title: A space-time analysis of Mycoplasma bovis: bulk tank milk antibody screening results from all Danish dairy herds in 2013-2014.
abstract: BACKGROUND
  Mycoplasma bovis is an important pathogen causing severe disease outbreaks in cattle farms. Since 2011, there has been an apparent increase in M. bovis outbreaks among Danish dairy cattle herds. The dairy cattle industry performed cross-sectional antibody screening for M. bovis on four occasions, using the indirect BIO K 302 M. bovis enzyme-linked immunosorbent assay (ELISA) (Bio-X, Belgium) in bulk tank milk from all dairy herds between June 2013 and July 2014. The objective of this study was to investigate the evolution of the spatial distribution of M. bovis in the Danish dairy herd population throughout the study period. Repeated bulk tank milk samples were used as a proxy for the herd-level diagnosis. Descriptive and spatial analyses were performed for the four screening rounds. Based on a previous diagnostic test evaluation study, the M. bovis status for each herd was determined as test-positive or test-negative using a cut-off of 50 optical density coefficient %. The spatial global clustering was evaluated through a modified K-function method, and local clusters were identified by scan statistics.
  
  
  RESULTS
  The results showed that M. bovis test-positive herds had a dynamic pattern in space. The global clustering analysis showed that M. bovis test-positive herds were spatially correlated in rounds one, three and four. These findings were supported to some extent by the local clustering analysis, which found significant high- and low-risk spatial clusters in rounds one and three in the north and south of the mainland.
  
  
  CONCLUSIONS
  The clusters with a high risk of observing test-positive herds did not remain between sampling rounds, indicating that M. bovis did not tend to persist upon emergence in dairy herds. In contrast, the clusters with a low risk of observing test-positive herds persisted in the same area throughout the study period.
authors.affiliation: Section for Epidemiology, National Veterinary Institute, Technical University of Denmark, Bülowsvej 27, 1870, Frederiksberg C, Denmark. marared@vet.dtu.dk.
authors.forename: Margarida
authors.initials: M
authors.lastname: Arede
authors.affiliation: Section for Epidemiology, National Veterinary Institute, Technical University of Denmark, Bülowsvej 27, 1870, Frederiksberg C, Denmark. pkani@vet.dtu.dk.
authors.forename: Per Kantsø
authors.initials: PK
authors.lastname: Nielsen
authors.affiliation: Section for Epidemiology, National Veterinary Institute, Technical University of Denmark, Bülowsvej 27, 1870, Frederiksberg C, Denmark. sayah@vet.dtu.dk.
authors.forename: Syed Sayeem Uddin
authors.initials: SS
authors.lastname: Ahmed
authors.affiliation: Section for Epidemiology, National Veterinary Institute, Technical University of Denmark, Bülowsvej 27, 1870, Frederiksberg C, Denmark. tahbh@vet.dtu.dk.
authors.forename: Tariq
authors.initials: T
authors.lastname: Halasa
authors.affiliation: Department of Large Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Grønnegårdsvej 2, 1870, Frederiksberg C, Denmark. liza@sund.ku.dk.
authors.forename: Liza Rosenbaum
authors.initials: LR
authors.lastname: Nielsen
authors.affiliation: Section for Epidemiology, National Veterinary Institute, Technical University of Denmark, Bülowsvej 27, 1870, Frederiksberg C, Denmark. ntoft@vet.dtu.dk.
authors.forename: Nils
authors.initials: N
authors.lastname: Toft
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000032:analysis; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology* / Q000382:microbiology; D003430:Cross-Sectional Studies; D003612:Dairying; D003718:Denmark / Q000453:epidemiology; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D008892:Milk / Q000382:microbiology*; D009175:Mycoplasma Infections / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D045682:Mycoplasma bovis / Q000302:isolation & purification*; D012621:Seasons
chemical_list: D000907:Antibodies, Bacterial