Disease introduction is a primary concern. Destabilization of an existing health status without changing the disease profile is another. Finally, the impact of health problems in newly arrived animals, on their long term productivity and longevity in the herd must also be considered. This paper will focus on some of these concerns, and review changes in the methods used to introduce new animals to swine units. There are many biosecurity procedures employed on swine farms to prevent disease introduction via vectors such as people, vehicles, or equipment.
Live animals continue to represent the greatest risk as a source of disease however.
Key practices such as purchasing stock from herds with intense biosecurity and health monitoring systems, single source purchases and well researched source changes will help protect the recipient herd. Disease can still be transferred unexpectedly though, if animals are incubating an early infection, but showing no signs of disease, or if they are carriers of an infection that is subclinical, and undetected in the source herd. There has also been a well publicized increase in swine operations in some areas, such that some seedstock herds have become compromised by new neighbours due to the potential for direct aerosol disease transmission to their herds. As regions become more densely populated with swine farms, area spread of disease through regions, though not fully understood, also impacts on previously isolated farms. There have been two key changes implemented in the transfer of genetic material that have helped to reduce potential disease transfer.