Infectious laryngotracheitis infection in chickens raised in Western Canada: Molecular characterization and vaccine efficacy studies
Date
2021-07-30
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Abstract
Genomic surveillance of circulating infectious laryngotracheitis virus (ILTV) in specific geographical areas is vital for the control of the disease caused by ILTV, infectious laryngotracheitis (ILT). ILTV is endemic in backyard flocks in some Canadian provinces including Alberta (AB). Sporadic outbreaks of ILTV are reported throughout Canada in both commercial and non-commercial poultry flocks. However, there is a lack of information on the molecular nature of circulating ILTV strains associated with ILT in Canada. Vaccines are used for the control of ILT, and vaccination is employed only in certain provinces due to concerns of limitations of the currently available vaccines. In AB, only breeder flocks are vaccinated routinely in addition to a portion of the backyard flocks. Out of the two commercially available vaccines, the recombinant viral vector vaccines are considered the safest. This is due to their lack of bird-to-bird transmission and reversion to a virulent form. The first part of the thesis work was focussed on genotyping ILTV isolates linked to ILT clinical cases in AB and British Columbia (BC). Through partial sequencing of open reading frame (ORF) a and b using Sanger sequencing technology, we were able to genotype 27 ILTV isolates from AB and 5 ILTV isolates from BC. We demonstrated that the most common genotype causing ILT outbreaks in AB were chicken embryo origin (CEO) vaccine revertant ILTV strains and then, wild-type ILTV strains. In BC, we identified CEO vaccine and CEO revertant ILTV strains as cause of ILT outbreaks. The second part of this thesis was focussed on determining if recombinant herpesvirus of turkeys- laryngotracheitis (rHVT-LT) commercial vaccine could protect chickens from ILT induced by a wild-type ILTV strain isolated from AB. Our results showed that the rHVT-LT can decrease viral shedding though the oropharyngeal route. However, it did not mitigate clinical signs at the peak of the disease, and it failed to reduce viral replication in the feather tips. Overall, the work described in the thesis contributed to the knowledge on ILTV molecular epidemiology and vaccine-mediated control of ILT.
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Keywords
infectious laryngotracheitis, Sanger sequencing, live attenuated vaccine, rHVT-LT, chicken, back yard poultry
Citation
Barboza Solis, C. (2021). Infectious laryngotracheitis infection in chickens raised in Western Canada: Molecular characterization and vaccine efficacy studies (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.