title: Growth kinetics and transmission potential of existing and emerging field strains of infectious laryngotracheitis virus.
abstract: Attenuated live infectious laryngotracheitis virus (ILTV) vaccines are widely used in the poultry industry to control outbreaks of disease. Natural recombination between commercial ILTV vaccines has resulted in virulent recombinant viruses that cause severe disease, and that have now emerged as the dominant field strains in important poultry producing regions in Australia. Genotype analysis using PCR-restriction fragment length polymorphism has shown one recombinant virus (class 9) has largely replaced the previously dominant class 2 field strain. To examine potential reasons for this displacement we compared the growth kinetics and transmission potential of class 2 and class 9 viruses. The class 9 ILTV grew to higher titres in cell culture and embryonated eggs, but no differences were observed in entry kinetics or egress into the allantoic fluid from the chorioallantoic membrane. In vivo studies showed that birds inoculated with class 9 ILTV had more severe tracheal pathology and greater weight loss than those inoculated with the class 2 virus. Consistent with the predominance of class 9 field strains, birds inoculated with 10(2) or 10(3) plaque forming units of class 9 ILTV consistently transmitted virus to in-contact birds, whereas this could only be seen in birds inoculated with 10(4) PFU of the class 2 virus. Taken together, the improved growth kinetics and transmission potential of the class 9 virus is consistent with improved fitness of the recombinant virus over the previously dominant field strain.
authors.affiliation: Asia-Pacific Centre for Animal Health, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Victoria, 3010, Australia.
authors.forename: Sang-Won
authors.initials: SW
authors.lastname: Lee
authors.affiliation: Asia-Pacific Centre for Animal Health, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Victoria, 3010, Australia.
authors.forename: Carol A
authors.initials: CA
authors.lastname: Hartley
authors.affiliation: Asia-Pacific Centre for Animal Health, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Victoria, 3010, Australia.
authors.forename: Mauricio J C
authors.initials: MJ
authors.lastname: Coppo
authors.affiliation: Asia-Pacific Centre for Animal Health, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Victoria, 3010, Australia.
authors.forename: Paola K
authors.initials: PK
authors.lastname: Vaz
authors.affiliation: Asia-Pacific Centre for Animal Health, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Victoria, 3010, Australia.
authors.forename: Alistair R
authors.initials: AR
authors.lastname: Legione
authors.affiliation: Asia-Pacific Centre for Animal Health, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Victoria, 3010, Australia.
authors.forename: José A
authors.initials: JA
authors.lastname: Quinteros
authors.affiliation: Asia-Pacific Centre for Animal Health, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Werribee, 3030, Australia.
authors.forename: Amir H
authors.initials: AH
authors.lastname: Noormohammadi
authors.affiliation: Asia-Pacific Centre for Animal Health, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Victoria, 3010, Australia.
authors.forename: Phillip F
authors.initials: PF
authors.lastname: Markham
authors.affiliation: Asia-Pacific Centre for Animal Health, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Victoria, 3010, Australia.
authors.forename: Glenn F
authors.initials: GF
authors.lastname: Browning
authors.affiliation: Asia-Pacific Centre for Animal Health, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Victoria, 3010, Australia.
authors.forename: Joanne M
authors.initials: JM
authors.lastname: Devlin
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D002645:Chickens / Q000821:virology; D005260:Female; D005838:Genotype; D001352:Herpesvirus 1, Gallid / Q000145:classification* / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D007700:Kinetics; D008297:Male; D013045:Species Specificity; D014779:Virus Replication