As of December, 2024, TPH is currently investigating an increase in cases of multidrug-resistant (MDR) Shigella sonnei, particularly among the underhoused population in Toronto. More information.
The primary mode of transmission is fecal-oral. Transmission occurs through person-to-person contact, contact with contaminated inanimate objects, ingestion of contaminated food or water, and through exposure to feces during sexual contact.
Direct transmission is common in children, and among men who have sex with men (MSM). Risk of transmission increases for individuals engaging in anal-oral sex or in settings where personal hygiene is inadequate.
As few as 10-100 bacteria have been shown to cause disease.
Cases may continue to have Shigella bacteria in their stools for up to four weeks.
Symptoms usually start around one to three days after being exposed to Shigella bacteria but can start anywhere from 12 hours to seven days after exposure.
Clinical signs and symptoms of shigellosis include:
Illness is usually self-limiting, lasting an average of four to seven days. Serious illness may cause dehydration, although this is rare.
Rare complications include hemolytic-uremic syndrome (HUS), toxic megacolon, intestinal obstruction, colonic perforation, proctitis, rectal prolapse, and reactive arthritis.
To assist with case and contact management, TPH is requesting that the following information be collected and documented, particularly as it pertains to potential risk factors for individuals who have been diagnosed with or suspected to have Shigella:
Follow PHO’s Enteric – Bacterial Culture test information sheet.
Patients with suspected shigellosis should have a stool specimen collected for culture. Routine stool culture includes testing for Shigella.
Stool culture testing for community health care providers is available through community or hospital laboratories. Notify TPH if an outbreak is suspected.
Some community labs may offer rectal swab cultures for enteric bacteria. If stool collection (preferred method) is not possible, a rectal swab can be performed for culture instead. Please confirm with labs in advance.
Any stool specimens positive for Shigella will automatically have antimicrobial susceptibility testing performed by the Public Health Ontario Lab.
Oral rehydration with electrolyte replacement is essential in patients who are dehydrated.
Most patients will improve without antibiotic treatment. Antibiotic therapy should be reserved for patients with severe disease (e.g., hospitalization) and immunocompromised patients. Given the rise in multidrug-resistant (MDR) and extensively drug-resistant (XDR) Shigella, antibiotics therapy should be guided by antimicrobial susceptibility testing.
Antimotility agents (e.g., loperamide) are generally discouraged as they may prolong the duration of illness.
PHAC – For health professionals: Shigellosis (Shigella) Treatment
Emergence of XDR Shigella outbreaks have been reported in the UK, the US, and Ontario since 2022. XDR shigella is currently defined as resistant to the following five antimicrobials: ampicillin, fluoroquinolones, third-generation cephalosporins, azithromycin and trimethoprim-sulfamethoxazole.
Antibiotic treatment options for XDR Shigella are currently very limited. Consultation with an infectious diseases specialist is recommended to determine appropriate treatment options.
All suspected and confirmed cases of shigellosis must be reported to TPH by: