Infection through the farm gate

Sammanfattning: This thesis is based on studies of movements of livestock, on-farm biosecurity and disease awareness among farmers in Sweden; factors which can affect the spread of contagious livestock diseases. The structure of the cattle and pig movements were analysed using data obtained from the Swedish Board of Agriculture. Most movements were within 100 km, however, there were also long distance movements up to 1200 km for cattle and 1000 km for pigs. This supports an initial total standstill in case of an outbreak of foot-and-mouth disease. Network analysis was used to investigate the contact patterns. Many of the farms did not sell or buy animals or had only limited trade, whereas some farms had many contacts. The measure 'ingoing infection chain' was constructed to capture indirect movements, some farms with few direct contacts had many indirect contacts and this measure can potentially be very useful for disease control and risk based surveillance. On-farm biosecurity was investigated through a posted questionnaire study to 1498 farmers and response was retrieved from 34% of them. Among farmers declining participation, the major reason was not having livestock. There was large variation in biosecurity routines among farmers. In general farmers with pigs had higher biosecurity compared to farmers with cattle, sheep/goats or mixed species or hobby farmers. Many farmers and visitors did not have sufficient routines to prevent spread of disease and some reported inconsistent routines, indicating a lack of knowledge of how to prevent spread of disease. A need for improvement of onfarm biosecurity was identified. Disease awareness and information retrieval among pig farmers in relation to an outbreak of PRRS in 2007 was investigated using posted questionnaires to 153 farmers. Farmers with large herds were in general aware of the outbreak and how to protect their farm. However, hobby farmers were identified as a group difficult to reach with information in case of an outbreak. Active search for information was associated with distance from the outbreak. The Swedish Animal Health Service, followed by the veterinary authorities, were considered the most important and reliable source of information.