Candida is a genus of yeasts – not bacteria; nevertheless, they are also unicellular microorganisms which are everywhere around us. They can be found in the environment, on the human and animal skin and, if we focus on causal agents of mastitis, they occur in large amounts on farms, especially on those where bad silage is fed.
There are many yeast species; the Candida genus itself comprises of more than 50 species. The yeasts can be found in the terminal (distal) parts of the excretory ducts of the mammary gland but under normal circumstances in a healthy herd they do not cause the disease; the occurrence of yeast mastitis is about 2-10%. If negative factors apply (antibiotic overuse, low hygiene standards, mistakes in feed for cows with subclinical metabolic disorders, teat injuries, a deficiency of vitamin A) their occurrence can increase rapidly.
In most cases, the yeasts of the Candida genus are isolated from milk samples (C. albicans, C. krusei, C. rugosa, C. kefyr – newly named Kluyveromyces marxianus); the other yeasts are uncommon.
Clinical signs of yeast mastitis are usually mild to moderate but a chronic form the disease can also develop. The skin of the mammary gland is tight, warm, the udder is tough, slightly swollen. Impairment of the overall health is not distinct but a decrease in the milk yield and mild anorexia may be expected.
Milk is changed – grey-yellow colour, mucous with tiny flakes. In some animals, spontaneous recovery without treatment is possible but in other animals mastitis can progress to the chronic form with gradual changes in the udder.
Diagnosis is confirmed by microbiological testing.