title: Fraction of bovine leukemia virus-infected dairy cattle developing enzootic bovine leukosis.
abstract: Enzootic bovine leucosis (EBL) is a transmissible disease caused by the bovine leukemia virus that is prevalent in cattle herds in many countries. Only a small fraction of infected animals develops clinical symptoms, such as malignant lymphosarcoma, after a long incubation period. In the present study, we aimed to determine the fraction of EBL-infected dairy cattle that develop lymphosarcoma and the length of the incubation period before clinical symptoms emerge. These parameters were determined by a mathematical modeling approach based on the maximum-likelihood estimation method, using the results of a nationwide serological survey of prevalence in cattle and passive surveillance records. The best-fit distribution to estimate the disease incubation period was determined to be the Weibull distribution, with a median and average incubation period of 7.0 years. The fraction of infected animals developing clinical disease was estimated to be 1.4% with a 95% confidence interval of 1.2-1.6%. The parameters estimated here contribute to an examination of efficient control strategies making quantitative evaluation available.
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, Japan. Electronic address: tsutsui@affrc.go.jp.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Tsutsui
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, Japan.
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, Japan.
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, Japan.
authors.forename: Takehisa
authors.initials: T
authors.lastname: Yamamoto
mesh_terms: D000818:Animals; D002417:Cattle; D016583:Enzootic Bovine Leukosis / Q000453:epidemiology* / Q000821:virology; D005260:Female; D007564:Japan / Q000453:epidemiology; D001909:Leukemia Virus, Bovine / Q000502:physiology*; D016013:Likelihood Functions; D008228:Lymphoma, Non-Hodgkin / Q000453:epidemiology / Q000662:veterinary* / Q000821:virology; D015995:Prevalence; D016036:Seroepidemiologic Studies
keywords: Bovine leukemia virus; Enzootic bovine leukosis; Incubation period