Candida and Aspergillus: fungi that cause disease in birds
Candidiasis (‘thrush’, caused by Candida spp) and Aspergillosis (caused by Aspergillus spp) are fungal infections that occur in birds. It is important to know whether a disease is caused by a fungus or a bacteria as bacterial infections are generally treated with antibiotics while treating a fungal infection with antibiotics can make the disease worse and even cause death.
Candida fungi is a budding yeast that can be associated with several disease conditions, usually because the bird’s immune system is not functioning optimally, such as with young birds or those with other underlying diseases. Humans can carry Candida albicans, the most common type, usually without showing signs of disease. We can pass the organism on when we handle birds and trigger problems.
Crop infections. Young birds being hand reared in sub-optimal conditions (e.g. if the food is unsuitable or fed too cold or the temperature at which the chick is being kept is too cold, or where there is poor hygiene) can develop candidiasis. These birds may show crop stasis, regurgitation, diarrhoea, weight loss or respiratory problems associated with regurgitating food and it going down ‘the wrong way’, into the lungs.
Chicks suspected of candidiasis of the crop should be checked by a veterinarian who will look at a sample of material from the crop under the microscope to see if Candida organisms are present. Bacterial infection can cause similar signs and sometimes both abnormal bacteria and budding Candida may be present simultaneously. Treatment will usually involve using anti-fungal drugs such as nystatin as well as correcting feeding and husbandry factors. If abnormal bacteria are present both anti-fungal as well as antibiotic medication may be needed.
Mouth infections. Older birds, especially cockatiels and rainbow lorikeets can sometimes develop candidiasis (thrush) in their mouths, often associated with long term poor diets. As with crop candidiasis, it is important to take the bird to an avian vet who can confirm whether the problem is thrush or/and a bacterial infection and advise re treatmentand diet correction.
Candidiasis following antibiotic treatment. Birds being treated with prolonged courses of antibiotics can develop a yeast overgrowth and show diarrhoea and worsening health. It is important that antibiotics be used only as directed and if your bird is not improving your vet may need to check droppings under the microscope to see if yeast overgrowth may be a problem.
Aspergillus fungi are fluffy moulds such as grow on mouldy bread. They are common in the environment and will generally not cause harm in healthy individuals. However, as with Candida spp, if a bird is in poor health, has been on a poor diet, is immunocompromised or if they inhale overwhelming numbers of fungal spores, respiratory disease may occur. Sometimes granulomas (pockets of fungal infection) will form in the syrinx (the bird’s voice box) causing voice change and breathing difficulties or they may form in air sacs or in the lungs, again interfering with respiration. Sometimes aspergillus granulomas can form in the brain or spinal cause, causing neurological problems.
Baby chickens kept in confined surroundings, penguins kept on straw, parrot chicks in moist nesting hollows or adult parrots kept in fungi laden environments and fed all seed diets are examples of situations where aspergillosis may occur. Treatment is often challenging and complex, but depends on the severity of the illness. Diet and husbandry issues need to be addressed. Mild cases may respond to oral medication with anti-fungal drugs such as itraconazole but, rarely, some birds may be sensitive to this drug. Long term nebulisation with antifungal drugs or medication given directly into the trachea or air sacs may be needed.