Candidiasis
Introduction
Candidiasis is a fungal infection caused by Candida spp.,
most commonly Candida ablicans that affects many species.
The yeast is normally present on skin and in the GI tract. Symptoms of disease are usually only seen in immunocompromised animals following opportunistic infection. It is most common in the bird but has also been reported in rabbits, horses, pigs, cows, sheep, cats and dogs - in particular neonates.
Clinical signs
Lesions are found on mucous membranes and at mucocutaneous junctions most commonly. The disease will usually remain localised to the mucocutaneous junctions, but on rare occasions it may spread systemically.
Gross clinical signs include:
- Exudative, papular, pustular to ulcerative dermatitis
- Raised, circular white plaques or ulcers with overlying scabs
- Keratinous thickening of tissue
- Stomatitis and otitis externa
Microscopically there is evidence of:
- Spongiotic neutrophilic pustular inflammation
- Parakeratosis
- Ulcerations
- Superficial exudate containing organisms
Infection may cause a also cause a variety of other clinical signs depending on the species and the site of infection, for example mastitis, arthritis, diarrhoea and general malaise.
Predisposing factors
- Immunosuppressive drugs
- Immunosuppressive disease
- Indwelling urinary or intravenous catheters
- Antibiotic administration
Diagnosis
Diagnosis can be confirmed via microscopic examination and identification of the fungus following a skin scrape of the lesion. The fungus should be visible after staining with a Gram, Methylene Blue or Wrights stain. It is a gram-positive ovoid, budding yeast with or without hyphae. Culture of a sample in Sabourauds Dextrose agar or Blood agar should also confirm diagnosis.
Treatment
Topical or systemic anti-fungals are used to treat the infection.
Prognosis
Prognosis depends on both the severity of infection and the animal affected.
Candidasis in birds
Signalment
Candidiasis aka thrush/sour crop/crop mycosis is common in neonatal psittacine birds. It occurs primarily as a result of immunosuppression and trauma to the ingluvies. Hypothermia, feeding too cold or too hot formula which results in crop-burn, poor nutrition, longterm antibiotic therapy, hypovitaminosis A and systemic illness from other causes are all predisposing causes.
Clinical Sings
The bird may present with inflammation and delayed emptying of the ingluvies. On examination of the crop surrounding structures, there are normally grey-white lesions and a whitish necrotic material present. There may also be thickening of the crop wall.
Diagnosis
Diagnosis is based on identification of oval yeasts and hyphae on cytological smears taken from swabs and crop washes or aspirates. Wrights stain can be used to demonstrate the yeasts. There should be no evidence of an inflammatory response. The presence of hyphae indicates that the crop may have been penetrated and the infection has spread systemically.
Treatment
An antifungal drug is indicated for the treatment of candidiasis. The presence of hyphae is suggestive of invasion of the mucosa by the yeast and the potential for a systemic infection. Therefore, a systemic antifungal such as oral itraconazole (for 7 days) is recommended along with a topical antifungal such as nystatin BID or TID for 7–10 days.
Prognosis
The presence of hyphae on cytological examination suggests a severe infection and potential systemic spread, and therefore a poor prognosis. Without evidence of hyphae the prognosis is improved.
References
Forbes NA & Altman RB (1998) Self-Assessment Colour Review Avian Medicine Manson Publishing Ltd
Girling, S (2004) Diseases of the digestive tract of psittacine birds In Practice 2004 26: 146-15
Merck & Co (2009) The Merck Veterinary Manual (Ninth Edition), Merial
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