Candidiasis, Biology


Candidiasis (Moniliasis) is a disease of man, animals and birds and is caused chiefly by Candida albicans. Crop mycosis (thrush) of poultry is caused by C. albicans and outbreaks have been reported in many species of birds. Other species of the genus Candida viz. C. tropicalis, C. parasillosis, C. vishwanathii, C. stellatoidea and C. guilliermondii have also been incriminated occasionally. C. albicans occurs as a commensal of the skin, oral cavity, vagina and gastrointestinal tract of normal healthy persons and many species of animals. About 90% of human infection is associated with C. albicans. The infection is endogenous. A number of predisposing factors which include debility, emaciation, infancy, old age, malnutrition, over-crowding, diabetes, chronic disease and pregnancy may help the fungus to become more invasive and to flare-up the disease. The fungus occurs as saprobe, but has not been frequently isolated from the environmental sources.
Avian candidiasis occurs sporadically in nature. However, major outbreaks have also been recorded resulting in mortality of 80%. The disease has been reported in turkey, geese, duck, partridge, quail, pigeon, pheasant, parrot and guinea- fowl. The disease is more common in baby chicks and is associated with malnutrition and unhygienic conditions. The diseased bird shows reduced appetite, poor growth, listlessness and reduced weight. The crop, mouth, oesophagus, proventriculus, and gizzard are most frequently affected. At autopsy, lesions are usually observed in upper alimentary tract particularly crop. Lesions consist of plaques or pseudomembranes adherent to the mucosal surfaces. There is thickening of crop wall and the membranes are covered with yellowish-white necrotic material.

C. albicans has been isolated from cases of mastitis, stomatitis and rumenitis in cattle. The affected cattle show anorexia, mild fever, mucopurulent nasal discharge, watery eye discharge, chronic pneumonia, severe dyspnoea and chronic diarrhoea. Post-mortem examination reveals consolidation and caseated abscesses in the lungs besides lesions in the intestinal wall. The fungus has also been associated with mastitis in goat and sheep. Occasionally, C. parapsillosis has been isolated from aborted cows.

Sucking piglets are more commonly and severely affected and exhibit frequent vomition, emaciation, weakness, watery discharge and pseudomembrane on the tongue. The affected baby pigs die due to extreme emaciation.Dogs may sometimes suffer from renal infection and the fungus has been isolated from diseased subjects. Recently the role of C. albicans in cutaneous manifestation of a buffalo calf has also been reported.

Clinical symptoms are not characteristic to warrant diagnosis. However, demonstration of small, oval, thin-walled, budding, yeast-like cells 24 um with or without mycelia in the smear made from lesions and in tissue sections confirm the diagnosis. The isolation of the yeast may be attempted on Sabouraud‘s medium which show whitish creamy, small, circular, convex colonies. Thick-walled chlamydospores,7-17 um in diameter, develop on corn-meal agar at 25°C. Experimentally, Candida infection can be produced in mice and rabbits. Intravenous injection of C. albicans in rabbits causes death in 4 to 5 days with lesions in kidneys and other organs. Serological and skin tests are not of much diagnostic value in candidiasis.

Treatment and prevention
No treatment is effective in systemic candidiasis of large animals. Cutaneous infection may be treated with topical application of gentian violet, methylene blue, borax, sulphur or silver nitrate. In birds, copper sulphate 1 : 2,000 dilution in drinking water may be useful. Addition of mystain (Mycostatin) in the dosage of 10-100 mg/l g of feed is effective in controlling outbreaks of candidiasis. In addition, the pen should be daily cleaned to keep hygienic condition at poultry farm. Vitamin A and vitamin B complex may also help indirectly by relieving the signs of malnutrition.

Posted Date: 9/17/2012 8:09:13 AM | Location : United States

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