Seroprevalence of Ornithobacterium rhinothracheale Infection in Commercial Layers in Tunisia

Ornithobacterium rhinotracheale (ORT) infection is a worldwide disease in commercial poultry production. It is caused by a gram-negative bacterium, inducing respiratory and articular infections. The present study investigated the seroprevalence of ORT in commercial laying chicken farms in the Sfax region of South-eastern Tunisia. Diagnosis of ORT is based on the clinical signs such as respiratory distress, sneezing, cough, and limping, gross pathology in post-mortem examination (fibrinous tracheitis, fibrinous pneumonia, caseous arthritis, and tendinitis), and laboratory investigations, including isolation and identification, molecular and serological analysis. In the current study, 470 serum samples were collected from 25 commercial layer flocks (18 to 20 blood samples/flock) and tested using an indirect enzyme-linked immunosorbent assay (ELISA), which revealed that all 25 flocks (100%) demonstrated evidence of past or recent ORT infection. Seropositivity of the tested sera indicated the presence of antibodies against ORT, ranging widely from 7.69% to 100% within individual layer hens flocks. The average antibody levels varied considerably among flocks, from 1425.67 to 15233 in different flocks. The current findings indicated widespread ORT exposure in commercial layer farms in the Sfax region of South-eastern Tunisia, signifying the potential for horizontal transmission of ORT, particularly in multi-age layer integrations where older flocks can act as a source of infection for younger pullets.