Munyua Peninah, Onyango Clayton, Mwasi Lydia, Waiboci Lilian W, Arunga Geoffrey, Fields Barry, Mott Joshua A, Cardona Carol J, Kitala Philip, Nyaga Philip N, Njenga M Kariuki
Division of Global Health protection, United States Centers for Disease Control and Prevention-Kenya, Nairobi, Kenya.
Faculty of Veterinary Medicine, University of Nairobi, Nairobi, Kenya.
PLoS One. 2018 Feb 9;13(2):e0192721. doi: 10.1371/journal.pone.0192721. eCollection 2018.
Influenza A virus subtypes in non-human hosts have not been characterized in Kenya. We carried out influenza surveillance in selected domestic animals and compared the virus isolates with isolates obtained in humans during the same period.
We collected nasal swabs from pigs, dogs and cats; oropharyngeal and cloacal swabs from poultry; and blood samples from all animals between 2010 and 2012. A standardized questionnaire was administered to farmers and traders. Swabs were tested for influenza A by rtRT-PCR, virus isolation and subtyping was done on all positive swabs. All sera were screened for influenza A antibodies by ELISA, and positives were evaluated by hemagglutination inhibition (HI). Full genome sequencing was done on four selected pig virus isolates.
Among 3,798 sera tested by ELISA, influenza A seroprevalence was highest in pigs (15.9%; 172/1084), 1.2% (3/258) in ducks, 1.4% (1/72) in cats 0.6% (3/467) in dogs, 0.1% (2/1894) in chicken and 0% in geese and turkeys. HI testing of ELISA-positive pig sera showed that 71.5% had positive titers to A/California/04/2009(H1N1). Among 6,289 swabs tested by rRT-PCR, influenza A prevalence was highest in ducks [1.2%; 5/423] and 0% in cats and turkeys. Eight virus isolates were obtained from pig nasal swabs collected in 2011 and were determined to be A(H1N1)pdm09 on subtyping. On phylogenetic analysis, four hemagglutinin segments from pig isolates clustered together and were closely associated with human influenza viruses that circulated in Kenya in 2011.
Influenza A(H1N1)pdm09 isolated in pigs was genetically similar to contemporary human pandemic influenza virus isolates. This suggest that the virus was likely transmitted from humans to pigs, became established and circulated in Kenyan pig populations during the study period. Minimal influenza A prevalence was observed in the other animals studied.
肯尼亚尚未对非人类宿主中的甲型流感病毒亚型进行特征描述。我们在选定的家畜中开展了流感监测，并将病毒分离株与同期从人类身上获得的分离株进行了比较。
我们在2010年至2012年期间收集了猪、狗和猫的鼻拭子；家禽的口咽拭子和泄殖腔拭子；以及所有动物的血液样本。向农民和贸易商发放了标准化问卷。通过逆转录实时荧光定量聚合酶链反应（rtRT-PCR）对拭子进行甲型流感检测，对所有阳性拭子进行病毒分离和亚型鉴定。通过酶联免疫吸附测定（ELISA）对所有血清进行甲型流感抗体筛查，阳性结果通过血凝抑制试验（HI）进行评估。对4株选定的猪病毒分离株进行了全基因组测序。
在通过ELISA检测的3798份血清中，甲型流感血清阳性率在猪中最高（15.9%；172/1084），鸭中为1.2%（3/258），猫中为1.4%（1/72），狗中为0.6%（3/467），鸡中为0.1%（2/1894），鹅和火鸡中为0%。对ELISA检测呈阳性的猪血清进行HI检测显示，71.5%对A/加利福尼亚/04/2009（H1N1）具有阳性滴度。在通过逆转录实时荧光定量聚合酶链反应（rRT-PCR）检测的6289份拭子中，甲型流感流行率在鸭中最高[1.2%；5/423]，猫和火鸡中为0%。从2011年收集的猪鼻拭子中获得了8株病毒分离株，亚型鉴定确定为A（H1N1）pdm09。系统发育分析显示，猪分离株的4个血凝素片段聚集在一起，与2011年在肯尼亚传播的人类流感病毒密切相关。
在猪中分离出的甲型流感（H1N1）pdm09与当代人类大流行性流感病毒分离株在基因上相似。这表明该病毒可能是从人类传播到猪身上，在研究期间在肯尼亚猪群中定殖并传播。在其他研究动物中观察到的甲型流感流行率极低。
