Avian Gastric Yeast (Megabacteria)

Causes

Avian Gastric Yeast (AGY), like Candida, is caused by a yeast organism. Under a microscope, the yeast resembles a long straight rod. Because they look a lot like very large rod shaped bacteria, they were once called Megabacteria. It was not until later that it was discovered to be a yeast organism - at which time, it was renamed.

AGY can be caused by exposure to an infected bird or by stress-related factors. While exposure to infected birds is a possible cause, I have not found this problem to be particularly contagious. Many vets believe that AGY in small numbers is a normal part of the gut flora. Illness occurs when they are allowed to reproduce out of control. However, I very rarely see AGY in the droppings of healthy birds. If one or two should pop up in a smear, some vets will regard this as normal in an otherwise healthy bird. I look at it as the sign that something is starting up, since I really do not think I should find any AGY in the droppings of a healthy bird.

I have heard that AGY can be passed from parents to chicks and therefore, eggs/chicks from infected parents should be fostered by healthy birds. I have no experience with AGY in a breeding situation and so cannot comment on this.

Symptoms

In my experience, AGY produces similar symptoms to Candida - gradual fluffed bird syndrome, low energy level, and excessive eating at the food dish. According to my vet, birds react to AGY in one of two ways: either the gradual wasting along with the symptoms I have described or sudden death with no obvious symptoms prior to death. According to my vet, birds with AGY frequently have some yellow staining around the vent area, although not always. I tend to see this in about half the birds with AGY infections.

AGY can also cause undigested seed in the droppings. These undigested seed are usually not whole seed, but instead seed fragments. The undigested seed may not be obvious by just looking at the droppings - however, if you try to flatten the dropping, you may find hard pieces inside. I have found that once AGY gets to the point of producing undigested seed in the droppings, it becomes very difficult to treat.

I have seen that advanced AGY sometimes produces solid, dry, charcoal grey colored droppings. They are perfectly formed, but very dry.

Prevention

To my knowledge, there is not much that can be done regarding prevention, aside from keeping the environment as clean as is reasonable. While probiotics do nothing to treat AGY, I have wondered if they may have a preventative effect. Microscopic screening of the aviary to catch the problem early and to remove infected birds before they pass the infection on may help.

I have seen some birds be treated effectively, only to succumb again the following year. My guess is these birds have some type of compromised immune system. My preference would be to remove such individuals from my breeding program, just in case there may be a genetic predisposition to their condition.

Treatment

AGY is more problematic than Candida because there is only one known treatment: Amphotericin-B. Amphotericin-B is hard to come by without a prescription and is also a very harsh toxic drug (although my vet says that the suspension they use is prepared in such a way as to be much gentler on the bird than the injections used in humans). Many times, the drug just doesn't work and you are simply out of luck. These are the worst cases, as there is nothing left for you to do but wait for the bird to eventually die (and it sometimes takes a while).

Amphotericin-B cannot be sold in the US without a prescription. However, it can be purchased in the US from other countries for your own personal use as an avian supplement in the form of Vetafarm's Megabac-S. I personally do not purchase Megabac-S. Megabac-S is very expensive. Add international shipping, and the cost increases further. For me, it is cheaper to see my vet, even including the price of an exam and fecal. However, for those without access to an avian vet, this may be your only option.

Megabac-S is also a water-based treatment. I read about one study (article no longer available online) that showed, in budgerigars, Megabac-S was not as effective as Ampho-B given in a suspension. However, budgerigars and finches are different in that finches are obligate drinkers (they must drink their water or die) and budgies can potentially go for a month without drinking if they sense something is off with their water. Thus, it is possible that the difference in efficacy was due to the fact that the birds just didn't drink enough water to get the appropriate dosage of medication. With finches, such a factor shouldn't be an issue.

Whether or not it is worth it to try Megabac-S is up to the aviculturist; however, I would strongly urge not to use this drug as a preventative or maintenance treatment. Aside from the fact that Amphotericin-B can take a toll on the bird, it is also the only effective drug we have against AGY. If AGY develops further resistance to this drug, it may become untreatable in the future.