"two lines of thought have developed"
DR. RICK PHILLIPS

Following the presentations by Collett and Roney, the symposium's moderator, Dr. Rick Phillips of Schering-Plough Animal Health, noted that "two lines of thought have developed" about gangrenous dermatitis.

One pegs GD as a "scratch-related issue," while the other asks whether GD is coming through the gut as well," he said.

"If you look at other species - cattle and sheep, for example - clostridia play a major role, it's gut associated. It showers the blood, settles out and then creates problems later," Phillips added.

The veterinarian thinks that vulnerability in both the skin and in the lining of the intestine probably plays a role in allowing GD to gain entry.

"One of the things we've seen in posting sessions coast to coast is that operations that have different kinds of programs for managing coccidiosis often have dramatic differences in their rates of dermatitis," he said.

What was notable in many of the operations that had lowered their rates of GD was that they had used coccidiosis vaccine to modify the window of coccidial cycling. "On their earlier programs, they were cycling about 8 days earlier than with the vaccine. And that peak cycling was occurring right at the time the dermatitis would kick in," Phillips reported. When those operations began using the vaccine, they effectively moved outside of that coccidia-cycling window and the rate of dermatitis decreased significantly.

Phillips emphasized that it is by no means clear the exact role that vaccination can play in managing dermatitis. More work needs to be done to determine how coccidiosis and gangrenous dermatitis interact with each other.

But, he added, "Doing that kind of research is a priority for us. It's very important for us in the industry to decide if the intestinal issue is associated with the development of GD. Because if it is, that demands a whole different management strategy."

Spring 2008

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