cryptococcosis

Cryptococcal infections occur sporadically in all parts of the world. Infection is more frequent in adults than children, and males are more commonly infected than females. This may relate to differences in occupational exposure.

Infection can also occur in cats, dogs, horses, cows, monkeys and other animals.

Reservoir of cryptococcus

Cryptococcus has saprophytic growth in the external environment. C. neoformans occurs worldwide, frequently in association with pigeon or other bird droppings. C. gattii occurs in endemic foci in the tropics and subtropics, where certain eucalypts provide an ecological niche.

Mode of transmission of cryptococcus

Transmission is presumed to be by inhalation.

Period of communicability of cryptococcosis

Cryptococcosis is not spread directly from person to person, and is not spread between animals and people.

Susceptibility and resistance to cryptococcosis

Human resistance is presumed to be considerable, given the widespread distribution of the organism and the rarity of infection. It is not known whether infection confers immunity.

Susceptibility is increased in those who smoke and those taking corticosteroid or TNF-alpha therapy or medications following transplantation. Predisposing conditions include immune deficiency disorders (especially HIV infection) and disorders of the reticuloendothelial system, particularly Hodgkin’s disease, sarcoidosis, and cirrhosis of the liver.

Control measures for cryptococcosis

Preventive measures

No vaccine is available. Some patients may require maintenance antibiotics to prevent repeat infections.

Those who are immunosuppressed should avoid contact with birds and avoid digging and dusty activities in areas heavily contaminated with bird droppings.

Control of case

Clinicians should consider referral to a specialist centre for treatment. Typical treatment often involves amphotericin B with flucytosine or fluconazole. Amphotericin B and flucytosine are both available through the Special Access Scheme.

Patients with HIV/AIDS may require continuing maintenance therapy (secondary prophylaxis), typically fluconazole orally daily.

Consult the current version of Therapeutic guidelines: antibiotics.

Control of contacts

No action required.

Control of environment

Large accumulations of bird droppings should be removed after first being wetted or chemically disinfected to reduce aerosolisation.

Outbreak measures for cryptococcosis

Case clusters are rare. Environmental investigations focus on potential reservoirs of infection, such as bird droppings, although a definitive source is rarely found.

Special settings

Reports of hospital-associated transmission of Cryptococcus are very rare. Incidences were associated with contaminated needlestick injury, corneal transplant and possibly contaminated respiratory equipment.