Felis ISSN 2398-2950
Cryptococcus neoformans
Synonym(s): C. neoformans
Contributor(s): Stephen Barr, Susan Dawson, Grace Mulcahy
Introduction
Classification
Taxonomy
- Genus: Cryptococcus.
- Species: neoformans.
- Perfect form (serotypes A and D): Filobasidiella neoformans.
- Perfect form (serotypes B and C): Filobasidiella basillispora.
Etymology
- Gr: kruptos - hidden; kokkos - grain, berry, seed.
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Clinical Effects
Epidemiology
Habitat
- Surface dust and dirt.
- High concentrations in pigeon droppings, which are rich in creatinine and inhibit other organisms.
- Birds may be subclinical carriers.
Transmission
- Usually via inhalation from environment.
- Occasionally percutaneous.
Pathological effects
- Immunosuppression may predispose to infection; 20-30% of cats with cryptococcosis have feline leukemia virus infection Feline leukemia virus disease.
- Capsular polysaccharide depletes complement and causes immune paralysis and antibody masking.
- Antiphagocytic, immunosuppressive capsule → encapsulated yeast cells ignored by phagocytes in absence of antibody.
- Inflammatory response is minimal.
- Large amounts of free capsular antigen in disseminated disease may depress the humoral immune response and bind antibody, resulting in anitbody titers of zero.
- With successful treatment levels of antigen fall and antibody titers rise.
- Cell-mediated immunity (macrophages) dispose of the agent.
- Virulence is largely associated with the antiphagocytic and immunosuppressive capsule.
- Route of infection: usually respiratory, resulting in lesions in nasal cavity or sinuses with possible extension to the brain (involvement of the optic nerve causing blindness), and meninges.
- Due to lack of effective immunity and inflammatory response, colonies grow → large myxomatous masses consisting of capsular slime and yeast cells → eventually surrounded by histiocytes, epithelioid cells and giant cells.
- High incidence of nasal lesions (about 50% of cases)
; some localized skin infections occur.
- Organisms often disseminate → uveal tract, meninges, lymph nodes, lungs, joints, bones and other organs.
- Often chronic disease: anorexia, wasting and fever.
- Granulomas of subcutaneous tissue and the nose with possible central nervous system (CNS) involvement in dogs and cats; nasal passage granulomas in horses, mastitis in cattle, respiratory disease and meningitis in humans.
- Clinical signs depend on location of infection; in cats, most commonly upper respiratory tract.
- Radiographs of nasal passages show soft tissue proliferation.
Other Host Effects
- Birds are commonly subclinically infected and can act as reservoir hosts.
- Human infection often associated with pre-existing immunosuppression.
- Humans most commonly infected from environmental sources (pigeon feces).
Control
Control via animal
- Localized lesions may be excized prior to drug therapy.
Control via chemotherapies
Control via environment
- Disinfect contaminated surfaces with lime solution prior to physical cleaning.
Masks must be worn.
- Hydrated lime powder kills the organism.
Vaccination
- Autogenous bacterins have been used.
- No commercial vaccines available.
Diagnosis
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Further Reading
Publications
Refereed papers
- Recent references from VetMed Resource and PubMed.
- Noxon J O et al (1986) Ketoconazole treatment in canine and feline cryptococcosis. JAAHA 22, 179.
- Medleau L et al (1985) Cutaneous cryptococcosis in three cats. JAVMA 187, 169.
- Provost E, McKee J M & Crawford P (1982) Successful medical management of severe feline cryptococcosis. JAAHA 18, 111.
- Wilkinson G T (1979) Feline cryptococcosis - a review and seven case reports. JSAP 20, 749.
Other sources of information
- Medleau L (1989) Feline cryptococcosis. In: Current Veterinary Therapy X. Ed R W Kirk and J D Bonagura. Philadelphia: W B Saunders. pp 1109-1112. ISBN 0 7216 2858 3. (A useful overview with North American bias.)
- Jacobs G J & Medleau L (1998) Cryptococcosis. In: Infectious diseases of the dog and cat. Ed C E Greene. Philadelphia: W B Saunders. pp 383-390. ISBN 0 7216 2737 4.