What Is Yersiniosis?

Introduction

Yersiniosis is the name given to illnesses or infections caused by Yersinia bacteria, which are typically encountered by eating contaminated food. Two types of bacteria give rise to Yersiniosis: Yersinia enterocolitica and, more rarely, Yersinia pseudotuberculosis.

Yersiniosis is a zoonotic disease, meaning it can be transmitted from animals to humans.¹ Yersiniosis is the third most common zoonotic disease in Europe.² The United States Center for Disease Control (CDC) estimates that Yersinia infections cause 35 deaths a year. As such, it is important to be aware of how Yersiniosis is contracted so you can better protect yourself and your loved ones from these infections.

The purpose of this article is to give you a deeper understanding of Yersiniosis, its symptoms, how you can contract it and ways to prevent infection. Importantly, it will also cover what to do if you become unwell. 

Overview

Causative agent 

The Yersinia genus of bacteria has 11 species, three of which are known to cause disease in humans. These are Yersinia pestis (which causes bubonic plague), Yersinia enterocolitica, and Yersinia pseudotuberculosis.³ Today, Yersiniosis is mainly caused by Y.enterocolitica.

Prevalence and incidence

The prevalence of Yersiniosis varies from country to country. In a recent meta-analysis based on the culture and isolation of Y.enterocolitica, the World Health Organisation (WHO) found that Yersinia bacteria were most prevalent in the regions of Africa and the Eastern Mediterranean. However, this study also showed a statistically significant difference in Yersiniosis cases between high and low-income countries, with the prevalence of Yersiniosis cases being more than 7% in low-income countries compared to 1.35% in high-income countries. Although Yersiniosis remains rare compared to other infections that can cause similar gastrointestinal symptoms, 6876 cases of Yersiniosis were reported in Europe in 2021, with 33% of infected individuals being hospitalised.²

Causes of yersiniosis

Contaminated food 

Undercooked or raw food is the main route by which humans are infected with Yersinia.^1,2 Although pigs are the main reservoir for Y.enterocolitica, this bacterium is also found in poultry, cattle, sheep and wild animals, such as deer and boar. Importantly, infected pigs do not show signs of the disease. Food can be contaminated by direct contact with infected meat or by contact with infected equipment or surfaces. These food sources, if not properly prepared or cooked, become major sources of Yersiniosis infection.^3,4

Yersinia bacteria not only survive but grow in low temperatures. As such, meat must be fully cooked to kill any bacteria within it. At low temperatures, Yersinia bacteria produce a toxin that is thermostable and can resist temperatures of 120 degrees Celsius for 30 minutes. Yersinia bacteria are also tolerant to freezing and can remain active for months.^1,4

Chitlins is a food product made from raw pork intestines and is a traditional food in some areas of the world. When preparing chitlins, extra care needs to be taken to avoid Yersinia infections and the cross-contamination of other foods and surfaces. This includes careful hand hygiene and the thorough cooking of meat.⁵

Waterborne transmission

Besides food, people can be infected with Yersinia by drinking contaminated water or milk products that have not been sufficiently pasteurised.^2,4 

Person-to-person transmission

Rarely Yersinia infections can pass from person to person. Infections may pass from an infected person or from someone who has come into contact with Yersinia bacteria and has not washed their hands sufficiently. Children under 5 years of age, elderly people, and immunocompromised individuals are all at high risk of Yersiniosis.¹

Symptoms of yersiniosis

Yersiniosis symptoms typically develop after an incubation period of 4 -10 days after exposure to Yersinia bacteria. This does not tend to vary based on when in the year you are infected.² 

Gastrointestinal symptoms

The most common symptoms of Yersiniosis are gastrointestinal, including diarrhoea, abdominal pain, and vomiting alongside fever. Right-sided abdominal pains may be mistaken for appendicitis. The diarrhoea can be severe, with blood potentially being present in the stool. It tends to be worse in those under the age of 5 years and typically lasts for 1-3 weeks. Immunocompromised individuals may develop sepsis, which is fatal in 50% of cases.^2,3,4

Other possible symptoms

Extra-enteric symptoms (symptoms affecting regions other than the gut) of Yersiniosis are rare but can include:

