Synonyms LT & ILT
Gallid herpesvirus 1
Occurrence and Economic Significance
Laryngotracheitis is distributed worldwide but is frequently regional in prevalence or seasonal in incidence. Mild LT results in lowered growth rate and feed conversion efficiency and elevated mortality and condemnation in broilers. Decreased egg production occurs following exposure of mature susceptible flocks. Moderate to severe strains of LT result in proportionately higher morbidity and mortality in both mature and rearing stock with losses approaching 50% with concurrent environmental stress and other infections.
Direct contact with affected chickens or recovered permanent carriers
through dust-laden vehicles
contaminated personnel or equipment
Wind dispersal over 3 km
The severity of LT is influenced by the strain of virus, immune status of the flock and environmental conditions
embryos or tissue culture
egg-embryo propagated vaccine administered in drinking water to broilers, immature breeders and commercial pullets at 14 – 20 days.
The spray route is less effective especially with tissue-culture propagated vaccines
Commercial egg pullets and breeders are vaccinated at 6-10 weeks of age by administration of tissue-culture origin modified live virus which has a lower potential for reversion to virulence than chick-embryo origin vaccine virus. Since flocks immunized with chick embryo origin virus serve as permanent carriers of the vaccine virus, LT may be transmitted to susceptible flocks or to unaffected areas following movement of vaccinates. New vaccine candidates based on recombinant DNA technology should overcome the problem of reversion associated with live modified vaccines.
Fowl cholera is a contagious, bacterial disease that affects domestic and wild birds worldwide. It usually occurs as a septicemia of sudden onset with high morbidity and mortality, but chronic and asymptomatic infections also occur.
Newcastle disease is an infection of domestic poultry and other bird species with virulent Newcastle disease virus (NDV). It is a worldwide problem that presents primarily as an acute respiratory disease, but depression, nervous manifestations, or diarrhea may be the predominant clinical form. Severity depends on the virulence of the infecting virus and host susceptibility. Occurrence of the disease is reportable and may result in trade restrictions.
Fowl cholera is the reason for great economic loss of poultry in bangladessh