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Title: Mosquito-borne arboviruses of horses : vector presence, competence and disease prevention in the UK
Author: Chapman, Gail Elaine
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2017
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Mosquito-borne arboviruses cause significant morbidity and mortality in horses worldwide and can have substantial welfare and economic ramifications. Eight main arboviruses of equids are discussed in this thesis: the flaviviruses West Nile Virus (WNV), Japanese encephalitis virus (JEV), Murray Valley encephalitis virus (MVEV), and the alphaviruses Eastern equine encephalitis, Western equine encephalitis virus (WEEV), Venezuelan equine encephalitis virus (VEEV), Ross River virus (RRV), and Getah virus (GETV). Except for Getah virus, these viruses cause disease in humans as well as equids. To investigate the risk to horses in the UK, work included in this thesis comprised investigation of mosquito species presence on equine premises, and assessment of vector competence for equine arboviruses. Strategies for protection of horses from mosquito-biting were investigated, and the knowledge of horse owners with regards to equine arboviral diseases, vectors and control and prevention was explored, as this knowledge is important in disease preparedness, surveillance and control. Known and potential vectors of equine arboviruses are present on equine premises across England. The most widespread was found to be Culiseta annulata, which was also demonstrated to be a competent laboratory vector for JEV and has been shown previously to be competent for WNV. The most abundant species trapped was Ochlerotatus detritus, which has been previously shown to be a competent vector for some flaviviruses (JEV, WNV) and was demonstrated here to be laboratory competent for RRV. Container habitats of Culex pipiens were commonly found on equine premises and this species was shown here to transmit JEV at high rates at 18°C, which represents average temperatures which may be experienced in a warm summer period in the south of England. Both Cs. annulata and Oc. detritus were only inefficient laboratory vectors of epizootic VEEV. Apparent virus clearance and nonlinear temperature-transmission relationships were demonstrated for several virus-vector pairs studied. Horse-owner knowledge of equine arboviral disease was shown to be limited. Spray repellents were shown to have some benefit in the protection of individual horses from mosquito biting, and the potential for some degree of utility in reducing the risk of infection by arboviruses, under low to moderate infection pressure, and in situations in which there is no vaccine available.
Supervisor: Archer, Debra ; Baylis, M. ; Solomon, T. ; Torr, S. J. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral