If you've kept birds for any length of time, you have probably heard of Megabacteria. That rather obscure yet dreadful sounding illness isn't as uncommon as it once was. In fact Megbacteria is a very old and common pathogen that had eluded scientists for years. After years of study it was discovered that Megabacteria wasn't even a bacteria. The organism is actually yeast, which explains why antibiotics did little to help birds afflicted with this organism.

Given this fact, Megabacteria was summarily renamed "Avian Gastric Yeast" or AGY. The new name doesn't quite have the same powerful and unforgettable ring to it. This explains why you will still hear the organism refereed to Megabacteria. For sake of accuracy I am going to refer to it at Avian Gastric Yeast (AGY) from this point forward.

AGY are long cylindrical shaped organisms about 20 times the size of most common bacteria. Of course you would still need a microscope to see them. They are most commonly found in Australian birds such as Budgerigars, Gouldians and Zebras. AGY can also be found in pigeons, poultry and any species of bird exposed to it.

AGY is almost always a secondary infection:
I know this statement sounds a little strange but it is the truth. Most birds have some AGY in their system or have been exposed to it at some point. AGY on its' own won't necessarily make a bird ill, rather the bird is already sick or stressed, and this allows the AGY organism to flourish.

Stress is the most common reason AGY becomes a problem in the first place. Poor diet and care come in a close second. If you have had trouble with AGY in your aviary I am not saying that you aren't taking good care of your birds. Birds, especially finches can stress very easily, and this is when AGY becomes a problem. Something as simple as moving to a new environment (home) can cause a lot of stress in a finch's life. Poor diet refers to the birds being fed old, stale or spoiled food. This can be either seeds or soft foods. Allowing your bird's cage to become highly soiled with droppings or living in a very wet cold environment may also initiate the AGY take over.

Other diseases can allow AGY to grow and become a problem in your bird. In particular Coccidiosis is a common primary infection that leads to the addition of the AGY infection. That being said even a simple viral or bacterial infection can also allow AGY to become a problem.

Does AGY effect the breeding season?
Yes and this is the time of year it is most noticeable. If a large portion of your chicks died within weeks of fledging you can almost always count AGY was the primary cause. The chicks will appear healthy and active upon fledging, then as they wean you'll notice them looking fluffy and less active. If you feel the breastbone and it is protruding you must act fast. For the oldest chicks it may already be to late but you can save the chicks to follow if you treat your entire flock for AGY right away.

The reason the juveniles are so dramatically affected is because of their age and stress level. Once they fledge the chicks are instantly exposed to a new world. Add to that the fact that they are learning to eat on their own and interact in a complex social order for the first time. Plus they have also not been alive long enough to develop the natural immunity to the AGY as their parents have.

AGY is one possible cause of Failure to Thrive.

A natural immunity:
Surprising as it is, yes birds' can and do develop a natural immunity. The avian gut (digestive system) is designed in such a way it actually prevents excessive growth of the AGY organisms. The avian gut maintains a slightly acidic pH level. This creates an inhospitable environment for yeast, bacteria and protozoa. While some may be present in the gut at any given time, they aren't usually a threat to the birds' health unless the bird has been exposed to a lot of one particular pathogen, to a new pathogen, or has been under a lot of stress.

Using natural remedies such as added citric acid to your bird's diet once a month can help maintain the normal pH levels in the bird's gut. Probiotics also have the same beneficial effect.

How do birds get AGY?
Most birds pick it from the environment. Especially those birds living in an outdoors aviary. A rainy or humid environment is ideal for the spread of the AGY organism. Birds may pick up AGY from the ground, other birds droppings, or any oral exchange of fluids. This is the manor in which the young chicks become exposed, via the feedings from their parents.

What does AGY do to the bird as it grows?
The first symptom you will see is loose or watery droppings, the bird may also appear fluffed out and less active. As the yeast grows it breaks down the inner lining of the birds stomach. This leads to an ulcer in the stomach and makes normal digestion difficult. This will cause very noticeable weight loss if you handle the bird much. Feel for the breastbone. If it is sticking out, the bird is under weight.

As the disease progresses the stomach may bleed, this will cause a foul smell in the droppings and the bird will become anemic. If you were to examine your finches skin at this point it would appear very pale and the feet would be cold the touch. Eventually the bird will be unable to digest food at all and will essentially starve to death.

In addition to having AGY, plus whatever triggered the AGY outbreak, your bird will be highly susceptible to other infections while suffering the effects of AGY.

Treating AGY:
To treat a bird suffering the effects of AGY it is helpful to know what factor allowed the AGY to become a problem in the first place. Treating the AGY isn't usually enough; you must also correct the initial problem. If the problem is stress or environment caused you'll need to rethink how you are caring for your birds and make appropriate improvements. If the cause was a dietary deficiency you will want to alter the diet plan.

As with all illnesses it is always wise to move the sick bird to a hospital cage for treatment and rest.

When it comes time to treat AGY there are 2 methods:
   1) Treat with Amphotericin B, which is an anti-yeast/anti-fungal medication.
   2) Use a more natural treatment – citric acid.

Amphotericin B is the drug of choice by veterinarians while AGY is actively making your bird ill. Birds given this medicine are already losing weight, puffy, and listless. If treatment isn't started early enough the bird will not recover, even with treatment. Amphotericin B is available as Megabac-S from Vetafarm Australia. However if your birds are suffering from AGY now, it will take far to long to have Megabac-S shipped to you to be effective. When your bird is in need of immediate treatment I suggest you contact your local vet for the medication.

The Citric Acid treatment is only effective as a preventive treatment. If one of the birds in your aviary becomes ill and is diagnosed with AGY, give all the rest of your healthy birds Citric Acid. This will help to prevent the growth of the AGY organism but it will not usually completely kill it. If given Citric Acid on a somewhat regular basis it can help maintain the overall health of your flock. Plus it is safe, natural, and non-toxic. Probiotics may also be used in place of Citric Acid but they may be less effective.

After treating your bird for AGY it is often best to treat with a broad-spectrum antibiotic (Amoxitex). This done to clear up any other infections that may have settled in while your bird was weakened with the AGY.

Article © Myra Markley 2004

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