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Infectious laryngotracheitis virus infection in chickens raised in Alberta: Molecular characterization and vaccine efficacy studies

2021 CPRF
Infectious laryngotracheitis virus (ILTV) is endemic in backyard flocks in some Canadian provinces. Sporadic outbreaks of ILTV are reported throughout Canada in both commercial and non-commercial flocks. Vaccine practices vary between provinces. Alberta (AB) only vaccinates its parental commercial flocks and recent reports show that only 13% of backyard owners vaccinate against the disease. There are two types of vaccines commercially available, the live attenuated vaccines and the recombinant viral vector vaccines. Alberta’s Ministry of Agriculture and Forestry recommends the use of the tissue culture origin (TCO) live attenuated vaccine in the face of outbreaks. However, there is evidence that shows that live attenuated vaccines can revert to their virulent from after bird-to-bird passages and cause disease. Further, recent studies have found that there are recombinant strains circulating the country as a product of misusage of TCO vaccines. These strains have often been associated to be more virulent and pathogenic than wild-type strains. Because of this, recombinant viral vector vaccines are considered the safest available option. Surveillance of circulating ILTV is needed to carry out an effective management of ILTV outbreaks. There is a lack of information about the molecular nature of the circulating ILTV strains associated with clinical disease in Canada. As such, the first objective of this research was to characterize ILTV isolates obtained from outbreaks in AB (n=46) and British Columbia (BC, n=9) from the year 2009 to 2018. In our findings show that the main cause of outbreaks in backyard poultry in AB are strains related to live attenuated vaccines and in a second degree wild-type strain. In BC, all processed samples were found to be related to live attenuated vaccines. For the second objective of our work, we wanted to determine if recombinant vaccines can protect chickens from ILTV induced by a wild-type strain from AB. Our results show that the vaccine can protect chickens from bodyweight loss and 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. This work emphasis on the need to develop efficient, accessible, and safer vaccines.
Tags :
Infectious laryngotracheitis virus,vaccine efficacy
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MSc Student

University of Calgary

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