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Shigellosis

Shigellosis is an infectious disease caused by a group of bacteria called Shigella. These bacteria are commonplace in Canada, and live in the intestines of infected persons. Shigellosis is a common cause of diarrhea, including bloody diarrhea.

Causes

What causes shigellosis? How is it spread?

People who eat food or drink water contaminated with Shigella bacteria can become ill with shigellosis. The illness is highly infectious and can also be spread from person to person.

The disease is usually spread through direct or indirect fecal-oral contact. This happens when

  • someone does not wash their hands carefully after using the washroom or changing a diaper and then prepares food for others;
  • small children play together, especially in untreated wading pools or play fountains; or
  • vegetables or fruits come into contact with contaminated water or sewage run-off.

Shigellosis can also be spread by flies that come into contact with contaminated feces or water. Outbreaks have also occurred among men who have sex with men.

Symptoms

What are the symptoms of shigellosis?

Like other food borne illnesses, the symptoms of shigellosis mainly involve the gut. They can include

  • fever;
  • diarrhea (often bloody; may contain mucous);
  • stomach cramps;
  • nausea and vomiting; and
  • rectal pain.

Symptoms usually appear one to three days after exposure to the bacteria, but can appear as early as half a day and as late as a full week after exposure.

Some people who are infected with shigellosis may have no symptoms at all, but they can still spread the infection to others.

How long do the symptoms last?

People who are sick with shigellosis are usually ill for four to seven days.

How long are people infectious?

People with shigellosis are infectious while they are sick, and usually for four weeks after illness.

Risks

Are there certain foods that increase the risk of getting shigellosis?

Food is most commonly contaminated with Shigella bacteria from water polluted by human sewage. Food can also become contaminated if it is handled by a person with shigellosis or by cross-contamination because of unsanitary food handling practices. The following foods have been associated with shigellosis:

  • foods exposed through handling—salads, including chicken, fruit, lettuce, macaroni, pasta, potato, shrimp, tuna, turkey, and vegetable;
  • foods exposed through polluted water—raw oysters and other shellfish and vegetables.

Exposure to water contaminated with sewage can also cause shigellosis.

Are certain people more likely than others to get sick from shigellosis?

Anyone who comes in contact with infected stool can get shigellosis, however most cases occur among children under the age of 10.

Men who have sex with men are at higher risk of becoming infected with shigellosis.

Is shigellosis dangerous? Is it more dangerous for certain people?

Shigellosis is estimated to cause about 600,000 deaths annually worldwide. Children under the age of 10 account for two-thirds of cases and most of the deaths. In Canada, deaths related to shigellosis are rare. In 2004, one death was attributed to shigellosis. The disease is usually more severe in young children.

Complications from shigellosis are possible and can include blood poisoning (septicaemia) infections elsewhere in the body. A small number of people may develop Reiter’s Syndrome, which can lead to chronic arthritis, neurologic complications (seizures) and hemolytic uremic syndrome (HUS), in which the red blood cells are destroyed and the kidneys fail.

Treatment

How is shigellosis diagnosed and what is the treatment?

Shigellosis is diagnosed by a laboratory test.

Most patients recover without complications within five to seven days without specific treatment. Anyone with diarrhea should drink plenty of fluids to avoid dehydration. This is particularly important for seniors, children and those with weakened immune systems. In severe cases, patients may need to be given fluids intravenously.

Consult a healthcare provider if you have bloody or severe diarrhea.

Those suffering from illness should drink plenty of fluids to prevent dehydration – a possible serious health effect of a foodborne illness. The most helpful fluids for protecting against dehydration are oral rehydration fluids. These products are sold as pre-mixed fluids and are commonly found in drug stores. Other drinks that do not contain caffeine or alcohol can also help with mild dehydration; however, these drinks may not replace the nutrients and minerals lost during illness.

Young children, the elderly and people with other illnesses are at greatest risk for dehydration. Symptoms of dehydration in adults and children include a decrease in urination, a dry mouth and throat and dizziness upon standing. A dehydrated child may cry with few or no tears and be unusually sleepy or fussy. Severe dehydration can be serious and the ill person may require re-hydration in a hospital. If you think you or someone under your care is dehydrated, contact your healthcare provider.

Severe cases of shigellosis can be treated with antibiotics. Shigellosis is generally self-limited and the infection will clear without antibiotics. In severe cases and for public health reasons antibiotics can be prescribed.

Prevention

How can shigellosis be prevented?

Proper hygiene and safe food handling and preparation practices are key to preventing the spread of all foodborne illnesses, including shigellosis.

  • Wash your hands thoroughly with warm water and soap after using the washroom and before preparing food.
  • Make sure that you wash your hands thoroughly with warm water and soap after changing diapers. Dispose of dirty diapers properly.
  • If your child is sick with shigellosis, keep him or her home from daycare or school, and reduce contact with other children.
  • Ensure that your children wash their hands thoroughly, especially if they have persistent diarrhea. This is particularly important for children who are still in diapers.
  • Use only clean water to water vegetable/fruit/herb gardens. Shigella bacteria can live in contaminated water and might contaminate the food you eat.
  • If you are travelling, particularly in the developing world, make sure that you drink water from a safe source (for example, treated or boiled water). Avoid swallowing water if you are swimming or bathing in untreated water. Eat only cooked hot food and fruit that you peel yourself.

If you think you are infected with shigellosis or any other foodborne illness, do not prepare food for other people unless you wear disposable gloves and follow safe food handling procedures.

Surveillance

Does the Public Health Agency of Canada keep track of shigellosis cases across the country?

Yes, the Public Health Agency of Canada works with the provinces and territories to track the number of cases of shigellosis across the country.

When people get sick and go to the doctor, those doctors in many cases take samples from the patients and send them to a provincial, territorial or federal lab for testing.

Those labs test the samples to identify the genetic fingerprint of the bacteria, virus or parasite responsible for the illness.

The lab then posts the results for bacterial illnesses on PulseNet Canada, a national network that allows microbiologists to track and share genetic fingerprints for comparison across the country.

All labs then compare their results with those posted on PulseNet to find matches and identify outbreaks.

PulseNet Canada is coordinated by the Public Health Agency of Canada’s National Microbiology Laboratory in Winnipeg.

Are shigellosis outbreaks common in Canada?

Food-borne illnesses are relatively common in Canada. The Public Health Agency of Canada estimates that about 4 million Canadians suffer from a food-related illness each year.

In recent years, reports of shigellosis in Canada averaged about 813 cases per year.

A case refers to illness in one person whereas an outbreak refers to two or more people linked by a common exposure within a specific time frame.

A national outbreak occurs when illness is linked in two or more provinces or territories.

Protect yourself against food-borne illness by following safe food handling practices. For even more information about food safety, go to www.foodsafety.gc.caExternal Link.