Japanese Encephalitis: A Neglected Viral Disease and Its Impact on Global Health (original) (raw)
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Epidemiology, Disease Transmission and Pathogenesis Caused by JE Virus: Its Prevention and Control
In the present review article epidemiology of Japanese encephalitis, disease incidences and its control measures have been described in detail. Among important reasons of JE outbreak are registered demographic clustering, ecological imbalance, and insecticide resistance in target mosquito species, poor economy, lack of socio cultural environment and timely therapeutics. Other complex reasons are negative anthropogenic activities like mixed agro-pig farming practices, paddy farming and sanitation. Water contamination led to the spillovers of the virus from its wildlife reservoir into pig population as well as other vertebrate hosts. This article also explains emergence of new mutant variants/ new genotypes /ecological strains of JE virus and its spread in endemic to non-endemic areas. Due to re-circulation of virus among various hosts and insect vectors, disease is causing vey high mortality and morbidity in rural and suburban endemic areas. In addition, presence of revertants in ove...
Distribution of Japanese Encephalitis Virus, Japan and Southeast Asia, 2016–2018
Emerging Infectious Diseases
T he locations of epidemics of arthropodborne viruses (arboviruses) are strongly associated with the distribution of their vectors. In general, the distribution of arboviruses can expand through the dispersal, transfer, and migration of their vector arthropods and reservoir animals. Mosquitoes transmit a variety of viral pathogens (e.g., dengue, Zika, and chikungunya viruses) and have caused a number of arboviral epidemics throughout the world (1). Japanese encephalitis virus (JEV; family Flaviviridae, genus Flavivirus) is a mosquitoborne arbovirus that causes a severe form of encephalitis in humans. JEV is distributed across most of Asia, the western Pacific, and northern Australia (2). The World Health Organization has estimated that the annual number of Japanese encephalitis cases worldwide exceeds 60,000 (2). JEV is transmitted primarily by mosquitoes of the Culex vishnui subgroup, principally Cx. tritaeniorhynchus Giles; pigs and wading ardeid birds, such as egrets and herons, are known to be the major amplifying hosts (3). On the basis of their genome sequences, JEVs are classified into 5 genotypes (4). JEV genotype I (GI), which has been further classified into subgenotypes GIa and GIb, and JEV GIII are the dominant lineages and have been detected widely throughout Asia. JEV GII is the third most common lineage and has been found in Indonesia, Singapore, South Korea, Malaysia, and Australia. JEV GIV and GV are rare lineages; only a few viruses of these genotypes have been isolated from Indonesia, Malaysia, and China as of October 2019. Over the past 30 years, JEV GIa has displaced GIII as the dominant lineage in many countries of Asia (5). Although the origin and spreading pattern of JEV genotypes across the world have been investigated in some reports (6,7), the exact mechanisms of JEV genotype shift remain unclear. The Study To study the epidemiology of arbovirus infection, we, an international team of researchers in Japan, Thailand, the Philippines, and Indonesia, conducted arbovirus surveillance in our respective countries during 2016-2018 with the support of our governments. In each country, we collected mosquitoes in and around cattle or pig housing using sweeping
Japanese Encephalitis: A Persistent Threat
Proceedings of the National Academy of Sciences, India Section B: Biological Sciences, 2012
JE is a vector (mosquito) borne viral zoonotic disease, caused by flavivirus belonging to family Flaviviridae. The virus has five genotypes which mainly affect the central nervous system. Previously genotype III was the most widely distributed genotype in Asian countries including India with the prototype of Nakayama strain but in recent years genotype I is largely replacing genotype III (Karthikeyan et al., 2017).The World Health Organization (WHO) has attributed JE to be the most important cause of mosquito borne viral encephalitis in endemic Asian countries especially in the pediatric age group (0-14 years), where 75% of the cases occur. An estimated 67,900 cases of JE are reported annually, with approximately 13,600-20,400 deaths, while 2 billion people are at risk located in 24 WHO member countries. India and China experience 95% of the reported disease burden of JE. Two thirds of the at risk population for JE is in China and India only (Rustagi et al., 2019). Japanese encephalitis (JE) is a major threat with case fatality rate up to 30%.It causes severe neuro-psychiatric sequelae that necessitates lifelong support amounting towards considerable socioeconomic burden. The natural maintenance reservoir for JE virus are birds of the family Ardeidae (herons and egrets). Pigs act as important amplifiers of the virus producing high viraemias which infect mosquito vectors (OIE, 2019). The infection causes a spectrum of clinical illness that begins with flu-like symptoms, neck stiffness, disorientation, coma, seizures, spastic paralysis and eventually death.The ideal method for laboratory confirmation of JEV is testing cerebrospinal fluid (CSF) or serum for JEV-specific IgM antibody (Kulkarni et al., 2018). Currently, there is no cure for JEV, and treatment is mainly supportive. National Vector Borne Disease Control Programme (NVBDCP), Govt. of India, works towards prevention and control of six important vector borne diseases and Japanese encephalitis is among one of those diseases. The effectiveness of vector control strategies is limited due to the complex eco-epidemiology of the virus. Vaccination is the most effective means of prevention, where JEV is a major public health problem.
