Gallid alphaherpesvirus 1

Gallid alphaherpesvirus 1 (GaHV-1) is a species of virus in the order Herpesvirales, family Herpesviridae, subfamily Alphaherpesvirinae, and genus Iltovirus. Originally recognised in chickens in the United States in 1926, this virus causes avian infectious laryngotracheitis (abbreviated as AILT, ILT, or LT), a potentially fatal, economically deleterious disease, widely recognised as one of the most contagious diseases in the poultry industry. The virus and its associated disease also occur in pheasants.

Taxonomy
Gallid alphaherpesvirus 1 is classified in the genus Iltovirus. The only other species in this genus, and therefore its closest known relative, is Psittacid alphaherpesvirus 1, which affects parrots.

There are two other herpesviruses that affect chickens: Gallid alphaherpesvirus 2 (cause of Marek's disease) and Gallid alphaherpesvirus 3. Both of these are in a separate genus to Gallid alphaherpesvirus 1; Mardivirus, which is united with Iltovirus under the same subfamily; Alphaherpesvirinae.

Transmission
GaHV-1 is shed in respiratory secretions and transmitted by droplet inhalation or via fomites. A previously unexposed flock will develop cases for two to eight weeks following introduction. The incubation period is two to eight days.

Clinical signs and diagnosis
Symptoms include coughing, sneezing, head shaking, lethargy, discharge from the eyes and nostrils (sometimes bloody), and difficulty breathing. The name comes from the severe inflammation of the larynx and trachea. A diphtheritic membrane may form in the trachea, causing obstruction. There may be problems in egg laying and the production of abnormal or thin-shelled eggs. Mortality is typically less than 15 percent.

Histopathology, PCR, ELISA, immunofluorescent staining, and viral isolation are all possible methods of diagnosis.

Treatment and control
A vaccine is available (ATCvet code: ), but it is susceptible to undesired recombination and it does not prevent latent infections. It can be used during an outbreak to decrease morbidity and deaths.

A confirmed case will usually result in the establishment of a quarantine zone around the farm. Inside this quarantine zone, poultry workers will avoid poultry farms to prevent the spread of the virus. Biosecurity measures including quarantine, isolation, and disinfection are very important in controlling the spread of an outbreak.