Sick, sneezing, wheezing, skinny !!PLEASE HELP!!

[Spring Fleet Chickens]

Good morning everyone, I am at a loss right now as to what to do. I have some kind of upper respiratory in my flock. I have no idea where it came from. It starts out as a sneeze, then wheezing, then swollen sinuses and eyes with discharge, a coughing sound, clear-ish discharge from the mouth if picked up, loss of weight, pale combs and if I don't treat with anything- death.
I have a flock of 35 birds of all ages. The "teenagers" (5mo) and my roosters (1yo) are the worst, my laying hens seem perfectly fine. I'm not sure what to treat with, I have Tylan 50 inj. and Baytril tablets on hand now and I'm not sure what I should be treating them with.
I have a Mereks test coming in the mail, and I can also send blood samples to the lab to test for other things but I'm not sure what all to check off on the list. There are a ton of things I can test for but my money tree is looking pretty sad right now. So I'm trying to only test for the most probable things.
I also don't want to wait too long to try and get them on an antibiotic as a few are looking really bad.
I lost a young goose a few weeks back that I had necropsied that came back inconclusive. She was not tested for Mereks but they are suspecting it was due to the spots on the liver.
She was only 5 mo.. and died in my arms. I'm not sure it's Mereks because isn't Mereks species specific? Our state vet who looked at her said it's very uncommon for geese to get Mereks. But they never actually ran the test (I was not aware that they wouldn't be testing for it when I have her to them).
Any insight would be wonderful. As I love my flock.
Thanks

 

[sweaterthebroodyrooster]

It sounds like Newcastle or Mereks.
You mentioned having mixed ages and that it’s your younger birds getting sick. The older birds my have a certain strain of respiratory illness that they are immune to but your younger birds are not. We you mix ages in flocks there’s always a risk of a respiratory outbreak but it normally only affects one age group.

 

[Briosafarm]

I'm sorry you've been dealing with this. My first instinct is to look for MG (mycoplasma gallisepticum) and coryza, but that doesn't rule out having Marek's as well. I'm tagging @dawg53 and @azygous as I've seen them be very knowledgeable and helpful about coryza and respiratory issues.

 

[dawg53]

Unfortunately when it comes to chickens, there is no immunity against respiratory diseases. Respiratory diseases can quickly spread through a flock no matter what age a bird is.

@Spring Fleet Chickens
Do you smell a foul odor around the head area of any of your birds? If so, it's Coryza.
If there isnt a foul odor, I suspect MG.
Treatment for Coryza is a sulfa drug such as sulfadimethoxine or SMZ-TMP in addition to Baytril or Tylan.
Treatment for MG is Baytril or Tylan.

 

[Renee848]

Where do you get your mail order mereks blood test?