Direct and indirect contacts between cattle farms in north-west England.

Little is known regarding the types and frequencies of contact that exist between farms and which of these may act as pathogen transmission routes; however it is likely that farms demonstrate considerable heterogeneity in such contacts. In this cross-sectional study, we explored the direct and indirect contact types and frequencies that exist between cattle farms within a region, focusing on potential routes of pathogen transmission. The owners/managers of 56 farms located in a 10 km by 10 km study area in north-west England were administered an interview-based questionnaire between June and September 2005. Information was obtained relating to contact types and frequencies, including those involving animal movements, equipment sharing between farms and any contractors or companies visiting the farms. The data was explored using hierarchical cluster analysis and network analysis. There was considerable variation between farms arising from different contact types. Some networks exhibited great connectivity, incorporating approximately 90% of the farms interviewed in a single component, whilst other networks were more fragmented, with multiple small components (sets of connected farms not linked with other farms). A range of factors influencing contact between farms were identified. For example, contiguous farms were more likely to be linked via other contacts, such as sharing of equipment and direct farm-to-farm animal movements (p<0.001 and p=0.02, respectively). The frequency of contacts was also investigated; it is likely that the amount of contact a farm receives from a company or contractor and whether or not biosecurity is performed after contact would impact on disease transmission potential. We found considerable heterogeneity in contact frequency and that many company and contractor personnel undertook little biosecurity. These findings lead to greater understanding of inter-farm contact and may aid development of appropriate biosecurity practices and control procedures, and inform mathematical modelling of infectious diseases.

[1]  R. Huirne,et al.  Risk factors for existence of Bovine Herpes Virus 1 antibodies on nonvaccinating Dutch dairy farms. , 1998, Preventive veterinary medicine.

[2]  Christl A. Donnelly,et al.  Culling and cattle controls influence tuberculosis risk for badgers , 2006, Proceedings of the National Academy of Sciences.

[3]  J. W. Wilesmith,et al.  Descriptive epidemiology of the 2001 foot-and-mouth disease epidemic in Great Britain: the first five months , 2001, Veterinary Record.

[4]  C. Webb,et al.  Farm animal networks: unraveling the contact structure of the British sheep population. , 2005, Preventive veterinary medicine.

[5]  L Matthews,et al.  Epidemiological implications of the contact network structure for cattle farms and the 20–80 rule , 2005, Biology Letters.

[6]  Alex Donaldson,et al.  Managing foot-and-mouth , 2001, Nature.

[7]  Hichang Cho,et al.  A Social Network Contagion Theory of Risk Perception , 2003, Risk analysis : an official publication of the Society for Risk Analysis.

[8]  A. A. Dijkhuizen,et al.  Quantification of contacts between Dutch farms to assess the potential risk of foot-and-mouth disease spread. , 1996 .

[9]  Torben Mikkelsen,et al.  Investigation of airborne foot-and-mouth disease virus transmission during low-wind conditions in the early phase of the UK 2001 epidemic , 2003 .

[10]  R. Hanneman.  Introduction to Social Network Methods , 2001 .

[11]  R. Christley,et al.  Exploring the role of auction markets in cattle movements within Great Britain. , 2007, Preventive veterinary medicine.

[12]  Subhash Sharma.  Applied multivariate techniques , 1995 .

[13]  M. Bigras-Poulin,et al.  Network analysis of Danish cattle industry trade patterns as an evaluation of risk potential for disease spread. , 2006, Preventive veterinary medicine.

[14]  M. Gilbert,et al.  Cattle movements and bovine tuberculosis in Great Britain , 2005, Nature.

[15]  D. Pfeiffer,et al.  Use of social network analysis to characterize the pattern of animal movements in the initial phases of the 2001 foot and mouth disease (FMD) epidemic in the UK. , 2006, Preventive veterinary medicine.

[16]  J. Anderson.  Biosecurity—a new term for an old concept , 1998, The Bovine Practitioner.

[17]  R. Christley,et al.  Infection in social networks: using network analysis to identify high-risk individuals. , 2005, American journal of epidemiology.

[18]  R S Morris,et al.  Social-network analysis of Mycobacterium bovis transmission among captive brushtail possums (Trichosurus vulpecula). , 2003, Preventive veterinary medicine.

[19]  Adam Duncan.  Health security In cattle herds , 1990, A & A Practice.

[20]  T E Carpenter,et al.  Direct and indirect contact rates among beef, dairy, goat, sheep, and swine herds in three California counties, with reference to control of potential foot-and-mouth disease transmission. , 2001, American journal of veterinary research.

[21]  A. Tibary,et al.  Biosecurity and biocontainment in alpaca operations☆ , 2005, Small Ruminant Research.

[22]  R S Morris,et al.  The potential extent of transmission of foot-and-mouth disease: a study of the movement of animals and materials in Southland, New Zealand. , 1993, New Zealand veterinary journal.