Brief overview
- What is yersiniosis? Infection with Yersinia bacteria (mostly Yersinia enterocolitica, more rarely Yersinia pseudotuberculosis), triggering a diarrheal disease mostly caused by food.
- How do you get yersiniosis? Most often, yersiniosis occurs from contaminated raw animal foods; less commonly, animals transmit the bacteria in direct contact with humans.
- Treatment: If the disease is uncomplicated, therapy of symptoms such as vomiting and diarrhea, if necessary supply of fluids and minerals via a venous drip. People with weakened immune systems and severe disease receive antibiotics (e.g., ciprofloxacin, ceftriaxone, cotrimoxazole) for treatment.
- Symptoms: Mostly gastrointestinal symptoms, often diarrhea, abdominal pain, fever, swollen lymph nodes; in children, some of the pain resembles appendicitis; in adults, symptoms include sore throat and symptoms of a flu-like infection. Rarely, in persons with a weakened immune system, the pathogens also affect other organs (e.g. liver, heart), or blood poisoning (sepsis) occurs. Consequential diseases are possible, such as a special form of joint inflammation (reactive arthritis), special type of skin inflammation (nodular erythema or erythema nodosum), irritable bowel syndrome.
- Diagnosis: Detection of Yersinia bacteria by laboratory examination of stool, blood or, less frequently, a tissue sample from inflamed lymph nodes.
- Prevention: Observe hygiene rules when handling animal foodstuffs, cook pork thoroughly, consume pasteurized dairy products.
What is yersiniosis?
Yersiniosis is an infection with Yersinia bacteria that usually causes gastrointestinal illness. Yersinia infection is a zoonosis: it refers to a disease that is transmissible from animals to humans. Along with bacteria such as Salmonella and Campylobacter, Yersinia are among the most common foodborne diarrheal pathogens.
In most cases, people become infected through contaminated raw food of animal origin. Raw pork in particular, and more rarely other animal products such as raw milk, may be contaminated with the pathogen.
Most often, infection with Yersinia results in gastrointestinal illness with diarrhea. In people with a weaker immune system (e.g., due to an underlying disease, infants and young children, elderly persons), more severe courses of the disease also occur. In these cases, the bacteria affect other organs, such as the liver or the heart.
Frequency
Children younger than five years are more likely to contract yersiniosis than older children or adults. In addition, the infection more often affects people who have a weakened immune system. Susceptible groups of people include pregnant women, the elderly, or people who have a weaker immune system due to another illness or certain medications (e.g., cortisone, immunosuppressants).
How do you get yersiniosis?
Most commonly, people become infected through animal foods contaminated with Yersinia. Pigs in particular often harbor the pathogen. Therefore, raw or insufficiently heated pork (e.g., ground pork, “minced pork”) is an important source of infection. Poor kitchen hygiene (e.g., contaminated hands, cutting boards, or knives) also favors Yersinia infection.
In addition, cases of yersiniosis caused by contaminated, non-pasteurized milk (raw milk) are known. In countries where fruit and vegetables come into contact with animal excrement (e.g. through fertilization), there is also a risk of contracting Yersinia. However, this only occurs if these foods are eaten raw.
In addition, contaminated drinking water is a source of infection with the diarrheal pathogen.
How to get rid of yersiniosis?
Treatment of yersiniosis depends mainly on the severity of the disease. As a rule, it is sufficient to treat the symptoms. Since a Yersinia infection is usually accompanied by diarrhea, affected persons often lose a lot of fluids and minerals (electrolytes). As a result, infants and young children in particular quickly run the risk of dehydration.
Patients who lose a lot of fluid therefore receive infusions for therapy. The body receives fluid and electrolytes back via a venous drip. These measures are often sufficient for treatment, and the disease subsides on its own after one to three weeks.
In patients who are very severely ill, suffer from complications (e.g. sepsis, involvement of other organs) or in whom the disease does not improve on its own, the doctor administers antibiotics, for example with the active ingredients ciprofloxacin, cotrimoxazole or ceftriaxone.
If the course of the disease is uncomplicated, simple measures such as bed rest and drinking plenty of fluids (water, unsweetened herbal tea) are part of the therapy.
How do I recognize yersiniosis?
Symptoms
Typical symptoms of a Yersinia infection are severe, cramping abdominal pain, fever and diarrhea (watery, sometimes bloody), and vomiting. In older children and adolescents, the intestinal lymph nodes may become inflamed. If so, they are more likely to suffer from nonspecific abdominal pain.
