Efficacy of Three Vaccines in Protecting Western Scrub-Jays (Aphelocoma californica) from Experimental Infection with West Nile Virus: Implications for Vaccination of Island Scrub-Jays (Aphelocoma insularis)

Abstract

The devastating effect of West Nile virus (WNV) on the avifauna of North America has led zoo managers and conservationists to attempt to protect vulnerable species through vaccination. The Island Scrub-Jay (Aphelocoma insularis) is one such species, being a corvid with a highly restricted insular range. Herein, we used congeneric Western Scrub-Jays (Aphelocoma californica) to test the efficacy of three WNV vaccines in protecting jays from an experimental challenge with WNV: (1) the Fort Dodge West Nile-Innovator Ò DNA equine vaccine, (2) an experimental DNA plasmid vaccine, pCBWN, and (3) the Merial Recombitek Ò equine vaccine. Vaccine efficacy after challenge was compared with naïve and nonvaccinated positive controls and a group of naturally immune jays. Overall, vaccination lowered peak viremia compared with nonvaccinated positive controls, but some WNV-related pathology persisted and the viremia was sufficient to possibly infect susceptible vector mosquitoes. The Fort Dodge West Nile-Innovator DNA equine vaccine and the pCBWN vaccine provided humoral immune priming and limited side effects. Five of the six birds vaccinated with the Merial Recombitek vaccine, including a vaccinated, non-WNV challenged control, developed extensive necrotic lesions in the pectoral muscle at the vaccine inoculation sites, which were attributed to the Merial vaccine. In light of the well-documented devastating effects of high morbidity and mortality associated with WNV infection in corvids, vaccination of Island Scrub-Jays with either the Fort Dodge West Nile-Innovator DNA vaccine or the pCBWN vaccine may increase the numbers of birds that would survive an epizootic should WNV become established on Santa Cruz Island.

Detection of Persistent West Nile Virus RNA in Experimentally and Naturally Infected Avian Hosts

“…Samples of spleen and kidney, and a full panel of tissues, were collected and fixed in 10% neutral-buffered formalin for histopathologic and immunohistochemical (IHC) analyses using reported methods. 27 The spleen was divided into three approximately equal portions; two samples were immediately frozen at -80 C and reserved for RNA extraction and virus isolation, and the remaining sample was formalin-fixed for histopathologic analysis and IHC. Two kidney samples with a volume of approximately 5 mm 3 were frozen at -80 C and reserved for RNA extraction and virus isolation.…”

West Nile virus from an avian conservation perspective

“…Species within the family Corvidae are most severely affected, with lethality ranging from 100% among American crows Corvus brachyrhynchos and Black‐billed magpies Pica hudsonia , to between 55% and 75% among Fish crows Corvus ossifragus , Jungle crows Corvus macrorhynchos , Blue jays Cyanocitta cristata and Western scrub‐jays Aphelocoma californica (Komar et al ., ; Shirafuji et al ., ; Nemeth et al ., ; Wheeler et al ., ). In addition, an estimated 65% of a well‐studied free‐ranging American crow population was lost to WNV in Oklahoma in 2003 (Caffrey et al ., ).…”

“…Although there are currently no vaccines licensed for use in birds, vaccination has become routine in some zoological, private and educational collections, and has served as a management strategy for threatened or endangered species (Clark et al ., ; Chang et al ., ; Boyce et al ., ; Glavis et al ., ; Wheeler et al ., ; Jarvi et al ., ). In general, vaccines licensed for use in horses, as well as numerous proprietary or experimental vaccines, have yielded inconsistent results in birds, often eliciting limited or no anti‐WNV antibody production.…”

A Review of Vaccine Approaches for West Nile Virus

“…This vaccine was also shown to be one of the two best vaccine options in protecting scrub jays ( Aphelocoma sp. ) [147]. …”