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Listeriosis outbreak marks largest in history

by Wyoming Livestock Roundup

A recent outbreak of Listeriosis linked to a Colorado farm has resulted in 133 infections and 28 deaths, as well as one miscarriage, across 26 states as of Oct. 25.

Reports from the Center for Disease Control and Prevention (CDC) identified the disease as linked to whole cantaloupes from Jensen Farms in Colorado.
When the Colorado Department of Public Health and Environment reported seven cases of Listeriosis to the CDC, which have since been linked to the Rocky Ford brand of cantaloupe shipped from Jensen Farms July 29 through Sept. 10 to 17 states across the nation, Jensen Farms voluntarily recalled the produce.

On Sept. 14, the Food and Drug Administration (FDA) responded by issuing a press release warning consumer not to consume Rocky Ford cantaloupes.

It wasn’t until Sept. 23 that Carol’s Cuts of Kansas City, Kan. and Fresh Fruit Up of Buffalo, N.Y. initiated recalls on fresh cut cantaloupe and cut mixed fruit.

Wyoming saw four cases of Listeriosis and one fatality as a result of the outbreak. A Sheridan county woman marked the fourteenth death as a result of the Listeria bacteria, and two Laramie County adults were sickened after consuming cantaloupe. A Lincoln County man was also identified with Listeriosis.
Most people affected by the Listeriosis outbreak were over 60 years old and 98 percent were hospitalized as a result, according to CDC data.

There are about 800 cases of Listeriosis and three to four outbreaks reported each year in the United States. Prior to this year’s outbreak, the largest outbreak occurred in 2002 with only 54 illnesses and eight deaths reported.

“This outbreak has the highest number of deaths of any U.S. foodborne outbreak since a Listeriosis outbreak in 2002,” said the CDC.

Because of the time required for Listeriosis to manifest itself and be reported, the FDA estimates that illnesses occurring after Sept. 28 may not have been reported yet.

Listeriosis occurs when food contaminated with the bacterium Listeria monocytogenes is consumed.

“While all people are susceptible to Listeria, older adults, persons with weakened immune systems and pregnant women are at particular risk,” said the FDA in a press release. “Listeriosis can be fatal, especially in certain high-risk groups.”

Typically, symptoms include fever or muscles aches and gastrointestinal symptoms. Pregnant women may also experience mild flu-like symptoms that could result in miscarriage, stillbirth, premature delivery or infection of the newborn. Septicemia and meningitis are common clinic presentations in older adults.

After identification of the bacteria through a blood or spinal fluid test, Listeriosis can be treated with antibiotics and cured, though 10 to 30 percent of people experience residual neurological problems, according to UW professor Kurt Miller.

Listeria is not typically linked to cantaloupe, but rather deli meats, hot dogs and soft cheese made with unpasteurized milk.

“Because of this unusual circumstance, FDA’s newly formed Coordinated Outbreak Response and Evaluation (CORE) Network is working with FDA districts, CDC, the states and other regulatory partners on a root cause analysis to determine where in the supply chain and what circumstances likely caused the implicated cantaloupe to be contaminated,” said the FDA.

A joint investigation by the CDC and FDA tested the growing environment, packing facility and cold storage areas for the source of the Listeria bacteria. The results showed a number of possible origins that would provide for the bacteria to thrive.

In their summary report issued Oct. 19, the FDA says, “Low level sporadic Listeria monocytogenes in the agricultural environment and incoming cantaloupe may have contributed to the introduction of the pathogen into the packing facility.”

Aside from the growing environment, the packing facility and cold storage may have contributed to bacterial introduction, growth and spread.

“A truck used to haul culled cantaloupe to a cattle operation was parked adjacent to the packing facility and could have introduced contamination into the facility; facility design allowed for the pooling of water on the packing facility floor adjacent to equipment and employee walkway access to grading stations; the packing facility floor was constructed in a manner that was not easily cleanable; the packing equipment was not easily cleaned and sanitized; the washing and drying equipment used for cantaloupe packing was previously used for postharvest handling of another raw agricultural commodity; and there was no pre-cooling step to remove field heat from the cantaloupes before cold storage,” says the FDA.

Tests revealed that cantaloupes in cold storage were also contaminated with the bacteria, and Jensen Farms was issued a warning letter by the FDA, requiring them to correct violations of FDA policy.

“Each year roughly one in six Americans (or 48 million people) gets sick, 128,000 are hospitalized, and 3,000 die of foodborne diseases,” explains the CDC.

The CDC identifies Listeria monocytogenes as the third most prevalent pathogen contributing to domestically acquired foodborne illness that results in death, contributing approximately 19 percent of fatalities resulting from foodborne illness.

For more information on Listeriosis or the recent outbreak visit Saige Albert is editor of the Wyoming Livestock Roundup and can be reached at

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