Avian Gastric Yeast Formerly Megabacteria Part I: Description

white capped pionusMegabacteria is a large gram positive rod shaped organism that causes severe debilitating disease in numerous species of psittacines and passerines in captivity and in the wild. (Note the large rod-shaped organisms in the photo.)

Megabacteriosis or Avian Gastric Yeast is most common in budgies. Cases have also been reported in parrotlets, lovebirds, King parrots, red winged parrots, cockatoos, cockatiels, lorikeets, ringneck parakeets, macaws, finches, canaries, ostriches and quail.

Megabacteria was originally believed to be a bacterial organism, but now is thought to be fungal.

Megabacteria is currently referred to as Avian Gastric Yeast. Previous names for the disease caused by this organism includes “going light”, budgie wasting disease, Proventicular Ventricular Disease and Megabacterial Proventriculitis.

The organism colonizes the proventriculus or glandular stomach and is present in the mucus covering the mucosal surface.

Megabacteria causes two disease syndromes – acute and chronic. Acute disease occurs when large numbers of birds in a flock become ill suddenly and die within 12 – 24 hours. The birds often appear severely depressed and may regurgitate blood-tinged fluid.

Chronic disease is more common. Progressive weight loss leading to emaciation occurs. Birds appear lethergic, depressed and try to eat, but don’t ingest food. Some display difficulty swallowing and repeatedly stretch their necks and gape. Regurgitation of a clear to white slime coats the headd, causing the feathers to be matted. Blood may be present in the regurgitated material. Scant watery droppings or diarrhea may be present, often with undigested seeds.

Megabacteria in the proventriculas interferes with the digestion by decreasing gastric acid formation. As a result of the increase in ph, enzyme activity responsible for hardening the Koilin lining of the ventriculus is hindered, causing the normally hard Koilin to become soft and thin. This Koilin in the ventriculus (gizzard) is important in the grinding of food particles.

The next article, Avian Gastric Yeast Formerly Megabacteria Part II, will cover the transmission, diagnosis, treatment and prevention of this disease.