eastern equine encephalitis
Introduction
Introduction to Oriental Horse Encephalitis Eastern equine encephalitis (easternequineencephalitis) is a zoonotic viral disease caused by the Eastern equine encephalitis virus, mainly invading horses and humans. Because of the disease in 1933, the horses were popular in some farms in the eastern United States. In the same year, TenBroeck and Merrill isolated the virus from the diseased horses, hence the name is Eastern Horse Encephalitis. Clinically, it is characterized by high fever and central nervous system symptoms. People are infected by chance, but the mortality rate can be as high as 50%. basic knowledge Proportion of disease: low incidence, about 0.001% Susceptible people: no specific people Mode of infection: non-infectious Complications: cerebral palsy, pulmonary edema
Cause
Causes of Oriental Horse Encephalitis
(1) Causes of the disease
Oriental horse encephalitis belongs to the arbuscular virus group A, and its representative strain is Ten Broeck strain. Under the electron microscope, the virus particles are spherical RNA viruses, and there are capsules with a diameter of 40-60 nm, diethyl ether, formaldehyde ultraviolet light, sodium deoxycholate. Sensitive, insensitive to pancreatic enzyme, capable of agglutinating 1 day old chicks and adult goose red blood cells, can be inactivated by heating at 60 °C for 10 min, long-term storage at -70 °C, virus is unstable at pH 5.1-5.7, the virus is in chicken embryo The hamster kidney, guinea pig kidney, monkey kidney, duck kidney and other groups are well-cultured, and have strong invasiveness and virulence to experimental animals such as mice, guinea pigs and chickens. Intracerebral inoculation and subcutaneous vaccination can make many Birds and rodents develop disease, and some birds, rodents, livestock, and poultry can be infected.
In addition, there are also variants of the oriental equine encephalitis virus in some regions of Central America and South America. The antigenicity is significantly different from that of the Ten Broeck strain, which can cause acute neurological diseases in the equine population and rarely cause human disease.
(two) pathogenesis
After being bitten by an infected arthropod, the virus replicates in local tissues and local lymph nodes. The occurrence and persistence of viremia depends on the stage of viral replication in local tissues outside the nervous system, the speed at which the mononuclear-macrophage system clears the virus, and the specificity. The emergence of sexual antibodies, and thus the clinical manifestations of large differences.
The brain is filled with blood and water, and has extensive neuronal degeneration. There are multiple hemorrhagic foci in the brain tissue. Microscopic examination shows degeneration and necrosis of nerve cells, lymphocytes around the blood vessels, monocytes and polymorphonuclear leukocytes infiltrate, forming " Perivascular sleeves, some glial cell hyperplasia and polymorphonuclear leukocyte accumulation form nodules, lesions mainly found in the basal ganglia of the brain, brain gray matter and white matter, can also invade the cerebellum and spinal cord.
Prevention
Eastern equine encephalitis prevention
Vaccination with an effective vaccine can prevent the occurrence of viral encephalitis. At present, the monovalent (eastern equine encephalitis) vaccine, the bivalent (East Ma Jiaxima) vaccine and the trivalent (Dongma, West Malaysia and Venezuelan equine encephalitis) vaccines have a good protective effect on horses and other livestock. The current population vaccination is still in the experimental stage. The use of recovery serum has a certain protective effect and therapeutic effect on the human population.
Complication
Eastern equine encephalitis complications Complications, cerebral edema
Concurrent cerebral edema, cerebral palsy, and pulmonary edema.
Symptom
Eastern equine encephalitis symptoms common symptoms chills convulsions coma nausea central heating organic nerve damage abdominal pain high fever breathing irregular
The incubation period is 7 to 10 days. Except for some patients with prodromal symptoms such as burnout, loss of appetite, abdominal pain, sore throat and headache, the clinical process is divided into three stages.
1. Acute onset during the initial heat period, sudden chills, high fever, severe headache, nausea and vomiting, conjunctivitis and other symptoms, body temperature quickly rose to above 39 ° C, lasting 2 to 3 days, slightly decreased, then rise again Extreme period.
2. The extreme period is mainly characterized by persistent high fever (above 40 °C) and obvious central nervous system symptoms, signs, patients with severe headache, vomiting, increased muscle tone, paralysis or lethargy, and soon into coma or convulsions, neck stiffness is obvious, Kay Erniig's sign positive, abdominal wall reflex and cremaster reflex disappeared, limbs muscle spasm, some patients showed paralysis, some patients have eye muscle paralysis, eyelid drooping, partial vision, severely ill due to severe brain edema developed into cerebral palsy, causing breathing Irregular, until the heartbeat stops, can also die due to a combined lung infection, death mostly occurs within 2 weeks after the disease, this period generally lasts 7 to 8 days.
3. After about 10 days of recovery, the body temperature begins to decline, and various symptoms gradually improve and recover. The severe fever lasts longer. Usually there are language barriers, lethargy, poor orientation, and indifference to the surrounding things. Disorders, etc., the cranial nerves and the nerve palsy that innervates the muscles of the limbs are mostly permanent damage.
Examine
Oriental horse encephalitis check
1. The blood leukocyte counts in the peripheral blood are mostly at (10-15)×109/L, and the neutrophils are above 0.9. Some patients have leukemia-like reactions. By the recovery period, the blood is almost normal.
2. Cerebrospinal fluid pressure is slightly higher, the cell count is (0.1 ~ 1.0) × 109 / L, mostly below 0.3 × 109 / L, most of the disease is neutrophils at the beginning, followed by lymphocytes, protein slightly increased, sugar, Chloride is normal.
Diagnosis
Diagnosis and identification of oriental equine encephalitis
The disease mainly relies on serological examination and epidemiological data to make a diagnosis. Although the virus is isolated in nature in China, it is also found that the population is positive for serum antibodies, but this case report has not been seen. Therefore, it is necessary to be cautious in the diagnosis. In the recovery period, double serum neutralizing antibody or coagulation inhibition test antibody can be diagnosed by a 4-fold increase. In addition, the brain tissue of the deceased is used for intracerebral inoculation or chicken embryo inoculation for virus isolation, and a positive result can be obtained.
In the Americas, this disease must be differentiated from Western equine encephalitis, St. Louis encephalitis, and herpetic encephalitis.
