Marked differences in virulence of three Australian field isolates of infectious laryngotracheitis virus in meat and layer chickens

Title
Marked differences in virulence of three Australian field isolates of infectious laryngotracheitis virus in meat and layer chickens
Publication Date
2020
Author(s)
Shahid, Nazir
Yegoraw, Addisu A
Charlesworth, Richard P G
( author )
OrcID: https://orcid.org/0000-0002-4557-1419
Email: rcharle3@une.edu.au
UNE Id une-id:rcharle3
Williamson, Sarah
Sharpe, Sue
Walkden-Brown, Stephen W
( author )
OrcID: https://orcid.org/0000-0002-0638-5533
Email: swalkden@une.edu.au
UNE Id une-id:swalkden
Gerber, Priscilla F
( author )
OrcID: https://orcid.org/0000-0002-8343-8299
Email: pgerber2@une.edu.au
UNE Id une-id:pgerber2
Type of document
Journal Article
Language
en
Entity Type
Publication
Publisher
Taylor & Francis
Place of publication
United Kingdom
DOI
10.1080/03079457.2020.1801987
UNE publication id
une:1959.11/30958
Abstract
The objectives of this study were to compare the virulence of contemporary infectious laryngotracheitis virus (ILTV) field isolates of classes 9, 10, and 14 in meat and layer chickens, and to evaluate cloacal and oropharyngeal swabs and dust as sample types for ILTV detection. A total of 211 chickens were divided into groups and inoculated with ILTV class 9, 10, or 14, or sham-inoculated via eye drop at 15 or 22 days of age. Chickens were euthanized at 5 and 9 days post-infection. Virulence was assessed by scoring of clinical signs (conjunctivitis, dyspnoea, and demeanour), ILTV genomic copies (GC) in oropharyngeal and cloacal swabs, mortality and microscopic lesions in conjunctiva and trachea. Class 14 caused subclinical infection, while inoculation with class 9 or class 10 resulted in severe clinical signs and microscopic lesions. Compared to class 14 (2.25 ± 0.36 log10 GC), higher viral load was observed in oropharyngeal swabs of classes 9 (7.86 ± 0.48) and 10 (7.53 ± 0.36), with a higher proportion of positive oropharyngeal and cloacal swabs in the latter groups (P < 0.0001). Viral detection in cloacal swabs was delayed at early stages of infection compared to oropharyngeal swabs. Dust samples from class 9- and class 10-inoculated groups showed a trend towards higher GC than that of class 14. Overall, clinical scores, mortality, viral load, and microscopic lesions were similar for classes 9 and 10, but class 9 caused more severe disease in layer chickens than meat chickens. In summary, ILTV classes 9 and 10 exhibited severe virulence, while class 14 exhibited very mild virulence.
Link
Citation
Avian Pathology, 49(6), p. 600-610
ISSN
1465-3338
0307-9457
Pubmed ID
32720515
Start page
600
End page
610

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