Analysis of Korean strains of infectious laryngotracheitis virus by nucleotide sequences and restriction fragment length polymorphism

Rapid detection and characterization from field cases of infectious laryngotracheitis virus by real-time polymerase chain reaction and restriction fragment length polymorphism

“…Determination of virulence in the two recent NI field isolates was considered necessary since up to 20% of birds from the infected flocks from which one of isolates was obtained showed respiratory distress and increasing levels of mortality over a 72-h period. However, RFLP and sequence analysis of the TK gene demonstrated that the two recent NI isolates were not highly virulent according to the criteria previously described (Han & Kim, 2001b;OIE, 2004). The identification of the isolates from NI cases as low virulent seems appropriate, even though the clinical symptoms and mortality levels associated with the cases (such as the one involving 04 16713) were increasing, as mortality rates in highly virulent cases have been reported to reach 80% (Han & Kim, 2001b).…”

“…However, RFLP and sequence analysis of the TK gene demonstrated that the two recent NI isolates were not highly virulent according to the criteria previously described (Han & Kim, 2001b;OIE, 2004). The identification of the isolates from NI cases as low virulent seems appropriate, even though the clinical symptoms and mortality levels associated with the cases (such as the one involving 04 16713) were increasing, as mortality rates in highly virulent cases have been reported to reach 80% (Han & Kim, 2001b). The low virulence of these isolates was subsequently confirmed through experimental infection, where no clinical signs of the disease were observed.…”

“…In order to examine the molecular determinants of virulence of field strains 04 14677 and 04 16713, a 1.296-kbp fragment of the TK gene was amplified from the DNA. Digestion of the PCR amplicons with Hae III, Sau 96 and Nci I, gave a RFLP pattern indicative of low virulence, according to RFLP patterns previously described (Han & Kim, 2001b;OIE, 2004). Sequence analysis of these field isolates in the 649-bp region of the TK gene showed the presence of a threonine at amino acid position number 252, which again was indicative of isolates of low virulence (Han & Kim, 2001a,b).…”

“…These methods have included the detection of field strains using polymerase chain reaction (PCR) coupled with non-radioactive probes (Abbas et al ., 1996), while differentiation between field and vaccine strains has been demonstrated through the use of PCR coupled with restriction fragment length polymorphism (RFLP) (Chang et al ., 1997;Clavijo & Nagy, 1997;Graham et al ., 2000;Han & Kim, 2001a). Differentiation between field isolates of high and low virulence has also been achieved through the use of PCR, RFLP and sequence analysis (Han & Kim, 2001b), while multiplex PCR has been used for ILT diagnosis (Pang et al ., 2002). The use of PCR for ILTV has also been described for the evaluation of vaccine purity (Vögtlin et al ., 1999).…”

Molecular epidemiology of infectious laryngotracheitis: a review

“…Group 1 consisted of the TCO vaccine and TCO-like field strains, Group 2 includes the CEO vaccine and CEO-like field strains, and Group 3 includes vaccine-unlike field strains. In Korea, three groups of field strains were differentiated using the TK gene alone (Han & Kim, 2001). Group 1 consisted of virulent strains, group 2 of low-virulence strains, and group 3 of vaccine strains.…”