Submitted to: Avian Pathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/20/2010
Publication Date: 8/20/2010
Citation: Li, G., Lillehoj, H.S., Lee, K.Y., Park, M.S., Jang, S.I., Pages, M., Buchan, G.R., Gay, C.G., Ritter, D., Bautista, D., Newumann, A.P., Rehberger, T.G., Siragusa, G.R. 2010. An outbreak of gangrenous dermatitis in commerical broiler chickens. Avian Pathology. 39(4):247-253. Interpretive Summary: Gangrenous dermatitis (GD) is caused by the Gram-positive spore-forming anaerobic bacilli Clostridium perfringens (CP) type A and C. septicum (CS) and both CP and CS may synergistically contribute to severe disease pathology associated with GD. However, factors which contribute to the outbreak of GD remains unknown. While the incidence of GD outbreaks has decreased with the advent of in-feed antibiotics, recent voluntary or legally-mandated withdrawal of antibiotic growth promoters (AGPs) and anti-coccidial drugs (e.g. ionophores) threatens the re-emergence of GD as a major emerging disease in poultry and turkey. According to the United States Animal Health Association’s Committee on Transmissible Diseases of Poultry and other Avian Species, GD has consistently ranked as a top priority disease for the poultry industry in recent years. In this report, ARS scientists working together with scientists from University of Delaware Extension Service, Mountaire Farms and Danisco Laboratory investigated a field outbreak of GD in the Eastern Shore farms in Maryland and conducted a detailed molecular characterization, immunohistology and enzyme-linked immunoassays to identify pathogens involved in GD in order to better understand host-pathogen immunobiology. Immunofluorescence staining revealed Clostridium-like bacilli in skin and intestine and CP and CS genomic sequences were identified by PCR in bacterial cultures isolated from skin, muscle, and intestine from diseased birds. Immunological studies revealed heightened inflammatory response and high levels of pro-inflammatory cytokines in local tissues affected by GD. These results provide the basic knowledge on pathogenesis mechanism of GD that will help to understand innate and adaptive immune response of GD for development of comprehensive treatment of this disease.
Technical Abstract: Gangrenous dermatitis (GD) is an emerging disease with increasing economic importance. This experiment was undertaken to describe symptoms, patholgocial changes and diagnosis of GD and to study their immunopathology and cytokine expression alterations. In addition to description of symptoms, pathological lesions and diagnosis of GD, ten GD-likely birds, and 5 clinical-healthy birds were selected for sample collection to study nitric oxide (NO), acute phage protein (AGP), immunopathologic changes and the alterations of cytokine expression. There observed typical clinical symptoms, gross lesions included discoloration of skin around the breast, abdomen, and wings as a result of congestion, necrosis, and emphysema (gas accumulation), discoloration of muscle with serosanguineous fluid, and fibronecrotic enteritis. Histopathological findings included hemorrhagic lesions, degeneration, and necrosis of parenchymatous cells, especially of skin, muscles, and intestines. Immunofluorescence staining revealed Clostridium-like bacilli in skin and intestine. C. perfringens (CP) and C. septicum (CS) genomic sequences were identified by PCR in bacterial cultures isolated from skin, muscle, and intestine and in frozen tissues from diseased birds. Serological analysis demonstrated that both diseased and healthy birds had high antibody titers against CP, CS, Eimeria, CAV, and IBDV. For the immunopathology and cytokine expression changes, The splenocyte proliferative function stimulated with Con A and LPS was significantly depressed in GD-likely chickens compared with those of clinical healthy chickens; GD chickens could produced more NO and a-1-AGP in serum; More K55, K1, CD8, MHC II positive cells in skin, and K55, K1, CD8, TCR1, TCR2, Bu1, MHC II positive cells in intestine of GD birds were observed; The expression levels of mRNAs encoding immune related cytokines decreased and pro-inflammatory and chemokine increased in GD birds. These results provide the foundation for elucidation of pathogenesis mechanism of GD and for future analysis of innate and adaptive immune response of GD and comprehensive prophylaxis and treatment of this disease.