Whole chicken flock dead within a week - what could it be?

[SLDiva]

We had four chickens - three of them were about four years old and one we'd hatched last August. A week ago, one of the older chickens was dead one morning. We put it down to old age and her just being a bit of a feeble chicken anyway. We went on holiday - left the chickens shut in their run with my parents to check on them every other day. Just under a week later and the youngest chook was dead. Then when we got home, we found the other two dead. Apart from the first chicken who was always a bit sickly looking, the others were all in excellent healthy, laying well etc - what could have killed them all within a week? I'm particularly worried because we've another four (two hens and two cocks) that we hatched a few months ago - they're in a different enclosure to the others so I want to make sure whatever it was that killed the others doesn't pass to this lot. I don't know if it's probative but we have runner ducks who are in the area too.

Any ideas?
Thanks

 

[Wyorp Rock]

Sorry for you loss.

There is no way to determine what the cause of death was without a necropsy. With that many dying in such a short time you should really send one in.
Contact you local vet or if you have something like an Agricultural Agent they should be able to direct you to the right place.