Looks like one of my hens is symptomatic. What I noticed to begin with was looking at her eye. It looked normal but not. I think maybe it's bulging very slightly. She is bony and having bright green poop. She can not eat because her crop is full of fluid, and every time she bends over, the fluid comes out and blocks her airway. I've tried to raise her food up but, nothing is going down, so she can't eat.
QUOTE:
Similarly, the involvement of the vagus nerve can result in the paralysis and dilation of the crop seen in this photo. Crop impactions and pendulous crops that are quite often seen in Show chickens are often attributed to Marek’s disease as the virus infiltrates the nerves of this region. Crop impaction may also be unrelated to Mareks Diseases when chickens of any age but mostly mature hens over-engorge on grass or other fibrous matter. The fibre in grasses accumulates in a entangled mass that prevents the crop from emptying properly causing it to distend and become impacted (see article in this section on Crop and Gizzard impactions).
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This is the pattern of my symptomatic birds, however, if they don't have symptoms prior to 8 months, it seems that they live for a few years until the tumors, I guess, start to affect them. And they waste away.