Respiratory Issues in Chicks - Lifelong carriers?

[LittlePigeon]

Hi there.
Long story short, I got a few very sick chicks from somebody selling them from Cackle Hatchery.
All of the birds had respiratory issues - sneezing, runny eyes, crackling lung sounds when breathing... the works.
I nursed these chicks back to health with electrolytes and vitamins in the water and a lot of TLC. Their symptoms have improved by 80%. I lost a few of the weaker ones in the process. But I still have 10 left out of the 15. A few still sneeze and have some residual crackling.

Now... let's say I want to expand this flock of birds and introduce more eventually. Are these chickens carriers for life now and should I never introduce more to them?

Should I cull these birds if I ever plan to have more chickens...???

Advice?

 

[Yardmom]

I would guess it depends on what the cause was. If it was simply environmental such as dust in the bedding then you could add birds now. If it was a respiratory illness then more cautious should be taken. I am not aware of the respiratory illnesses being something that can be passed on after symptoms have resolved, but please check other sources because there are a few diseases that birds can spread after symptoms have passed.