title: Risk based surveillance for early detection of low pathogenic avian influenza outbreaks in layer chickens.
abstract: Current knowledge does not allow the prediction of when low pathogenic avian influenza virus (LPAIV) of the H5 and H7 subtypes infecting poultry will mutate to their highly pathogenic phenotype (HPAIV). This mutation may already take place in the first infected flock; hence early detection of LPAIV outbreaks will reduce the likelihood of pathogenicity mutations and large epidemics. The objective of this study was the development of a model for the design and evaluation of serological-surveillance programmes, with a particular focus on early detection of LPAIV infections in layer chicken flocks. Early detection is defined as the detection of an infected flock before it infects on average more than one other flock (between-flock reproduction ratio Rf<1), hence a LPAI introduction will be detected when only one or a few other flocks are infected. We used a mathematical model that investigates the required sample size and sampling frequency for early detection by taking into account the LPAIV within- and between-flock infection dynamics as well as the diagnostic performance of the serological test used. Since layer flocks are the target of the surveillance, we also explored whether the use of eggs, is a good alternative to sera, as sample commodity. The model was used to refine the current Dutch serological-surveillance programme. LPAIV transmission-risk maps were constructed and used to target a risk-based surveillance strategy. In conclusion, we present a model that can be used to explore different sampling strategies, which combined with a cost-benefit analysis would enhance surveillance programmes for low pathogenic avian influenza.
authors.affiliation: Department of Epidemiology, Crisis organization and Diagnostics, Central Veterinary Institute (CVI) part of Wageningen UR, P.O. Box 65, 8200 AB Lelystad, The Netherlands; Department of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, P.O. Box 80, b51, 3508 TD Utrecht, The Netherlands. Electronic address: jluis.gonzalesr@gmail.com.
authors.forename: J L
authors.initials: JL
authors.lastname: Gonzales
authors.affiliation: Department of Epidemiology, Crisis organization and Diagnostics, Central Veterinary Institute (CVI) part of Wageningen UR, P.O. Box 65, 8200 AB Lelystad, The Netherlands. Electronic address: gertjan.boender@wur.nl.
authors.forename: G J
authors.initials: GJ
authors.lastname: Boender
authors.affiliation: Department of Epidemiology, Crisis organization and Diagnostics, Central Veterinary Institute (CVI) part of Wageningen UR, P.O. Box 65, 8200 AB Lelystad, The Netherlands. Electronic address: armin.elbers@wur.nl.
authors.forename: A R W
authors.initials: AR
authors.lastname: Elbers
authors.affiliation: Department of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, P.O. Box 80, b51, 3508 TD Utrecht, The Netherlands. Electronic address: J.A.Stegeman@uu.nl.
authors.forename: J A
authors.initials: JA
authors.lastname: Stegeman
authors.affiliation: Department of Epidemiology, Crisis organization and Diagnostics, Central Veterinary Institute (CVI) part of Wageningen UR, P.O. Box 65, 8200 AB Lelystad, The Netherlands. Electronic address: aline.dekoeijer@wur.nl.
authors.forename: A A
authors.initials: AA
authors.lastname: de Koeijer
mesh_terms: D000818:Animals; D002645:Chickens; D004196:Disease Outbreaks / Q000662:veterinary*; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000378:metabolism; D009980:Influenza A virus / Q000378:metabolism / Q000472:pathogenicity*; D005585:Influenza in Birds / Q000175:diagnosis* / Q000453:epidemiology / Q000821:virology; D009426:Netherlands / Q000453:epidemiology; D011159:Population Surveillance; D012307:Risk Factors; D013997:Time Factors
chemical_list: D019267:Hemagglutinin Glycoproteins, Influenza Virus; C109963:hemagglutinin, avian influenza A virus
keywords: Avian influenza; Early detection; LPAI; Risk-based surveillance; Sample size; Sampling frequency; Surveillance