Pathogenicity differences between South African isolates of Ornithobacterium rhinotracheale.

Three selected South African Ornithobacterium rhinotracheale field isolates were identified and inoculated via the caudal abdominal airsac into 28-day-old broilers, which were monitored under controlled laboratory conditions. It was concluded from data that the O. rhinotracheale isolates were capable of causing primary disease, with statistically significant resultant mass loss. Respiratory and arthritis symptoms were reproduced. However, no sinusitis was observed. Airsacculitis- and arthritis-lesion scoring techniques showed significant pathogenicity differences between isolates. Furthermore, differences in symptomatology were also seen between isolates. A highly significant reisolation of O. rhinotracheale was made from the brains of broilers challenged with isolate 2. In conclusion, the economic importance and financial loss due to Ornithobacterium rhinotracheale infections in poultry were highlighted.