Understanding the risk of disease transmission through farm contacts
By Rob Hannam, Director of Business Development
Ongoing hog disease issues, and even the recent Covid-19 pandemic, continue to raise the awareness and understanding of the importance of biosecurity. Whether its on-farm practices like showering in and out of barns, restricting farm access to approved personnel only or implementing health screening protocols, our industry is increasingly prioritizing health and biosecurity.
Many of us have a good understanding of how contact tracing relates to biosecurity and managing the health of livestock and poultry. But, according to Dr. Glen Duizer, an animal health surveillance veterinarian from Manitoba’s Chief Veterinary Office, any disease outbreak investigation also relies heavily on efficient and timely contact trace-outs. He breaks down contact tracing for animal disease investigations into three types: direct, indirect and area.
“Most farmers have a good understanding of how diseases are transmitted through direct contact, like the movement of animals or surrounding environmental contact that comes from non-human sources like birds or weather conditions,” says Duizer. “But, while indirect contact of people, vehicles and equipment is a lower risk, it happens more frequently than animal movement.”
Why it matters
Tracking the movement of animal disease through contacts is an essential part of biosecurity and managing the risk of disease transmission. “Keeping disease out of your barn can come down to your ability to trace the indirect movements in and out of your farm operation and evaluate the risks of each of those contacts,” says Duizer.
The challenge can be accurately recording the movements of personnel and vehicles. “Think of the number of people that come onto your farm throughout a week, other than employees,” says Duizer. “Depending on the size of your operation, your visitors might include maintenance crews, feed deliveries, animal deliveries, garbage trucks, hydro readers and veterinarians.”
In addition to recording the movements of personnel and vehicles, each indirect contact will carry a different level of disease risk. For example, while a feed truck may only enter a controlled access zone (CAZ), they are still likely to visit multiple farms each day. Or consider a maintenance crew – while they won’t be visiting multiple farms in one day and may have downtime protocols, they are likely working in restricted access zones (RAZ) with more direct contact to animals. Plus, they carry tools that may require additional cleaning and disinfecting.
Duizer says tracking the movement of these indirect contacts is necessary to assess disease risk and prevent transmission in the event of an outbreak. And when it comes to managing these risks, the timeliness or speed of evaluating each contact is crucial if a disease outbreak is identified on your farm, or an area farm where contacts may have visited.
“Our industry has done a good job tracing and recording direct contacts, using visitor logs, transport manifests and tools like PigTrace to track the movements of hogs, but we have a lot of work to do when it comes to tracking people, vehicles and equipment on farms,” says Duizer. “If a disease is suspected, trace-out reports for contacts can take days, dramatically increasing the risk of transmission.”
