title: Social group size affects Mycobacterium bovis infection in European badgers (Meles meles).
abstract: 1. In most social animals, the prevalence of directly transmitted pathogens increases in larger groups and at higher population densities. Such patterns are predicted by models of Mycobacterium bovis infection in European badgers (Meles meles). 2. We investigated the relationship between badger abundance and M. bovis prevalence, using data on 2696 adult badgers in 10 populations sampled at the start of the Randomized Badger Culling Trial. 3. M. bovis prevalence was consistently higher at low badger densities and in small social groups. M. bovis prevalence was also higher among badgers whose genetic profiles suggested that they had immigrated into their assigned social groups. 4. The association between high M. bovis prevalence and small badger group size appeared not to have been caused by previous small-scale culling in study areas, which had been suspended, on average, 5 years before the start of the current study. 5. The observed pattern of prevalence might occur through badgers in smaller groups interacting more frequently with members of neighbouring groups; detailed behavioural data are needed to test this hypothesis. Likewise, longitudinal data are needed to determine whether the size of infected groups might be suppressed by disease-related mortality. 6. Although M. bovis prevalence was lower at high population densities, the absolute number of infected badgers was higher. However, this does not necessarily mean that the risk of M. bovis transmission to cattle is highest at high badger densities, since transmission risk depends on badger behaviour as well as on badger density.
authors.affiliation: Institute of Zoology, Regent's Park, London NW1 4RY, UK. rosie.woodroffe@ioz.ac.uk
authors.forename: Rosie
authors.initials: R
authors.lastname: Woodroffe
authors.forename: Christl A
authors.initials: CA
authors.lastname: Donnelly
authors.forename: Gao
authors.initials: G
authors.lastname: Wei
authors.forename: D R
authors.initials: DR
authors.lastname: Cox
authors.forename: F John
authors.initials: FJ
authors.lastname: Bourne
authors.forename: Terry
authors.initials: T
authors.lastname: Burke
authors.forename: Roger K
authors.initials: RK
authors.lastname: Butlin
authors.forename: C L
authors.initials: CL
authors.lastname: Cheeseman
authors.forename: George
authors.initials: G
authors.lastname: Gettinby
authors.forename: Peter
authors.initials: P
authors.lastname: Gilks
authors.forename: Simon
authors.initials: S
authors.lastname: Hedges
authors.forename: Helen E
authors.initials: HE
authors.lastname: Jenkins
authors.forename: W Thomas
authors.initials: WT
authors.lastname: Johnston
authors.forename: John P
authors.initials: JP
authors.lastname: McInerney
authors.forename: W Ivan
authors.initials: WI
authors.lastname: Morrison
authors.forename: Lisa C
authors.initials: LC
authors.lastname: Pope
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D001835:Body Weight; D017753:Ecosystem; D005260:Female; D054884:Host-Pathogen Interactions; D008297:Male; D045969:Mustelidae; D009163:Mycobacterium bovis; D011157:Population Dynamics; D015995:Prevalence; D012919:Social Behavior; D013997:Time Factors; D014376:Tuberculosis / Q000662:veterinary*