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Histoplasmosis
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- 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
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- 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
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Zygomycosis
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- Also known as mucormycosis, hyphomycosis and phycomycosis
- Caused by strains of Mucor, Absidia, Rhizopus and Mortierella
- Mucor circinelloides(rare), Rhizomucor pusillus and R. meihi
- Absidia corymbifera often causes zygomycosis in cattle and pigs
- Rhizopus arrhizus, R. microsporus and R. rhizopodormis
- Mortierella wolfi implicated in bovine abortion (mycotic placentitis), M. hygrophila in fowl and M.polycephala in cattle
- 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
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- Mostly localised lesions but can be generalised
- Pigs
- Mediastinal and submandibular lymph nodes lesions
- Embolic tumours in the liver and lungs
- Can also be present in gastric ulcers
- Cattle
- Bronchial, mesenteric and mediastinal lymph nodes lesions
- Ulcers of the nasal cavity and abomasum also occur
- Often contaminate the placenta
- Horses, dogs, cats, sheep, mink, guinea-pigs and mice can also be infected
- Microscopically:
- Fragments of non-septate hyphae which are branched and coarse
- Rhizomucor produce a thick, grey mycelium and have short, black, spherical sporangia
- Mucor produce thick, colourless mycelium with no rhizoids. Globose spoangia with small spores are present and sporagiospores are simple or branched.
- Absidia resemble Rhizopus grossly
- Mortierella produce white, velvet colonies on Sabouraud's Dextrose and Blood agar
- Grows on Sabauraud's Dextrose agar
- Common contaminants
- Treatment is with Amphotericin B
- Surgery is also an option in treatment
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