Skip to content

News Archives

 

Volume 3 No 31; 7 August 2009

Escherichia coli O157 outbreak in Wrexham, North Wales – July 2009

The National Public Health Service for Wales (NPHS) and Environmental Health Officers from Wrexham County Borough Council (WBCC) are currently investigating four cases of Vero cytotoxin-producing E. coli O157 (VTEC O157) in the Wrexham area.

The cases are all females, aged 3, 23, 32 and 32 years. Onset dates were 20 July (one case) and 21 July (three cases). Two cases, aged 3 and 32, have been admitted to hospital and are seriously ill. All reported eating different products from a fast-food outlet in the area in the week before becoming unwell.

Faecal samples from all the cases were confirmed as positive for E. coli O157. Confirmation and typing at the Laboratory of Gastrointestinal Pathogens (LGP) has shown them all to belong to phage type (PT) 2 and to possess genes encoding Verocytotoxin VT2. Food and environmental samples have been taken from the food outlet for laboratory investigations.

The food outlet was visited by Environmental Health Officers from WBCC on 30 July. As a precaution an Emergency Prohibition Notice was issued and the outlet is currently the subject of a Closure Order. The owners of the premises are co-operating fully with the investigation.

Active case finding has been pursued using local GPs, but there have been no further cases reported to date. Laboratory investigations are ongoing.

The LGP reviewed its VTEC O157 database and informed the NPHS that PT2 has represented around 10% of isolates in England and Wales since 2005, compared with the most prevalent type - PT21/28 - that accounted for up to 40% of isolates [1,2]. PT2 may be associated with the development of serious illness.

Since the start of 2009 up to 3 August, the LGP confirmed 24 isolates of VTEC O157, of any phage type, received from Welsh sending laboratories.

References

1. HPA. Verocytotoxin-producing Escherichia coli O157: 2006. Health Protection Report 2007: 1(32), http://www.hpa.org.uk/hpr/archives/2007/hpr3207.pdf

2. HPA. Verocytotoxin-producing Escherichia coli O157: 2007 and 2008. Health Protection Report 2009: 3(10), http://www.hpa.org.uk/hpr/archives/2009/hpr1009.pdf.

Reptile-associated salmonella infections (S. Typhimurium DT 191a) – an update

In December 2008, the Health Protection Agency Centre for Infections (CfI) detected a gradual but sustained increase in a new phage type of Salmonella Typhimurium, designated definitive type 191a (DT 191a). Most isolates received at the Laboratory of Gastrointestinal Pathogens (LGP) were resistant to the antimicrobial tetracycline. A case control study found an association between contact or handling pet reptiles and infection [1]. Most cases reported contact with snakes, predominantly colubrids (corn snakes), that were fed on thawed frozen mice. Reports of this serotype continue to be received at LGP. To date, in England and Wales, 204 cases with resistance to tetracyclines have been received since August 2008, at an average of four cases per week (figure 1). Over one third of reports are in children under five years of age. A similar association has also been found in Scotland, affecting the same age group of patients.

An environmental investigation to determine the source of the outbreak followed-up major importers and wholesalers of frozen feeder mice for the pet reptile trade. Frozen mice specimens were collected from six major import and distribution companies in England (representing approximately 80% of market supply lines, and 90% of import lines to the UK) and were analysed at the Veterinary Laboratory Agency, Weybridge.

Positive isolates were found in products from a single UK importer ('importer A'), who sourced his stock from a single producer in the United States. Isolates were phage typed as S. Typhimurium DT 191a, and further found to have Pulse Field Gel Electrophoresis (PFGE) patterns indistinguishable from human isolates. The importer voluntarily ceased to trade the implicated stock pending the investigation results and informed his supplier in the USA. Fifty seven percent of samples from importer A were positive, with nine out of 10 product lines tested having at least one positive sample.

A multinational, multi agency Incident Control Team (ICT) convened on 26 June to determine how to address the issues relating to both withheld imported stock and future imports. The decision reached by the ICT was to allow the withheld feed to be marketed with the condition it was labelled indicating the potential for infection and to advise hand washing after handling the produce. To strengthen controls, new import authorisations have been issued, requiring: clear labelling of imported stock "Intended for feeding to reptiles only"; commercial documents to accompany consignments; and making it clear that random testing at Border Inspection Posts would commence, with positive results passed to the relevant inland local authority. This allows for random testing for such contaminants as salmonella, if required, but these conditions are not the same across the EU as national rules apply.

The HPA will continue to monitor the incidence of Salmonella Typhimurium DT191a as cases are reported and the situation will be kept under review by the ICT.

The public needs to be aware of the salmonella-related risks associated with pet reptile ownership. Up to 90% of reptiles intermittently shed salmonellae in their life [2], though carriage rates vary depending on the type of reptile [3]. Raw frozen mice used as snake feed have also been found to be a potential source of salmonella and present a risk of contamination to those who handle them. Children and those who are immunocompromised are especially vulnerable to salmonella infection and children under five years of age are particularly at risk of catching salmonella from reptiles. The risks arise from handling, feeding and caring for pet reptiles and their vivariums, and also handling frozen or thawed mice or chicks that may be infected prior to feeding reptiles. These risks can be significantly reduced by ensuring good hygiene whenever pets are handled or fed, and whenever vivariums are cleaned out. Revised guidance for reptile owners and handlers has been published on the HPA website [4].

Figure 1. Temporal distribution of reported cases of tetracycline-resistant Salmonella Typhimurium DT 191a, England and Wales 2008 - 2009
Week of specimen report (from end-June 2008)

References

1. Ongoing investigation into reptile associated salmonella infections. Health Protection Report 3(14); 9 April 2009, http://www.hpa.org.uk/hpr/archives/2009/news1409.htm#reptiles.

