{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,11,4]],"date-time":"2026-11-04T13:05:18Z","timestamp":1793797518787,"version":"4.6.1"},"reference-count":34,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2021,3,24]],"date-time":"2021-03-24T00:00:00Z","timestamp":1616544000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100012236","name":"Alberta Agriculture and Forestry","doi-asserted-by":"publisher","award":["10020202"],"award-info":[{"award-number":["10020202"]}],"id":[{"id":"10.13039\/100012236","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Egg Farmers of Alberta","award":["10022788"],"award-info":[{"award-number":["10022788"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Viruses"],"abstract":"<jats:p>Infectious laryngotracheitis (ILT) is an infectious upper respiratory tract disease that impacts the poultry industry worldwide. ILT is caused by an alphaherpesvirus commonly referred to as infectious laryngotracheitis virus (ILTV). Vaccination with live attenuated vaccines is practiced regularly for the control of ILT. However, extensive and improper use of live attenuated vaccines is related to vaccine viruses reverting to virulence. An increase in mortality and pathogenicity has been attributed to these vaccine revertant viruses. Recent studies characterized Canadian ILTV strains originating from ILT outbreaks as related to live attenuated vaccine virus revertants. However, information is scarce on the pathogenicity and transmission potential of these Canadian isolates. Hence, in this study, the pathogenicity and transmission potential of two wildtype ILTVs and a chicken embryo origin (CEO) vaccine revertant ILTV of Canadian origin were evaluated. To this end, 3-week-old specific pathogen-free chickens were experimentally infected with each of the ILTV isolates and compared to uninfected controls. Additionally, na\u00efve chickens were exposed to the experimentally infected chickens to mimic naturally occurring infection. Pathogenicity of each of these ILTV isolates was evaluated by the severity of clinical signs, weight loss, mortality, and lesions observed at the necropsy. The transmission potential was evaluated by quantification of ILTV genome loads in oropharyngeal and cloacal swabs and tissue samples of the experimentally infected and contact-exposed chickens, as well as in the capacity to produce ILT in contact-exposed chickens. We observed that the CEO vaccine revertant ILTV isolate induced severe disease in comparison to the two wildtype ILTV isolates used in this study. According to ILTV genome load data, CEO vaccine revertant ILTV isolate was successfully transmitted to na\u00efve contact-exposed chickens in comparison to the tested wildtype ILTV isolates. Overall, the Canadian origin CEO vaccine revertant ILTV isolate possesses higher virulence, and dissemination potential, when compared to the wildtype ILTV isolates used in this study. These findings have serious implications in ILT control in chickens.<\/jats:p>","DOI":"10.3390\/v13040541","type":"journal-article","created":{"date-parts":[[2021,3,24]],"date-time":"2021-03-24T21:36:51Z","timestamp":1616621811000},"page":"541","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":10,"title":["Pathogenic and Transmission Potential of Wildtype and Chicken Embryo Origin (CEO) Vaccine Revertant Infectious Laryngotracheitis Virus"],"prefix":"10.3390","volume":"13","author":[{"given":"Ana","family":"Perez-Contreras","sequence":"first","affiliation":[{"name":"Health Research Innovation Center 2C53, Faculty of Veterinary Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6378-8171","authenticated-orcid":false,"given":"Catalina","family":"Barboza-Solis","sequence":"additional","affiliation":[{"name":"Health Research Innovation Center 2C53, Faculty of Veterinary Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9767-8341","authenticated-orcid":false,"given":"Shahnas M.","family":"Najimudeen","sequence":"additional","affiliation":[{"name":"Health Research Innovation Center 2C53, Faculty of Veterinary Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9118-2721","authenticated-orcid":false,"given":"Sylvia","family":"Checkley","sequence":"additional","affiliation":[{"name":"Health Research Innovation Center 2C53, Faculty of Veterinary Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Frank van der","family":"Meer","sequence":"additional","affiliation":[{"name":"Health Research Innovation Center 2C53, Faculty of Veterinary Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Tomy","family":"Joseph","sequence":"additional","affiliation":[{"name":"Animal Health Centre, Ministry of Agriculture, Abbotsford, BC V3G 2M3, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Robin","family":"King","sequence":"additional","affiliation":[{"name":"Agri Food Laboratories, Alberta Agriculture and Forestry, Edmonton, AB T6H 4P2, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Madhu","family":"Ravi","sequence":"additional","affiliation":[{"name":"Animal Health and Assurance, Alberta Agriculture and Forestry, Edmonton, AB T6H 4P2, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Delores","family":"Peters","sequence":"additional","affiliation":[{"name":"Animal Health and Assurance, Alberta Agriculture and Forestry, Edmonton, AB T6H 4P2, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kevin","family":"Fonseca","sequence":"additional","affiliation":[{"name":"Provincial Laboratory for Public Health, Calgary, AB T2N 4W4, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4528-541X","authenticated-orcid":false,"given":"Carl A.","family":"Gagnon","sequence":"additional","affiliation":[{"name":"Swine and Poultry Infectious Diseases Research Center (CRIPA-Fonds de Recherche du Qu\u00e9bec), Facult\u00e9 de M\u00e9decine V\u00e9t\u00e9rinaire, Universit\u00e9 de Montr\u00e9al, 3200 rue Sicotte, Saint-Hyacinthe, QC J2S 2M2, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Davor","family":"Ojkic","sequence":"additional","affiliation":[{"name":"Animal Health Laboratory, University of Guelph, Guelph, ON N1G 2W1, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mohamed Faizal","family":"Abdul-Careem","sequence":"additional","affiliation":[{"name":"Health Research Innovation Center 2C53, Faculty of Veterinary Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2021,3,24]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"142","DOI":"10.5501\/wjv.v1.i5.142","article-title":"Infectious laryngotracheitis virus in chickens","volume":"1","author":"Ou","year":"2012","journal-title":"World J. 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