Porcine reproductive and respiratory syndrome (PRRS)–a devastating reproductive disease that increases the rate of stillborn piglets and is easily spread among animals–costs the U.S. pork industry at least $664 million per year, the USDA estimates. Using blood tests to monitor the disease is a hassle for food producers, who often have to wrestle pigs to get them to cooperate.

Veterinarians at Iowa State University have been working for the past decade on an alternative to blood tests that’s about as low-tech as they come: ropes that can be hung from the pigs’ pens. The idea emerged from observations that pigs like to explore their environments by chewing on objects that are available to them. So a research team at Iowa State refined a process of hanging ropes from pigs’ pens and then collecting saliva samples from them.

The researchers discovered that the saliva samples can be used to detect a wide range of infections, including PRRS and foot-and-mouth disease. Jeff Zimmerman, a professor of veterinary diagnostic and production animal medicine at Iowa State, said in a press release that the saliva samples lead to diagnostic accuracy that’s at least as good as conventional techniques, but it’s often better, and it saves farmers time.

“The pigs aren’t happy about collecting blood samples, and neither are the people,” Zimmerman said in the release.

Another advantage of the rope method, Zimmerman’s team discovered, is that it requires little to no training. Piglets that are four weeks old or older are instinctively drawn to the ropes, which are irresistible to them, the researchers found. Younger pigs may require a half-hour or so to get accustomed to the ropes but they, too, will eventually start chewing. After testing cotton, hemp and nylon ropes, the vets determined that cotton produced the most accurate testing results, according to the release.

The rope technique is starting to catch on around the world. Iowa State’s veterinary diagnostic lab ran 176,167 saliva samples in 2015, up from 10,268 five years earlier, the school reported in the release.

The mounting damage from PRRS to the swine industry has prompted a stepped-up search for new solutions to fight the disease. Merck ($MRK) Animal Health introduced a vaccine to fight PRRS in 2014. More recently, U.K.-based Genus teamed up with the University of Missouri to develop a gene editing technique for creating pigs that are resistant to the virus.

– read more from Iowa State University

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