What is Australian Encephalitis?
Australian Encephalitis (syn.: Encephalitis of the Murray Valley, Australian X-Disease) is an acute infectious disease from the group of mosquito viral fevers caused by the same-name arbovirus of group B; it is extremely difficult, characterized by hyperthermia, deep stupefaction, meningeal phenomena and epileptiform seizures; is found in Australia.
In 1917-1918 Australian encephalitis was observed in Australia (New South Wales) in the form of epidemic outbreaks that affected mainly children under the age of 5 years. Mortality reached 70%. Smaller outbreaks were observed in 1922 and 1926. Doctors who have studied Australian encephalitis, suggested that it is a meningitis form of acute polio. In 1919, the independence of the disease, which was called the “X-disease”, was proved.
In 1951, in the valley of the Murray and Darling rivers, during another epidemic of encephalitis, a virus called the Murray Valley virus was isolated.
Causes of Australian Encephalitis
Australian encephalitis virus has a size of 20-50 microns. Pathogenic for mice and monkeys after intracerebral administration. The clinical picture in infected animals is accompanied by convulsions and paralysis of the hind limbs. Some pets, wild and domestic birds are susceptible to the virus.
The virus multiplies in chicken embryos and in tissue cultures with a cytopathic effect. On antigenic properties close to the Japanese encephalitis virus.
Pathogenesis during Australian encephalitis
A characteristic epidemiological feature of Australian encephalitis is its seasonality. Australian encephalitis occurs from January to April, with a maximum in February and March. These months correspond to the summer months of the Eastern Hemisphere. All diseases were found in New South Wales, in settlements that are separated from each other at a considerable distance, mainly in cattle-breeding areas.
Australian encephalitis is not contagious. Transmission of viruses occurs through mosquitoes.
The pathoanatomical picture of Australian encephalitis is characterized by edema and hyperemia of the brain and meninges. In the brain and spinal cord are detected punctate hemorrhage, the phenomenon of neuronophagy. In the gray and white matter, perivascular infiltrates are noted, in the cortex – miliary necrosis. The cerebellum is intensely affected with the destruction of Purkinje cells. Pathological changes in the white matter are concentrated in the subcortical zone with foci of demyelination.
According to the general pathological picture, Australian encephalitis can be attributed to acute diffuse meningoencephalomyelitis.
Symptoms of Australian Encephalitis
The incubation period is 5-12 days. The acute phase of the disease is sometimes preceded by: headache, fatigue, hypersensitivity, limb weakness. Often prodromal phenomena are absent. The temperature rises to 38.5-40 °. Infectious-toxic, cerebral and meningeal symptoms develop rapidly. As early symptoms, drowsiness, muscle weakness, movement disorder, confusion, delirium, tonic spasm, limb tremor, convulsions are observed. With a progressive course, a coma develops.
Australian encephalitis lasts about 2 weeks. Residual effects in those who are ill are absent.
In cases with an unfavorable outcome, death occurs on the 2-5th day.
Diagnosis of Australian Encephalitis
The final diagnosis is made after receiving the results of blood and cerebrospinal fluid tests in rtga, RAC and PH, as well as ELISA (IgM).
Treatment of Australian Encephalitis
Pathogenetic and symptomatic agents are used.
Prevention of Australian Encephalitis
The basis of prevention is the fight against mosquitoes and protection from their attacks. The use of formol-vaccine from the brain of infected mice creates short-term immunity in vaccinated people.