DNA Vaccination of American Robins (Turdus migratorius) Against West Nile Virus

Abstract

West Nile virus (WNV) has caused at least 1150 cases of encephalitis, 100 deaths, and an estimated 30,000-80,000 illnesses in 6 of the last 7 years. Recent evidence from several regions has implicated American robins (Turdus migratorius) as an important host for feeding by Culex mosquitoes, and, when integrated with their host competence for WNV, demonstrates that they are a key WNV amplification host. We evaluated the efficacy of a DNA plasmid vaccine at reducing the viremia and infectiousness of hatch-year American robins. We found that a single dose of vaccine injected intramuscularly resulted in more than a 400-fold (10(2.6)) decrease in average viremia. Although sample sizes were small, these results suggest that vaccinated robins exhibit viremias that are likely to be mostly noninfectious to biting Culex mosquitoes. More broadly, if an orally effective formulation of this vaccine could be developed, new control strategies based on wildlife vaccination may be possible.

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)

“…In a second study (Turell et al 2003), where Fish Crows received a single vaccination, 56% of the birds developed a PRNT 80 detectable antibody response at a serum dilution of 1:20 by 14 days postvaccination; however, by day 42 postvaccination antibodies were no longer detectable at PRNT 80 . In agreement with our findings, American Robins vaccinated with the pCBWN vaccine also failed to produce detectable antibodies when given a single vaccination and tested by PRNT 90 at a serum dilution of 1:10, 14 days postvaccination (Kilpatrick et al 2010). Likewise, antibodies were not detected in 10 free-ranging Island Scrub-Jays that were vaccinated a single time with the Fort Dodge West NileInnovator DNA vaccine (Boyce et al 2011).…”

“…Naturally infected birds that were antibody positive at capture had PRNT 90 titers, which ranged from 1:80 to >1:640 at both 2 and 4 weeks. As found with the Island Scrub-Jays vaccinated with a single dose of either the Fort Dodge West Nile-Innovator killed or DNA vaccines (Boyce et al 2011) and American Robins vaccinated with pCBWN (Kilpatrick et al 2010), none of the vaccinated Western Scrub-Jays developed an antibody response before infection detectable by enzyme immunoassay or PRNT 90 at a dilution of 1:20.…”

“…Especially at risk are species with limited distribution confined to areas with high levels of enzootic WNV transmission; for example, the California endemic Yellow-billed Magpie (Pica nuttalli) experienced marked declines upon the arrival of WNV into central California (Crosbie et al 2008, Wheeler et al 2009). Mortality associated with WNV has led managers of zoo collections and conservationists to vaccinate vulnerable species (Nusbaum et al 2003, Chang et al 2007, Okeson et al 2007, and in the interest of public health, researchers have investigated the potential for wildlife vaccination to interrupt WNV transmission (Turell et al 2003, Kilpatrick et al 2010). …”

Disease and the dynamics of extinction

“…Rabies is, however, a rather unusual case in that its impact on human health means that there has been considerable investment in developing a vaccine. There has been some success in vaccinating American robins against West Nile virus [113], another wildlife disease with serious zoonotic effects, although this was not done with a conservation aim. Developing vaccines for pathogens that affect only wildlife is likely to be prohibitively expensive in most cases.…”

Evaluation of Cross-Protection of a Lineage 1 West Nile Virus Inactivated Vaccine against Natural Infections from a Virulent Lineage 2 Strain in Horses, under Field Conditions

“…Experimental vaccinations in birds have been applied outside Europe (although bird vaccines against WNV are not commercially available) to a limited extent, especially in endangered bird species (e.g., in California condors) to protect them from fatal WNV infection or in bird reservoir hosts (e.g., American crows and robins), with the aim of reducing WNV viremia in them and preventing subsequent transmission of the virus to competent vectors (22)(23)(24)(25)(26). With regard to dead-end hosts, for humans only passive immunization (intravenous immunoglobulin or hyperimmune gammaglobulin administration) has been used to a limited extent for treatment of patients with WNND (27).…”