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Cryptococcal infection (cryptococcosis)
Page content: Victorian statutory requirement | Infectious agent | Identification | Incubation period | Public health significance & occurrence | Reservoir | Mode of transmission | Period of communicability | Susceptibility & resistance | Control measures | Outbreak measures
Victorian statutory requirement
Notification and school exclusion are not required.
Infectious agent
Cryptococcus neoformans, an encapsulated yeast-like fungus. There are two principal variants:
C. neoformans var. neoformans (serotypes A & D) and C. neoformans var. gattii (serotypes B & C).
Identification
Clinical features
Cryptococcal infection usually presents as sub-acute or chronic 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.
Method of diagnosis
Encapsulated budding forms of the fungus may be seen in the 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 andurine) or by histopathology (Mayer’s mucicarmine staining).
Pulmonary cryptococcosis in non-HIV infected persons usually manifests as a nodule which must be distinguished from a malignancy. Malignancies may co-exist.
Incubation period
The incubation period is unknown. Pulmonary infection may precede infection in other sites by months or years.
Public health significance & occurrence
Human infection is rare in the absence of immunosuppression. Persons at increased risk of infection include patients with impaired immunity due to HIV/AIDS infection, corticosteroid therapy, lymphoma or sarcoidosis.
Cryptococcal infections occur sporadically in all parts of the world. Adults are more commonly infected with males more commonly infected than females.
Reservoir
Cryptococcus has saprophytic growth in the external environment. C. neoformans var. neoformans occurs worldwide, frequently in association with pigeon or other bird droppings. C. neoformans var. gattii occurs in endemic foci in the tropics and sub-tropics where certain eucalypts provide an ecological niche.
Mode of transmission
Transmission is presumed to be by inhalation.
Period of communicability
Not spread directly from person to person, nor spread between animals and people.
Susceptibility & resistance
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 during corticosteroid therapy, immune deficiency disorders (especially AIDS), and disorders of the reticuloendothelial system, particularly Hodgkin’s disease and sarcoidosis.
Control measures
Preventive measures
No vaccine is available. Some patients may require maintenance antibiotics to prevent repeat infections (see below).
Control of case
Clinicians should consider referral to a specialist centre for treatment. Typical treatment often involves amphotericin or flucytosine.
Patients with HIV/AIDS may require continuing maintenance therapy (secondary prophylaxis), typically fluconazole orally daily.
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
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
Where nosocomial transmission is suspected in single cases or clusters, the risk of further infections should be reduced through appropriate control of the external environment, with investigation of the internal environment within facilities as appropriate.
