**6. New drug development**

The life cycle of arboviruses *in vivo* is not well understood, even though a great amount of detail on the comprehensive biology of these viruses *in vitro* has been intensively investigat‐ ed and uncovered. As aforementioned, the genetic material for a majority of the arbovriuses is positive-sense single-stranded RNA, which can function as mRNA and be infectious by itself. It has been proposed that this genomic viral RNA can become encapsulated within the biological material from the host cell to form an infectious vesicle.These particles may fuse with other biologically functional identities, potentially leading to the initiation of new in‐ fections, which can result in the formation of completed and perfect virions. Interference with the processes and network signaling involving classical virion formation has been a common target for drug development. However, in reality, the perfect virion *in vivo* has not been visualized, suggesting an alternate form of virion may exist *in vivo*. Consequently, the real structures needed to design the intervention remains elusive. Furthermore, diseases in‐ duced by arboviruses are acute illnesses where timing is critical. Infected individuals nor‐ mally delay in seeking professional help, resulting in the subjects arriving at the hospital in a far worsen condition. Thus, the availability of intervention drugs, the timing of the admin‐ istration and the effect of the drugs on the arboviral infections remain critical issues.

As for WNV, an approved and efficacious vaccine for humans is not available, even though equine WNV vaccines are in use [99]. However, it is anticipated that a WNV vaccine for hu‐ man use will be available within a couple of years. In addition, inactivated TBEV vaccine is

Arboviral Encephalitis

85

http://dx.doi.org/10.5772/52327

For others, such as the Alphaviruses, human vaccines are available only as Investigational New Drugs, and thus are not in widespread use.The rest of the arboviral vaccines are cur‐ rently undergoing clinical phase III trials, and are anticipated to be available for public us‐ age within 5 years if everything goes as planned. While some of these vaccines have currently only received approval for animal usage, newer versions for human use are in the

New challenges in vaccine development have been met with new technologies in vaccine re‐ search. Many of the newer vaccines are now being developed by recombinant DNA technol‐ ogy [100]. For example, chimeric virus vaccines have been developed using infectious clone technology for many arboviruses including, WNV, JEV, and TBEV. Other successful ap‐ proaches have involved the use of naked DNA encoding and subsequently expressing the desired protective epitopes. Naked DNA vaccines have been used for TBEV and JEV and are currently under development for use against WNV. The development of less expensive, more authentic animal models to evaluate new vaccines against arboviral diseases will be‐ come increasingly important as these new approaches in vaccine research are realized.

However, technical issues do exist in the nature of these viruses. One of the unique biologi‐ cal features in a majority of arboviruses is the constitution of the genetic material. The posi‐ tive-sense single-stranded RNA genome can function as mRNA, which is capable of producing an infectious virus if the RNA is inside a biologically functional identity. To add the second layer of difficulty in vaccine development, arboviruses may have multiple life cy‐ cles, since the physical morphology of these virions may be a mosaic form *in vivo* [62]. These features may be one of the reasons why developing a vaccine against arboviruses is such a difficult task. Despite the potential dilemma, there are some successes; though continued improvement in developing arboviral vaccines that are capable of preventing encephalitis is

Other foreseeable methods for areas where arboviral encephalitis is prevalent include insec‐ ticide spraying, which may be used to control outbreaks. Wearing insect repellent and

Arboviral encephalitis is a very significant human disease and is caused by a large group of viruses distributed across multiple virus families. The virus is introduced to human beings by hematophagous arthropods, mainly mosquitoes and ticks. With a wide spectrum of clini‐ cal manifestations, the diseases are very difficult to diagnose and treat. Although arboviral infections are vaccine preventable and treatable diseases, only a couple of anti-viral thera‐

avoiding outdoor activities when mosquitoes are active may also be helpful.

currently available in Europe [100].

process of being evaluated or developed.

an urgently needed and challenging task.

**9. Conclusion and perspective**
