Successful control of infectious laryngotracheitis on a multiage laying hen farm

INFECTIOUS laryngotracheitis (ILT) caused by Gallid herpesvirus 1 is an acute infection associated with respiratory distress, mortality and decreased egg production in poultry. The virus naturally infects chickens and, more rarely, pheasants, peacocks and turkeys (Guy and Garcia 2008). In chickens, ILT is characterised by periods of latency in recovered birds (Bagust and others 1986) followed by episodes of intermittent virus shedding, which may be associated with stresses such as re-housing and start of laying (Hughes and others 1989 and 1991). In many parts of the world, ILT is an endemic disease that is controlled by vaccination. Major disadvantages of modified live (ML) vaccines include establishment of latency and regained virulence (Bagust 1986, Guy and others 1991). Eradication is difficult because of latency, but will likely be achievable with recombinant vaccines (Bagust and Johnson 1995). Before the case reported here, the last ILT outbreak in a commercial flock in Sweden occurred in 1959 (Swedish Board of Agriculture, unpublished observation). Since 1997, more than 100 outbreaks have been diagnosed countrywide in Sweden in backyard chickens and show breeds and two outbreaks occurred in 2007 in commercial layers. An ML vaccine (Nobilis ILT; Intervet/Schering-Plough Animal Health) became available in 2006 for non-commercial chickens. This short communication describes an outbreak on a multiage laying hen farm in addition to successful control measures. The …