Candidiasis is a fungal disease that affects mucous membranes and the skin. It is most commonly caused by species of the yeast-like fungus Candida albicans. The genus Candida is comprised of approximately 200 species. This group is ubiquitous, found on many plants, and is normal flora in the gastrointestinal tract and external genitalia of dogs and cats. The organism becomes pathogenic when conditions favor excessive growth. This may happen when a patient's immune system is compromised or when a malignant tumor is present. C. albicans may produce serious local infection and systemic invasion of the internal organs such as kidney, liver, lungs, brain, and heart. This pathogen has also been associated with infections of the external ear, perineum (the tissue between the anus and scrotum in the male), nail folds, mouth, eye, and urinary tract. Factors thought to promote candidal urinary tract infections in dogs and cats include antibiotics and glucocorticoid therapies, radiation exposure, and local alterations in the urinary tract environment due to diabetes mellitus, acidic urine pH, or urinary catheters. Studies indicate that animals have to be considered as potential sources of Candida infections of human individuals, especially in immunodeficient people.
Fungal infections of the urinary tract are rare in dogs and cats and are most often diagnosed in the colder months, with the highest number occurring in November and December. Most animals are believed to drink more during hot weather (May through September) and drink less during the cooler months (October through February). Development of changes in water drinking may subsequently change the volume of urine produced and the frequency of urination. Decreased production of urine in the colder months may result in increased fungal contamination and increased adherence of fungi. Other contributing factors are concurrent or preceding diseases, such as bladder stones, hypothyroidism, and diabetes mellitus.
Signs of fungal urinary tract infection vary and most often include diarrhea, depression, loss of appetite, increased frequency of urination, lack of urination, weight loss, dehydration, fever, weakness, and skin lesions. These are sometimes difficult to interpret, as the abnormalities may be associated with either the fungal infection or the concurrent diseases. It should be noted, though, that weight loss, lethargy, dehydration, and weakness are more common in animals with fungal UTI than with bacterial UTI. Fever can also be a common finding and may be associated with the fungal infection, the underlying disease, or both. Identification and correction of predisposing risk factors are initially addressed in most of the affected animals. Antibiotics and glucocorticoids are discontinued; indwelling urinary catheters are removed, and treatment for diabetes mellitus or other concurrent conditions is performed.
Cutaneous candidiasis (fungal skin infection) is an uncommon disease in dogs. The most common causative agent is Candida albicans, followed by Candida parapsilosis and Candida guilliermondii. There are several forms of cutaneous candidiasis: exudative, squamous, and scabious (extremely rare) and otitis externa. In exudative form, the primary characteristics of the disease are skin lesions, persistent hair loss, crusts, ulcers, scales, itchiness, and whitish discharge. In squamous and scabious forms, hyperkeratosis (overgrowth of the horny layer of the skin), thick scabs, and folliculitis are present. Predisposing factors such as the use of corticosteroids, concurrent presence of an autoimmune disease (pemphigus foliaceus) or a rickettsial disease, are commonly observed. Two forms of treatment are used for cutaneous candidiasis: topical and systemic. Topical treatment involves the use of chlorhexidine or azole derivatives such as econazole, miconazole, while systemic treatment uses ketoconazole or fluconazole. Both types of treatment are recommended, since they allow the yeasts to be killed irrespective of their localization. Digestive candidiasis, which is frequently associated with cutaneous lesions, may also be cured using these therapies.
- Yipeng Jin, DVM and Degui Lin, DVM, PhD. Fungal Urinary Tract Infections in the Dog and Cat: A Retrospective Study (2001-2004)
- Cutaneous candidiasis (RoyalCanine)