**6. Diagnosis**

Patients with JE present many signs of acute encephalitic syndrome. There are various possible causes of acute encephalitic syndrome; therefore laboratory confirmation is crucial for the accurate diagnosis of JE [Table 2], which is a tough task because of very low viremia. Reverse passive hemagglutination, immunofluorescence and staphylococcal coagglutination tests using polyclonal or monoclonal antibodies have proved the value of antigen detection in Cerebrospinal fluid (CSF) for rapid diagnosis of JE. Advanced methods like Immunogold silver staining (IGSS), have been effectually used in the detection of antigen in mononuclear cells of peripheral blood and CSF of patients. Immunohistochemistry has been used to detect viral Japanese Encephalitis: A Neglected Viral Disease and Its Impact on Global Health http://dx.doi.org/10.5772/58529 9

**Figure 3.** Transmission cycle of Japanese encephalitis virus. Infected Culex mosquitoes (vectors) play the role in the spread of JEV. Pigs are the amplifying hosts and birds (egrets) are the maintenance hosts while humans are the deadend hosts.

antigens in the CNS. Histopathology inspection is also very obliging for clinical association and diagnosis of JEV. Diagnosis is accordingly targeted towards the detection of antibodies in serum and cerebrospinal fluid. Cases like cross-reactivity of antibodies to other flaviviruses cause confusion in the diagnosis of JEV. IgM capture ELISA has been the most extensively used diagnostic method for JE detection [Hobson-Peters *et al*., 2012; Palani *et al*., 2013; Borthakur *et al*., 2013]. Currently, dipstick method, JEV-CheX and reverse transcriptase PCR are some of the methods which are used for the early detection of JEV [Yang *et al.,* 2013; Seo *et al*., 2013; Zheng *et al.,* 2013].


**Table 2.** Laboratory diagnostic tools for Japanese encephalitis

spread hypertonia, cogwheel rigidity and other irregularities in movement [Dutta *et al*., 2010]. Paralysis of the upper body is more common than that of legs. Nearly 30% of survivors have genuine persistent motor deficits and approximately 20% have severe cognitive and language

The JE virus exists in a zoonotic transmission cycle between mosquitoes and pigs and/or water birds; humans get infected only accidentally when bitten by an infected mosquito [Fig 3] and are a dead-end host [Gould *et al*., 2008]. JEV has been isolated from many mosquito species in field studies, and even though the major mosquito vectors differ in diverse geographical regions, the most important is *Culex tritaeniorhynchus*. For Eastern Asia, Southern Asia and Southeastern Asia, the chief vector is *C. tritaeniorhynchus* [Rao *et al*., 2001]. For Northern Australia, the chief vector is *C. annulirostris.* From India's outlook, there are several other secondary vectors such as *Anopheles peditaeniatus*, *A. subpictus, C. epidesmus, C. gelidus, C. pseudovishnui, C. whitemorei, Mansonia uniform* and *M. Indiana* [Borah *et al*., 2013]. Pigs are the key component in the transmission cycle with respect to human infection, while egrets, herons and other ardeid birds are significant maintenance hosts [Hecker *et al*., 2013; Sarkar *et al*., 2013]. Of other vertebrates, horses can develop CNS infection but are a dead-end host; Other domestic animals may also get infected, but do not show any evidence of viremia. Rodents are refractory to infection; and amphibians, bats and reptiles can be infected experimentally and virus can persist, but the role of these species in hibernating and maintaining the virus in the

There are two epidemiological forms of transmission: an endemic form in tropical areas with virus circulation almost throughout the year, but with a wide seasonal peak probably due to irrigation practices; and an epidemic form in more temperate areas with clear summer seasonality [Schuh *et al.,* 2013; Gao *et al*., 2013]. Subsequently, JE is mainly a rural disease, where *Cx. tritaeniorhynchus* mosquitoes breed in rice paddies and pigs provide the main source of blood meals, with the consequence of transmission cycles in close proximity to human

Patients with JE present many signs of acute encephalitic syndrome. There are various possible causes of acute encephalitic syndrome; therefore laboratory confirmation is crucial for the accurate diagnosis of JE [Table 2], which is a tough task because of very low viremia. Reverse passive hemagglutination, immunofluorescence and staphylococcal coagglutination tests using polyclonal or monoclonal antibodies have proved the value of antigen detection in Cerebrospinal fluid (CSF) for rapid diagnosis of JE. Advanced methods like Immunogold silver staining (IGSS), have been effectually used in the detection of antigen in mononuclear cells of peripheral blood and CSF of patients. Immunohistochemistry has been used to detect viral

impairment [Mackenzie *et al*., 2004].

**5. Transmission**

8 Trends in Infectious Diseases

environment is undisclosed.

habitation.

**6. Diagnosis**
