Candidiadis of Urinary Tract and Skin

Among the 50,000 to 250,000 species of fungi that have been described, fewer than 200 have been associated with human or animal disease. With few exceptions, fungal infections in animals originate from an external source in the environment and are acquired through inhalation, ingestion, or traumatic implantation. Certain fungi such as Candida spp. are benign colonizers of mucosal surfaces. For disease to occur, host defenses must be weakened.

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 humans, dogs, and cats. The organism becomes pathogenic (causes disease) when conditions favor excessive growth. when a patient's immune system is compromised or when a malignant tumor is present. Candida albicans and C. parapsillosis are the most common isolates from normal dogs.

Factors thought to promote candidal urinary tract infections in dogs, cats, and humans include antibiotic administration, decreased cellular defense mechanisms after glucocorticoid administration or radiation exposure, and local alterations in the urinary tract environment due to diabetes mellitus, acidic urine pH, or urinary catheters.

C. albicans may produce serious local infection and/or systemic invasion of the internal organs (such as kidney, liver, lungs, brain or heart). C. albicans has been associated with clinical cases in dogs with the involvement of different sites: external ear, the tissue between the anus and scrotum in the male (perineum), the nail folds, the mouth, the eye and the urinary tract.

Candidiasis of the Urinary Tract

Fungal infections of the urinary tract have been uncommonly recognized in dogs and cats. In general, less than 1% of all urinary tract infections are thought to be caused by fungi. Because bacteria are commonly associated with urinary tract disorders, fungal cultures may not be performed.

Many cases of fungal urinary tract infections are 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). Changes in water drinking may subsequently change the volume of urine produced and the frequency of urination. Increased production of urine in the warmer months may result in flushing of the urinary tract, with decreased fungal contamination and decreased adherence of fungi.

Many animals with fungal urinary tract infections (UTIs) also have concurrent or preceding diseases such as bladder stones (cystic calculus), hypothyroidism and diabetes mellitus. Candidal urinary tract infections have occurred in cats in association with a poorly controlled diabetes mellitus, bacterial cystitis, and possible Cushing's disease (hyperadrenocorticism).

Signs of fungal urinary tract infection vary and most often include diarrhea, depresseion, loss of appetite, increased frequency of urination, lack of urination, weight loss, dehydration, fever, weakness, and skin lesions.

Diagnosis Diagnosis of fungal UTI is based upon clinical signs, laboratory tests, and identification of the microbe. Signs of candidiasis of the urinary tract are sometimes difficult to interpret as the abnormalities may be associated with either the fungal infection or the concurrent diseases. 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.

Treatment 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

Cutaneous candidiasis (fungal skin infection) is an uncommon disease in dogs and Candida albicans is recognized as the most common agent in canine dermatitis. Candida parapsilosis and Candida guilliermondii have also been involved. Candida albicans is not a member of the normal skin flora and its presence is always the indication of an underlying disease.

There are several forms of cutaneous candidiasis: exudative form, squamous and scabious form (extremely rare), and ear infection (otitis externa). In exudative form, the primary characteristics of cutaneous candidiasis are skin lesions, persistent hair loss, crusts, ulcers, scales, itchiness, and whitish discharge form skin lesions. In squamous and scabious form, overgrowth of the horny layer of the skin (hyperkeratosis), thick scabs and associated folliculitis (inflammation of the hair follicles) are present. Predisposing factors such as the use of corticosteroids, the concurrent presence of an autoimmune disease (pemphigus foliaceus) and a rickettsial disease such as ehrlichiosis caused by Ehrlichia canis are commonly observed.

Treatment Topical treatment (chlorhexidine or azole derivatives such as econazole, miconazole or enilconazole twice a day) and systemic treatment (ketoconazole, 10-20 mg/kg twice daily for 1-2 weeks, or fluconazole, 5 mg/kg/day). Both types of treatment are recommended since they allow the yeasts to be killed irrespective of their localization and digestive candidiasis is also cured which is frequently associated with cutaneous lesions.

Studies indicate that animals have to be considered as potential sources of Candida infections of human individuals especially when humans are immunodeficient.

References
1. Fungal Urinary Tract Infections in the Dog and Cat: A Retrospective Study (2001–2004) Yipeng Jin, DVM and Degui Lin, DVM, PhD
2. Cutaneous candidiasis