During a 15-year period a total of 26 foodborne outbreaks were due to consumption of raw, unpasteurized milk in England and Wales, according to results of a study. A review published in the journal Epidemiology and Infection reports the risk of illness from raw drinking milk (RDM) has increased since 2014.
Between 1992 and 2002, there were 19 outbreaks linked to raw milk or products made with raw milk, involving 229 people, of which 36 were hospitalized. The most outbreaks recorded in one year was three, as seen in 1993, 1994, 1996 and 2000.
There was an 11-year period from 2003 to 2013 where no outbreaks linked to RDM were reported. However, since 2014 seven outbreaks, three of E. coli O157:H7 and four of Campylobacter jejuni, caused by contaminated RDM were investigated. Between 2014 and 2017, there were 114 patients, five hospitalizations and one death.
Increased risk in recent years
In 2017, there were four outbreaks, the highest since such data collection began in 1992. Two other incidents, one involving Listeria monocytogenes and the other Salmonella Dublin, were investigated and each involved one person, with epidemiological and microbiological links to RDM, but were not listed as outbreaks.
Despite labeling requirements and recommendations that children should not consume RDM, children made up almost a third of outbreak patients. In total, 18 of 54 lab confirmed cases were children under 16 years old.
There has also been an increase in consumer popularity and registered producers in the United Kingdom. In January 2018, there were 165 sites registered for production of RDM for public consumption, compared to the 107 registered producers in April 2014.
In the U.K., raw milk is mostly sourced from cows, and to a lesser extent from goats, sheep and buffalo.
Pathogens commonly associated with illness after drinking unpasteurized, raw milk are Campylobacter, Salmonella, Brucella melitensis, Mycobacterium bovis, tick-borne encephalitis virus and Shiga Toxin-producing E. coli (STEC).
Modified controls possible
In England and Wales, RDM can only be sold by registered producers directly to customers at the farm gate or farmhouse catering operation, by farmers at farmers’ markets, distributors using a vehicle as a shop such as a milk route, direct online sales or vending machines at farms. It must be labeled with a health warning. In Scotland, the sale of raw drinking milk is banned.
During the study period, there were 12 outbreaks associated with pasteurized milk, including 10 caused by pasteurization failures and two due to post-pasteurization contamination of milk.
Analysis of surveillance questionnaires for infections reported between May 2015 and mid-December 2017, identified 19 of 1,284 sporadic cases of STEC and 13 of 535 cases of listeriosis that reported exposure to RDM. People are often exposed to more than one potential risk factor for infection, and it is not possible to confirm consumption of RDM caused symptoms.
Since 2015, routine whole genome sequencing (WGS) at Public Health England (PHE) has been used but all RDM-associated E. coli O157:H7 outbreaks to date have been detected through epidemiological links established by local health protection teams prior to the availability of WGS results.
In July 2015, controls governing the sale and marketing of RDM were reviewed by the Food Standards Agency and no changes were recommended. However, in February this year a consultation was launched on proposed enhanced controls in the production of raw milk. It closed at the end of April.
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