The number of reported Salmonella infections in 2015 was 9,485 compared to 8,078 in 2014, found the annual report on zoonoses.
Reporting of Salmonella spp shows a consistent seasonal pattern with a peak of infection in the third quarter of the year.
Salmonella Enteritidis remained the most commonly reported serovar in 2015, accounting for 33.2% of cases for which a serovar result was available.
Salmonella Typhimurium (including monophasic strains) was the second most commonly reported serovar and increased by 23.8% from 2014.
Salmonella outbreaks and WGS
Eleven foodborne outbreaks of Salmonella were reported in 2015, compared with ten in 2014.
Eight were caused by S. Enteritidis, one by S. Typhimurium and two by other Salmonella serovars.
The most common associated food type was poultry products (eggs and chicken meat).
Whole Genome Sequencing (WGS) is routinely performed for several gastrointestinal pathogens, including Salmonella spp., Shigella spp., Listeria monocytogenes and pathogenic strains of E. coli.
Effective implementation of WGS for routine surveillance of gastrointestinal pathogens is not without difficulties, according to the report.
A large amount of data is generated for analysis and requires a high-level of expertise to interpret it with the epidemiological evidence.
“Since April 2014, 334 clusters of five or more genetically related isolates, clustering at the 5-SNP level, of Salmonella spp. have been detected and assessed. The majority of reported clusters are small, but all need to be assessed in order to effectively prioritise clusters that warrant further investigation.
“A further significant complication is that knowledge of the potential genetic variation within and between genetically related clusters of Salmonella spp that can be expected over time and under certain conditions defined by host, pathogen and environment interactions is still limited.”
Campylobacter lab reports decrease
Laboratory reports of Campylobacter in the UK (63,292) decreased 10% when compared with 2014.
This decrease was evident in England where the rate of reported infections declined to the lowest since 2008. Northern Ireland continues to report rates lower than the rest of the UK.
Less than half of chicken skin samples tested positive for Campylobacter at any level, according to Food Standards Agency figures based on tests of 1,051 whole fresh chickens sampled during January to March 2017.
The survey found a positive rate of 48.8% compared to 50% positive in the same period last year.
In 2015, there were 11 foodborne outbreaks of campylobacteriosis in the UK, similar to the 12 recorded in 2014.
Seven outbreaks were associated with poultry meat products, of which five were chicken liver parfait or pate and two were chicken meat dishes.
One outbreak was associated with red meat (calves liver); another with mixed meats; one with pasta/noodle salad and for one the implicated food vehicle was unknown.
Great increase in cryptosporidiosis
The number of cryptosporidiosis infections greatly increased in 2015, with 6,149 cases - a 33.7% increase on 2014.
This represented an excess of C. hominis cases between July and September, of whom a greater proportion than expected travelled to Spain. Enhanced surveillance and questionnaires did not identify specific exposures.
There was also an excess of C. parvum cases from November 2015. Investigations suggested salad or sandwich items in a coffee chain, sometimes within supermarkets, was a likely route of exposure.
Alternatively, a contaminated salad item might have been supplied to both coffee shops and supermarkets, explaining the geographical spread of the outbreak.
In 2015, there were 15 outbreaks of Cryptosporidium infection. One was foodborne and 14 were non-foodborne.
E. coli below 1,000 per year
Laboratory reports of Shiga toxin producing E. coli (STEC/ VTEC) fell to 867 (665 in England and Wales, 170 in Scotland and 32 in Northern Ireland) compared to 1,186 in 2014. This is the first time the number of reports has fallen below 1,000 per annum since 2005.
Although still greatly underdiagnosed, non-O157 STEC reports increased to 372 from 306.
Eleven outbreaks of STEC were detected and investigated affecting 130 cases in 2015. Ten of the outbreaks involved STEC O157 and one involved STEC serogroup O26.
Six foodborne outbreaks were linked to burgers; venison; coconut; mixed salad leaves; cross-contamination of raw and cooked foods at a butcher’s shop; and associated with a local restaurant where the source was not determined.
There were 189 cases of listeriosis in the UK in 2015, compared to 188 in 2014.
A total of 12 cases of brucellosis were identified, all of which were acquired abroad, compared with 11 in 2014 and there were 44 cases of human yersiniosis compared with 65 in 2014.