You've lost a few this week. That's hard. You don't say how old the sick birds were. The lame bird who appeared healthy apart from the lameness sounds very typical of marek's disease, but your testing results will shed more light on that I hope. In case it is Marek's I'll post some info about that below.
On lice infestations, they are always worse in cases where the birds are sick for other reasons, broody, or can't dust bathe in a normal way. My suspicion is that Bruno's severe infestation was a result of his health. It's not always the case, but if often is. His pale and shrunken comb tells you that something was wrong. It could have been many different things including various infections. You say he had some diarrhea - perhaps that indicates some type of bacterial infection of the digestive system, but it's impossible to say. Had he been wormed? Another disease that can produce wasting and decline is leucosis, but you would need a pm to have any real idea. We'd need more information about your birds to have a better guess, but even then it would be just that - a guess.
If you have something infectious go through the flock, a cleanout is a good idea. I would remove all litter and droppings and give everything a good scrub. Then I like to rest a sick pen for a few weeks before putting birds back in if that's possible. Most respiratory viruses don't live long outside the host. Those that do cannot usually be destroyed by bleach. You don't want a sterile environment. That's not healthy either. If you are cleaning out water containers with bleach then make sure that you rinse very, very well. There's a small amount of chlorine in our drinking water which doesn't hurt us, but rinsing well when using it keeps it down to a minimal level. I wouldn't advise bleaching the whole run. Bleaching everything in sight will just favour some organisms over others and cause more issues - but that's Mike's favourite lecture so he can expand on that one.
The reality is that chickens usually get illnesses from other chickens. Direct contact is the most common method of transfer. Some viruses such as marek's disease are airborne and can move over distances from one property to another in dust particles. Some diseases of chickens are also carried by wild birds which is why some people choose to net off their runs. You will never create an environment which is completely pathogen-free. Birds get acclimatised to their own environment. After exposure, they develop an immune response and learn to deal with it. When disease seems to spring from nowhere it is often latent infection that break out in response to stress of some kind. Sometimes birds that appear healthy can be carrying disease.
If I were you, I would do a big clean out and scrub out. Then I'd review the feeding and housing conditions and see if they are all working. Avoid mixing young growing birds with older birds and feed everything on good quality balanced rations appropriate to the job they are doing.
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