Research on Salmonella in cattle lymph nodes continues

BlackAngusCow2_blogRecent research has been showing that the foodborne pathogen Salmonella can be apparent in the lymph nodes of cattle causing contamination in undercooked ground beef.  Commonly thought of as a concern in undercooked poultry instead of beef, Salmonella may be showing up in ground beef because the lymph nodes are not typically removed during the grinding process.

According to a recent article, the Centers for Disease Control and Prevention estimates that actually 23% of the outbreaks attributed to beef between 2009 and 2013 were caused by Salmonella. “Recent multi-state outbreaks linked to ground beef include Salmonella Enteritidis, which infected 46 people in nine states in 2012, and Salmonella Typhimurium, which infected 22 in six states in late 2012 and early 2013.”

“What we have found is that, in certain times of the year and in certain regions of the country, it’s not uncommon to recover Salmonella from some of the peripheral lymph nodes,” Guy Loneragan, a veterinarian epidemiologist and professor of food safety and public health at Texas Tech University, told Food Safety News.

In one study, the team found a diversity of Salmonella among the lymph nodes within carcasses, which according to the article means that the Salmonella probably got there from multiple different routes.

While the pathogen is typically transferred from the animal’s hide or intestines to the carcass during slaughter and processing, this recent research means that other testing may need to be developed in order to accurately test for Salmonella during the production process.

“We don’t think that traditional paradigm is sufficient to explain what we actually observe with Salmonella in these peripheral lymph nodes,” Loneragan said. In fact, according to the article the research group also believes flies may have a part to play in some of the transmission and have hypothesized that biting flies or other parasites transfer Salmonella into a cow’s skin, causing the infection.

The group has also conducted another study where they looked at smaller lymph nodes dispersed throughout the carcass and found that, as opposed to the larger ones, it’s rare to recover the pathogen from the very small ones. According to the article, this is a good thing because it means interventions don’t need to be as targeted on the small nodes.

Additional research and testing of how cattle lymph nodes contribute to Salmonella contamination is one element of USDA’s Salmonella Action Plan that was released in December 2013.

“What needs to be established is the extent to which the Salmonella remains in the lymph nodes. Because the purpose of the lymphatic system is to fight infection and then dispose of attackers, you might find Salmonella in a lymph node today, but if you tested that lymph node a week from now, that Salmonella might have cleared the lymphatic system,” Dr. David Goldman, acting USDA chief medical officer, said to Food Safety News.

For more information, click here.

Comments are closed.