Candidiasis is a usually localized mucocutaneous disease due to species of the yeastlike fungus Candida, most commonly C albicans. It is distributed worldwide in a variety of animals.
C albicans is a normal inhabitant of the nasopharynx, GI tract, and external genitalia of many species of animals and is opportunistic in causing disease. Factors associated with candidal infections are immunosuppressive diseases or drugs; disruption of mucosal integrity; indwelling intravenous or urinary catheters; and administration of antimicrobials.
The organism most frequently infects birds, involving the oral mucosa, esophagus, and crop. Superficial infections limited to the mucous membranes of the intestinal tract have been described in pigs and foals. Systemic candidiasis has also been described in cattle, calves, sheep, and foals secondary to prolonged antibiotic or corticosteroid treatment.
In cats and dogs, candidiasis is rare but has been associated with oral and upper respiratory disease, pyothorax, ocular lesions, intestinal disease, and urocystitis. Infections are rare in adult horses; however, Candida spp have been considered a cause of arthritis in horses and mastitis and abortion in cattle. Candida infections occur in humans; however, whether animals can transmit the organism to humans is undetermined.
Clinical Findings and Lesions in Candidiasis in Animals
Clinical signs are variable and nonspecific and are often more associated with the primary or predisposing conditions than with the candidiasis itself. In birds, crop and esophageal lesions are circular white ulcers with raised surface scabs that produce thickening of the mucosa; an easily removed pseudomembrane is common. Affected chicks are listless and have decreased feed intake and growth rate.
Courtesy of Dr. Maria Dashek.
Gross lesions of the skin and mucosae in other species are generally single or multiple raised circular white masses covered with scabs. The organism can penetrate keratinized epithelium and cause marked thickening of the mucosae of the tongue, esophagus, and rumen.
Calves with forestomach candidiasis have watery diarrhea, anorexia, and dehydration, with gradual progression to prostration and death.
Porcine candidiasis affects the oral, esophageal, and gastric mucosa, with diarrhea and emaciation the most consistent clinical signs.
Foals with oral and esophageal candidiasis may show an almost terrycloth-like texture to the tongue and oral mucosa.
GI or mucocutaneous candidiasis may have a characteristic sour or yeasty odor.
Urinary candidiasis may occur in cats and, rarely, dogs, particularly those with perineal urethrostomies or indwelling urinary catheters. Disseminated candidiasis has been reported, with clinical signs referable to the body systems colonized. Diabetes mellitus is a substantial risk factor.
Diagnosis of Candidiasis in Animals
Culture of the organism from a sterile site
Cytologic evidence from ears, skin, GI or urogenital tract
Ultrasound
Fungal organisms are numerous in proliferating epithelial tissue, and diagnosis can be made by examining scrapings or biopsy specimens from mucocutaneous lesions or by examination of urine sediment. C albicans are gram-positive ovoid budding yeast cells (3–7 mcm in diameter) with thin walls, or they occur in chains that produce pseudohyphae when the blastospores remain attached after budding division. Filamentous, regular, true hyphae also may be visible.
Courtesy of Dr. Rosalie Ierardi.
Candida grows on standard blood agar; however, if candidiasis is suspected, then fungal culture should be requested.
Cats and dogs with urinary candidiasis may have ultrasonographically visible fungal balls in the bladder.
Treatment of Candidiasis in Animals
Systemic or urinary candidiasis: fluconazole or amphotericin B
Intravesicular clotrimazole may be necessary for UTIs
GI or cutaneous candidiasis: typically treated with nystatin or amphotericin B
Nystatin ointment or topical application of amphotericin B or 1% iodine solution may be useful in the treatment of oral or cutaneous candidiasis. Disseminated or urinary candidiasis in small animals is treated with fluconazole for 4–6 weeks; intravesicular treatment with 1% clotrimazole with a 1-hour dwell time may be necessary to resolve urinary tract infection.
Itraconazole, amphotericin B, and echinocandins have been used for invasive disease. Amphotericin B, 500 g in 1 L of 5% dextrose, was administered IV, every 48 hours for 24 days and then every 72 hours for 15 days, to successfully resolve arthritis induced by C fumata in a horse. Fluconazole (5 mg/kg every 24 hours, PO, for 4–6 weeks) was also used to successfully treat disseminated candidiasis in foals. No antifungals are labeled for use in ruminants.
Poultry are treated with nystatin or other antifungals in the feed or water; copper sulfate in the water may be used as a preventative. In all cases, immunosuppressive or predisposing conditions should be addressed if possible.
Key Points
Candida is a ubiquitous yeast that overgrows if immunosuppression or other predisposing conditions are met.
Diagnosis is made by culture, cytology, or histopathologic evaluation, though characteristic lesions may be sufficient.
Treatment is usually nystatin or azoles, depending on affected site.
