Investigations on the role of flea antigen in the pathogenesis of German shepherd dog pyoderma (GSP).

Skin reaction patterns to the intradermal injection of a whole-body flea extract were examined in five physically healthy dogs and in 24 dogs with German Shepherd dog Pyoderma (GSP) at 15 and 30 minutes and at 1, 2, 4, 8, 24, 48 and 72 hours after the injection. In 10 out of 24 GSP dogs a positive skin reaction was observed macroscopically after 15 minutes. Delayed reactions at 24 or 48 hours were not observed. In the control group neither immediate nor delayed reactions were observed. The histopathologic skin changes were basically the same in both groups: an initial polymorphonuclear reaction followed by a mononuclear cell reaction. In the GSP dogs, however, these changes occurred earlier and were more prolonged than in the normal dogs. No flea-antigen-specific IgGd antibodies could be demonstrated by enzyme-linked immunosorbent assay. It is concluded that delayed type hypersensitivity to flea antigen does not play a role in the pathogenesis of GSP. Immediate type hypersensitivity may contribute to the disease in some cases.