Molecular Epidemiology of Rabies Viruses in Taiwan, 2013-2014

WC Hsu1*, MS Lee1, KR Tsai1, YC Tu1, JC Chang1, SC Hu1, WC Li1, WC Chuang1, SH Lee2

1Animal Health Research Institute, Council of Agriculture, Executive Yuan

2Animal Drugs Inspection Branch, Animal Health Research Institute, Council of Agriculture, Executive Yuan

Abstract

Taiwan has been considered a rabies-free country since 1961. However, three Formosan ferret-badgers (Melogale moschata subaurantiaca) in Nantou County and Yunlin County were diagnosed as rabies positive via direct fluorescent antibody test (FAT), reverse transcription polymerase chain reaction (RT-PCR), and immunohistochemistry (IHC) in July, 2013. After these first three cases were diagnosed, a massive surveillance on wild carnivores was carried out. From July 1, 2013 to December 31, 2014, 4,732 animal brain tissues were submitted to the Animal Health Research Institute and 442 cases were tested rabies-positive by FAT. The positive rates of rabies were 38.82% (439/1,131) in Formosan ferret-badger, 0.58% (1/173) in house shrew (Suncus murinus), 0.47% (1/215) in Formosan gem-faced civet (Paguma larvata taivana), and 0.04% (1/2,651) in dog. The results from the surveillance efforts showed that the disease is still restricted in wild Formosan ferret-badgers. The nucleoprotein gene based phylogenetic analysis showed that the rabies viruses isolated from Formosan ferret-badgers were clearly divided into two groups, namely the Middle and Southern group (TW-MS), covering the regions of Nantou, Taichung, Yunlin, Chiayi, Tainan, and Kaohsiung and the Eastern group (TW-E), covering the regions of Hualien, Taitung, and Pingtung. The nucleotide identities of nucleoprotein genes between TW-E subgroups and TW-MS subgroups ranged from 91.4 to 93.5%. Our study revealed that the ferret-badger-associated rabies virus in Taiwan has already evolved into two distinct strains.

KeyWords: Rabies, ferret-badger, molecular epidemiology.