A $3 million grant from the USDA National Institute of Food and Agriculture Translational Genomics Program will study the genetic basis of resistance or susceptibility to Johne's disease over the next five years.
Johne's disease is a contagious, untreatable and fatal gastrointestinal disease of domesticated ruminant livestock. It ranks as one of the most costly infectious diseases of dairy cattle, affecting 65% of U.S. dairies.
Paul Coussens, professor in the Michigan State University departments of Animal Science and Microbiology and Molecular Genetics, is working on the project.
The objective of the five-year program, he says, is to understand why only some cattle get sick following infection with Mycobacterium avium subspecies paratuberculosis – the causative agent of Johne's disease – and to determine if it is possible to breed cattle that are more resistant to Johne's.
The slow, progressive nature of Johne's disease makes diagnosis difficult, especially during the early preclinical stages. There are no cost-effective therapies, and vaccines—which aren't used in the United States—do not prevent infections or stop the spread of the disease to other animals.
"The new Translational Genomics Program from USDA NIFA allows us enough time and funds to track animals over a long period of time. This is critical in research on Johne's disease because the disease can take two to five years to develop following initial infection," Coussens said.
During the first and second years of the project, the researchers hope to determine the genetic makeup of each of the animals in the study and monitor the progress of each animal in a producer setting in commercial herds.
"The goal is to be able to identify animals very early on that have a high probability of being resistant to the infection to begin with," Coussens said.
The second part of the research will involve tracking young calves over four years as they enter herds known to be contaminated with paratuberculosis to examine what type of immune response they have when exposed, and to track whether they become sick with the disease.
"Generally all these calves will be exposed, but only a small percentage will develop the disease, so we believe that the genetics to properly control the infection and be resistant to the disease are already in our herds," Coussens said. "We just never looked for them before. It's a new way of thinking about this disease and how to control it."
The project is made possible with the tools of modern-day genetics. Coussens hopes that the work will enhance knowledge of basic immune responses in cattle and be useful in many diseases in cattle and possibly in humans.
"Our ultimate objective is to work with dairy producers and breeders to ensure that our results are used in the industry to breed cattle that are resistant to Johne's disease and thereby improve profitability, animal welfare and the overall safety of our food supply," Coussens said.
Also working on the project are C. Titus Brown, an assistant professor in the MSU departments of Computer Science and Engineering, and Microbiology and Molecular Genetics, and Brian W. Kirkpatrick, an animal sciences professor at the University of Wisconsin-Madison.