Development and application of multiplex PCR assays for detection of virus-induced respiratory disease complex in dogs

PIEWBANG, Chutchai; RUNGSIPIPAT, Anudep; POOVORAWAN, Yong; TECHANGAMSUWAN, Somporn

ed by coinfection with more than one pathogen. Recently, Jeoung et al. (2013) used both NS and whole blood samples for CIRDC virus detection, but found that only CDV (and not CIV and CRCoV) could be detected from the whole blood samples [10]. Correspondingly, respiratory swabs have been reported to be appropriate samples for the detection of respiratory pathogens [9, 16] . Thus, NS and OS served as appropriate sample sources in our study due to their ease of and noninvasive sampling nature and that they lie on the viral shedding routes. This study also suggested that the virus should be screened for in NS and OS, with detection levels at each site depending on the type of virus. The CAdV-2 and CaHV-1 mostly replicate in the lower respiratory tracts and shed via respiratory discharge, consisting with our finding that they were mostly detected in the OS, even though NS could often detect these viruses as well. However, the CAdV-2 primer pair used in this study was able to amplify CAdV-1 DNA virus which also shows airborne transmission and replicates in tonsil [3] . Therefore, the positive PCR reaction for canine adenovirus could not discriminate between CAdV-1 and CAdV-2 in this study. Additionally, CaHV-1 can be latent in various nerve ganglions, resulting in negative results from nucleic acid-based CaHV-1 detection in respiratory discharges in non-symptomatic dogs [12] . In this study, 3 out of 15 vaccinated dogs receiving, at least once, combined vaccine against CPIV, CDV and CAdV-2 showed PCR positive results for CIRDC virus detection (2 CDV positive dogs and 1 CPIV positive dog). Even though live attenuated vaccines can give false positive results with molecular testing, it is essential to discriminate between wild-type infection and recent vaccination for the prevention of false positivity in the future. This study documented CaHV-1 and CRCoV circulation in Thailand for the first time. In 2012, CIV H3N2 was discovered in Thailand from dogs with flu-like symptoms [2] . Here, CIV and CRCoV were the most frequently detected viruses in CIRDC-infected dogs, suggesting that the viruses might spread rapidly. These viruses were not only found in single infections, but they were also found as co-infections together or with other viruses.