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Severe necrotic dermatitis in the combs of line 63 chickens infected with Marek’s disease virus

Author:
Heidari, Mohammad, Wang, Dan, Fitzgerald, Scott D., Sun, Shuhong
Source:
Avian pathology 2016 v.45 no.5 pp. 582-592
ISSN:
1465-3338
Subject:
Mardivirus, Micrococcus, T-lymphocytes, cellulitis, chickens, connective tissues, dermatitis, etiological agents, histopathology, inducible nitric oxide synthase, interleukin-12, interleukin-18, interleukin-6, interleukin-8, macrophages, necrosis, neoplasms, oncogenes, quantitative polymerase chain reaction, spleen, viruses, wattles
Abstract:
Marek’s disease virus (MDV), the aetiological agent of Mareks' disease (MD), is a highly cell-associated oncogenic α-herpesvirus that replicates in chicken lymphocytes and establishes a latent infection within CD4 ⁺ T cells. We investigated the possible effect of MDV infection on the exacerbation of necrotic dermatitis in the combs of MD-susceptible (7 ₂) and MD-resistant (6 ₃) chicken lines at 21 days post infection. MDV-infected birds of line 6 ₃ are relatively resistant to tumour development but exhibit an unusual necrosis of combs, wattles, and footpads that is intensified when infected with MDV. Chickens from line 7 ₂, on the other hand, are highly susceptible to MDV infection and tumour development. Real-Time PCR analysis revealed that IL-6, IL-8, IL-12, IL-18, iNOS, and IFNγ were all up regulated in the comb tissues of MDV-infected susceptible line 7 ₂ with no visible necrotic damage. With the exception of IL-8 and iNOS, the expression of all the other tested genes was barely detected in the necrotic combs of the resistant line 6 ₃. Real-Time PCR analysis revealed the MDV meq oncogene transcripts in the spleen tissues of both infected lines but in the comb tissues of only the susceptible line 7 ₂. A significant infiltration of macrophages and lymphocytes was detected in the comb tissues of both resistant and susceptible lines. Histopathological analysis also showed thinning and erosion of epidermis and inflammation, lympho-plasmocytic infiltration, heterophilic, and histocytic cellulitis within the connective tissues of the necrotic combs. Gram stain of the sectioned frozen comb samples exposed the presence of Gram-positive micrococcus.
Agid:
5555032