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New research will help to unravel the mysteries of Johne's disease

xEvery day, more than 16 million gallons of milk are consumed in the United States. And despite the technology and safety standards currently in place, some of that milk contains a nasty bacterium with identified links to Johne ’s disease in cattle and possible connections to Crohn’s disease in people. With a new grant, Cornell researchers will continue their research to identify the bacterium in milk, determine risk factors for milk contamination and document recommended intervention strategies to make milk safe.

The bacterium, known as Mycobacterium avium subspecies paratuberculosis or MAP, incites an infection in ruminant animals that takes approximately four years to show clinical signs. In the meantime, dairy cows have had two calves that may contract the infection during pregnancy or birth and have also produced thousands of gallons of milk headed for store shelves. Recent studies have shown that MAP present in milk can survive pasteurization, which has raised human health concerns due to the widespread nature of MAP in modern dairy herds.

Once MAP has infiltrated a herd, the cows are widely susceptible to Johne’s disease, which is contagious, chronic and often fatal in cases of clinical disease. The disease affects primarily the small intestine of ruminants and is blamed for financial losses that total upwards of $250 million annually among the dairy community in the United States.

The newly received $500,000 grant from the USDA’s National Institute of Food and Agriculture (NIFA) will build on the results of the current $2.5 million project, which was funded by the Agricultural Research Service, USDA, Johne’s Disease Integrated Project (JDIP) and other sources and has been underway since 2009, making this project one of the few in the world to span nearly a decade.

“In the 9-year longitudinal study, we will have DNA from four generations of cows and bacteria,” said Dr. Ynte Schukken, principal investigator for the study and professor of Epidemiology and Herd Health at Cornell’s College of Veterinary Medicine. “Our study covers the entire spectrum, with data and samples collected from the field, cultured in the lab and bacteria and host DNA sequenced using the most modern genomic methods. Because of this unparalleled 9-year data set, we have the potential to unravel the mysteries of Johne’s disease, a very slow-going and devastating infection on dairy farms.”

To do this, the team of researchers, which includes scientists from Penn State University, the University of Pennsylvania, the University of Maryland, and Drs. Schukken and Yrjo Grohn from Cornell, will walk through four steps: They will validate the use of a current test used to identify MAP; analyze data from two herds with a known MAP infection prevalence and cross-sectional data from 300 dairy herds with the complete range of MAP infection prevalence, focusing on the relationship between management practices and MAP contamination of milk; use the collected data to develop risk assessment models that explain and predict MAP contamination of raw milk; and use the collected data and the developed models to design optimal sustainable MAP-free milk programs.

The grant is one of 17 research projects that were announced by NIFA in November 2012, all designed to improve food safety by helping control microbial and chemical contamination in various foods. Schukken’s investigation will extend prior results that have already explained transmission patterns of MAP at the molecular level, developed mathematical models for predicting transmission, devised control programs, and monitored those programs’ success rates.

“Our immediate goal is to provide dairy farmers with the tools they need to produce milk that is free of MAP bacteria,” said Schukken. “Evidence from previous work we’ve done proves that a high percentage of dairy farms in the US have MAP-infected cattle, so reducing viable MAP in raw and pasteurized milk is of importance. First for the health and well-being of the cows, but also, because of the possible connections to Crohn’s disease, for the health and well-being of people.”