Outbreak of Infectious Laryngotracheitis Following Vaccination in Pullet Flock
2001
Ebrahimi, M.M., Razi Vaccine and Serum Reseach Institute. Tehran. Iran. | Shahsavandi, S., Razi Vaccine and Serum Reseach Institute. Tehran. Iran. | Gholami, M.R., Razi Vaccine and Serum Reseach Institute. Tehran. Iran.
An outbreak of infectious laryngotracheitis (ILT) in a large flock following vaccination against ILT is described. Laryngotracheal samples were obtained from some of infected pullets. Isolation and characterization of agent virus were carried out on chorioallantoic membrane (CAM) of embryonated specific pathogen free (SPF). Several pocks on CAM were observed after five days of incubation. The isolated virus was neutralized by mono-specific antiserum against vaccinal ILT virus. For evaluation of pathogenicity of the isolated virus twenty 8-week-old SPF chicks were eye drop inoculated with 103 and 104 EID50% virus respectively and observed upto 7 days. Only two chickens in group 2 were shown moderate signs including conjunctivitis and swelling of lower eyelid. Histopathologic features in tracheal of both infected pullets and experimental SPF chicks were epithelial hyperplasia, multinuclear giant cells (syncytia) with eosinophilic intranuclear inclusion bodies and infiltration of inflamatory cells, which was milder in latter. These findings indicate that the isolated virus was similar to vaccine strain. Our study suggests that under improper ILT vaccine administration and generally bad management practice conditions, the ILT may occur following vaccination.
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