Yersiniosis is a natural focal disease caused by Yersinia pseudotuberculosis and Yersinia enterocolitica and is characterized by fever, diarrhea, and abdominal pain, as well as extraintestinal symptoms in few patients.


Causes

Yersinia is mainly transmitted through the digestive tract, and is transmitted through the feces, urine, and secretions, as well as animal excretions. Contaminated water sources or foods such as milk, vegetables, soy products, and pork can cause outbreaks. Infected flies can be the main vector for the disease, and fleas carrying the bacteria can transmit the disease through sucking blood.

Both Yersinia enterocolitica and Yersinia pseudotuberculosis are 1.O - 2.0μm long, 0.5 - 1.0μm wide, oval, non-lactose fermenting, aerobic, Gram-negative bacillus, with flagella, grow slowly on the medium, the optimum growth temperature is 28 °C, and they can proliferate below 10 °C.

Yersinia enterocolitica can produce enterotoxin at room temperature and 37 °C, with heat resistance, can survive at 121 °C for at least 30 minutes, with acid resistance, cannot be inactivated at pH 1 - 11. Enterotoxin can be produced rapidly, up to a peak in 48 hours.

Patients and animals can be sources of infection. Some animals such as swine, rats, dogs, cats, cows, horses, sheep, goats, rabbits, pigeons, geese, fish, and fleas can be carriers of the bacteria for a long time.

Pathogenesis

After bacterial strains invade intestinal epithelial tissue, exudative diarrhea and mucous stools or bloody stools occur clinically, causing extraintestinal lesions such as adenomesenteritis, abscesses of aggregated lymphatic follicles, sepsis, and metastatic abscesses of other organs.

The pathological changes of the disease are mainly in the ileum and colon, and diffuse hyperemia of the intestinal mucosa, different sized superficial ulcers, and sometimes ulcers deep into the lamina propria can be seen. In the ileum, oval ulcers, local neutrophils and monocytes infiltration, and few lymphocytes and plasma cells are present. In severe cases, enterobrosis or enterorrhagia may occur. In the colon, ulcers can be covered with pseudomembrane formed by mucus and necrotic tissue, and at the bottom of the superficial ulcers, necrosis of the intestinal gland epithelial cells and local inflammatory cell infiltration can be seen. Multiple abscesses can be seen in the mesenteric lymph nodes and can involve the appendix, causing ulcers, necrosis, and peripheral inflammation.


Signs and Symptoms

The incubation period is several hours to 10 days.

Intestinal yersiniosis

Intestinal yersiniosis is the most common, mainly in children aged below 3 years. The initial symptoms are fever, predominantly moderate to high fever, and body temperature can reach 40 °C. Subsequently, nausea, vomiting, diarrhea, and abdominal pain occur. Abdominal pain is located in the umbilicus and lower abdomen, mostly spasmodic pain, rarely colic pain, and acute pain in the lower right abdomen of few children resembles appendicitis. Diarrhea and abdominal pain are concurrent, more than 10 times a day, and the stools are myxoid, purulent, or bloody. Some patients have fatigue and headaches. 2 - 3 days after onset, extraintestinal symptoms such as pharyngitis, cough, and bronchial pneumonia appear. Generally, clinical symptoms are mild, the disease is self-limiting, and patients recover in about a week. The disease can last for 1 - 2 weeks. In severe cases, dehydration, hypokalemia, hypoproteinemia, febrile seizures or intussusception can occur.

Terminal ileitis, appendicitis, and adenomesenteritis

Clinical manifestations are acute abdominal syndrome, including fever, nausea, vomiting, abdominal pain or diarrhea. Abdominal pain is spasmodic or colic, around the umbilicus and in the right lower abdomen, and local tenderness, muscle guarding, or rebound tenderness may be present.

Erythema nodosum

A small number of patients present with rashes, including erythema nodosum, maculopapular rash, and erythema multiforme, spontaneously subsiding after the condition improved.

Arthritis and tenosynovitis

Clinical presentations are chronic, repeatedly recurrent arthritis, mostly pauciarticular, and knee, hip, wrist, and ankle joints can be involved, predominantly knee joints. The clinical features are joint pain and unobvious redness and swelling. Symptoms subside within approximately 3 months and some patients carry HLA-B27.

Sepsis

While fever, nausea, vomiting, abdominal pain, and diarrhea, patients develop paleness, listlessness, apathy, clammy limbs, weak pulse, tachycardia, and hypotension. The endotoxin of the Gram-negative bacteria can be detected in limulus lysate test, which is helpful for diagnosis.

Other extraintestinal complications

It has been reported that a small number of patients infected with Yersinia may develop abdominal abscess, hepatitis, urethritis, myocarditis, meningitis, uveitis, hemolytic anemia, osteomyelitis, and pulmonary abscess.


Diagnosis

Diagnosis is mainly based on clinical manifestations, increased antibody titers over 1:160, and positive fecal bacterial culture.


Treatment

Mild patients can spontaneously heal without the need of systematic antibiotic treatment. If the infection persists for several weeks and the complications are severe, tetracycline, doxycycline, sulfonamide, and trimethoprim can be administered at regular doses. Aminoglycosides or fluoroquinolone antibiotics can also be used. Penicillin and cephalosporin are effective against Yersinia pseudotuberculosis, but ineffective against Yersinia enterocolitica. Aspirin and other prostaglandin inhibitors can be selected to control joint inflammation.