Satellite Tracking on the Flyways of Brown-Headed Gulls and Their Potential Role in the Spread of Highly Pathogenic Avian Influenza H5N1 Virus Parntep Ratanakorn 1 , Anuwat Wiratsudakul 1 , Witthawat Wiriyarat 1 , Krairat Eiamampai 2 , Adrian H. Farmer 3 , Robert G. Webster 4 , Kridsada Chaichoune 1 , Sarin Suwanpakdee 1 , Duangrat Pothieng 2 , Pilaipan Puthavathana 5 * 1 Faculty of Veterinary Science, Mahidol University, Nakhon Pathom, Thailand, 2 Department of National Park, Wildlife and Plant Conservation, Ministry of Natural Resource and Environment, Bangkok, Thailand, 3 Wild Ecological Solutions, Fort Collins, Colorado, United States of America, 4 Division of Virology, Department of Infectious Diseases, St. Jude Children Research Hospital, Memphis, Tennessee, United States of America, 5 Department of Microbiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand Abstract Brown-headed gulls (Larus brunnicephalus), winter visitors of Thailand, were tracked by satellite telemetry during 2008–2011 for investigating their roles in the highly pathogenic avian influenza (HPAI) H5N1 virus spread. Eight gulls negative for influenza virus infection were marked with solar-powered satellite platform transmitters at Bang Poo study site in Samut Prakarn province, Thailand; their movements were monitored by the Argos satellite tracking system, and locations were mapped. Five gulls completed their migratory cycles, which spanned 7 countries (China, Bangladesh, India, Myanmar, Thailand, Cambodia, and Vietnam) affected by the HPAI H5N1 virus. Gulls migrated from their breeding grounds in China to stay overwinter in Thailand and Cambodia; while Bangladesh, India, Myanmar, and Vietnam were the places of stopovers during migration. Gulls traveled an average distance of about 2400 km between Thailand and China and spent 1–2 weeks on migration. Although AI surveillance among gulls was conducted at the study site, no AI virus was isolated and no H5N1 viral genome or specific antibody was detected in the 75 gulls tested, but 6.6% of blood samples were positive for pan- influenza A antibody. No AI outbreaks were reported in areas along flyways of gulls in Thailand during the study period. Distance and duration of migration, tolerability of the captive gulls to survive the HPAI H5N1 virus challenge and days at viral shedding after the virus challenging suggested that the Brown-headed gull could be a potential species for AI spread, especially among Southeast Asian countries, the epicenter of H5N1 AI outbreak. Citation: Ratanakorn P, Wiratsudakul A, Wiriyarat W, Eiamampai K, Farmer AH, et al. (2012) Satellite Tracking on the Flyways of Brown-Headed Gulls and Their Potential Role in the Spread of Highly Pathogenic Avian Influenza H5N1 Virus. PLoS ONE 7(11): e49939. doi:10.1371/journal.pone.0049939 Editor: Yi Guan, The University of Hong Kong, China Received June 15, 2012; Accepted October 18, 2012; Published November 28, 2012 Copyright: ß 2012 Ratanakorn et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This study was a part of the ‘‘Avian Influenza Surveillance in Thailand-Studies at Human-Animal Interface’’ project supported by Cooperative Agreement Number 1U19CI000399 from the Centers for Disease Control and Prevention (CDC). Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the CDC. PP, the grant’s principal investigator, is supported by Thailand Research Fund for Senior Research Scholar. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: siput@mahidol.ac.th Introduction To date, 17 hemagglutinin (HA) and nine neuraminidase (NA) subtypes of influenza A viruses have been identified. All the HA and NA subtypes have been isolated from wild aquatic birds, particularly from orders Anseriformes (ducks, geese, and swans) and Charadriiformes (gulls, terns, and shorebirds). Therefore, aquatic birds are widely accepted as the main natural reservoirs of influenza A viruses. Influenza viruses isolated from these birds are the mostly avirulent, low pathogenic avian influenza (LPAI) viruses [1–3]. Only some members of the H5 and H7 subtypes are highly pathogenic, but the H5N1 viruses were more virulent [1,3]. In the first identified occurrence of H5N1 HPAI infection in humans in Hong Kong in 1997, 18 humans were infected and 6 died (case fatality rate 33.3%) [4]. The HPAI H5N1 virus re-emerged in Hong Kong in 2001, twice in 2002, and subsequently in 2003 in poultry, waterfowl and wild birds [5]. The viruses isolated in Hong Kong before 2002 were pathogenic in gallinaceous birds but not domestic or wild waterfowl. Death of aquatic birds from the HPAI H5N1 virus was first recognized in the 2002 outbreak [5]. The resurging HPAI H5N1 strain is highly virulent in both avian and humans, with a fatality rate of approximately 60% being reported in infected humans [6,7]. In January 2004, an outbreak of H5N1 HPAI was reported in poultry and humans in Thailand. The virus initially isolated in Thailand belonged to clade 1; while clade 2.3.4 virus was introduced into northeast Thailand in 2006 [8,9]. However, all of the virus isolates in central Thailand still remained in clade 1. There were 25 cases reported in humans, with 17 deaths (case fatality rate 68%). No cases of human infection have occurred since August 2006, but there were some avian influenza virus (AIV) outbreaks in poultry until 2008 [6,7]. Based on virological data and satellite telemetry studies, many groups of investigators have linked migratory birds with H5N1 HPAI spread [10–17]. The first evidence that supported this claim PLOS ONE | www.plosone.org 1 November 2012 | Volume 7 | Issue 11 | e49939