Bird Vet Melbourne

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 Treatment of Megbacteria or  Macrorhabdus omithogaster Infection in Budgerigars  


Avian Gastric Yeast, or Megabacteria is a common cause of gastrointestinal disease in budgerigars (Melopsittacus undulatus) presented to the bird vets. 

 The megabac yeast is diagnosed by an experienced avian vet, by microscopic examination of fresh fecal samples. Male budgerigars of all ages are more affected. Most clinical signs in birds with confirmed megabac at the  Melbourne Bird Vet were undigested seeds in the feces, and weight loss. Although x-rays help in confirming magabac disease – the appearance of a dilated proventriculus is indicative of a M ornithogaster infection, it is difficult to recognize because of the small size of the budgerigars. Birds with megabacteria  are treated by the bird and Budgie vets with amphotericin B. Treatment can be stressful for the birds because of the handling required and the long treatment duration. . An increased occurrence of the infection in association with other pathogens was noted at the Melbourne Bird clinic.. 

Megabacteria in Budgerigars - bird vet

A picture of the typical microscopic appearance of AGY , avian Gastric yeast.  The bird vet thinks the mega organisms look like cucumbers or hand made cigars

One of the most common causes of gastrointestinal disease in budgerigars is Mega bacteria also called avian gastric yeast. This fungal microorganism can be found in clinically healthy budgerigars also. Stressors, such as , bullying, poor cage layout, cold, poor nutrition, breeding, molting, poor hygiene, and change of owner- ship can contribute to the onset of the megabacteria associated disease as seen by the bird vets. 


Megabacteria  has been detected in many bird species. Common clinical signs in Budgerigars with Mega presented to the best bird vets are vomiting, diarrhea (sometimes with undigested seeds), and chronic weight loss. Other nonspecific clinical signs avian vets see are lethargy and usually a good apatite. A dilated proventriculus may be seen on X-rays.  


The Mega disease is diagnosed by your bird vet by microscopic examination of fresh feces. In dead birds, the mega microorganism can be detected by an avian vet an impression preparation of the isthmus. The mega yeast is clearly and easily recognized by an experienced vet for Budgerigars. Because the pathogen megabacteria is easily identified by a good bird vet by microscopic examination of budgie poo, fungal culture for Megabac is not usually needed.  


Treatment of disease caused by M ornithogaster is difficult. If clinical signs of gastrointestinal disease caused by Mega bacteria are present, Budgerigars can be medicated with amphotericin B twice daily for 4 weeks.  

Although another treatment option is nystatin (20 000 U orally twice daily for 10 days) , avian vets do NOT find it that effective.  

 Sodium or potassium benzoate have also been used by bird veterinarians with poor results.