Introduction Of Japanese Encephalitis Virus Research Articles

Revisiting the risk of introduction of Japanese encephalitis virus (JEV) into the United States – An updated semi-quantitative risk assessment

Japanese encephalitis virus (JEV) is associated with encephalitis in humans and reproductive and neurological illness in pigs. JEV has expanded beyond its native distribution in southeast Asia, with identifications in Europe (2010) and Africa (2016), and most recently, its spread into mainland Australia (2021−2022). The introduction of JEV into the United States (US) is a public health risk, and could also impact animal health and the food supply. To efficiently and cost-effectively manage risk, a better understanding of how and where diseases will be introduced, transmitted, and spread is required. To achieve this objective, we updated our group's previous qualitative risk assessment using an established semi-quantitative risk assessment tool (MINTRISK) to compare the overall rate of introduction and risk, including impacts, of JEV in seven US regions. The rate of introduction from the current region of distribution was considered negligible for the Northeast, Midwest, Rocky Mountain, West, Alaska, and Hawaii regions. The South region was the only region with a pathway that had a non-negligible rate of introduction; infected mosquito eggs and larvae introduced via imported used tires (very low; 95% uncertainty interval (UI) = negligible to high). The overall risk estimate for the South was very high (95% UI = very low to very high). Based on this risk assessment, the South region should be prioritized for surveillance activities to ensure the early detection of JEV. The assumptions used in this risk assessment, due to the lack of information about the global movement of mosquitoes, number of feral pigs in the US, the role of non-ardeid wild birds in transmission, and the magnitude of the basic reproduction ratio of JEV in a novel region, need to be fully considered as these impact the estimated probability of establishment.

Assessment of data on vector and host competence for Japanese encephalitis virus: A systematic review of the literature

Japanese encephalitis virus (JEV) is a virus of the Flavivirus genus that may result in encephalitis in human hosts. This vector-borne zoonosis occurs in Eastern and Southeastern Asia and an intentional or inadvertent introduction into the United States (US) would have major public health and economic consequences. The objective of this study was to gather, appraise, and synthesize primary research literature to identify and quantify vector and host competence for JEV, using a systematic review (SR) of the literature.After defining the research question, we performed a search in selected electronic databases and journals. The title and abstract of the identified articles were screened for relevance using a set of exclusion and inclusion criteria, and relevant articles were subjected to a risk of bias assessment, followed by data extraction.Data were extracted from 171 peer-reviewed articles. Most studies were observational studies (59.1%) and reported vector competence (60.2%). The outcome measures reported pertained to transmission efficiency, host preference, and vector susceptibility to infection within vector competence; and susceptibility to infection within host competence. Regarding vector competence, the proportion of JEV infection reported across all 149 mosquito species in all observational studies ranged from 0 to 100%. In experimental studies, infection, dissemination, and transmission rates varied between 0 and 100%. Minimum infection rates (MIR) varied between 0 and 333.3 per 1000 mosquitoes. Maximum likelihood estimation (MLE) values ranged from 0 to 53.8 per 1000 mosquitoes. The host species in which mosquitoes mostly fed consisted of pigs and cattle (total of 84 blood meals taken by mosquitoes from each of these host species). As for host competence, the proportion of JEV infection varied between 0 (in rabbits, reptiles, and amphibians) and 88.9% (cattle).This SR presents comprehensive data on JEV vector and host competence, which can be used to quantify risks associated with the introduction of JEV into the US.

European Monitoring Plans for the Management of Outbreak of JEV(Japanese Encephalitis Virus)

Japanese Encephalitis Virus (JEV) is one of the most important endemic encephalitis in the world especially in Eastern and Southeastern Asia. JEV affects over 50,000 patients and results in 15,000 deaths annually [1]. JEV is the leading cause of viral encephalitis in 14 Asian countries. Approximately, 60% of the world’s population lives at risk in JEV-endemic regions of these countries. JEV is an acute, vector borne, noncontagious, and zoonotic viral infection of the central nervous system transmitted by the bite of infected mosquitoes [2]. JEV is a single stranded RNA virus and belongs to the family Flaviviridae [3]. JEV is transmitted between animals by mosquito species Culex, Anopheles, Mansonia [4]. Humans become infected with JEV coincidentally when living or travelling in close proximity to the enzootic cycle of the virus [4]. Encephalitis was first described in Japan in 1871, followed by outbreaks very few years. In 1924 the disease was named Japanese B encephalitis to distinguish it from von Economo’s encephalitis, or type A encephalitis (encephalitis lethargic); this was probably a form of autoimmune or post-infectious encephalitis, which caused an outbreak from 1916 to 1927. However, since then, the term “type A encephalitis” has not been used, and the terms Japanese B encephalitis has also fallen out to use [5]. Viral infection is maintained in enzootic cycles between birds and pigs. Water birds are the main reservoir for disseminating the JEV, whereas pigs are the amplifier hosts. Pigs usually do not show signs of the infection other than abortion and stillbirth, but they show continuous viremia, which allows the transmission of the virus to a human via mosquitoes. Humans and other large vertebrates including horses are not considered as efficient amplifying hosts and are, therefore “dead-end” hosts for the JEV [6]. The period of incubation is about 6-8 days, with a range of 4-15 days. JEV has a prodrome of a few days characterized by fever, headache, nausea, diarrhea, vomiting and myalgia, and they may last for several days. These symptoms are subsequently follows by altered mental status, which can range from mild confusion to coma. Headache and meningismus are more common in adults; seizures develop most often in children. Unintentional, rhythmic muscle movements are common, and mutism has been described as a presenting symptom. Sometimes, especially when there is an involvement of spinal anterior cells, JEV cause a syndrome of acute flaccid paralysis, resulting in a poliomyelitislike presentation. Generally fever disappears in about two weeks as long as with the other neurological symptoms [7]. Therapy for JEV infection is supportive. Different kinds of vaccines (inactivated, attenuated and chimeric) are available and used in several Asiatic countries. In Europe an inactivated vaccine is currently available. Another way to prevent Japanese encephalitis infection is to avoid mosquito bites in endemic rural areas more specifically close to irrigated rice fields and pig farms. Many mosquitoes are most active at dusk and dawn. People can use insect repellents when they are outdoors and wear long sleeves and trousers at these times, or consider staying indoors during these hours [8]. Sporadic introduction of JEV to new areas by migratory birds or by other ways may not necessarily lead to local viral circulation. JEV represents a human health threat in Europe merits further investigation [9]. The presence of JEV in Passeriformes of Tuscany constituting the first evidence of this antropo-zoonotic virus in Italy and also in Europe. The positivity to JEV of some house-sparrows confirms the potential epidemiological role of this bird in the Flavivirus Mosquito-borne JEV group spread, as observed for other viruses of JEV complex [10]. Confirmation of potential introduction of JEV to Italy and other European countries is urgently needed [11]. In order to increase surveillance in Europe improving diagnosis, monitoring and treatment of JEV different elements should be considered. First of all, at the present time there are no standard protocols on how to notify JEV infection and how “contact tracing” should be carry out thought different EU countries. For that reason education is extremely important, focusing especially on transmission pathways and preventive measures; it is also crucial to provide adequate resources to contrast the transmission of this disease. Moreover, in many countries at risk of infection, standard operating procedures and protocols for data exchange are not settled between human and animal health services. Therefore designing and creating a surveillance system for these vectortransmitted diseases should be targeted to develop common procedures and protocols for data exchange.