Japanese encephalitis is widespread across the Asian continent. Over 3 billion people, or half of the world’s population, live in JE endemic regions and are at risk of infection. Water birds, such as herons and egrets, are the natural reservoirs of the virus, from where spillover to humans and pigs via the Culex mosquito can lead to large-scale outbreaks.
Every year, approximately 50,000 individuals are sickened and 10,000 individuals die, as a result of JE infection. However, since many cases of JE are never reported or clinically identified, it is likely that the true incidence is much higher.
Japanese encephalitis usually begins with flu-like symptoms, such as high fever, nausea, and headaches, from where it may progress to changes in behavior, lethargy, and confusion. In severe cases, patients may experience seizures and become comatose. Infected individuals who show no obvious symptoms gain immunity to the disease.
Prevention is key
Since no cure for the disease exists, the most effective and cost-efficient form of prevention is vaccination. However, the JE vaccine requires multiple doses, which has been a significant barrier in past immunization campaigns. In resource-limited settings, high delivery and storage costs act as financial obstacles for vaccine administration. Additionally, the three-dose regiment compromises compliance rates for individuals unable to return to health care facilities for numerous dosages.
Environmental management of rice paddies, the breeding ground for the Culex mosquito, could also be a potential strategy for vector control. However, this requires improved infrastructure, governmental support, and access to sufficient water at specific times; which cannot always be guaranteed in countries most affected by JE. Additionally, since pigs act as amplifying hosts, pig rearing among rice farmers should be avoided or managed with this in mind.
In the past, chemical control of vector populations with the use of pesticides was successful in breaking the transmission cycle. However, this is now only considered a short-term solution due to increased levels of insecticide resistance.