Abstract
The mosquito-borne West Nile virus (WNV) is a highly neurovirulent Flavivirus currently representing an emergent zoonotic concern. WNV cycles in nature between mosquito vectors and birds that act as amplifier hosts and play an essential role in virus ecology, being, thus, WNV a threat to many species. Availability of an efficient avian vaccine would benefit certain avian populations, both birds grown for hunting and restocking activities, as well as endangered species in captive breeding projects, wildlife reservations, and recreation installations, and would be useful to prevent and contain outbreaks. Avian vaccination would be also of interest to limit WNV spillover to humans or horses from susceptible bird species that live in urbanized landscapes, like magpies. Herein, we have addressed the efficacy of a single dose of a WNV recombinant subviral particle (RSP) vaccine in susceptible magpie (Pica pica). The protective capacity of the RSP-based vaccine was demonstrated upon challenge of magpies with 5 × 103 plaque forming units of a neurovirulent WNV strain. A significant improvement in survival rates of immunized birds was recorded when compared to vehicle-inoculated animals (71.4 vs. 22.2%, respectively). Viremia, which is directly related to the capacity of a host to be competent for virus transmission, was reduced in vaccinated animals, as was the presence of infectious virus in feather follicles. Bird-to-bird transmission was recorded in three of six unchallenged (contact) magpies housed with non-vaccinated WNV-infected birds, but not in contact animals housed with vaccinated WNV-infected magpies. These results demonstrate the protective efficacy of the RSP-based vaccine in susceptible birds against WNV infection and its value in controlling the spread of the virus.
Highlights
Human and animal health has to face changes in the ecology of pathogens resulting from globalization and climate warming
Hundreds of bird species are susceptible to the infection, and several develop competent viremia to efficiently transmit the virus to vectors, playing an essential role in virus maintenance (Komar et al, 2003)
The virus re-emerged in the 90s, being responsible of more frequent and severe outbreaks in humans, horses, and birds, as exemplified by the outbreak in 1999 in New York (Martin-Acebes and Saiz, 2012)
Summary
Human and animal health has to face changes in the ecology of pathogens resulting from globalization and climate warming. Flaviviruses represent one of these emerging challenges and are currently spreading worldwide, as exemplified by the recent pandemic of Zika virus (Saiz et al, 2016) and the increasing outbreaks of WNV WNV is a highly neurovirulent pathogen naturally maintained in an enzootic cycle between ornithophilic mosquitoes and certain birds. It is responsible for sporadic outbreaks in humans and horses, in which the infection is mainly asymptomatic even though it can have a fatal outcome and result in epidemics and epizootics (Martin-Acebes and Saiz, 2012). Assessment of the protective capability of vaccine candidates in birds that are natural hosts and virus amplifiers can be very useful to control WNV outbreaks
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