This news report updates that published last September concerning an outbreak of serious gastro-intestinal illness associated with consumption of watercress, the underlying cause of which remains uncertain. Further investigations uncovered a second, smaller outbreak associated with consumption of watercress; environmental investigations revealed a field containing cattle close to one of the farms supplying the watercress. It seems likely that the cause of this second outbreak was transfer of VTEC from the field to the watercress bed, either from wildlife entering the watercress farm or run-off water.
In September 2013, a national increase in cases of VTEC O157 phage type 2 VT2 was observed in England. Between 30 August and 19 September, 19 cases (14 in England, four in Wales and one in Scotland) were reported sharing the same distinct Multi Locus Variable Number Tandem Repeat Analysis (MLVA) pattern (and single locus variants), not previously seen in the UK. Onset dates ranged from 17 to 29 August and the cases had an unusual demography for VTEC cases: they were predominantly female with a median age of 64 years. Seven cases were hospitalised, although no deaths or cases of haemolytic uraemic syndrome (HUS) were reported [1]. Interviews with patients and the use of detailed food questionnaires revealed the link to the consumption of pre-packaged watercress purchased from a particular supermarket chain. This led to the prompt voluntary withdrawal and recall of watercress products by the retailer [1-3].
Despite trace-back investigations, microbiological testing of watercress and environmental sampling at farms, the source of contamination of the watercress remains unclear. Two additional cases with an identical MLVA profile were retrospectively identified with onset dates in February 2013. One had consumed watercress and one pre-packaged salad, both from retailers representing a different supply chain, suggesting that the contamination is unlikely to have occurred at the farms. Following restocking of watercress at the supermarket chain, one additional case was reported with an onset date of 21 October 2013. The case reported consuming bagged mixed salad containing watercress from that supermarket. No further cases of the outbreak profile have been reported.
FoodWorld 