Swine veterinarians preparing for emergence of more diseases

About 1 million pigs cross state lines each week destined for other farms, where they are fed or bred, said Dr. Jeffrey J. Zimmerman. That total does not include pigs sent to slaughter. With that rate of migration, outbreak responses need to start within hours of discovering infectious diseases, he said.With more movement of pigs, trucks, and feed, the probability of a disease transmission event increases until it “becomes a certainty,” he said.Dr. Zimmerman, a professor of diagnostic and production animal medicine at Iowa State University College of Veterinary Medicine, said growth in pig herd sizes over the past several decades also has made the herds more vulnerable to diseases.“Larger herds reduce our ability to achieve herd immunity, and basically, we have relied on herd immunity forever,” he said. “It’s been our friend. Why was influenza seasonal before? Because we achieved herd immunity.“Those herds of 50 or 100 animals—you could achieve solid herd immunity, and the virus disappears.”