By Katie Kerwin McCrimmon

The deadly listeria contamination at Colorado’s Jensen Farms may have begun with imperfect cantaloupes that were hauled to a nearby cattle ranch.

The dump truck carrying those misshapen cantaloupes was parked right next to the open-air processing plant. The truck may have inadvertently brought listeria from cow manure back to the farm and spread the disease to prized Colorado cantaloupes, which were then shipped across the country.

Federal officials released their findings today from an investigation of the listeria outbreak. While a team of health detectives from various state and federal agencies is certain that the outbreak began at Jensen Farms, they cannot pinpoint how the listeria first arrived at the facility or exactly how it spread.

Investigators said the processing plant did not have an adequate system for chilling cantaloupe from the field and that the packing facility was not easy to clean. Water pooling on the ground also became a perfect area for listeria to thrive, grow and spread.

Officials had never previously inspected the farm, but said it’s not typical of cantaloupe processing facilities.

“I would say they were fairly unique,” Sherri McGarry, senior advisor for the U.S. Food and Drug Administration’s Coordinated Outbreak Response and Evaluation (CORE) team, said during a Wednesday press conference.

The investigation remains open and new cases of the illness continue to be reported. Officials from Jensen Farms have vowed not to distribute more cantaloupe next summer before state and federal official can certify that their operation is safe.

But anger among Colorado cantaloupe growers in Rocky Ford, nearly 100 miles away, has been boiling over as farmers fear that the reputation of their sweet melons has been marred permanently.

So far, 25 people have died from the listeria outbreak. One pregnant woman has miscarried and 123 cases of listeria have been reported. Cases are continuing to surface, but new reports are beginning to decrease.

“This is the deadliest food borne outbreak in the U.S. in more than 25 years,” said Dr. Barbara Mahon, deputy chief at the Centers for Disease Control and Prevention. “It’s too soon to declare the outbreak over. We will monitor for two more weeks.”

The outbreak marks the first time that whole cantaloupes have been implicated in spreading listeria.

“This is huge. It’s awful. Our hearts go out to the families of these patients and the folks that passed away,” said John Salazar, Colorado Commissioner of Agriculture. “We are working as a department to make sure we can minimize any possibility of infection in the future.”

Alicia Cronquist

Colorado health officials said the first sign of the listeria outbreak emerged on Aug. 29 when two cases of listeria were reported on the same day. That is “highly unusual,” said Alicia Cronquist, an epidemiologist with the Colorado Department of Public Health and Environment.

tate and county health officials began conducting standardized interviews with the victims. Colorado health officials contacted the FDA on Sept. 6 and within three days were confident that cantaloupe was the source.

A cantaloupe from one victim’s refrigerator and two stores where others had purchased suspected cantaloupe tested positive for listeria.

McGarry of the FDA’s rapid response team said investigators were able to use the equivalent of DNA fingerprinting to link the illnesses to Jensen Farms.

“Multiple samples tested positive,” McGarry said. “These results indicated that the cantaloupe contained a poisonous substance. The firm was packing cantaloupes under unsanitary conditions.”

Investigators decided to conducted a full-scale environmental assessment on Sept. 23 and 24 to try to find the root cause of the outbreak.

“The team visited and surveyed cantaloupe growing facilities, cold storage, food safety, post harvest and agricultural production,” McGarry said.

Experts found that the water used at the farm was safe. All of the samples from the field also tested negative for listeria.

That left the packing facility as the most likely culprit for contamination.

Either cantaloupe were contaminated with listeria in the field, then were improperly cooled and the bacteria grew and spread. Or, the dump truck became contaminated and brought listeria to the facility.

“This was an open-air facility where the produce was packed. Defective cantaloupe would be put into a dump truck that hauled it to a cattle ranch,” said Jim Gorny, a senior advisor for produce safety for the FDA. “Cattle are definitely a reservoir of listeria. They could have transported listeria back. The truck was parked right next to where the food was handled.”

Gorny said listeria was fairly widespread throughout the processing facility, however, and it could have also come in from the field with the cantaloupe.

“Once it was established, it spread,” he said.

Both federal and state officials emphasized the need for prevention and said the newly passed federal food safety act will improve monitoring and prevention.

“It’s very important for farms to employ good agricultural practices. Equipment should be designed so it can easily be cleaned and sanitized,” McGarry said. “Recognizing points of contamination and putting controls in place will prevent outbreaks like this.”

Added Margaret Hamburg, commissioner of food and drugs: “The tragic deaths and illnesses have again demonstrated the need to continually address food safety issues. If we’re to have a food safety system that prevents illness, we must all practice prevention.”