• Reactive arthritis which affects the larger joints (such as the knees, ankles, and wrists). This usually appears a couple of weeks after initial gastrointestinal symptoms and can last weeks to months
• Skin eruptions (also known as erythema nodosum), where subcutaneous fat becomes inflamed. This classically presents as painful red nodules on the shins but can occur on other areas of the body, for example, the forearms. Skin reactions are more common in adult females and typically resolve within a month

Diagnosis of yersiniosis

Laboratory testing

Yersiniosis is usually diagnosed with a stool culture (isolating, growing, and identifying bacteria from the stool). However, serological tests, such as antibody tests (IgG and IgM detection), and PCR (polymerase chain reaction) are also available.^2,3

Differential diagnoses 

The symptoms of gastroenteritis are not unique to Yersiniosis and so need to be distinguished from other illnesses (for example, Salmonella and Campylobacter infections). In older children, who are more likely to experience abdominal pain, Yersiniosis can mimic appendicitis.

Complications associated with yersiniosis

In addition to the symptoms noted above, Yersinia infections can cause inflammation of the kidneys (nephritis), heart (myocarditis) or liver (hepatitis) as well as infection of the blood (bacteraemia). Patients with Yersiniosis can pass Yersinia bacteria in their stool for up to 3 months, highlighting the importance of public education and hand hygiene to prevent further infections and outbreaks.^2,3,4 

Treatment and management

Self-care and hydration

With any illness that causes diarrhoea, it is likely that a person will become severely dehydrated. Therefore, supportive care, hydration, and electrolyte replacement are vital to ensure you stay hydrated. In extreme cases of dehydration, you may need to be admitted to the hospital. 

Antibiotics

Although Yersiniosis and its symptoms generally resolve on their own, antibiotics may be used in certain circumstances. Antibiotics are normally given to immunocompromised patients or those with severe infections requiring hospital admission. Antibiotics used for Yersiniosis include aminoglycosides, co-trimoxazole and tetracyclines.^1,3,4 

Preventing yersiniosis

Food safety measures

Cooking meat products correctly kills bacteria within them, so meat must be thoroughly cooked to ensure food safety. Checking internal meat temperature is one way to ensure this, as well as including a rest time for the meat to ensure its juices have also reached an appropriate temperature. You can prevent cross-contamination by using separate surfaces and equipment for raw meats and other produce.

Hygiene practices

Ensure safe hand washing practises are followed after handling meat and using the bathroom to prevent the spread of infection by cross-contamination or the faecal-oral route. You should wash your hands thoroughly before and after handling and preparing foods, as well as after contact with animals. You should also ensure surfaces used for raw meat preparation are cleaned with hot, soapy water between uses.⁴ 

Yersiniosis and public health

Public health measures

In many countries, Yersinia is a notifiable condition, meaning that public health authorities are notified when a new case emerges. This allows outbreaks to be monitored, helping to understand the origin of the cases and to look for ways to prevent further cases. Unfortunately, this is not the case in every country, and as Yersinia is not a common cause of diarrhoea, many countries do not routinely test for Y. enterocolitica. This means that cases may go undiagnosed and underreported.

As such, educating people on the importance of thoroughly cooking meat, carefully handling food, and maintaining hand hygiene is vital in helping prevent Yersiniosis. 

Outbreaks

Investigating outbreaks can help understand individual risk factors for Yersiniosis and develop targeted public health approaches. For example, an investigation into a Yersiniosis outbreak in November 2001 in Tennessee found that individuals involved in chitlin preparation were at an increased risk of Y.enterolotica infection. This can help target public health campaigns to increase awareness among people who participate in activities which may put them at risk of infection.⁵

Summary

Yersiniosis is an illness which mainly affects the gut. Infected individuals typically present with diarrhoea, which can be bloody and last for up to 3 weeks. Yersiniosis can mimic appendicitis, especially in older children, and often goes undiagnosed. Yersiniosis is mainly associated with contact or consumption of undercooked meat, particularly pork. Symptoms vary but generally are self-limiting and resolving. Some patients may benefit from antibiotic treatment, but keeping well hydrated is important for all cases. Careful handling of raw meat, hand hygiene, and ensuring meat is cooked thoroughly are important public health measures that need to be taken to reduce infections.