Report of outbreak of Infectious Laryngotracheitis inthree layer flocks in Semnan Province

Infectious Laryngotracheitis (ILT) is an acute infection of the upper respiratory tractin chickens. ILT virus is a member of the Herpesviridae family; Gallid herpesvirus. Three layer pullet flocks (Sorkheh, Semnan Province) which composed of ۸۳,۰۰۰, ۴۰,۰۰۰ and ۸۹,۰۰۰ birds were referred to veterinary research and teaching clinic of Semnan University. An outbreak of a respiratory distressin clinical signs, such as coughing,sneezing, nasal discharge andlacrimation was detected on November ۲۰۱۹. The mortality rate was ۳.۵ to ۸%. The affected flocks’ age was ۹ to ۱۲ weeks. After necropsy,the main signs were seen in larynx and trachea with massive hemorrhage and tracheitis with no signs in lungs and air sacs.Segments of trachea approximately۳cm caudal to the larynx was were in ۱۰% buffered formalin and processed routinely. Sections were cut in ۵ microns and stained with hematoxylin & eosin. There was massive fibrinous hemorrhagic exudate in trachea and epithelium of trachea was necrotic and lymphocytic infiltration was seen.Theeosinophilic intra nuclear inclusion bodies were observed in epithelial cells of trachea. Giant cell syncytia were observed in epithelial cells of trachea, too.Also, in necropsy, some sections from trachea and conjunctiva were cut for PCR testing and the result confirmed the existence of ILTvirus. ILT vaccination is forbidden in poultry flocksin Semnan province. Vaccination program is dependent on local Iran Veterinary Organization policy. Moreover, some provinces such as Mazandaran, Guilan and Semnan are not permitted to vaccinate for ILT. This is the first report of ILTincident in Semnan; and it could be necessary to revise and change ILT control strategy in this province.

کلیدواژه ها:

Histopathology ، Infectious Laryngotracheitis ، layer pullet ، PCR ، Semnan Province ، Vaccination