台灣貓隻A型流感病毒調查

Abstract

雖然 A 型流感病毒不被認為是貓常見的呼吸道感染病原，但是很多能感染貓隻的A 型流感病毒亞型被分離出來，例如:H3N2, H5N1和 H1N1。流感病毒為重要的人畜共通傳染疾病。由於伴侶動物與主人有親密的接觸，因此伴侶動物被認為人畜共通的重要媒介。因此，對於伴侶動物的重要人畜監控、獸醫領域和公共衛生，其中貓隻是否會感染A 型流感病毒是一個重要的課題。在台灣有禽流感H5N2 及H6N1 和人流感pandemic H1N1 和seasonal H3N2 的流行，但是卻沒有對於貓隻A型流感病毒感染情形的文獻研究。本研究目的是利用血清學調查和RT-PCR 病毒核酸基因檢測法來調查台灣地區貓隻A 型流感病毒感染情形，以及進行A 型流感病毒分離及親源樹的建構，進一步分析病毒的來源。以blocking ELISA 血清學檢測結果，來自國立台灣大學生物資源暨農學院附設動物醫院就診的家貓陽性率為4.1% (13/320)，流浪貓陽性率為0.0% (0/538)。在13 個ELISA 陽性檢體，針對human pandemic H1N1 的血清凝集抑制試驗(HI test)，結果有9 個檢體為陽性，力價為16-64，其他4 個檢體為陰性，力價為0-8。純種貓的ELISA 陽性7.2% (6/83)大於混種貓的ELISA 陽性率0.9% (7/775)。台灣北部的ELISA 陽性率2.7% (12/442)最高，台灣東部的ELISA 陽性率0.0% (0/77)，台灣中部的ELISA 陽性率0.0% (0/217)，台灣南部的ELISA 陽性率0.8% (1/122)，都具有統計上的意義。RT-PCR 檢測部分，家貓陽性率為28.1% (18/64)，流浪貓陽性率為9.3% (4/43)。台灣北部的RT-PCR 陽性率28.9% (22/76)為最高，台灣東部的RT-PCR 陽性率0.0% (0/12)，台灣中部的RT-PCR陽性率0.0% (0/7)，台灣南部的RT-PCR陽性率0.0% (0/12)，都具有統計上的意義。RT-PCR 陽性檢體中，從六隻貓的呼吸道檢體，成功從第二代雞胚尿囊液中分離出A 型流感病毒。NP 基因親緣圖得出本研究的病毒與pandemic H1N1有高度相似性，推測本研究的病毒可能來自於人pandemic H1N1 流感病毒。依據血清學調查的結果顯示台灣貓隻對於A 型流感病毒感染的情況，本研究亦可提供關於貓隻感染A 型流感病毒確切的資訊，利於台灣A 型流感病毒流行病學上的監控與防範。

Although influenza A virus is not considered to be a common etiologic agent for respiratory infections in cats, many subtypes of influenza A viruses have been isolated from cats around the world, such as H3N2, H5N1 and H1N1. Influenza is an important zoonosis. Since pets are in close contact with their owners, a role for household pets as vectors for disease transmission within families should be considered. Influenza A virus infection in cats has important implications in veterinary medicine and public health. The prevalence of human H3N2, human H1N1, avian H5N2 and avian H6N1 has been documented in Taiwan, but influenza A virus infection in cats is little known. The aim of this study is to investigate influenza A virus infection in cats in Taiwan using serological survey, RT-PCR for virus detection and virus isolation. The results showed that the seroprevalence of household cats was 4.1% (13/320) and the seroprevalence of rural cats from NTUVH was 0.0% (0/538) using blocking ELISA. Among the 13 ELISA positive sera, the HI test against human pandemic H1N1 showed positive in 9 sera (titer＝16-64) and negative in 4 sera (titer＝0-8).The positive ELISA rates of pure breed cats and mixed cats were 7.2% (6/83) and 0.9% (7/775), respectively. The positive ELISA rates of cats living in the northern Taiwan, in the eastern Taiwan, in the middle Taiwan and in the southern Taiwan were 2.7% (12/442), 0.0% (0/77), 0.0% (0/217) and 0.8% (1/122). Household cats, pure breed cats and cats living in the northern Taiwan were most commonly seropositive for pandemic H1N1. The positive RT-PCR rates of household cats and rural cats were 28.1% (18/64) and 9.3% (4/43), respectively. The positive RT-PCR rates of cats living in the northern Taiwan, in the eastern Taiwan, in the middle Taiwan and in the southern Taiwan were 28.9% (22/76), 0.0% (0/12), 0.0% (0/7) and 0.0% (0/12). Household cats and cats living in the northern Taiwan had the highest RT-PCR positive rate. Among those positive cases, influenza A virus was preliminary from 6 cats through second passage in allantoic fluid of embryonic eggs. Phylogenetic analysis of NP gene showed samples in this study are majorly clustered with pandemic H1N1 strains. Based on the seroprevalence and RT-PCR evidences, the results indicated that influenza A virus indeed exists in cats in Taiwan. The investigation could provide the epidemiological information on influenza A virus in cats and the perspective on the zoonotic roles of cats in Taiwan.