Dynamics of ILT spread and role of dust in epidemiology, diagnostics and control

University of New England

  • Project code: PRJ-010639

  • Project stage: Closed

  • Project start date: Tuesday, May 30, 2017

  • Project completion date: Thursday, January 20, 2022

  • Journal Articles From Project: A practical method for assessing infectious laryngotracheitis vaccine take in broilers following mass administration in water: Spatial and temporal variation in viral genome content of poultry dust af Veterinary Microbiology (Issue: 241 on 31/12/2020), Characterization of poultry house dust using chemometrics and scanning electron microscopy imaging Poultry Science (Issue: 100 on 15/6/2021), Assessment of A20 infectious laryngotracheitis vaccine take in meat chickens using swab and dust samples following mass vaccination in drinking water. Veterinary Microbiology (Issue: 251 on 31/12/2020), Comparison of tracheal and choanal cleft swabs and poultry dust samples for detection of Newcastle disease virus and infectious bronchitis virus genome in vaccinated meat chicken flocks. PLoS ONE (Issue: 16 on 15/6/2021), Methods to prevent PCR amplification of DNA from non-viable virus were not successful for infectious laryngotracheitis virus. PLoS ONE (Issue: 15 on 15/6/2020), A Melanin bleaching method to prevent non-specific immunostaining of chicken feathers. MethodsX (Issue: 7 on 31/12/2020), Marked differences in virulence of three Australian field isolates of infectious laryngotracheitis virus in meat and layer chickens. Avian Pathology (Issue: 49 on 31/12/2021), Detection of infectious laryngotracheitis virus (ILTV) in tissues and blood fractions from experimentally infected chickens using PCR and immunostaining analyses. Research in Veterinary Science (Issue: 134 on 30/3/2021), Genomic Stability for PCR Detection of Infectious Laryngotracheitis Virus and Infectious Bronchitis Virus in Poultry Dust Samples Stored Under Different Conditions Avian Diseases (Issue: 64 on 31/12/2020), Transmission of infectious laryngotracheitis virus vaccine and field strains: the role of degree of contact and transmission by whole blood, plasma and poultry dust. Veterinary Research (Issue: 52 on 30/6/2021), Airborne Transmission of Vaccinal and Wild Type Infectious Laryngotracheitis Virus and Non-infectivity of Extracts of Excreta from Infected Chickens. Avian Diseases (Issue: 65 on 31/3/2021), Variability in practices for drinking water vaccination of meat chickens against Infectious Laryngotracheitis Animal Production Science (accepted) (Issue: N/A on 30/11/2022), Field Application of qPCR Monitoring of Infectious Laryngotracheitis Virus in chicken house dust and its Role in Control of a Major Outbreak. Avian Diseases (in Press) (Issue: N/A on 30/11/2022), Protection provided by variable vaccination coverage with A20 vaccine against infectious laryngotracheitis challenge in meat chickens. Vaccine (submitted) (Issue: N/A on 31/12/2022), Protective effect in broiler chickens of variable vaccination coverage with the Serva live infectious laryngotracheitis vaccine against virulent challenge at 7 and 21 days post-vaccination. Avian Diseases (submitted) (Issue: N/A on 31/12/2022)

  • National Priority: CME-Priority 3-Contributing to efficient and secure chicken production systems

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Summary

ILTV is shed in faeces and is detectable at high levels in poultry dust both experimentally and in field samples using qPCR (Roy et al., 2015; 2016). ILTV infection is via the respiratory route and transmission in dust is strongly implicated in its epidemiology (Dufour-Zavala, 2008). This project will determine whether faecally shed ILTV is infective and what its likely epidemiological significance is. We assess the influence of temperature, humidity and sunlight on virus survival in that material using a cell culture assay validated by animal challenge. We have shown that ILTV in dust reflects ILTV shedding rate, and is readily detectable at high levels in field dust samples from vaccinated broiler flocks. We will therefore undertake longitudinal monitoring of vaccinated broiler, breeder and layer flocks (if supported by AECL) to determine if differences in dust levels may usefully indicate differences in shedding in response to stressors or differences in replication rate and transmission potential between vaccines or wild-type genotypes. We will also work with unvaccinated flocks to assess the potential of dust tests as a measure of cleanout success and a means of population level surveillance for ILTV. The project has industry support and UNE will bear the bulk of the salary costs by contributing 40% of a prospective post-doctoral fellow, Dr Priscilla Gerber to the project. We are aware of the Peter Groves ILT proposal and feel that our work is complementary to the work proposed in that project and would happily collaborate with him if required to.

Program

Chicken Meat

Research Organisation

University of New England

Objective Summary

The broad objective of this project is to improve our understanding and management of ILT in Australia by addressing the following specific research questions:

a) Is ILTV in faeces infective and does it comprise the bulk of detectable ILTV in dust?

b) What is the persistence of infectivity in dust and what factors influence this?

c) What are the longitudinal profiles of ILTV in dust in vaccinated broilers, broiler breeders and layers and what factors are associated with spiking in levels (eg. pickup, coming into lay, other stressors)?

d) Are differences in ILTV profiles in dust associated with differences in virulence and transmissibility between vaccine strains, and between wild-type strains of different groups?

e) Is use of dust testing useful for testing the efficacy of cleanout procedures and as a method for regional surveillance for ILTV in low prevalence areas (eg . Tamworth)?

 
The expected outcomes from addressing these questions are

  • Clear determination of whether the current transmission model for ILT (via respiratory aerosols) requires modification to account for aerosolised faecally shed virus. 
  • Determination of extent of ILTV survival in dust (irrespective of respiratory or faecal origin) and factors influencing it (eg. temperature, moisture and light).
  • Determination of whether monitoring of ILTV levels in dust in vaccinated and/or unvaccinated flocks is practicable and useful as either a research or a management tool.