Hen died...completely emaciated...worms or something else?

It could be that she was just not right, bad heart or say a problem with another organ and not eating got thin and died. Parasites will pick on the not well ones worse then the well. Eight months it is just possible to have built up a bad worm load, but it may be one explanation. If you think it was, you could find a vet to do a fecal float test for worms. You should be able to feel the keel bone on a chicken, the lighter the breed the more you should feel.

 

I don't know what kind of environment your birds are in, but you have work to do. There are a number of diseases that cause birds to lose weight and die. Coccidiosis, histomoniasis, cholera, botulism, are a few of those. Mite and louse infestations can cause anemia and secondary infections can take place.

For heavy infestations, I suggest you either dip them up to their necks using Permectrin II mixed with water on a warm day, or dust them with Sevin-5. When dusting, lay the bird on a table and part the feathers as you dust. Keep it away from the bird's head. Putting a big handful of powder in panty hose limits the amount of dust dispersed in the air, and keeps it on the bird. The problem with dusting is you have to do it again 12 days later. If you choose dipping birds, use OB gloves, and be careful not to let the bird flap it's wings and splash the treated water in your face. If it is a light infestation, you can mix up a bottle of spray using Permectrin II and part the feathers as you spray. Don't forget the area around the vent, where mites tend to congregate.

Clean out your coops of all litter. Vacuum it out, and sanitize the floor ,walls, roosts, nests, cracks, and crevices with Oxine AH or Biophene disinfectant, or something comparable. Wear a respirator, or at least a dust mask. Let it dry, then mix some Permectrin II or Ravap EC according to the label and spray everything listed above down until runoff. Permectrin II and Ravap EC are emulsified concentrates, meaning they have oil that assists residual activity. Both are labeled for use on poultry. Ever since I followed a regiment of doing this years ago, my birds have remained mite and louse free. No health problems have resulted from doing this.

Oxine AH is a valuable disinfectant. It is great for sanitizing feeders and waterers, as well as a preventative for many viral, fungal, and bacterial problems that can occur. Here's some information about its uses: http://www.shagbarkbantams.com/oxine.htm

 

Bummer. Impacted gizzard would be my first guess but since you can't rule out an infectious process I would err on the side of caution. Coccidiosis is another usual suspect with an emaciated bird so once you've done the housekeeping watch for runny poop. With this bird not being handled it's impossible to know all the symptoms but if your only symptoms were dead emaciated hen and everybody else looks good in the weeks to come then likely you had an impacted gizzard or congenital problem.

I don't personally dip a bird that does not have visible signs of mites. And I avoid the chemicals that will kill them if at all possible. I use DE in my coop and runs and never have an issue with them.

I really hope this was an isolated incident and am sorry for your loss.

Just to add a laugh. I had to edit this post because I couldn't convince my ipad that your poor hen was emaciated and NOT emancipated.