A five-year surveillance study of vaccination schedules using viral-vectored vaccines against infectious laryngotracheitis in a high-density layer region

Authors: SANTOS, WILLIAN - Universidade Federal De Minas Gerais; Spatz, Stephen; ECCO, ROSELENE - Universidade Federal De Minas Gerais; WENCESLAU, RAPHAEL - Universidade Federal De Minas Gerais; HERGOT, IZABELLA - Mining Institute Of Agriculture; DE ROCHA, CHRISTIANE - Universidade Federal De Lavras; FERREIRA, HELENA - Universidade De Sao Paulo; RESENDE, MAURICIO - Universidade Federal De Minas Gerais; MARTINS, NELSON - Universidade Federal De Minas Gerais; DE OLIVEIRA, LETICIA - Universidade Federal De Minas Gerais; LEÃO, PHILIPE - Universidade Federal De Minas Gerais

Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/24/2022
Publication Date: 6/6/2022
Citation: Santos, W.H., Spatz, S.J., Ecco, R., Wenceslau, R., Hergot, I.G., De Rocha, C.M., Ferreira, H.L., Resende, M., Martins, N.R., De Oliveira, L.B., Leão, P.A. 2022. A five-year surveillance study of vaccination schedules using viral-vectored vaccines against infectious laryngotracheitis in a quarantine high-density layer region. Avian Diseases. 42:Article e07037. https://doi.org/10.1590/1678-5150-PVB-7037.
DOI: https://doi.org/10.1590/1678-5150-PVB-7037

Interpretive Summary: ILT continues to be a problem in Brazil and according to an OIE (Office International des Epizooties - World Organization for animal health) report, ILT, as of 2018, was present in more than one region. Large field studies on the effectiveness of viral-vectored recombinant vaccines in controlling ILT outbreaks have not been previously reported. Here, we report a prospective longitudinal observational study on the efficacy of viral-vectored recombinant vaccines against ILT in high- density (eight million) multiple- age layer hens from a single quarantined region of Brazil. During this long-term monitoring study from 2014 to 2018, various clinical and molecular methods were used to investigate the occurrence of GaHV-1 infection and ILT clinical disease in layer hens vaccinated with either FPV or HVT-based recombinant vaccines using different immunization protocols.

Technical Abstract: The effectiveness of vectored recombinant vaccines to control infectious laryngotracheitis (ILT) in chickens from a region (State of Minas Gerais, Brazil) with ~10 million layers was evaluated under field conditions from 2014-2018. During this period, only recombinant turkey herpesvirus (rHVT) or fowl poxvirus (rFPV) vaccines that express antigens of infectious laryngotracheitis virus (Gallid herpesvirus-1; GaHV-1) were used. Layer chickens (n=1,283), from eight different egg-producing companies, were individually sampled and examined (active surveillance), and in instances when government poultry health veterinarians were notified due to respiratory disease (passive surveillance). Clinical, macroscopic, and histopathology examinations were performed to diagnose ILT as well as molecular techniques for the detection and characterization of the GaHV-1 DNA from the trachea and trigeminal ganglia (TG). The layer hens sampled and examined belonged to flocks and farms that used different vaccination protocols (non-vaccinated, single dose vaccination, and prime/ boost vaccination). This is the first long-term field study of the effectiveness of ILT vectored vaccines in a high-density multiple age layer hen region. Using various diagnostic methods, the occurrence of GaHV-1 infection and ILT clinical disease in layer hens vaccinated with vectored recombinant vaccines in one quarantined region of Brazil were investigated. The number of ILTV positive chickens by PCR and ILT clinical disease cases was lower in farms when all chickens were vaccinated with at least one vaccine. However, the difference in the detection rates of GaHV-1 infection was significant only when compared farms with prime/boost and farms using single dose of HTV-LT.