Abstract
Non-vaccinated flocks and vaccinated flocks against infectious laryngotracheitis (ILT) virus were adjacently raised in the same pen at a layer chicken farm in Chiba Prefecture, Japan. In January 2009, non-vaccinated flocks showed watery eyes, swelling of the infraorbital sinuses, and serious conjunctivitis. Six chickens were examined. Similar pathological and microbiological findings were obtained from the chickens. Necropsy revealed yellowish caseous exudate in the infraorbital sinuses and nasal cavities, and hypertrophy of the nasal mucosa. Histopathologically, many intranuclear inclusion bodies in the epithelial cells and fibrinopurulent exudates with gram-negative bacilli were detected in the infraorbital sinuses and nasal cavities. On microbiological examination, ILT virus and Pasteurella multocida (P. multocida) capsular type A were isolated from swabs of the infraorbital sinus. The virus showed small unclear border plaques on the chorioallantoic membrane, and consistent RFLP patterns and ICP4 gene sequences with the vaccine strains of vaccinated flocks. This farm had not had an occurrence of ILT for a long time, and vaccinated flocks were in peak laying season. These results indicated that the isolated virus was an ILT vaccine strain of vaccinated chickens, and it was transmitted to the non-vaccinated chickens. The ILT virus and P. multocida infection would have induced the facial swelling.
