title: Epidemiological analysis of bovine ephemeral fever in 2012-2013 in the subtropical islands of Japan.
abstract: BACKGROUND
  Bovine ephemeral fever (BEF) is a febrile disease of cattle that is transmitted by arthropod vectors such as mosquitoes and Culicoides biting midges. An outbreak of BEF recently occurred in Ishigaki Island and surrounding islands that are located southwest of Japan. In this study, an epidemiological analysis was conducted to understand the temporal and spatial characteristics of the outbreak. Factors associated with the disease spread within Ishigaki Island were investigated by hierarchical Bayesian models. The possibility of between-island transmission by windborne vectors and transmission by long-distance migration of infected vectors were examined using atmospheric dispersion models.
  
  
  RESULTS
  In September 2012, the first case of the disease was detected in the western part of Ishigaki Island. In 1 month, it had rapidly spread to the southern part of the island and to surrounding islands, and led to 225 suspected cases of BEF during the outbreak. The dispersion model demonstrated the high possibility of between-island transmission by wind. Spatial analysis showed that paddy fields, farmlands, and slope gradients had a significant impact on the 1-km cell-level incidence risk. These factors may have influenced the habitats and movements of the vectors with regard to the spread of BEF. A plausible incursion event of infected vectors from Southeast Asia to Ishigaki Island was estimated to have occurred at the end of August.
  
  
  CONCLUSIONS
  This study revealed that the condition of a terrain and land use significantly influenced disease transmission. These factors are important in assessing favorable environments for related vectors. The results of the dispersion model indicated the likely transmission of the infected vectors by wind on the local scale and on the long-distance scale. These findings would be helpful for developing a surveillance program and developing preventive measures against BEF.
authors.affiliation: Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture and Food Research Organization, 3-1-5 Kannondai, Tsukuba, Ibaraki, 305-0856, Japan. hayama@affrc.go.jp.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Hayama
authors.affiliation: Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture and Food Research Organization, 3-1-5 Kannondai, Tsukuba, Ibaraki, 305-0856, Japan. moriguchi@gs.niigata-u.ac.jp.|Department of Environmental Science Graduate School of Science and Technology, Niigata University, Niigata, Japan. moriguchi@gs.niigata-u.ac.jp.
authors.forename: Sachiko
authors.initials: S
authors.lastname: Moriguchi
authors.affiliation: Kyushu Research Station, National Institute of Animal Health, National Agriculture and Food Research Organization, Kagoshima, Japan. tyanase@affrc.go.jp.
authors.forename: Tohru
authors.initials: T
authors.lastname: Yanase
authors.affiliation: Yaeyama Livestock Hygiene Service Center, Okinawa Prefectural Government, Okinawa, Japan. suzukimo@pref.okinawa.lg.jp.|Okinawa Prefectural Institute of Animal Health, Okinawa, Japan. suzukimo@pref.okinawa.lg.jp.
authors.forename: Moemi
authors.initials: M
authors.lastname: Suzuki
authors.affiliation: Okinawa Prefectural Institute of Animal Health, Okinawa, Japan. niwatsuy@pref.okinawa.lg.jp.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Niwa
authors.affiliation: Okinawa Prefectural Institute of Animal Health, Okinawa, Japan. ikemiygk@pref.okinawa.lg.jp.
authors.forename: Kazufumi
authors.initials: K
authors.lastname: Ikemiyagi
authors.affiliation: Yaeyama Livestock Hygiene Service Center, Okinawa Prefectural Government, Okinawa, Japan. nittays@pref.okinawa.lg.jp.
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Nitta
authors.affiliation: Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture and Food Research Organization, 3-1-5 Kannondai, Tsukuba, Ibaraki, 305-0856, Japan. mtbook@affrc.go.jp.
authors.forename: Takehisa
authors.initials: T
authors.lastname: Yamamoto
authors.affiliation: Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture and Food Research Organization, 3-1-5 Kannondai, Tsukuba, Ibaraki, 305-0856, Japan. sotaco@affrc.go.jp.
authors.forename: Sota
authors.initials: S
authors.lastname: Kobayashi
authors.affiliation: Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture and Food Research Organization, 3-1-5 Kannondai, Tsukuba, Ibaraki, 305-0856, Japan. kmvet@affrc.go.jp.
authors.forename: Kiyokazu
authors.initials: K
authors.lastname: Murai
authors.affiliation: Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture and Food Research Organization, 3-1-5 Kannondai, Tsukuba, Ibaraki, 305-0856, Japan. tsutsui@affrc.go.jp.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Tsutsui
mesh_terms: D000383:Agriculture; D000818:Animals; D002417:Cattle; D004196:Disease Outbreaks / Q000662:veterinary*; D004199:Disease Vectors; D004810:Ephemeral Fever / Q000453:epidemiology* / Q000635:transmission; D007564:Japan / Q000453:epidemiology; D008954:Models, Biological; D015233:Models, Statistical