Slide on West Nile Virus

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  JEV  We discuss mosquito vectors and models with respect to a subgroup of the mosquito-borne flaviviruses .  Falvivirus are very small and composed of a positive single-strand R! and can cause Encephalitis  JEV serocomple within the Flavivirus genus contains several #oonotic sources of encephalitis  Wild wading birds $such as herons or bitterns% are the primary amplifying hosts& although over '( bird species are )nown to be hosts of JEV. *n urban areas swine are the dominant reservoirs.  +he primary vector of JEV is the mosquito species ,ule tritaeniorhynchus& but secondary vectors of JEV include ,ule gelidus& ,ule fuscocephala& and ,ule annulirostris. Rice fields are the most favorable locations.  +hree different vaccines for JEV are in use  *t has the potential to quic)ly cross large distances as it can infect migratory birds  WV infection was found in more than ( species of mosquitoes as well as numerous other arthropod species such as tic)s- primary vector are of ,ule genus& different species in different areas of the world. *n orth !merica& transmission is highest in agricultural and urban habitats  sutu Virus $/V% is first found in /! but became famous after invasion in Europe through !ustria& where it reached mostly by birds   *n 011'& /V first demonstrated pathogenicity in humans with neuro invasive infections in *taly and apart from bird& it has been isolated from both ,ule and !edes mosquito species  2urray Valley Encephalitis first discovered in !ustralia. +he main amplifying hosts are birds& while the main vector is ,ule annulirostris  +he ma3or encephalitic virus in the !mericas& /t. 4ouis Encephalitis. 5irds serve as the primary reservoir and ,ule mosquitoes as transmission vectors  ,ule genus and the !edes genus are of concern for the JEV viruses& although ,ule much more so. From rural and wild landscapes in !sia to the heart of ,hicago& ,ule species are found around the world.  ,ule species have been characteri#ed through their distributions& genetic relationships& abilities to overwinter viruses& host preferences& mating behaviors& and virus competencies  !edes mosquitoes are primary vectors of several of the mosquito-borne flaviviruses including dengue and yellow fever  !edes aegypti is not )nown as a vector for any virus of the JEV serocomple & yet one study has shown that !edes aegypti& once infected& are capable of transmitting WV through their bite  !sian +iger mosquito& !edes albopictus is competent for at least 00 arboviruses& including WV and /V  !edes albopictus in its success as a rural maintenance vector of arboviruses is able to replace populations of !edes aegypti in all but urban environments and susceptible to WV more than ,ule pipiens.  2odel +ypes  2osquito population models fall broadly into two categories& deterministic and stochastic  /tochastic models usually produce ranges for each output and require more computational resources than comparable deterministic models. *n general& stochastic models can more realistically represent real processes than deterministic models  6eterministic& mechanistic models generally use a set of differential equations to describe realistic processes evolving through time  +he growth stages can be modeled with compartments& where a mosquito advances from one compartment to the ne t  5asic Reproductive Ratio and Equilibrium analysis to predict the possibility of Epidemic  6eterministic models are analytical and 7ne advantage of the analytical nature of some of these models is their suitability for optimi#ation. +his feature permits mathematically optimal solutions for the control of vectors and disease outbrea)s  /tochastic models are used to capture ncertainty in model parameters and internal processes.  +hey use difference equations instead of 6E. 2osquito movements can be described as e ponential stochastic processes.  ,omputations are very comple in stochastic models than their deterministic counterparts. 5ut e tra care should be ta)en to avoid unrealistic outcomes when using deterministic models.   maturation rates& biting rates& egg-laying rates& e trinsic incubation period& mortality& and virus transmission efficiencies are important parameters to be modeled  +hey depend on temperature& vegetation& and rainfall  When the model includes a mosquito-borne virus& sub-models of all hosts with relevant demographic and disease parameters and the vector-host interactions should be added  !s the mosquito life cycle is fast enough compared to host& the host portion of the model becomes irrelevant.  !mong the (8 basic assumptions on R2 model& only 9-8 are differed in last :1 years.
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