摘要:我國的禽流感自1960年代起,多以「低」致病性的禽流感病毒在流行,且多為「非H5、非H7亞型」。2003-2004年,首度發現「低」致病性H5N2禽流感病毒在臺灣雞群廣泛地流行; 2008年已出現本土的「高」致病性H5N2禽流感病毒,至2012年已有多處的「高」致病性禽流感H5N2在雞群之流行,此後每年均有大小不一的流行。至2015年臺灣首度發生演化分支2‧3‧4‧4 「高」致病性H5禽流感病毒在雞、鴨、鵝的大規模流行,且病毒包含H5N8、H5N2與H5N3三亞型,加上原已在雞群流行的似1994年墨西哥H5N2病毒,因此,全臺有四種禽流感病毒。2017年未測得H5N3亞型,但花蓮等地出現H5N6亞型,且在夏季也仍有流行。可見偵測失守,致後患無窮。
本研究欲嘗試協助農委會與防檢局如何強化禽流感的偵測,因研究計畫經費被大幅縮減,因此研究目標縮改為:(一)禽場的流行病學危險因子調查與數據蒐集;(二)由禽種分布,建立初步的風險圖;(三)明瞭不同禽種感染禽流感病毒後的病癥為何;及(四)改進野鳥的禽流感病毒分子偵測。
做法上,目標(一)將在臺灣擇一養禽縣,進行危險因子調查、單變項與多變項分析;目標(二)由農方釋出不同禽種數據,以地理資訊系統(geographical information system, GIS),建立風險地圖;目標(三)將明瞭臺灣常見禽種在近年感染禽流感H5病毒後的「早期」病癥各為何及其未來應用於症候群偵測的可行性;目標(四)與屏科大陳貞志老師合作,檢測野鳥禽流感病毒的帶原。目標(一)、與(三)由臺大公共衛生金傳春老師進行,目標(二)由中研究人社所詹大千老師進行,目標(四)由臺大獸醫系王儷蒨與陳貞志老師合作完成。
我們深信本研究由風險與流行病學著手,在人畜共通傳染病為一新嘗試,若未來有官方配合與大力支持,將對國內與亞洲的禽流感防疫有實質貢獻。
Abstract: In early years around 1960s, most of avian influenza viruses (AIVs) isolated were non-H5, non-H7 AIVs. Unfortunately, island-wide outbreaks of low pathogenic avian influenza (LPAI) H5N2 virus occurred with wide-spread during 2003-2004. In 2008, highly pathogenic avian influenza (HPAI) H5N2 virus appeared domestically. By the year of 2012, multiple epidemic sites of HPAI H5N2 happened in chicken farms. Since then, these 1994 Mexican-like H5N2 AIVs have become endemic in Taiwan. In 2015, large-scale epidemics caused by the clade 2.3.4.4 H5N2, H5N8 and H5N3 AIVs occurred in geese, ducks and chicken farms. In addition, the 1994 Mexican-like H5N2 AIVs have continuously spread, indicating that totally 4 types of AIVs were circulating. In 2017, H5N3 AIVs were not detected but H5N6 AIVs resulted in outbreaks at multiple sites, including Hualien and other areas. These clade 2.3.4.4 H5 viruses were still active even during summer months. In other words, failure in surveillance in Taiwan has led more outbreaks of AIVs in the future.
This study intended to help Council of Agriculture (COA) and Bureau of Animal and Plant Health Inspection and Quarantine (BAPHIQ) to find the best way to enhance surveillance of avian influenza (AI). Because the budget cut was more than 50%, we revised our four study aims focusing on: (1) epidemiological investigation and data collection on risk factors of avian flu, (2) using the distribution of avian species, preliminary of risk maps will be built, (3) understand the symptoms of different avian host species after their infection with AIVs, and (4) improve the molecular diagnosis methods in AIV surveillance among wild birds.
Among our approaches, Aim #1 will select one country with avian poultry farms to conduct a survey on risk factors and then carry out uni- and multiple variate regression analyses; Aim #2, that will use available poultry information and geographical information system (GIS) to set up host-dependent risk maps; Aim #3 will find out the common early symptoms/signs after the infection of H5 AIVs to see the feasibility to be applied for future syndromic Surveillance; and Aim #4 will focus on improving virological laboratory surveillance of AIVs in wild birds. Aims #1 and #3 will be carried out by Dr. Chwan-Chuen King at the College of Public Health, National Taiwan University (NTU-CPH), whereas Aim #2 will be directed by Dr. Ta-Chien Chan at the Academia Sinica and Aim #4 will be achieved through collaborative project between Dr. LC Wang at NTU Vet. Med. and Dr. CC Chen at Pingtung.
We believe that starting from risk factors and epidemiology on zoonotic infectious diseases will be very helpful to improve surveillance of avian influenza in Taiwan as well as in Asia, once we have enough support from government agencies in Agriculture.