Gangrenous dermatitis is usually caused by clostridium sp., in concurrence with staphylococcus and E.coli. The organisms are normal inhabitant of chicken. If there is any injury to skin the above said organisms enter the injured area and cause the disease. Hence minimizing the level of these bacterial organisms in the host by using acidifier and in the environment by regular spray of disinfectant is the first step in prevention. Apart from this use immunomodulators to enhance the immune level is also essential. To treat actual outbreaks choose appropriate antibiotics based on the ABST.
Gangrenous dermatitis is a more complicated disease than just the precense of the bacteria mentioned previously.
in many cases gangrenous dermatitis occurs in young chickens broilers or layers that suffer from immunossupression due to CAV (chicken anemia virus). on top of the immunossupression Clostridium , Staph or E. coli can easily multiply and cause the clinical picture of gangrenous dermatitis. in young chicks younger than 12 days gangrenous dermatitis is also known as blue wing disease and is also caused by CAV transmitted from the breeders to the progeny.
when conditions of litter are very bad there is damage to the skin and bactyeria from the litter can infected the skin thus causing cellulitis (mainly E. coli) but this is a more management related problem
The rational given by Dr Seny seems Ok, apart from it IBD titre need to be kept high with use of inactivated vaccines . Any sort of Immunosuppression may be coupled with dermatitis need to be taken care of. certain vitamins deficiency may lead to it as well.