Gastrointestinal & Zoonoses

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Gastrointestinal & Zoonoses

06 September 2016

General bacterial and protozoal outbreaks of infectious intestinal disease reported to HPS in 2015

ObSurv is the surveillance system established in 1996 for all general outbreaks of infectious intestinal disease (IID) in Scotland. For the purpose of ObSurv an outbreak is defined as an incident in which two or more linked cases experience the same illness or when the observed number of cases unaccountably exceeds the expected number. The system seeks information on general outbreaks, defined as outbreaks affecting members of more than one household or residents of an institution.

Bacterial outbreaks

During 2015, four general outbreaks of Verocytotoxigenic Escherichia coli (VTEC) were reported, all four being identified as serogroup O157. Of these, two were Phage Type 8, one was of Phage Type 21/28 and one Phage Type 32. The four outbreaks of VTEC reported in 2015 was a decrease compared to 2014, when there were seven outbreaks of E. coli O157, one outbreak of O125 and one of mixed VTEC serotypes. While the number declined in 2015 compared to 2014, it was comparable with other recent years with three in 2013 and six in 2012 and demonstrates how the incidence and number of outbreaks of VTEC can vary year by year.

The mode of transmission was known for three of the four outbreaks of E. coli O157 reported in 2015, and in all three foodborne was considered the main mode of transmission, and all three were outbreaks that affected more than one NHS board or were part of a larger UK-wide outbreak. In one of these foodborne outbreaks, venison was identified as the suspected vehicle (more information available at http://www.hps.scot.nhs.uk/giz/publicationsdetail.aspx?id=67832).

There were five general outbreaks of Salmonella reported in 2015, four of S. Enteritidis and one of S. Bovismorbificans. This is slightly higher than the number reported in 2014 when there were three, and 2013 and 2012 when there were two and four respectively, but again reflects the random year on year variation in the small number of outbreaks. In three of the Salmonella outbreaks reported in 2015 the suspected mode of transmission was considered to be foodborne, in two of which the suspected vehicle was eggs and, in the last, a chicken product. Four cases of S. Enteritidis PT8 in Scotland were part of larger UK outbreak associated with contact with reptiles or feeder mice used to feed reptiles. More information on this last outbreak is available at http://www.hps.scot.nhs.uk/ewr/redirect.aspx?id=65484. Guidance on reducing Salmonella infection from reptile handling can be accessed at https://www.gov.uk/government/publications/salmonella-reducing-infection-from-reptiles.

While Campylobacter is the most common bacterial cause of infectious intestinal disease, most cases are apparently sporadic, and, not unusually, no general outbreaks were identified in 2015. This continues the trend seen in recent years with one Campylobacter outbreak in each of 2012 and 2014, and none in 2013.

Protozoal outbreaks

Three general outbreaks of Cryptosporidium were reported in 2015, an increase compared to the one outbreak in 2014 but the same as in 2013 when there were also three outbreaks. One of these was an outbreak of Cryptosporidium parvum, of a particular molecular profile, this outbreak was part of wider UK outbreak with 18 confirmed cases in Scotland. Another was part of a UK-wide increase in the number of cases of Cryptosporidium seen in the summer and autumn of 2015, and, as this was a national increase compared to previous years, it was not possible to determine exactly how many cases were due to the increase and how many were part of the background incidence of Cryptosporidium (more information available at http://www.hps.scot.nhs.uk/ewr/redirect.aspx?id=66725).

There was one small outbreak of Giardia in 2015, with six confirmed cases in which the main mode of transmission was considered to be mainly person to person. General outbreaks of Giardia are relatively unusual in Scotland with the previous outbreak reported to ObSurv in 2009.

Toxin outbreaks

No outbreaks of scombrotoxin were reported in either 2015 or 2014, compared to one in each of the two preceding years.

HPS would like to thank all the consultants in public health medicine, health protection nurses, infection control nurses, environmental health officers and microbiologists who contribute to the outbreak surveillance system.

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Author(s): Prepared by: Alison Smith-Palmer Vol: 50 No: 36 Year: 2016 Page: