One of my chickens was recently diagnosed and treated by the vet for bumblefoot, and then this morning I noticed a swelling beginning on the feet of two more chickens! Is this condition contagious and what should I do?
We're sorry to hear your flock is having problems with bumblefoot! The more technical name for this problem is ulcerative pododermatitis, but most people, amateurs and professionals alike, refer to the problem by the common name of bumblefoot. Bumblefoot is a serious problem. First, call your vet again, and make sure your sick hens are getting the care they need for their bumblefeet. Don't worry--this illness is not contagious in the same way a cold is, for example, but there are still some causative factors you may be able to address if you are having frequent problems with bumblefoot in your flock.
First, consider how chickens get infected with bumblefoot. Most commonly, it occurs when a scratch or puncture on a bird's foot becomes infected with Staphylococcus aureus bacteria. This bacteria is found frequently in the environment, even on your own skin and in nasal passages--it's probably nothing you can eliminate from the coop (although good sanitation is always a good idea!). However this bacteria can even cause bumblefoot in birds when there has been no particular injury, if their skin gets irritated enough to let the infection take hold. For instance, if the bird is kept on wire, or if the roosts are too small or rough, it could cause the skin on her feet get irritated and allow the infection to take hold.
So, if these issues are something your birds are facing, you will want to address them first. Remove the wire floor and replace it with a solid floor and soft bedding. Change your roost to something like an elevated, flat 2 x 4 (chickens tend to prefer this, anyway, as they are ground nesting birds, not perchers). In addition, you will probably want to have a look around the yard or coop to see if there is some bit of sharp fencing, a splintered area on a roost, or something else that is injuring them. Look for things like nails or staples sticking out on the ramp to your coop, a splintered porch rail, a bit of broken glass or sharp metal on the ground.
Chronic bumblefoot infections in your flock can also be caused by a Vitamin A deficiency. This deficiency can make them susceptible to other things like conjunctivitis and sinusitis, too. If you can't find anything in your flock's environment that may be causing wounded feet--and if their perch is comfortable, wide and smooth--perhaps a Vitamin A deficiency could be an underlying cause. This is pretty unlikely in birds that have access to green pasture, since grass itself is a very good source of vitamin A. If you keep your birds confined to areas free of forage though, you might continue to see problems in this area.
If you suspect this deficiency is the issue, try increasing the access your flock has to good pasture. If that is just not a possibility, you might ask your vet if there is anything you can do to supplement the diet of your girls. Spirulina supplements are sometimes offered to caged birds like parrots--find out if this might be right for your chickens by asking your veterinarian.