European health officials tested more than 10,000 samples of food but never found any contaminated with the deadly E. coli O104:H4 that has caused nearly 4,000 illnesses and at least 44 deaths in the outbreaks in France and Germany linked to Egyptian fenugreek sprouting seeds.
A presentation on what eventually will be a final report from the EHEC Task Force of the German Federal Office of Consumer Protection and Food Safety (BVL) said “it is very difficult to detect low STEC (Shiga toxin-producing E. coli) contamination level in seeds and sprouts and there is no validated method.”
“To find the source of the EHEC outbreak was very difficult,” acknowledged Dr. Helmut Tschiersky-Sch√∂neburg, president of BVL, in an e-mailed statement to Food Safety News. “This was on the one hand due to the fact that EHEC bacteria have a very long incubation period, and on the other hand to the fact that sprouts have a very short shelf life.”
The task force, assembled in early June after initial efforts to find the source of the outbreak were unsuccessful, said that with this lack of contaminated-product evidence, “The only way out [was to] intensify the investigation on tracing back and tracing forward.”
As Bill Keene, senior epidemiologist at the Oregon Department of Health pointed out in an interview with Food Safety News last month, “Food testing, generally, and certainly in this case, can be extremely corroborative in supporting epidemiology if you get a positive result. If you get negative results, they essentially mean next to nothing. They don’t rule it out, but they don’t say anything.”
Because testing couldn’t provide a “smoking gun” in this case, experts had to rely on finding a pattern among what victims had eaten, and then figure out where that food had been distributed.
By June 3, the same day the Task Force was formed, the trail to sprout seeds was finally warming up. The Robert Koch Institute had identified five outbreak clusters — groups of affected individuals — and began detailed traceback interviews to identify common foods and supply chains. Ten days later the investigators had “41 well-described outbreak clusters.” All were linked to a single sprout grower in northern Germany.
But which sprouts were the problem? The Bienenbuettel grower sold different types of sprouts and sprout mixtures. Based on case patient interviews and menu information, health authorities implicated two as the likely culprits – the “Milde Mishchung” and the “Wurzige Miischung,” a mild mix and a spicy mix.
Only lentil sprouts and fenugreek sprouts were used in both those varieties, which narrowed the possibilities, but the lentil sprouts had also been used in other mixes that weren’t suspect. Fenugreek sprouts were used only in the mild and spicy mixes.
Further, three farm workers who fell ill with E. coli infections had worked on the three days when the fenugreek seeds were being sprouted. The question then became whether these workers were exposed to E. coli from the seeds, or whether they contaminated the sprouts themselves.
The leading working hypothesis of the Task Force was that “the infection of the people is probably caused by the sprouts,” according to the report. That theory was bolstered when cases of the outbreak strain of E. coli O104:H4 were identified in France and investigators discovered they’d been been served fenugreek sprouts. The seeds had come from a German importer, which had imported its seeds from Egypt. The task force investigators soon traced all the seeds involved in the outbreak to a single shipment from that country two years ago.
At this point, efforts turned toward a “detailed trace forward approach:” identifying where the seeds had been sold. According to the European Food Safety Authority, a total of 15,075 kg, or a little over 33,200 pounds of seeds, were distributed in Germany, the UK, Austria and Spain. Only 75 kg of this batch was sold to the German farm whose sprouts are linked to the majority of illnesses in the outbreak. The other 15,000 kg was divided among 16 other companies, which ultimately sold them to 70 more businesses.
While the shipment (lot 48088) has now been recalled, this wide network of distribution means that it will be a long time before all these seeds are tracked down. Many may have already been grown.
European authorities have put a ban on fenugreek seeds imported from Egypt, and have warned consumers against consuming raw sprouts.
Now, as the Task Force team report states, the remaining question is “What is the pathway of the contamination of the seeds?”
In the meantime, Europe is left to reflect on how it can improve its outbreak response system.
“The … involved authorities worked with great dedication and skills to find the source of the outbreak,” said Tschiersky-Sch√∂neburg. “However, things can always be done better. The task force had to type data of delivery orders and accounts into the analysis programme manually. This should be possible at the push of a button. I encourage producers and traders to establish the digital tracing of supply chains whenever it is possible.”
Tschiersky-Sch√∂neburg also stressed the importance of tightening safety measures in food production and shipment because, as evidenced by this epidemic, the global supply chain is a complex one.
“Rules of hygiene have to be adhered to by producers as well as by traders,” he says. “It is still unknown how Egyptian fenugreek seeds were contaminated with EHEC. But one thing is clear: in a globalised world food safety standards, have to be fulfilled everywhere.”© Food Safety News