Candida infections – also known as candidiasis – are common in many birds but symptoms vary in different species. The causative agent is almost always candida albicans, which is commonly found in the gut of almost all otherwise healthy animals. It is only when the bird is unwell from some other, probably trivial, cause that the candida can get a hold. In psittacine birds the candida usually causes problems with digestion. In other birds, it is more usual to find skin and eye problems. Some birds will show these plaques on their tongue or the back of the throat and this, taken with other symptoms, is diagnostic.
Causes of Candiasis
As candida is what’s known as opportunistic, it can infect a bird which has happily carried it in its gut for years if it is stressed or ill. Poor nutrition, particularly a lack of Vitamin A, or a generally limited diet can allow candida to take a hold. If the crop is emptying slowly for some other systemic reason, the candidiasis can take hold in the fermenting food. Poor hygiene is also a prime cause of candida; because it is a fungus it can survive, if not grow, outside the body and if old food is left lying about, it will thrive on that. Ironically, long use of antibiotics can also cause the yeast to flourish as this will unbalance the natural gut flora, giving it a chance to overwhelm the healthy bacteria which normally keep the pH at a level which keeps the yeasts at bay.
Diagnosis of Candida
Candida is relatively easily diagnosed, either by examining the bird by eye or by growing swabs in the laboratory. As a polymorphic yeast, candida albicans grows readily of fungal nutrient in the lab and the results are very quick to return, so that the bird can be started on a regime of anti-fungal medication. Also because candida is a polymorphic yeast, it means that it can change shape, putting out tubes called hyphae, binding the individual cells of candida together to form white plaques which are easily seen by the naked eye.
As it is normally found in the digestive tract, simply finding it there is not necessarily sign of a candida outbreak. It is important that the swabs are taken from plaques if present, to give the diagnosis more accuracy. The areas are easily identified; some vets call the appearance ‘cotton mouth’ as the candida plaques can look like threads of cotton wool spread on the mucous membranes. Another description is ‘milk curds’ as it looks like small patches of curdled milk. When it is rubbed, it sometimes leaves a raw patch. If there are a lot of plaques, care should be taken not to rub at them, as this will leave a lesion where yet another problem can arise.
Treatment of Candidiasis with Nystatin
As candida is a localised yeast infection it is relatively easy to treat. It is only really serious if it debilitates the bird to the extent that other infections and opportunistic viruses and funguses can take a hole. Nystatin is the anti-fungal of choice, but even though it is basically without side effects, it should not be given as an indiscriminate preventative as the candida in the bird’s system can easily become resistant, making recurrences more difficult to cope with. If it is possible, the nystatin (which comes as a liquid) should be given separately by mouth a short while before feeding. In this way it can come into direct contact with the plaques of candida and will therefore be that much more effective.
Other Methods of Treatment
If the bird will not tolerate this method of administration, or if the candidiasis is widespread amongst a large number of birds making it impracticable, then it is possible to mix it with food, but care should be taken to make sure that enough is eaten to represent the entire dose. Uneaten food should be removed immediately. The dose should be continued for at least five days, by which time the candida should have been eradicated. If the nystatin does not work for some reason, an alternative is diflucan or for very resistant strains, ketaconozole is available. The problem with ketaconozole (the brand name for this anti-fungal is Nizoral) is that it cannot really be used on birds which are compromised in other ways; it is difficult to give, being almost completely insoluble in water and is toxic in large amounts. It is the drug of last resort and only really needs to be used if indiscriminate use of nystatin has created a resistant strain of candida.
Prevention of Candida
As a yeast, candida is highly susceptible to disinfectants and everyday cleaning agents and so with normal cleanliness, it can be avoided. Care should be taken to make sure that the environment for the birds is kept scrupulously clean, with no food debris left around and no faeces or urine left to contaminate dry flooring material. The best care should be given to make sure that all birds are reacted with at least daily and any sickly behaviour or obvious digestive problems are addressed and if possible diagnosed and treated as quickly as possible.
Candida is naturally occurring and because one strain can affect across species, it is possible that a few spores of candida albicans can be carried in on the clothing of the owner or a visitor, or even be transferred from the hands when handling a bird. It should be policy that birds are handled as little as possible by strangers; this not only reduces the chances of diseases and infections such as candida being spread, but also ensures that the birds are not subjected to stress, which is well documented as a causative situation in allowing candida to take hold.