I am losing several of my hens. This only happens in the summer and this year is the worst. I live in Phoenix so I first suspected it to be over-heating but now I'm second guessing. We just lost one more hen to this last night and this morning another one is showing the same symptoms. They start off sneezing and having a hard time staying on their feet. They act like they're falling asleep on their feet and then jerk awake and stand back up. Their vent area is pulsating too. They pant heavily and strain to breath with their head stretched out. Then there is mucus and rattling when they breath. Their legs become paralyzed and they have a hard time staying upright when laying down. They usually die within 3 to 5 hours. The last one we kept alive for 2 days and she showed signs of improvement and then suddenly died. We thought it might be egg binding. We gave electrolytes, calcium, and water through a syringe and kept her in a cool place. She did lay an egg with a thin, fractured (but not broken inside her) shell. She improved after that, becoming more alert and like her old self but still not standing, only to die the next day. We have a mister in their large run to keep them cool. Could that be making them sick? Our day temps are in the 115s so the girls are very hot. They do have tons of shade, misters, and water, and I let them out in the yard to free range every day. Their chicken run is in/around oleandars but that hasn't been a problem in the past that I know of. Will chickens eat those? Also, we have scorpions and black widows. Could it be that? I'm very worried about parasites or viruses. Even though we keep our flock healthy and well taken care of, we have not vaccinated them. Please help, I am losing too many good egg layers. I am losing my 6 month olds along with 2 year olds.