| Infectious laryngotracheitis (ILT) is a respiratory disease of chickens caused by an alphaherpesvirus. Disease results in production losses due to condemnations, mortality and decreased egg production. ILT has been controlled using modified-live vaccines. Problems with vaccination include vaccine spread, reversion to virulence, development of carrier state with shedding, and adverse reactions.; Two experimental recombinant vaccines, Fowlpox Virus/Infectious Laryngotracheitis Virus vaccine (FPV/ILTV) and Herpes Virus of Turkey/Infectious Laryngotracheitis Virus vaccine (HVT/ILTV), expressing genes of ILTV, were tested in Specific-Pathogen-Free (SPF) chickens against PLT standard USDA virus challenge.; In experiment 1, 280 SPF chickens were divided into 6 treatment and 1 control groups. Forty chickens per group were challenged at 28 days with ILTV, using low (10{dollar}sp{lcub}3.5{rcub}{dollar}), standard (10{dollar}sp{lcub}4.0{rcub}{dollar}), or high (10{dollar}sp{lcub}4.5{rcub}{dollar}) doses and administration by the infraorbital sinus injection (IS) or the intratracheal inoculation (IT). This study demonstrated that clinical signs and mortality depended on the titer and challenge routes. Higher doses and IT challenges resulted increased mortality and shorter incubation period.; In experiment 2, 450 SPF chickens were divided into 6 treatment and 3 control groups. Chickens were immunized with a commercial cell embryo origin (CEO-moderate) vaccine or with a experimental recombinant FPV/ILTV vaccine at 1 or 21 days of age. At 42 days of age, chickens were challenged with the ILTV standard dose by the IS or IT routes. Chickens immunized at 1 day of age with CEO-moderate (CEO-M) vaccine had adverse vaccine reactions with 19% of mortality. After the challenge the CEO vaccinated groups had higher protection than the recombinant FPV/ILTV vaccinated groups. There were no adverse reactions or mortality, resulted from the recombinant vaccinated groups.; In experiment 3, 450 SPF chickens were divided into 5 treatment and 3 control groups. Chickens were immunized with commercial CEO-mild (CEO-m) at 1 day of age, CEO-M at 21 days of age, or recombinant HVT/ILTV vaccine at 1 day of age. At 42 days of age, chickens were challenged with ILTV. Chickens immunized with CEO-m vaccine at 1 day of age showed adverse reactions with 7% of ILT (+). The recombinant HVT/ILTV vaccine provided 100% protection.; The efficacy and safety of recombinant FPV/ILTV and HVT/ILTV vaccines were demonstrated. HVT/ILTV induced superior protection compared to the FPV/ILTV. The protection of the HVT/ILTV was comparable with the CEO vaccines. |
