The Nucleotide Sequence of Hemagglutinin and Phosphoprotein genes of Thai Isolated Canine Distemper Virus

Abstract

Canine distemper disease is an important disease with worldwide distribution, caused by the Canine distemper virus (CDV). CDV vaccines have been developed for many decades but infected dogs are still reported. The aim of this study is to analyze Thai isolates CDV nucleotide sequences of Hemagglutinin glycoprotein (H) gene and Phosphoprotein (P) gene regions and compare them with vaccines and other virulent strains in the Genbank. Nine clinical samples that showed CDV clinical signs and pathologic lesions were used in routine histopathological process, Immunohistochemistry (IHC) staining and virological study. The fresh samples of each cases were homogenized and isolated in Vero cell expressing canine signaling lymphocyte activation molecules with a tag (Vero-DST), followed by reverse transcriptase-polymerase chain reaction, nucleotide sequencing and compared with vaccine strains and other new isolates in the Genbank. Slide sections showed eosinophilic inclusion bodies in target cells from the lung, spleen and brain. CDV antigens were prominently found in the spleen, lung and intestine samples, but very few antigens were found in the brain samples. The result showed that our CDVs were not related to the vaccine lineage and could be divided in to 2 groups; one that joined the Asia-1 lineage and the other that didn’t join any previous found lineages. A previous Thai CDV study, on the nucleocapsid protein (N) gene found that the virus could be separated into 2 clusters, the vaccine lineage and the other virulent lineage. Thus, there are at least 3 strains of CDVs circulating in Thailand.