Candidiasis

Also known as

Moniliasis and candidemia

Description

Candidiasis is a localized mucocutaneous disease (limited to mucous membranes, skin and nails/hoof horn) caused by various species of the yeast-like fungus Candida, most commonly C. albicans. It is found worldwide in a variety of animals.

C. albicans is a normal inhabitant of the skin, nose and throat, GI tract, and external genitalia of many species of animals and is opportunistic in causing disease. Factors associated with candidal infections are disruption of mucosal integrity (injury to the mucous membranes); prolonged use of intravenous or urinary catheters; long-term administration of antibiotics; and immunosuppressive drugs (such as steroids) or other diseases.

Candidiasis can be superficial, affecting the skin or mucosal surfaces of the GI or urogenital tract, but spread of the organism can lead to candidemia (infection of internal organs).

The organism most frequently infects birds, but systemic candidiasis has also been seen in cattle, calves, sheep, and foals secondary to prolonged antibiotic or corticosteroid therapy. Candida infections have occasionally been a cause of arthritis in horses and mastitis and abortion in cattle.

Signs are variable. Calves with forestomach candidiasis have watery diarrhea, dehydration and lack of appetite, with gradual progression to weakness and death. Cows may develop mastitis.

Lesions of the skin and mucosae may be single or multiple raised, circular, white masses covered with scabs. This fungal pathogen can cause thickening of the mucosae of the tongue, esophagus, and rumen.

Diagnosis can be made by examination of scrapings or biopsy specimens from the lesions. The fungal cells generally are limited to epithelial tissue (outer layer or lining) and rarely extend into deeper tissues.

Chronic pneumonia caused by C. albicans has been seen in feedlot cattle. Clinical signs in these cases include severe dyspnea (difficulty breathing) which may cause mouth-breathing, but only moderate fever. There may be profuse stringy salivation and a thick brown-streaked nasal discharge.

The muzzle may show crusting, with dried material from oozing and seepage, but there are no ulcers, erosions or blisters on the muzzle nor in the mouth or nostrils.  The eyes may water profusely but there is no conjunctivitis.

The respiratory disease is slowly progressive; the animal eventually dies or is slaughtered. At necropsy there may be fluid in the lungs, and small abscesses in the lung tissue.  

Some cattle have profuse diarrhea, with local lesions in the intestinal wall. The fungus can be seen on smears from samples taken at necropsy, and can be cultured.

Signs

• Diarrhea
• Labored breathing,
• Lack of appetite,
• Crusted muzzle,
• Skin lesions,
• Swollen painful udder (mastitis)

Cause

Candidiasis is a fungal infection caused by a yeast (a type of fungus) called Candida. Yeasts are microscopic fungi consisting of solitary cells that reproduce by budding.

Although candidiasis is a relatively rare infection in animals, it is an important differential diagnosis to bacterial infections, and candidiasis can also occur secondary to bacterial infections. It should be considered as a possible option especially when animals do not respond to antibiotic treatment.

Several species of yeast can cause bovine mastitis. Cryptococcus neoformans and Candida albicans are by far the most common, but other Candida species have also been associated with bovine mastitis. The yeast infection is usually transmitted through contaminated milking machines, milkers’ hands or other material that touches the udder.

Candida species are a group of one-celled opportunistic organisms, ever present in the environment of cattle. In a dairy they may reside on milking machines, treatment instruments, the floor, straw, feed, dust, soil, etc. and are normal inhabitants of the skin of the udder and teats, in which they exist in low numbers.

When they invade mammary glands and cause clinical mastitis, the cow shows signs of pain, prolonged fever, tenderness, inflammatory reaction in the mammary gland and associated lymph nodes and reduction in milk yield and quality.

Some fungal infections in the udder such as Aspergillus fumigatus and various species of Candida may result in death of affected animals.

The incidence of mastitis due to yeast is usually low in dairy herds, but has increased during the last decade. Fungal mastitis often follows treatment directed against other pathogens using contaminated syringes, cannulas, catheters or contaminated antibiotic preparations.

Teat injuries may predispose the udder to establishment of a yeast infection. Yeast infections are responsible for about 10% of all clinical mastitis cases seen in veterinary practice and most of these cases are mild.

Candida is probably the most common pathogen isolated from cases of mastitis, but is often unnoticed in first treatment attempts. Administration of antibiotics may aggravate fungal mastitis. Treatment of fungal mastitis is a challenge, since  fungi do not respond to antibiotics. Fungal mastitis cases often linger and provide a source of infection for other cows.

Fungal mastitis may result from an ascending infection (up into the udder from the teat) due to incorrect administration of antibiotic preparations during the drying-off period.

Contamination of the teat end or cannulas by environmental yeasts and fungi associated with lack of hygiene during milking and poor equipment cleaning leads to penetration into the mammary gland. Dirt on the tube or on the teat end often gets pushed up into the teat canal, causing a yeast infection.

Large doses of antibiotics may cause reduction in vitamin A, leading to disruption of the udder’s epithelium and affecting the microflora of the mammary glands. These resident micro-organisms act as a natural defense, but if they are killed off by antibiotics, their absence allows invasion by fungi and yeasts. Administration of antibiotics may aggravate fungal mastitis.

Prevention

It is difficult to prevent yeast infections in general, since these tiny organisms are ever-present in the environment.

To prevent mastitis caused by yeasts, molds, fungi etc. care must be taken to keep the teats clean and dry, scrubbing them properly and then using a separate alcohol wipe for each teat after milking.

When treating mastitis make sure any teat insertions are done properly with a single-dose sterile tube or cannula. Most fungal infections enter the treat with a dirty infusion when treating some other cause of mastitis.
 
Since these yeast-like fungi are present in the environment and are normal inhabitants of many body surfaces, there is no way to completely prevent infections except by keeping animals healthy in a clean environment and trying to minimize injury to the skin, teats, etc. This may mean adequate soft bedding for dairy cows, avoidance of concrete floors, washing the udder and milkers’ hands with antiseptic before and after milking, cleaning and disinfecting milking machine and teat cups after each milking.

The healthy non-infected cows should be milked first and the known infected cows should be milked at last. Newly introduced cows should be milked separately and screened for mastitis. Teats should be dipped following each milking, with an appropriate solution. The udder and teats should be protected from injuries, and fly population should be controlled. Infected animals should be kept separate from other animals. Calves should not be allowed to suck infected teats. Milk from infected teats should be milked out daily three times and disposed of properly without contaminating the environment.

Treatment

Any disease condition that might possibly be caused by yeasts or fungi should be properly diagnosed by a veterinarian before treatment is attempted.

Antibiotic therapy for mastitis, without identifying the mastitis-causing organisms, is often the cause of fungal mastitis that then does not respond to any type of treatment.

Nystatin ointment or topical application of amphotericin B or 1% iodine solution may be useful in the treatment of oral or cutaneous candidiasis. Fluconazole has also been used successfully in some situations. Itraconazole and amphotericin B lipid complex are considered the treatments of choice in dogs.

Although antifungal drugs have been used for treatment of yeast mastitis, there is no clear evidence of the effectiveness of this therapy.