2. Burnham BR, Atchley DH, DeFusco RP, Ferris KE, Zicarelli JC, Lee JH et al (1998). Prevalence of faecal shedding of salmonella organisms among captive green iguanas and potential public health implications. J. Am. Vet. Med. Assoc. 213, 48-50.

3. Mitchell MA, Shane SM (2001). Salmonella in reptiles. Seminars in avian and exotic pet medicine, 10(1), January.

4. HPA. Reptile-associated salmonella. HPA website: Infections A-Z / Salmonella / General Information.
http://www.hpa.org.uk/webw/HPAweb&HPAwebPrinterFriendly/HPAweb_C/1239264199921?p=1239264198145

Increased Campylobacter cases in 2009

A marked increase in Campylobacter infections has been noted in England and Wales in 2009. Since a drop in the number cases in 2002-2004 (44,544 cases in 2004) the number of Campylobacter reports have increased, with higher numbers in the last two years (51,989 in 2007 and 50,006 in 2008). The largest increase has been in the last six months. Provisional data indicates there has been a 19% increase in Campylobacter cases in England and Wales in 2009 up to week 26 compared to 2004 and a 17% increase since 2008 (figure 1) [1]. The increase in 2009 has been seen in all regions and has also been occurring in Scotland [2].

The age distribution of cases in recent months continues a trend of increased cases in older people. In England and Wales, Campylobacter case numbers in weeks 1 to 26 have exceeded those for the period between 2004 and 2009 by 16% in people under 20 years old, by 5% in people aged 20 to 49 and by 41% in people aged 50 or more (figure 2). This change in age distribution has been previously noted [3,4].

Campylobacter is the commonest bacterial cause of diarrhoea in England and Wales. Two species - C. jejuni and C. coli - account for the majority of infections. A number of risk factors have been associated with Campylobacter infection, including undercooked meat (especially poultry), unpasteurised milk and untreated water [5-8]. However, the source of infection in most cases remains unexplained by recognised risk factors for infectious intestinal disease. While a number of factors could contribute to the increased cases in older people (e.g. an aging population, increased travel, more eating out, changes in health seeking behaviour, surveillance, proton pump inhibitor and nonsteroidal anti-inflammatory drugs use), and in people overall (eg increased contamination of raw meats or exposure from the environment), the causes of this increase currently remain to be established.

Figure 1. Campylobacter cases per week 2008 and 2009 weeks 1 to 26

Figure 2. Campylobacter cases by age 2004-2009 weeks 1 to 26

References

1. "Common gastrointestinal infections, England and Wales: laboratory reports: weeks 23-26/2009", Health Protection Report 3(27), 10 July 2009.

2. "Increase in Campylobacter laboratory reports", Health Protection Scotland Weekly Report, 29 July 2009.

3. Gillespie IA, O'Brien SJ & Bolton FJ. Changing age pattern of human campylobacteriosis in England & Wales, 1990-2007. Emerging Infectious Diseases, in press.

4. Advisory committee on the microbiological safety of food. Discussion paper: changing age structure of human campylobacteriosis in England and Wales, March 2009. Available at: http://www.food.gov.uk/multimedia/pdfs/committee/acm935campy.pdf.

5. Kessel AS, Gillespie IA, O'Brien SJ, Adak GK, Humphrey TJ, Ward LR. General outbreaks of infectious intestinal disease linked with poultry, England and Wales, 1992-1999. Commun Dis Public Health 2001; 4(3):171-177.

6. Neimann J, Engberg J, Molbak K, Wegener HC. A case-control study of risk factors for sporadic campylobacter infections in Denmark. Epidemiol Infect 2003; 130(3):353-366.

7. Morgan D, Gunneberg C, Gunnell D, Healing TD, Lamerton S, Soltanpoor N, et al. An outbreak of Campylobacter infection associated with the consumption of unpasteurised milk at a large festival in England. Eur J Epidemiol 1994; 10(5): 581-585.

8. Said B, Wright F, Nichols GL, Reacher M, Rutter M. Outbreaks of infectious disease associated with private drinking water supplies in England and Wales 1970-2000. Epidemiol Infect 2003; 130(3): 469-479.

Pandemic flu: UK situation at 6 August 2009

The latest HPA Weekly Pandemic Flu Update [1] notes the following developments as at 6 August 2009:

  • there was a clear indication that the number of cases in England decreased significantly during the past week;
  • weekly GP consultation rates decreased over in England, coinciding with the first full week of operation of the National Pandemic Flu Service (NPFS);
  • the majority of cases continued to be mild; there was no sign that the virus was changing, becoming more severe or developing resistance to antivirals; and
  • producing reliable estimates of new cases continued to be very challenging following start of operation of the NPFS. HPA modelling gives an estimate of 30,000 new cases in England for the week-ending 6 August (range 15,000 to 85,000). The decrease in estimated number of cases applied to all age groups and all regions. (This estimate incorporates data from NPFS and GP consultations.)

A more detailed review of epidemiological data for the week-ending 6 August 2009 (week 32) is available at: www.hpa.org.uk/swineflu/surveillance&epidemiology [2].

References

1. Weekly pandemic flu update (6 August 2009), (HPA press release of 6 August 2009). HPA website: National Press Releases.

2. HPA Weekly National Influenza Report (6 August 2009, week 32, PDF 90 KB), HPA website: Swine Flu / Surveillance and Epidemiology.