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Gangrenous dermatitis, a subcutaneous infection in poultry that’s often due to clostridial organisms, is topping the list of health problems at some US poultry companies.

When it strikes, the disease reportedly affects 10% to 25% of flocks, with mortality running about 2% to 4% — and sometimes higher, says Dr. Charles Broussard, US poultry technical service director, Intervet/Schering-Plough Animal Health.

It was once thought that gangrenous dermatitis started with a scratch that became infected with a bacterium, which proliferated when birds were immunosuppressed due to diseases such as infectious bursal disease (IBD) or chick anemia virus (CAV). But control of IBD and CAV has not resolved the problem for most producers, nor have management changes such as low lighting or special diets aimed at keeping birds calm to prevent scratching, he says.

Broussard points to research conducted by Dr. Steve Collett of the Poultry Diagnostic and Research Center, University of Georgia, Athens. Collett demonstrated that immunosuppression due to IBD and CAV did not increase the severity of gangrenous dermatitis lesions. The Georgia veterinarian also theorized that the skin and scratches are not always the way that clostridial organisms enter the body and cause dermatitis, and that an alternative route is most likely the gastrointestinal tract.

Indeed, field experience and trials suggest that late coccidial cycling predisposes birds to the development of gangrenous dermatitis, Broussard says. Dermatitis tends to be seen in flocks on chemical-to-ionophore and straight ionophore programs that allow late coccidial cycling. In contrast, flocks that are vaccinated against coccidiosis at 1 day of age tend not to develop dermatitis.

“It’s possible that coccidiosis might have been a cause of dermatitis all along,” he says. “Coccidiosis vaccination itself is not effective against gangrenous dermatitis, but it prevents late coccidial cycling. Reducing the severity of gut epithelial damage from coccidia, or shifting the time at which it occurs, could be an important means of preventing or at least reducing the prevalence of gangrenous dermatitis.”

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