Isolation and molecular characterization of canine distemper virus from India

Ocular swabs from canine distemper virus (CDV) suspected live or brain tissue from dead dogs were tested for the presence of CDV nucleoprotein (N) gene using reverse transcriptase polymerase chain reaction (RT-PCR). Partial "N" gene sequencing of the RT-PCR-positive samples and the local vaccine virus revealed that the Ind/Andaman 01/07 virus was highly divergent from the rest of the CDV isolates and from the vaccine strain. Quantitative real-time PCR (qRT-PCR) using SYBR Green I chemistry for CDV haemagglutinin "H" gene quantification showed C(t) values ranging from 29.76-30.67 in the RT-PCR-positive samples. Two of the positive samples, designated Ind/TN 01/07 and Ind/Andaman 01/07 were used for virus isolation in B95a cell line. Characteristic cytopathic changes such as rounding of cells, syncytia formation, and ballooning were seen from the first passage onwards. Specific cytoplasmic fluorescence was seen in infected cells with a commercial reference serum against CDV. To the best of our knowledge, this is the first report of CDV isolation from clinical cases in India.