Shiga toxin-producing E. coli O157 is not common in wild Scottish deer but when it is found there are usually high levels that can cause more severe illness, according to a report.

Experts said there was a real risk of future STEC O157 infections from eating venison contaminated with deer feces. They added hygiene measures should be taken when processing deer to avoid contamination of the carcass and mitigate this problem.

The report was commissioned by the Scottish Government and Food Standards Scotland (FSS) to better understand the risk of STEC contamination of wild venison following an outbreak of STEC O157 in venison products in 2015 that affected 12 people. Five patients required hospitalization but went on to recover. Products were supplied to a number of retailers by one approved game handling site. The likely source of infection was a heavily-contaminated deer carcass or carcasses.

Work mapped the venison industry in Scotland, assessed STEC prevalence in wild deer feces, and reviewed cross-contamination risks in the slaughter and processing stages from the field to larder.

STEC O157 rarely found
Scotland produces an estimated 3,000 to 3,500 tons of venison per year. One-third of UK-produced venison is exported to Europe and 1,000 tons of venison consumed in the UK is imported.

The legislation is in place for larger-scale wild and farmed venison production but exemptions exist for small-scale operators or those supplying venison for private consumption.

A prevalence study was done on wild Scottish deer between July 2017 and June 2018. Out of 1,087 fecal samples analyzed, three were positive for STEC O157. From 74 samples tested, non-O157 STEC strains were isolated from 68 fecal samples but the risk they pose is unclear.

Dr. Tom McNeilly, head of disease control at the Moredun Research Institute and project lead, said it was a collaboration between research scientists, government, and the deer industry.

“It has provided important information on STEC strains circulating in Scottish wild deer and the risk they pose to human health. Furthermore, this collaboration provides a blueprint for how academics, government agencies, and industry can work together effectively to address key public health issues.”

Contamination risk factors
The risk analysis also identified factors associated with an increased chance of contamination, such as environmental temperatures above 7 degrees C (44.6 degrees F) and longer distances from cull sites to Approved Game Handling Establishments (AGHE).

Other factors were if carcasses were stored for longer before being processed to venison and if they were wet and slimy, dirty, or contaminated with feces.

Compliance with good hygiene practices at every step is important, starting with shooting, through evisceration in the field and skinning, to chilling and processing, according to the report.

Dr. Marianne James, head of risk assessment at FSS, said the work gives a clearer understanding of the risks in the venison sector.

“We would like to take this opportunity to thank the industry for their funding contribution which has been instrumental in conducting all of the samplings and helping steer the project work. The report’s findings will be taken forward and are being used by FSS and the venison industry to review best practice guides.”

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