Shigella and norovirus increased but Listeria, Hepatitis A and E declined last year, according to gastrointestinal surveillance reports published by Health Protection Scotland (HPS).
In 2018, there were 115 reports of Shigella infections in Scotland. The most common species identified was Shigella sonnei with 77 patients infected. This is an increase compared with the 38 reports in 2017 and 44 incidents in 2016, but within the range of the past 10 years that saw between 38 and 90 cases annually.
There were 32 cases of Shigella flexneri infections in 2018. This is an increase from 23 patients in 2017, but lower than the 37 cases reported in 2016. Two cases of Shigella boydii and one case of Shigella dysenteriae were also recorded in 2018.
Since October 2017, the Scottish Microbiology Reference Laboratory has started routine whole genome sequencing (WGS) on all Shigella isolates in the country, replacing traditional typing techniques.
Norovirus and Listeria figures
HPS received 1,491 laboratory reports of norovirus last year. This was an increase of 514 on the 977 reports in 2017. However, it was within the range of the past nine years when 977 to 3,109 cases were reported annually.
The second study of infectious intestinal disease in the community estimated that 290 cases of norovirus occur in the community for every case reported to national surveillance. There was a seasonal trend, with the highest number during the winter months. However, infections can occur throughout the year.
Lab reports showed a distinct age distribution affecting predominantly the elderly and young, with 895 of 1,491 cases from those aged 65 years and over as well as 285 cases from those younger than 5 years old, while no other age bands accounted for more than 4 percent of reports.
The distribution among these age groups probably reflects those from whom samples are most likely to be taken, according to HPS.
There were 12 cases of Listeria monocytogenes reported in 2018, a slight decline on the 17 in 2017, and reflects the random year on year variation seen due to the small number, officials said.
Importance of Listeria monocytogenes arises not from the number of reported cases, which are relatively low, but due to the severity of infection and high mortality. Pregnant women, newborn infants, the elderly and immunocompromised are most at risk. Pregnancy associated infections are counted as one case, even when both the mother and infant are positive.
Hepatitis A and E
In 2018, HPS received 112 reports of hepatitis E (HEV) infection. This is a decline of 34.5 percent and 50.4 percent compared with case numbers in 2017 and 2016 respectively.
Reports of HEV infection in Scotland and elsewhere in the United Kingdom have increased in recent years. Lab reports in Scotland rose from 13 in 2011, to a peak of 226 in 2016. It is likely that more clinical recognition and testing of Hepatitis E contributed to this increase, according to HPS.
HPS, Food Standards Scotland, the Scottish Government, NHS boards and Public Health England are trying to improve understanding of HEV epidemiology, including risk factors and exposures, to help public health management and control.
Last year, there were 34 cases of Hepatitis A reported to HPS which is lower than the 153 cases in 2017. In 2018, case numbers decreased to be within historically reported levels of 19 to 48 cases.
Reports in 2017 included 91 cases associated with a foodborne outbreak of Hepatitis A in Lanarkshire. Most cases ate food produced by the baker JB Christie through outlets in Airdrie and Coatbridge.
Food and water hygiene to protect the public
HPS has also published a report on lab-confirmed travel-related infections in Scotland. Gastrointestinal infections continued to be the most common.
A total of 115 Shigella episodes were reported to the agency in 2018 and 32 were imported. Thirteen episodes of Vibrio cholerae were reported last year. There were also three of Vibrio parahaemolyticus. All Vibrio episodes were imported.
There were 226 episodes of Giardia in 2018, of which 59 were reported as imported. All 12 cases of Cyclospora were imported. Cryptosporidium continued as the most commonly reported gastrointestinal parasite with 537 infections in 2018.
“Organisms such as Shigella, Giardia and Cryptosporidium causing traveler’s diarrhea remain the most commonly reported infections. Infections caused by Vibrio species, including Vibrio cholerae have been identified in increasing numbers in Scotland in recent years. The small number of episodes of Vibrio parahaemolyticus is of interest, as this organism is found in warm seawater and thus may be encountered by travelers to areas with otherwise acceptable levels of hygiene,” according to the report.
“Episodes of cyclosporiasis are reported for a fourth year in 2018 although numbers are declining. Cyclospora infections have been reported in Europe and North America in recent years, with Mexico frequently appearing in travel history. Travel-related cyclosporiasis has been associated with consumption of salad and soft fruit such as raspberries. It should be noted that cyclosporiasis may occur in an environmental context where diverse gastrointestinal pathogens are common.
“Food and water hygiene remain essential methods for protecting the health of the travelling public, as gastrointestinal infections are again the most commonly reported. Vaccination is also available for prevention for some food and water-borne diseases i.e. hepatitis A, typhoid, cholera and poliomyelitis.”
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