Japanese Encephalitis
Challenging Threat to Human Health
-Dr. Arvind Singh
Japanese encephalitis is a fatal infectious disease caused by a virus that spreads by biting mosquitoes in human beings. It is an example of a neglected tropical disease which globally infects about 50,000 people annually. Since the disease was first reported in Japan in 1871 hence named as Japanese encephalitis. Japanese encephalitis primarily affects children, however, individuals of any age may be affected. More than 3 billion people in 24 countries across the world are at risk of Japanese encephalitis. The disease mainly occurs in China, Korea, Japan, Southeast Asia, the Indian sub-continent, and parts of Oceania.
What are neglected tropical diseases?
Neglected tropical diseases are those diseases that almost exclusively affect poor people living in rural areas or poor urban slums of low-income nations. They can be fatal, but they primarily cause chronic lifelong disabilities, leading to disfigurement, impaired child development, poor pregnancy outcomes, and impaired worker productivity. On national and regional scales, their effects are so severe that these diseases are considered conditions that promote and perpetuate poverty. Dengue fever, leptospirosis, onchocerciasis, schistosomiasis leishmaniasis, buruli ulcer, leprosy, chagas disease are the other examples of neglected tropical diseases.
What is Japanese encephalitis virus?
The Japanese encephalitis virus is an enveloped virus of the genus flavivirus. The single-stranded RNA genome is packed in the capsid (protein envelope covering nucleic acid in virus). The outer envelope is formed by envelope (E) protein and is the protective antigen. It aids in the entry of the virus to the inside of the cell.
The virus appears to have originated from its ancestral virus in the mid of 1500 A. D. in the Indonesian-Malaysia region and evolved into five different genotypes and spread across Asia.
Japanese Encephalitis in India:
Japanese encephalitis was first reported in India in 1955 from the state of Tamil Nadu. Today the disease has emerged as a major health problem in several states of India. The states affected by Japanese encephalitis include Uttar Pradesh, Bihar, Jharkhand, West Bengal, Assam, Manipur, Tripura, Odisha, Andhra Pradesh, Karnataka, and Tamil Nadu. Currently, Uttar Pradesh is the most affected state from Japanese encephalitis in India. Presently Japanese encephalitis has been reported from 39 Districts of Uttar Pradesh. The Gorakhpur Division of Eastern Uttar Pradesh is worst affected by the disease. Japanese encephalitis in Uttar Pradesh was reported the first time in 1978, however, since the year 2005 it has emerged as a serious health problem especially in Eastern Uttar Pradesh.
Japanese Encephalitis Causes:
Water logging and pig farming (in human settlement areas) are the two most important predisposing factors for the development and spread of Japanese encephalitis. The disease is spread by the biting of Culex species of mosquito (Culex tritaeniorhynchus, Culex vishnui, Culex gelidus, Culex fuscocephala etc.) which generally breeds in stagnant water bodies like ponds, pools, tanks, canals, rivers and in water logged paddy fields, therefore water logging provide ideal breeding grounds for the mosquitoes. The mosquitoes pick the virus from the pigs and occasionally from some wild birds (which are supposed to be the major reservoirs of the virus) and transmit to the human beings.
Japanese Encephalitis Symptoms:
Japanese encephalitis has an incubation period of 5 to 15 days and the vast majority of infections are asymptomatic; only 1 in 250 infections develop into encephalitis.
Japanese encephalitis is not a hemorrhagic disease like Dengue. It is mainly a brain fever hence in India vernacularly the disease is known with the name Mastishka jwar or Dimagi bukhar. Mild infections occur without apparent symptoms other than fever with headache. However, more severe infection is marked by quick onset of headache, high fever, neck stiffness, cachexia, hemiparesis, stupor, disorientation, tremor, occasional convulsions and spastic paralysis. Mental retardation developed from this disease usually leads to a coma. The mortality of this disease varies but is generally much higher in children.
Life-long neurological defects such as deafness, emotional labiality and hemiparesis may occur in those who have had central nervous system involvement.
Japanese Encephalitis Treatment:
The disease has no specific treatment. Antibiotics are not effective against the virus. Treatment is supportive to relieve symptoms and stabilize the patient.
Japanese Encephalitis Diagnosis:
The diagnosis is made primarily on the basis of the patient’s symptoms and the knowledge of the kind of illness endemic to a particular geographic area. To confirm Japanese encephalitis infection and to rule out other causes of encephalitis requires a laboratory testing of serum or, preferentially cerebrospinal fluid.
Japanese encephalitis is detected by antibodies in serum and cerebrospinal fluid test, by Ig M capture Enzyme-Linked Immunosorbent Assay (ELISA) which comprises antibodies against the virus in the infected person.
Japanese Encephalitis Prevention and Control:
Infection with Japanese encephalitis virus confers life-long immunity. All current vaccines are based on the genotype III virus.
Since vaccines are available against the disease, hence 100% vaccination should be ensured to control the disease. Japan, China, Korea, Thailand and Taiwan are the countries that have controlled the disease primarily by vaccination. As a precautionary measure mosquito nets and mosquito repellents should be used regularly to avoid mosquito bites. Water should not be allowed to stand in the surroundings. Temporary ponds and pools created in the rainy season should be strictly destroyed. Ponds, tanks and canals should be treated with insecticides at regular intervals for the control of mosquitoes. Malathion fogging should also be necessarily done at regular intervals to keep the mosquitoes at bay.
Since marigold (Tagetes erecta and Tagetes patula) possess mosquito repellent property, hence cultivation/plantation of marigold should be done on large scale in rainy season in the surroundings of the human settlement to deter mosquitoes. In addition to these, mosquito larvae feeding fish Gambusia affinis should be left and allowed to flourish in the wetlands. Similarly, fresh water turtles, which feed the mosquito larvae should also be left in the ponds, rivers, and canals to check the mosquito population. The fungi like Leptolegina caudata and Aphanomyces lavis parasitizing the mosquito larvae should also be used as bio-control agents to check the mosquito population.
Aquatic plants like Pistia lanceolata and Salvinia molesta which promote the breeding of Culex mosquito should be harvested and destroyed particularly during the rainy season. Water logged paddy fields serve as an ideal breeding ground for the mosquitoes, hence least water requiring paddy varieties should be brought in cultivation to avoid the water logging in paddy fields. Moreover, waterlogged paddy fields should be infested with water fern Azolla pinnata which deters the breeding of mosquitoes. Azolla pinnata will also serve as bio-fertilizer for paddy crop. Siltation often causes the overflow of canals in the rainy season leading to the problem of water logging. Therefore, desiltation of the canal is essential after regular intervals to avoid the overflow of the canals.
Since pigs are the major reservoir of the virus, hence pig farming should be done far from human settlement areas. Unhygienic conditions also favor the disease development hence all possible efforts should be made to maintain a neat and clean environment in the surroundings.
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Dr. Arvind Singh is M. Sc. and Ph. D. in Botany with area of specialization in Ecology. He is a dedicated Researcher having more than four dozen published Research Papers in the Journals of National and International repute. His main area of Research is Restoration of Mined Lands. However, he has also conducted Research on the Vascular Flora of Banaras Hindu University-Main Campus, India.
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