Systemic Mycoses

FUNGI

Adiaspiromycosis

• Haplomycosis

• Emmonsia crescens
  • Does not proliferate within the animal body
  • Each spore develops into a thick-walled spherule called an adiaspore

• Chrysosporium parvum, C. crescens

• Non-contageous, pulmonary mycosis

• Worldwide

• Found in soil

• Affects burrowing rodents and small animals

• Respiratory infection

• Spetate hyphae with large numbers of small, round conidia either singly or in groups on the ends of the short conidiospores can be seen

• Dimorphic

• Grows on Sabauraud's Dextrose agar and Blood agar

Aspergillosis

• Aspergillus fumigatus causes rhinitis and in respiratory tract inflammation, also sinusitis, guttural pouch mycosis
• Sometimes appears on lesions of ethmoidal haematoma

• May cause COPD

Blastomycosis

• North America

Coccidioidomycosis

• Coccidioides immitis

• Ocurs in the soil
  • Respiratory infections
  • Most commonly seen following dust storms

• Occurs in arid regions
  • E.g. South West USA and Mexico

• Non-contageous, systemic mycosis

• Affects dogs, cattle, sheep and humans

• Mainly affects the lungs
  • Dissemination can occur to other organs

• Causes nodule or granuloma formation
  • Localised
  • Gross lesions resemble Tb in cattle as are usually seen in the bronchial and mediastinal lymph nodes and occasionally lungs
  • Dissemination can occur, especially in primates and dogs, to the lungs, liver, spleen, brain and bones

• Thick-walled spherules in tissue
  • Large sporangia burst leaving 'ghost' spherules

• Saprophytic phase consists of coarse, septate, branching hyphae which fragment into thick-walled, barrel-shaped arthrospores which alternate with empty cells
  • Stained by Lactose Phenol Cotton Blue

• Grows on Sabouraud's Dextrose agar and Blood agar
  • Flat, moist colonies which develop a coarse, cotton-like aerial mycelium which varies from white to brown in colour

• Complement fixation test, latex agglutination and immunodiffusion tests can all be used
  • A positive skin test indicates exposure

Entomophthoromycisus

• Basidiobolmycosis

Histoplasmosis

• Histoplasma capsulatum

• Non-contageous, systemic mycosis

• Commonly pulmonary infections occur
  • Other organs can be involved
  • Involves the reticuloendothelial system
  • Intestinal form can also occur

• Acute and chronic disease can occur

• Endemic to the USA
  • Isolated cases have been reported in Europe

• Respiratory infection
  • Infection via ingestion can also occur

• Affects dogs, cats, cattle, horses and humans

• Found in soil contaminated by bird droppings, decaying vegetation and in caves inhabited by bats

• Fine, branching, septate hyphae with smooth-walled pyriform to spherical microconidia and large, thick-walled tuberculate macroconidia on simple conidiophores

• Dimorphic fungi

• Hard to demonstrate in smears as the organisms is very small
  • Stain with Giemsa or Wright and examine under oil immersion lens

• Present intracellularly in macrophages as oval yeast cells with few buds
  • Clear halo is seen around the darker staining central material

• Grows on Sabouraud's Dextrose agar
  • Creamy white colonies, turning tan coloured and then brown

• Also grows on Blood agar
  • Small, white yeast-like colonies

• Test using immunodiffusion, complement fixation and counterimmunoelectrophoresis
  • Skin test of little value as it only indicates exposure

• Treatment with Amphotericin B
  • If Amphotericin B is contra-indicated, imidazoles can be given orally

• The prognosis is poor in acute and disseminated cases

Zygomycosis

• Also known as mucormycosis, hyphomycosis and phycomycosis

• Caused by strains of Mucor, Absidia, Rhizopus and Mortierella
  • Occurs widely in nature

• Infection is by inhalation and ingestion

• Infects lymph nodes of the respiratory and alimentary tract
  • Lymph nodes enlarge and become caseous
  • Can cause stomach and intestinal ulcers

• Granulomatous lesions which can ulcerate

• Mostly localised lesions but can be generalised

Further Links

• Antifungal Drugs