Canid herpesvirus 1 (CaHV-1) is a member of the canine infectious respiratory disease complex (CIRDC). The outcome of CaHV-1 infection can be occasionally fatal. So far, no information on CaHV-1 circulation in Thailand has been reported resulting in a lack of preventive strategies. In this study, nasal (NS) and oropharyngeal (OS) swabs were collected from 100 live dogs with respiratory distress. Among them, 23 pleural effusions were aspirated. A panel of CIRDC-associated viruses was screened by (RT)-PCR, including CaHV-1, CIV, CPIV, CDV, CRCoV and CAdV-2, for all collected samples. The CaHV-1 was detected in 32 dogs. Additionally, CaHV-1 was consistently detected in six pleural effusions. Most CaHV-1 infected dogs were over 5 years of age (43.8%) and expressed a mild nasal discharge. Pathological results of four three-month-old puppies, naturally moribund from respiratory disease, revealed a severe multifocal necrotic-hemorrhagic disease in several organs without pathognomonic inclusion bodies. They were only found to be CaHV-1 positive by PCR. Phylogenetic analysis demonstrated concordant results of CaHV-1 circulation in Thailand. Although mostly found as a co-infection with other CIRDC viruses (68.8%) it also occurred alone. Therefore, rapid ante-mortem diagnosis might facilitate the investigation of unclassical CaHV-1 infection, which is fatal in neonates and causes illness in annually core-vaccinated adults.
