Scholars confirm that the rabies virus in Taiwan, China did not come from Chinese ferret-badgers
In July last year, a National Taiwan University team found the first case of rabies virus in 52 years in a ferret-badger. The Council of Agriculture initially pointed to China as the source of the virus, but six experts, including National Taiwan University Department of Veterinary Medicine professor Pang Fei, doctoral student Chiu Hui-ying, and National Taiwan Normal University Department of Life Science professor Wang Hung-yi, published a paper in May in the internationally renowned journal Emerging Infectious Diseases, comparing ferret-badger rabies viruses from various countries and confirming that the virus in Taiwan and Chinese virus strains had diverged as early as 200 years ago, and that rabies virus had existed in Taiwan for at least 100 years. Just why a large-scale outbreak occurred last year remains unknown.
This important finding ruled out the possibility of infection through border smuggling, and also highlighted the inadequacy of wildlife surveillance in Taiwan, while still failing to answer where the Taiwan virus strain came from. Chen Chen-chih, a veterinarian at the Pingtung University of Science and Technology Wildlife Rescue Center, called on the Council of Agriculture to strengthen wildlife surveillance and understand how virus strains change within animal bodies, so that the disease can be effectively managed.
Native virus strain has existed for a century
The team of National Taiwan University Department of Veterinary Medicine professor Pang Fei and doctoral student Chiu Hui-ying discovered last year the rabies virus that had been absent for half a century. As of April 28 this year, 358 ferret-badgers, 1 house shrew and 1 puppy had tested positive for rabies virus. Because the outbreak came fast and fierce, and because there had been cases in China of ferret-badgers infected with rabies virus, even biting people to death, the Council of Agriculture initially suspected that the rabies virus in Taiwan's ferret-badgers might have been brought in from China through border smuggling.
However, in August last year the Animal Health Research Institute of the Council of Agriculture conducted a genetic sequence comparison for the first time and found that the rabies virus in Taiwan's ferret-badgers had already diverged into three groups - Taitung; Taichung and Nantou; and Yunlin, Tainan and Kaohsiung - leading to the assessment that it might have been latent in Taiwan for some time.
The National Taiwan University Department of Veterinary Medicine research team, together with six people including National Taiwan Normal University Department of Life Science professor Wang Hung-yi, National Taiwan University Graduate Institute of Molecular and Comparative Pathobiology director Cheng Chien-jen, China Medical University Graduate Institute of Basic Medical Science professor Hsieh Chia-hung, and Taiwan Endemic Species Research Institute veterinarian Chan Fang-tse, completed the genetic sequence comparison of Taiwan's ferret-badger rabies virus last year, further confirming that the virus in Taiwan's ferret-badgers did not come from Chinese ferret-badgers.
The study pointed out that the virus strain in Taiwan's ferret-badgers is relatively similar to those of Chinese ferret-badgers and Chinese dogs, but had diverged as early as 158 to 210 years ago; the common ancestor of the three groups of virus strains seen in Taiwan today can be traced back to 91 to 113 years ago. In other words, Taiwan had an independent virus strain as early as 100 years ago, and it was not brought in from China in recent years.
Image: Ferret-badger. Illustration: Chen Yi-ming
Despite all the uncertainties, the report clearly conveyed one message: Taiwan needs more active wildlife surveillance. Chen Chen-chih, who has long followed wildlife epidemiology, said that wildlife surveillance in Taiwan is not sound enough; for example, ferret-badgers are mostly sent for testing only after they have died, but what is more important is to understand how the virus changes within wildlife bodies. "Only by identifying all possible influencing factors, such as time, season and space, can disease management be carried out."
Chen Chen-chih even believes that the "reservoir host" of rabies may not be the ferret-badger, because a reservoir host should not suddenly develop illness and die; in addition, in last year's rabies outbreak, only the ferret-badger population in the Taitung Coastal Mountain Range collapsed as a result. All these questions can only be answered through long-term wildlife surveillance.
Yen Sheng-hung, a professor in the Department of Biological Sciences at National Sun Yat-sen University, said that this incident revealed gaps in inter-ministerial coordination. The Ministry of Health and Welfare oversees human medicine, the Council of Agriculture's Department of Animal Industry oversees dogs and cats and animal welfare, the Forestry Bureau oversees wildlife, and if national parks are involved, they fall under the national park management authority. But inter-ministerial coordination seems to be "only people showing up, without filling the knowledge gaps." For example, stray cats and dogs that were once domesticated may become infected with the virus and then pass it on to other wildlife, but who monitors stray cats and dogs and how to catch them currently has no clear policy.
Chen Chen-chih also said that stray cats and dogs running into the wild involves wildlife management techniques, but they are not traditional wildlife, so they receive less attention; however, government agencies must face this problem squarely.
Regarding this study, Bureau of Animal and Plant Health Inspection and Quarantine Director-General Chang Su-hsien said that the U.S. Centers for Disease Control and Prevention had previously inferred that rabies virus has existed in Taiwan for 50 to 100 years, and that the Animal Health Research Institute had been asked to conduct further testing. It has also proactively set traps in Miaoli, Taitung and Nantou to monitor ferret-badgers, carried out epidemiological investigations one after another, and produced oral vaccines to clarify the virus's transmissibility.
However, she pointed out that domestic dogs and cats remain an important route of transmission to humans. International research has shown that as long as the vaccination rate exceeds 70 percent, rabies is unlikely to spread to humans on a large scale. At present, Taiwan's average vaccination rate is about 69 percent, and in the future publicity will be strengthened, in the hope that the public will cooperate more.