How disease ‘contact chains’ link farms near and far

It’s good to be connected to others in this world, but some networks are less than desirable — like disease networks.

Unwittingly introducing new diseases to a herd or flock is one of the biggest challenges in adding new animals. For this reason, farmers and ranchers employ biosecurity protocols and can quarantine the new animal to watch for signs of illness. In doing so, they help protect themselves from complex networks of disease “contact chains” that connect farms across the country.

Veterinary researchers at England’s University of Exeter dug deeper into these networks and how they affect much of the United Kingdom, looking particularly at beef and dairy farms. Their aim was to find patterns, or “pathways” for the spread of diseases that harm the cattle industries.

“We found that farms, even if they only bought cattle from one or two other farms, could be at the end of a chain connecting their farm and their animals to several thousand other farms,” said veterinary researcher Helen Fielding.

Armed with data from 75 million cattle movements occurring between 2001 and 2015, the researchers found that about half of all British cattle farms were linked by cattle movements to more than 1,000 other farms every year when they brought in cattle. They found that 16% were connected to more than 10,000 each year. The numbers were similar when looked at from a selling perspective. On average, over 13,000 farms had contact chains extending to more than 10,000 other farms both by buying and selling over the entire time period.

The researchers say that the most connected farms may be at a greater risk to the spread of infections.

“For example, one farm in Devon bought only six cattle in one year; those six cattle came from four farms, and those four farms were connected in two steps back to 10 others,” Fielding said. “Tracking back 12 months, the sequence of links to the one Devon farm extended to 11,132 farms, as far afield as Kent, North Wales and Orkney.”

For farmers and ranchers, this knowledge could be power.

“This research shows that even farms that buy their cattle very carefully might be exposed to infections from many other unknown farms across the whole country,” said lead author of a study on the research, Robbie McDonald. “Better understanding of the extensive connections formed by trading between British farms can help quantify the risks of disease spread and assist in the formulation of control strategies that work alongside efficient trading practices.”

Neogen is a global provider of animal safety solutions for cattle and other industries, including biosecurity tools to protect against some of the biggest diseases of concern to farmers and ranchers.