Overview
Eastern equine encephalitis (EEE) is a zoonotic acute viral infection caused by Eastern equine encephalitis (EEE) virus, which primarily affects horses and humans. Following the bite of an infected arthropod, the virus replicates in local tissues and local lymph nodes. The onset and persistence of viremia depends on the stage of viral replication in local tissues outside the nervous system, the rate of virus clearance by the monocyte-macrophage system, and the emergence of specific antibodies, resulting in a wide range of clinical manifestations. Clinically, high fever and central nervous system symptoms predominate.
Etiology
It is caused by the Eastern equine encephalitis virus (EEEV), which is transmitted by mosquitoes and birds, with the main vectors being Anopheles nigricollis and Culex tachyzoites.
Symptoms
The incubation period of Eastern equine encephalitis is 7 to 10 days. In addition to some patients with prodromal symptoms such as lethargy, lack of appetite, abdominal pain, sore throat, headache, the clinical process is divided into three stages.
⒈ initial fever
Acute onset, sudden chills, high fever, accompanied by severe headache, nausea and vomiting, conjunctivitis and other symptoms, the body temperature quickly rose to 39 ℃ or more, lasting 2 to 3 days, a slight decline, and then rise again into the extreme phase. In some patients, the body temperature continues to rise and directly enters the polar phase. A few patients have drowsiness, slightly resistant neck, most patients central nervous system symptoms signs are not obvious.
Peculiar phase
Onset of 4 to 10 days, the main manifestations of persistent high fever (above 40 ℃) and obvious central nervous system symptoms and signs. Patients have severe headache, vomiting, increased muscle tone, delirium or lethargy, and soon enter coma or convulsions. Neck tonus is obvious, Kernig’s sign is positive, abdominal wall reflex and tic reflex disappeared, muscle spasm of limbs, brain parenchyma inflammation and edema may also appear irregular breathing in severe cases, and if cranial hypertension further aggravates brain hernia occurs, which is life-threatening. Death can also be caused by combined lung infection. Death mostly occurs within 2 weeks after the disease. This period usually lasts 7-8 days.
3Recovery period
About 10 days after the disease, the body temperature begins to fall, various symptoms gradually improve and recover, the fever lasts longer in severe cases. Usually there are speech disorders, drowsiness, poor orientation, indifference to the surrounding things or gait disorders. Paralysis of the cerebral nerves and nerves innervating the muscles of the limbs is mostly permanent.
Examination
Serology: the diagnosis is confirmed by taking double serum neutralizing antibodies or 4-fold elevation of antibodies in the coagulation inhibition test during the acute and recovery phases. Detection of specific IgM antibodies is also diagnostic.
Diagnosis
The disease is diagnosed mainly by serologic tests and epidemiologic data.
Differential diagnosis
It must be differentiated from Western equine encephalitis, St. Louis encephalitis, and herpes simplex encephalitis.
Treatment
There is no specific treatment for this disease, and supportive therapy and symptomatic treatment are still the mainstay. Rescue measures for high fever, convulsions, and respiratory failure are the same as those for epidemic B encephalitis. If treated in time, most patients can pass through the extreme stage and recover.
Prevention
1. Anti-mosquito and anti-mosquito is an important part of preventing the disease.
2. Preventive vaccination: the use of monovalent (eastern equine encephalitis) vaccine, bivalent (eastern plus western horse) vaccine and trivalent (eastern, western and Venezuelan equine encephalitis) vaccine, the horses and other livestock have a good protective effect. Vaccination of the population is still in the experimental stage. The use of recovery serum has provided some protection and therapeutic effect in the population.