Defeat The Bite

Japanese encephalitis (JE) is a serious mosquito borne viral illness. Recently it has expanded beyond its traditional rural areas to urban and semiurban areas. JE is an inflammation of the brain caused by the JE virus, which is transmitted to humans by mosquitoes. JE is a disease of major public health importance worldwide due to its high epidemic potential, high case fatality rate (CFR) and neurologic sequelae among survivors as well as considerable economic costs. According to World Health Organization (WHO), approximately 3 billion people are living in countries, which are at risk of JE in Southeast Asia and Western Pacific. 

The first case of JE was documented in 1871 in Japan. It was first reported in India in 1955. It is endemic in states such as Assam, Bihar, Uttar Pradesh, Andhra Pradesh, West Bengal and Manipur. JE can present in forms of mild severity that heal spontaneously or in aggressive forms with a poor prognosis and severe neurological sequelae in survivors. There is currently no cure for JE.

Japanese encephalitis virus (JEV) is an RNA virus and belongs to the family Flaviviridae and genus Flavivirus. The virus is maintained in a cycle between mosquitoes and vertebrate hosts, primarily pigs and wading birds (herons, egrets). Humans are considered as dead-end host because they usually do not develop high enough concentrations of JE virus in their blood to infect feeding mosquitoes. JEV is transmitted to humans through bites from infected mosquitoes, primarily of the Culex species. The most important vector Culex tritaeniorhynchus, prefers low lying water bodies with abundant plants, so paddy fields are a major habitat of the larvae. Domestic pigs serve as key virus-amplifying host as they develop high and long-lasting viral load in their blood. The disease is predominantly found in rural and peri-urban areas and transmission is principally associated with the rainy season.

Epidemics coincide with the monsoon and post monsoon period, but sporadic cases may occur throughout the year in endemic areas. Transmission is most frequent when mosquitoes feed, between dawn and dusk. Most infections are asymptomatic or pauci-symptomatic, with fever and headache. Approximately 1 in 250 infected people develop a severe neuroinvasive illness that is characterised by rapid onset of high fever, headache, neck stiffness, disorientation, coma, seizures and paralysis, which can lead to death. The case fatality rate in severe disease is up to 30% and up to 50% of patients who survive severe illness have significant neurologic or psychiatric sequelae. The incubation period (time from infection until illness) is usually 5-15 days. All ages can be affected in a population without previous exposure. In endemic areas the paediatric population are usually affected as most people develop immunity by the time they reach adulthood. 

JE cannot be transmitted from human to human. It is a medical emergency requiring prompt diagnosis and urgent medical attention. There is no specific antiviral treatment. Diagnosis is established by detecting JEV specific IgM antibody in Cerebrospinal fluid or serum. Treatment is supportive and focuses on relieving symptoms and helping the body to recover. The best way to prevent JE is through vaccination and avoiding mosquito bites. Use of mosquito nets (preferably insecticide treated) while sleeping even during daytime, use of insecticide(vapour dispensing units) inside the house in the evening, avoiding outdoors at dawn and dusk, wearing full sleeve shirts and long trousers that are loose and light coloured along with closed shoes when outdoors, using mosquito repellent on skin, covering windows and doors with insect screens are advisable. Further used cans and bottles should be put into covered dustbins, all drains should be kept free from blockage, water storage tanks should be tightly covered and water for plants should be changed at least once a week, leaving no water in the saucers underneath flower pots. Swimming pools should be well maintained especially those in schools that may be neglected when not in use during summer vacation. Piggeries should be kept away from human dwellings as also cattle as they are ‘mosquito attractants’. Climatic conditions, abundance of mosquitoes and pigs, agricultural practices and floods together provide ideal conditions for JE in our state. Most cases are seen in the months of June, July and August. 

The annual flood situation has been worsened by climate change and also, by man-made factors like deforestation, hill cutting and encroachment of wetlands. Although considered a rural disease, emergence of JE in urban areas is a possibility as increased population density, unplanned expansion, poor sanitation, artificial floods, increased temperature and urban pig farming are all favourable to mosquitoes.

The government has included JE vaccination in the Universal Immunization Program but needs to implement vector control measures in mission mode. Inter departmental coordination between health and animal husbandry is of paramount importance. Robust surveillance system for identifying outbreaks and ensuring adequate training of health workers and availability of suitable health infrastructure in rural areas can lead to timely care and better results in all patients. Raising public awareness with the help of civil societies and sponsoring research should be given priority.  As applicable to all diseases, economic upliftment plays a crucial role in the fight against JE, as improved and secure access to sanitation, nutrition, healthcare along with conducive living conditions play a pivotal role in controlling and managing infections.

Climate change has altered the natural environment and behavioural patterns of mosquitoes and other vectors. This is turn has impacted the dynamics of disease transmission. Mosquitoes are found to be highly adaptable to new conditions, both short term and long term, suggesting that they may expand their ranges and increase transmission risks of JE.

Urbanization has increased the demand for food, bringing pig farming close to urban areas at the same time expansion of city have brought people close to the paddy fields. Urban flooding and global warming provide favourable conditions for breeding of mosquitoes. In warmer climates, the female mosquitoes take a blood meal more frequently. Eradication is difficult because the infection is transmitted from natural reservoirs like pigs and wading birds. However, fatality and morbidity can be significantly reduced by early diagnosis and appropriate supportive medical management. JE is a potentially devastating but vaccine presentable disease.

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