Flavivirus Encephalitis, 2011
et al., 1999). Limited outbreaks were also reported from the two Western Pacific Islands of Guam and Saipan, respectively in 1947-48 and 1990, but the enzootic cycle might be not sustainable and the virus was therefore very probably introduced there (Richards et al., 2010; Fisher et al., 2010). 1.2 Japanese Encephalitis epidemiology In nature, JEV is essentially transmitted by Culex mosquito species to wild and domestic birds and pig herds. In the transmission cycle, humans are accidental and dead-end hosts. The most prevalent vector for human infection is Culex tritaeniorhynchus which breeds in pools of stagnant water such as rice fields (Keiser et al., 2005; Richards et al., 2010). However, about fifteen other mosquito species belonging to genus Anopheles, Aedes, Armigeres, Mansonia and Culex and other species of true flies are recognized to carry the virus, but all of them are not equally competent to transmit the virus to new hosts (Mackenzie et al., 2007). Moreover, pigs are attractive hosts that are generally asymptomatic and are important virus amplifiers. As a consequence, human living close industrial or familial piggeries are at higher risk of transmission (Nitatpattana et al., 2011). 1.3 Japanese Encephalitis syndrome In terms of human morbidity and mortality, JE is one of the most important and widespread causes of arboviral encephalitis worldwide, with an estimated 35,000 to 50,000 cases and 10,000 deaths annually in Asia (Tsai, 2000). It is estimated that three billion people are at risk of infection. Human infections are generally asymptomatic (1 in 1000 cases), while 25% of symptomatic infections will present brain inflammatory signs and, among them, a quarter may result in permanent neurological and psychiatric sequel with a 25% mortality rate (Vaughn & Hoke, 1992; Solomon & Vaughn, 2002). 1.4 Japanese Encephalitis Virus JEV is a Flavivirus of the Flaviviridae family and a member of the Japanese encephalitis eponym serogroup, including ten antigenically related virus species as: Alfuy, Koutango, Kokobera, Kunjin, Murray Valley encephalitis, Japanese encephalitis, Stratford, Usutu, West Nile and St. Louis encephalitis viruses. JEV consists of a lipo-glicoprotein envelope surrounding a nucleocapsid of a single-stranded positive-sense RNA of 11-Kb nucleotide. A single open reading frame is flanked by two 5' and 3' untranslated regions (UTRs), and carry genes coding for structural proteins including a capsid (C), a membrane (cleavage product of a pre-membrane protein PrM), an envelope (E), and seven nonstructural (NS) proteins (Sumiyoshi et al., 1987). Based on nucleotide sequencing of C/PrM and E genes, four virus genotypes have been distinguished (Chen et al., 1990; Chen et al., 1992): genotype I (GI), genotype II (GII) and genotype III (GIII) are distributed all over the geographical area of Asia, and genotype IV (GIV) includes isolates from Eastern Indonesia (Solomon et al., 2003). In addition, a JEV strain named Muar, isolated once in Singapore from a patient who originated from Malaysia, may represents a fifth genotype (GV) (Hasegawa et al., 1994; Uchil & Satchidanandam, 2001). Although this fifth genotype remained uncertain, it has been recently argued that it would be the most genetically different from the other JEV four genotypes (GI to GIV) (Mohammed et al., 2011). Furthermore, this fifth genotype is believed to be the oldest of the JEV lineage which would have originated from an ancestral virus in the mid 1500s in the Indonesia-Malaysia region. As suggested by Solomon et al. (2003), the
Emergence of Japanese encephalitis virus genotype V in the Republic of Korea
Virology Journal, 2011
Background: Japanese encephalitis virus (JEV) genotype V reemerged in Asia (China) in 2009 after a 57-year hiatus from the continent, thereby emphasizing a need to increase regional surveillance efforts. Genotypic characterization was performed on 19 JEV-positive mosquito pools (18 pools of Culex tritaeniorhynchus and 1 pool of Cx. bitaeniorhynchus) from a total of 64 positive pools collected from geographically different locations throughout the Republic of Korea (ROK) during 2008 and 2010. Findings: Two regions of the JEV genome were sequenced from 19 pools; the envelope gene and the nonstructural protein 5 (NS5)/3'-untranslated region (UTR). Eighteen pools of Culex tritaeniorhynchus and one pool of Cx. bitaeniorhynchus were positive for genotype I and genotype V, respectively. Sequence alignment of the complete E gene from Cx. bitaeniorhynchus showed high amino acid similarity (98.8%) to the Muar strain, characterized as the first report of genotype V, isolated from an encephalitis patient in Malaysia in 1952.