They tend to pick on the ones at the bottom of the pecking order, or if they are weak. I would put your hen on a human weight scale. And her life may be in danger...
Not contagious to humans.
How is blackhead controlled by management?
prevention of exposure by quarantine or isolation, especially avoiding any contact with chickens or game birds, and.
use of migration barriers to prevent commingling of infected birds with uninfected birds.
It IS contagious...
I'm thinking Blackhead disease (histomoniasis) is an important poultry disease that affects turkeys, chickens, and game birds such as partridges, pheasants, and quail. The disease is caused by the protozoa Histomonas meleagridis, tiny, single-celled organisms that are spread to the bird by the...