Immunohistochemical evaluation of TLR-4, HSP-70 and caspase-3 expressions in lesioned areas in ecthyma disease

Contagious ecthyma (Orf) is an economically significant disease caused by a parapoxvirus (ORFV) belonging to the Poxviridae family, affecting sheep, goats, and wild small ruminants. It is characterized by the presence of thick, crusted lesions around the mouth, lips, tongue, and nostrils. The infection predominantly affects animals under one year of age, with the highest incidence observed in those between 3 to 4 months old. In immunocompromised young animals, the disease can result in nearly 100% mortality. The virus is highly resilient, remaining viable in the environment for months or even years. Due to the painful oral lesions, affected animals are unable to feed properly, leading to malnutrition, increased mortality, and significant production losses. The virus exhibits a strong tropism for epithelial tissue and replicates in epidermal keratinocytes. Although keratinocytes play a protective role in host defense, ORFV can efficiently evade these mechanisms. Toll-like receptor 4 (TLR-4), heat shock protein 70 (HSP-70), and Caspase-3 are molecules known to play crucial roles in cellular stress responses, inflammation, and apoptosis, and are thought to be significant in the pathogenesis of infectious diseases. The aim of this study was to investigate the expression of TLR-4, HSP-70, and Caspase-3 in lesional tissues of animals affected by ecthyma. For this purpose, 37 ecthyma lesions were examined histopathologically and immunohistochemically. The expression levels of all three markers were found to be increased in both epithelial and inflammatory cells within the lesional areas. The findings suggest that TLR-4, HSP-70, and Caspase-3 play important roles in the pathogenesis of ecthyma and may potentially serve as diagnostic or therapeutic targets in the future. Further studies are warranted to elucidate their precise roles.