Questions to ask before assuming what it may be.
- Sniff around her nares (nostrils), is there a foul fishy-like smell?
- Old old is she?
- Does she currently lay? If so, when was the last time she laid an egg?
- Is she having any other symptoms?
There are 2 possible diseases that may be the culprit of this cause, 1, being
Mycoplasma Gallisepticum (MG) or 2, being
Infectious Coryza.
Mycoplasma Gallisepticum (MG) or also known as
Chronic Respiratory Disease (CRD), is a bacterial infection of all poultry, being caused by the bacteria,
Mycoplasmosis/Mycobacterium. MG is a respiratory disease of poultry, causing what is similar to a cold in humans, symptoms may include sneezing, coughing, rales, difficulty breathing, swelling around 1 or both eyes, bubbly/foamy or watery eyes, sticky eye and nasal discharge. MG may or may not be combined with
Mycoplasma Synoviae (MS) which causes swelling and redness of the toes, legs or joints, nasal discharge and bubbly eyes in poultry. Both MG and MS are chronic diseases— meaning that it stays with the bird for life and symptoms will appear within times of stress. MG and MS can be easily passed from bird-to-bird through droppings, feathers, dander, respiratory secretions and other bodily fluids (saliva, blood, etc). If you plan on doing a breeding career, it's recommended not to breed from positive MG or MS birds as it can be spread through the egg to the embryo from the infected parents, making any hatching chicks, already infected with the bacteria.
Infectious Coryza is a bacterial disease of poultry, more specifically caused by the
Avibacterium/Haemophilus Paragallinarum bacterium. Infectious Coryza can cause what is similar to a cold in humans, symptoms may include sneezing, nasal discharge, coughing, tracheal rales, bubbles or ocular discharge, build-up of pus within the sinuses and eyes. The bacteria that causes Infectious Coryza, comes with a unique odor similar to a fishy-like smell or a carcass-like smell that comes from the nasal discharge— which is often a yellowish to whiteish in color. Soft or hardened pus may be in one or both eyes or even in the sinuses, that will need to be coaxed out for recovery. Infectious Coryza is a chronic disease— meaning that it stays with the bird for life and symptoms will reappear within times of stress. Infectious Coryza can be easily passed from bird-to-bird though droppings, feathers, dander, respiratory secretions and other bodily fluids (blood, saliva, etc). Luckily this disease cannot be passed through eggs.
I suggest getting PCR testing done as these diseases can mimic one another. However, I'm not in belief that your bird is ailing from either of these. She could've inhaled too much dust, choking or is having potential heart related issues causing it.