Product highlight: US CDC Shigella Prevention and Control Toolkit
What is Shigella?
Shigella are gram-negative bacteria belonging to the Enterobacteriaceae family.. Four species of pathogenic Shigella: S. dysenteriae, S. flexneri, S. boydii and S. sonnei are associated with the illness shigellosis. Shigatoxin, a potent cytotoxin, can be produced by S. dysenteriae, which is considered the most virulent of the four Shigella species. In Canada, shigellosis, a relatively common cause of diarrhea, is a national notifiable disease. Approximately 880 cases are reported annually. Surveillance for shigellosis in Canada is based on several systems including:
- FoodNet Canada
- PulseNet Canada
- the National Enteric Surveillance Program (NESP)
- the Canadian Notifiable Disease Surveillance System
Shigella are shed in the feces of infected persons during the course of illness and up to four weeks after symptoms subside. Asymptomatic carriers may also shed the virus. Shigellosis is highly contagious and is spread most often by contaminated hands following defecation. Shigella spreads easily via the fecal-oral route. Foods such as pre-packaged or deli salads, raw vegetables, dairy products, and meats may be contaminated through poor food handling and production processes or contaminated water sources. Other pathways include direct exposure to infected feces or indirect exposure to contaminated objects or fomites, or oral-anal sexual contact. Acute symptoms of shigellosis may include:
- Watery diarrhea, with blood and/or mucus
- Tenesmus (cramping rectal pain)
Severe complications include marked dehydration, intestinal perforation, toxic megacolon, bacteremia (presence of bacteria in bloodstream), septicaemia (systemic infection due to bacteria in bloodstream), toxaemia (bacterial toxins in bloodstream), seizures, septic shock, and Reiter’s syndrome, which is a longer-term consequence. Haemolytic uremic syndrome has also been linked to exposure to shigatoxin.
With appropriate hydration, shigellosis is usually a self-limiting illness lasting 4-7 days, although severe complications may require antibiotics or further medical intervention.
Mitigation and prevention of shigellosis
As Shigella is transmitted via the fecal-oral route, mitigating shigellosis transmission requires severing the chain of transmission. This can be achieved during food preparation and production by following general food safety guidance, such as proper hand hygiene after using the washroom and before handling food, appropriate cooking and storage temperatures, thoroughly washing fruits and vegetables before consumption, and ensuring a clean and potable water source. At the vendor and consumer levels, prevention strategies include following proper hand hygiene after using the washroom or handling soiled diapers, cleaning and disinfecting surfaces potentially contaminated with fecal matter, ensuring drinking water is from a clean and potable source, and keeping workers and children suffering from diarrheal symptoms away from work or daycares until they are no longer infected.
US CDC Shigella Prevention and Control Toolkit
In March 2021, the US Centre for Disease Control published a toolkit to provide guidance in Shigella outbreak investigations, transmission mitigation strategies, and sample communications resources for the public.
Past Shigella outbreaks have occurred in a wide variety of settings involving different populations. These include communities, schools, childcare, retirement homes, cruise ships, large events, and airplanes. Children, older adults, people experiencing homelessness, men who have sex with men, and displaced populations or refugees appear to be at greater risk of Shigella infection. Foodborne, waterborne, person-to-person, and sexual contact have all been implicated in past outbreaks.
To assist in enteric outbreak investigations, the CDC developed the National Hypothesis Generating Questionnaire to assist public health officials when interviewing ill individuals to determine the source and mode of transmission. This questionnaire contains questions pertaining to demographics, medical history, treatment information, and exposure information such as travel, recent activities, sexual history, and occupation. These questions may be tailored depending on the type of pathogen implicated in the outbreak.
Prevention and control measures
The Toolkit provides detailed sanitation and hygiene guidance to public health officials who may be assisting facility operators to develop comprehensive sanitation and hygiene plans in an effort to control transmission of enteric pathogens. Not only does the toolkit provide instructions on safe diapering, hand hygiene, and general cleaning and sanitation of facilities, links to additional related resources are also included.
Information about using bleach safely is also part of the toolkit to prevent misuse and accidental exposures. Disinfectants that are approved by the Environmental Protection Agency (US) may also be used. In Canada, surface disinfectants are regulated by Health Canada, and approved disinfectants are assigned a Drug Identification Number (DIN) before they can be distributed and marketed for sale. Health Canada has updated the guidance documents related to surface disinfectants and their safety and efficacy requirements. The drug products database allows users to search for disinfectant drug products approved in Canada.
One unique aspect of this Toolkit is the inclusion of internal and public communications strategies and templates to all partners and stakeholders that may be involved in a Shigella outbreak. Internal communications may include multiple departments within one organization who may have varying strengths and roles in outbreak investigation. Depending on the magnitude of the outbreak, media communications may be necessary. The Toolkit outlines strategies for developing press releases and key talking points when working with the media and other channels.
Additional materials in the Toolkit include templates for communicating with those affected by the outbreak, such as parents and patrons of an affected facility. Health communication materials such as sample fact sheets, infographics, palm cards, and social media messages have also been included in the Toolkit as reference materials for public health officials.
- Kansas Department of Health and Environment – Shigellosis Investigation Guideline
- Guidelines for the control of shigellosis, including epidemics due to Shigella dysenteriae type 1
- Infectious diseases protocol: Appendix A: Disease-Specific Chapters - Shigellosis
Chen T. Product highlight: US CDC Shigella Prevention and Control Toolkit [blog]. Vancouver, BC: National Collaborating Centre for Environmental Health; 2021 July 5. Available from: https://ncceh.ca/content/blog/product-highlight-us-cdc-shigella-prevention-and-control-toolkit.
Image Source: CDC/ Antibiotic Resistance Coordination and Strategy Unit