Japanese encephalitis is a brain infection caused by a type of virus called flavivirus. It is a vector borne disease spread by the bite of infected Culex mosquitoes. The main reservoir of virus is large domestic animals, especially pigs and water birds. Mosquitoes get infected when they bite the animals.
Culex mosquitoes breed in stagnant water, particularly in rice fields. Therefore the disease is more common in areas consisting pig farms and rice fields. The virus multiplies in pigs and birds without usually causing any overt illness in them. Man to man transmission does not occur.
The disease is endemic in certain countries of Asia such as China, Thailand, Korea, and many other parts of south East Asia. Although the first case of Japanese encephalitis was noted in Japan, the incidence has been progressively decreasing over the years. Epidemics usually occur in summer and monsoon season.
Symptoms Of Japanese Encephalitis
Children and adolescents mainly get affected from this disease. However, individuals of any age can be affected with Japanese Encephalitis. The incubation period ranges from 5 to 15 days. Most cases of Japanese encephalitis are mild without manifesting any noticeable symptoms.
It is only the occasional patient (1in 300 to 1 in 1000) who manifests the signs and symptoms of encephalitis. The onset of disease is abrupt. About 90 to 95 percent patients experience severe rigors (shivering) and high fever. Together with high temperature, patient complains of headache.
Neck stiffness, disorientation, and seizures are other manifestations of encephalitis. Convulsion is common in children suffering from Japanese encephalitis. Paralysis and inability to speak can develop due to damage to certain part of brain. Wasting of muscles and muscle weakness has been noted.
The mortality rate can increase from 20 to 40 percent. In people who survive, they may have persistent paralysis, convulsions from time to time, mental retardation, and sometimes Parkinsonism.
Treatment And Prevention Of Japanese Encephalitis
There is no treatment specifically available to treat the condition. No anti viral drugs are available till now that can significantly act upon the virus. Once Japanese encephalitis is suspected, patient should be hospitalized since the rate of mortality is high. Supportive treatment in the form of intravenous fluids, oxygenation, drugs to control seizures and cerebral edema are given. Vital signs such as pulse, blood pressure, temperature are monitored.
There is an effective vaccine available for JE. It should be given to high risk groups, especially children in epidemic prone areas. Measures should be taken to prevent breeding of mosquitoes. Insecticide spray is beneficial in controlling the outbreaks in summer and monsoon season.
People in such areas should use nets on their windows and doors. Children should be covered with full sleeve shirts, tops, trousers, and socks. Mosquito repellent should be applied on the exposed area of skin to prevent mosquito bite.