Megabacteriosis

Megabacteriosis, technically macrorhabdosis, is a disease of the stomach that most often affects budgies. For a long time the cause was thought to be a large bacterium, hence the name “megabacterium”, but we now know it is the yeast Macrorhabdus ornithogaster. The disease is typically chronic: the bird slowly loses weight even though it seems to be eating. The earlier it is recognised, the better the chances of recovery.

Macrorhabdus lives in the glandular part of the bird's stomach (proventriculus), where it joins the muscular gizzard. There it damages the lining, disrupts the secretion of stomach acid and digestion, and in more severe cases causes ulcers and bleeding.

Besides budgies, the disease also occurs in cockatiels, lovebirds, canaries, finches and other small birds, and it has been described in poultry too.

How it spreads:

• through droppings of an infected bird that get into food and water;
• from parents to chicks during crop feeding;
• by adding a new bird to the flock without quarantine.

Many birds carry the organism for years without any signs of disease. The disease develops when the bird is weakened, for example by stress, poor diet, moving, overcrowding or another illness.

The most typical sign is what breeders call “going light”: gradual weight loss even though the bird is eating, or at least constantly hulling seeds. The breastbone becomes more and more prominent and the muscles beside it waste away.

Digestive signs:

• whole, undigested seeds in the droppings;
• diarrhoea or looser, bulkier droppings, sometimes yellowish;
• dark or black droppings, which may indicate bleeding in the stomach;
• vomiting or regurgitation – the bird often shakes its head, so the feathers around the beak are matted;
• the bird eats slowly, hulls seeds but swallows few of them.

General signs:

• lethargy, apathy, ruffled and untidy feathers;
• weakness that makes flying harder and perching unsteady;
• a weaker voice or no more singing.

The disease can last for months, but it can also end suddenly in death, especially if there is bleeding in the stomach.

• the droppings are black or tarry;
• the bird vomits repeatedly or keeps shaking its head;
• the breastbone is sharp and sticks out a lot;
• the bird sits ruffled up on the floor of the cage and does not fly;
• it has not eaten for more than a day;
• in a flock, birds die one after another after gradually losing weight.

The organism is detected by examining fresh droppings under a microscope, where the characteristic long, rod-shaped organisms can be seen. The bird does not shed it all the time, so a negative result does not rule out the disease and the test is sometimes repeated. The vet may also do an X-ray or blood tests to assess the bird's condition. In a dead bird, a post-mortem reliably confirms the diagnosis, which is useful if you keep a flock.

Because the cause is a yeast and not a bacterium, antibiotics do not help. The vet prescribes an antifungal, most often amphotericin B given by mouth over a longer period, and sometimes other antifungals. The treatment must be completed, as otherwise the disease easily comes back. The vet will explain how and for how long to give the medicine and show you how to hold the bird without unnecessary stress.

Supportive care, easily digestible food and good hygiene are also important. For severely exhausted birds, the vet can give fluids and food by tube. Recovery is slower in birds that are already very thin, and some remain permanent carriers.

• Separate the sick bird from the others straight away.
• Keep it warm, in a quiet, dimly lit place without draughts.
• Put food and water low down so the bird can reach them easily.
• Do not force-feed it or pour water into its beak.
• If possible, weigh the bird on kitchen scales and keep a record of its weight – this helps the vet a lot.
• Keep a fresh droppings sample for testing.

• Keep every new bird in quarantine for a few weeks and have its droppings checked before introducing it to the flock.
• Wash the water and food bowls every day and remove droppings regularly.
• Avoid overcrowding and sudden changes that cause stress.
• Provide a varied diet, not just seeds.
• Monitor your birds' weight regularly, as weight loss is the first sign.
• If the disease is confirmed in the flock, arrange with the vet for the other birds to be checked too.

Megabacteriosis is not known to pass to people, but always wash your hands after handling birds anyway.

Megabacteriosis is a stomach disease caused by a yeast, not a bacterium, and it most often affects budgies. A bird that is losing weight despite eating, with whole seeds visible in its droppings, should have its droppings checked by a vet as soon as possible. Quarantine, hygiene and weight monitoring are the best protection for a flock.