Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help you with your wee ones today.
First, I am very sorry to hear that you are in the middle of an outbreak of respiratory disease in your flock. As I am sure you can appreciate, to have multiple birds showing a range of respiratory signs does give us a hint that we are not looking at a disease of the individual (ie throat obstruction, tumor, organ disease, etc) but rather an infectious process. And while it is surely frustrating to have an outbreak in a flock, it does remove some differentials right off the bat and allows us to focus on bacterial, viral, parasitic, nutritional and toxic causes for these signs.
Now as I am sure you can appreciate upper airway signs like these can be seen with a number of respiratory agents. Therefore, we have a lot of agents to consider here. Specific concerns include Infectious Coryza, Acute Fowl Cholera (Pasteurella multocida), Influenza, ILT IRT, infectious bronchitis, Chlamydiosis, and mycoplasma (Mycoplasma gallisepticum). Furthermore, since you noted that one bird is gasping (which can mean there is swelling, discharge, possibly infectious material or worms blocking up the throat) we can see localized throat based disease due to Trichomoniasis (canker), Fowl pox (wet form causes canker lesions in the throat) and Syngamus trachea (gape worm) infestations.
Now any respiratory infection of the bird must be taken seriously since respiration is critical to life. If you are comfortable handling this most poorly bird (and she doesn’t get to distressed with this), then you can potentially narrow down a few of these differentials at home. If you are comfortable doing so, you may consider having a peek down her throat to rule out you gapeworms. You may be lucky and see them or one of the other causative agents (ie the plaques of Fowl Pox or discharge of canker). If you can't see anything, since you can only look down a chicken throat so far, then you can try the "Q-tip test". To do this, you need to place the bird in your lap, gently open her beak, and swab a cotton bud down her throat (twirl it as you do this). Twirl as you bring it back up, and if she's got gapeworm, you'll see thin, red strings on the cotton bud. This way you will know if this is the cause. But if you end up with a cheesy discharge then canker or pox would be higher on the differential list. And if there is any other discharge, the bacterial causes would be suspect. And once you have identified what is present, you will be in a better position to know if you are treating them appropriately.
Otherwise, further measures to pinpoint the causative agent and increase your treatment success, you do want to consider involving your vet. Especially as the gaping bird is showing very advanced stages of disease and likely needs intensive care +/- oxygen if she is going to survive this. Therefore, she may be the ideal bird to have examined by your vet. They can listen to her lungs, examine her airway, and help you determine the disease local and therefore rule out some of these agents. Furthermore together you can collect some respiratory secretions from this bird to be cultured. This will tell you what agents are present and what treatment will actually clear them . As well, you might consider having a fecal exam performed as well to tell you if parasites are playing a role (directly or via compromising the immune system).
Now just to note since gapeworm is a concern here, if they are not up to date on worming then that is one step you can consider taking just now. Specifically, we’d want to use a preparation that will make sure you can rule out the gapeworm (ie Flubenvet). That way you can directly address one terribly common differential that very commonly manifests with these signs. And if you are keen and have a microscope, some poultry owners do check fecal samples themselves, and this may be an option for you to see if there is any sign of gapeworm eggs to help you determine if they are a threat here. You can find a good Fecal Sample Evaluation Guide here.
Furthermore, once you have samples for culture (which will tell you what drugs any pathogenic bacteria present are vulnerable to), you can consider a broad spectrum treatment to try and tackle as many of the bacterial causes as possible. There are a range of options that would include erythromycin, oxytetracycline, or fluoroquinolones (useful if Mycoplasma is diagnosed), macrolides. Other options may be tilmicosin, tylosin, or spiramycin.
Otherwise, supportive care is that key facet that we need to make sure you are addressing that for the lasses. Since there re multiple birds in differing states of infection, you need to just make sure they have a warm environment and that you are monitoring everyone's appetite and drinking. If anyone is off their food or water; then you may need to initiate hand feeding for them.
Just to note, for this poor gasping bird who is likely very congested (if not suffering form an inflamed airway), you can try to reduce her congestion by using a bit of steam treatment here. You can achieve this by putting her in a carrier in the bathroom while you run a hot shower. Or if you have a nebulizer/humidifier you can set up a wee steam tent (by putting her into a carrier and covering it and the humidifier with a bed sheet). This can just help reduce some of those airway clogging secretions and help her to breathe easier.
Overall, there are a range of agents that can be to blame for the signs you are seeing with the gasping lass and her friends. Therefore, since you already have a bird or two in advanced severe stages ,you need to initiate the above supportive care, monitor breathing, and take some of the above diagnostic steps to determine which is to blame for their signs. If you narrow down the differentials but cannot identify a cause (ie if its one of those more subtle ones or is lurking in the lungs), then it would be ideal to follow up with your vet. And this may be the best case for this gasping bird at this point to give her a chance. Especially because your vet will help you treat but also identify the agent present. And that will let you ensure you are treating everyone as effectively and economically as possible to make sure you are able to limit the disease's effects in the others and prevent spread to any other birds.
I hope this information is helpful.
If you need any additional information, do not hesitate to ask!
All the best,
If you have any other questions, please ask me – I’ll be happy to respond. Please remember to rate my service once you have all the information you need. Thank you and hope to see you again soon! : )