Some children complain of pain in the right lower abdomen, which initially cannot be distinguished from the symptoms of appendicitis. These symptoms occur because a specific part of the small intestine, located near the appendix, becomes inflamed.
Adults with yersiniosis sometimes have symptoms that resemble a flu-like infection, for example, sore throat, fever, and muscle aches.
Complications are possible in people with a weakened immune system, for example if the yersinia affect other organs. Then, for example, there is a risk of pus collecting in the liver (liver abscess), inflammation of the inner lining of the heart (endocarditis) or blood poisoning (sepsis).
Consequential diseases
Another secondary disease that occurs alone or in parallel with reactive arthritis is the so-called nodular erythema (erythema nodosum). This is a skin disease that manifests itself as red, nodular inflammation in the area of the lower legs.
Doctors also observe that some people develop irritable bowel syndrome following yersiniosis.
Causes and risk factors
Yersiniosis is caused by certain rod-shaped bacteria of the genus Yersinia. There are many different Yersinia species, but only two of them, Yersinia enterocolitica and Yersinia pseudotuberculosis, cause yersiniosis in humans. Yersinia enterocolitica is found in pigs, cattle, sheep, goats and in dogs – but pigs play the most important role as a source of infection.
Infected animals do not become ill themselves. The pathogens are found in the pharyngeal tonsils as well as in the lymph nodes and intestines of infected pigs and can be transferred from there to the animal’s meat during the slaughter process.
In contrast, the species Yersinia pseudotuberculosis is more commonly found in wild animals such as birds and small rodents. However, infection through contact with wild animals rarely occurs.
Risk factors
If the bacteria get onto the meat during slaughter, they remain active there. Yersinia can multiply even at relatively low refrigeration temperatures of four degrees Celsius. If contaminated meat is eaten raw or insufficiently cooked, the risk of contracting yersiniosis is high. The bacteria can also be “spread” to other foods through improper kitchen hygiene.
Typical mistakes in meat preparation can include:
- Preparing raw meat and food intended for raw consumption (e.g., vegetables, salad) with the same kitchen utensils (such as cutting boards or knives)
- Contamination of kitchen areas by splashing water (e.g., washing down meat).
The risk of contracting yersiniosis also depends on how many pathogens a person has ingested and how strong their defenses are.
Infants and young children have a higher risk of contracting yersiniosis because of their immature immune systems.
Certain groups of people whose defenses are compromised are also at greater risk for a more severe course of yersiniosis. These include:
- Pregnant women
- Elderly people
- Adults with pre-existing conditions (e.g., diabetes mellitus, cirrhosis of the liver)
- People taking drugs that weaken the immune system (so-called immunosuppressants, e.g. cortisone).
Diagnostics
The samples obtained are examined in the laboratory for the pathogen by various methods.
If the physician detects yersiniosis, he or she must report the disease to the public health department (mandatory reporting). Persons working in food production or catering must not work until the symptoms have disappeared. Special hygiene precautions must also be observed during the first four weeks after the symptoms have subsided.
Prevention
You can generally protect yourself well against Yersinia infection by heeding the following hygiene measures in the kitchen and household:
- Wash your hands before preparing food.
- Thoroughly clean all kitchen utensils (e.g., knives, cutting boards) that have been in contact with raw animal products before using them again.
- Do not wash meat in the sink – otherwise there is a risk of splashing water spreading bacteria to the surrounding area.
- Thaw frozen meat in a separate container. Be sure to remove the defrost water hygienically.
- Wash fruits and vegetables thoroughly before eating.
- Keep pets away from the kitchen area.
- Clean the refrigerator regularly with suitable products (e.g. vinegar cleaner).
- Change dishwashing sponges and dishcloths regularly, or wash them at a minimum of 60 °C.
- Put perishable foods such as meat in the refrigerator as soon as possible after shopping.
- Store meat (including fish) in the refrigerator separately from other products, especially vegetables and salad.
- Prepare ground meat the same day you buy it.
- To protect against yersiniosis, always cook pork completely. Other meats, fish, poultry and eggs may also contain pathogens and should be fully cooked.
- Reach for pasteurized milk and dairy products rather than raw milk. If you use raw milk, heat it before consumption. Especially for pregnant women, infants and young children, raw milk poses a risk of serious infections.