Cryptococcus

1. Epidemiology/Microbiology

· Worldwide distribution, incidence 8 times higher in cats than dogs.

· 2 species cause disease:

o C. neoformans – primarily infects immunocompromised people, viable for 2 years in environment (mostly pigeon guano).

o C. gatti – primarily associated with tropical climates. Found in plant material and soil (proximity to areas with soil disturbance is a risk factor in dogs/cats).

· Transmission primarily through inhalation.

· Nasal cavity likely primary site of infection in dogs/cats (lungs in humans), may lead to mycotic rhinitis or be asymptomatic. Once infection is established haematogenous spread to other sites, especially CNS. Incubation period is 2-13 months. Other sites include eye (optic neuritis/retinitis), skin, mandibular lymph nodes.

2. Clinical Findings

· Cats – young adult (2-3 years) increased risk, median age 6years.

· Dogs – young adult (50% under 4y), median age 4y.

· Cats

o Often chronic causing listlessness and weight loss.

o URT – sneezing, MP nasal discharge, sometimes epistaxis (unilateral or bilateral). Sometimes visible polyp in nostril, swelling over bridge of nose.

o LRT (uncommon) – tachypnoea/cough

o Neuro – obtundation, temperament change, twitching, seizures, circling, ataxia.

o Ocular – retinitis, retinal detachment, less commonly uveitis.

o Cutaneous – solitary or multiple soft tissue masses on bridge of nose. Multifocal, ulcerative skin lesions.

o Other – lymph node enlargement, renal involvement.

· Dogs

o Often develop severe disseminated disease.

o Commonly affected organ systems – CNS (multifocal), eyes, urinary system, nasal cavity

3. Diagnostic Investigations (incl sens/spec)

· Routine bloods – non-specific change, often neutrophilia (dogs).

· CSF (if neuro signs) – elevated protein & leukocytes (mixed cellular pleocytosis, occasionally eosinophilic).

· Cytology/histo – nasal swabs/washing, FNA’s of masses, BAL, pleural fluid, CSF, urine – readily identify organism.

· Fungal culture

· Serology – cryptococcal polysaccharide capsular antigen on serum or CSF. 90 to 100% sensitivity, 97 to 100% specificity.

· PCR also available.

4. Treatment/prognosis (incl MST & prognostic factors)

· Surgery

o Surgical excision of large aggregates of fungus infected tissues may be beneficial and improve response to therapy.

· Drug therapy – ideally based on sensitivity testing

o Amphotericin B – fungicidal and ? proinflammatory so improving host immunity.

o Flucytosine – used in combination with amphotericin as rapid resistance develops if used alone. Good penetration into CSF. Frequently causes cutaneous drug reaction after 10-14 days.

o Fluconazole – most effective azole for crypto.

· Specific management regimens:

o Cats with mild to moderate disease and no CNS involvement – Fluconazole until resolution of CS. Monitor antigen levels during treatment. Typically this takes 2-12 months (median 4 months).

o Cats with severe disease, CNS involvement or failed to respond above – Combination of amphotericin B and flucytosine.

o Dogs – Start with amphotericin B then move to an azole.

· Relapse reported as long as 10 years later so suggest continue therapy until antigen titer is zero.

· Prognosis:

o Cats – Approximately 75% treated successfully, 30% relapse rate. CNS disease negative prognostic factor.

o Dogs – 55% treated successfully in one study, 20-30% in another. Again CNS signs may be negative factor.

Recent Literature:

· Terbinafine reported to be successful for treatment of a dog with intestinal crypto, who had not responded to amphotericin and fluconazole.

· Report of a cat with coinfection with crypto and mycobacterium avium.

· Report of a cat infected with c. magnus

	Created by Andy Kent about 11 years ago

Crytpo info