Seroepidemiologic Survey of Potential Pathogens in Obligate and Facultative Scavenging Avian Species in California

Straub, Mary H.; Kelly, Terra R.; Rideout, Bruce A.; Eng, Curtis; Wynne, Janna; Braun, Josephine; Johnson, Christine K.

Several of the condors in our study were only vaccinated once against WNV, which may explain the lack of association between vaccination and serostatus in the multivariable analysis. Also, the relatively small number of condors that were not vaccinated against WNV, 16, of which six were seropositive, combined with the effect of natural exposure on titer may have resulted in our inability to detect an association between vaccination and serostatus. California condors receiving two vaccinations spaced three weeks apart have been reported to produce a strong antibody response by 60 days post vaccination [93] . However, a single WNV vaccination in other susceptible species, the western scrub jay (Aphelocoma californica) and island scrub jay (Aphelocoma insularis), has been reported to have minimal effect on titer [94, 95] . Age was significantly associated with seropositivity in condors released in Big Sur and Southern California. In addition, seropositive condors had significantly greater time since vaccination compared to seronegative condors. Natural exposure to WNV has been shown to produce strong antibody responses in other avian species such as the western scrub jay [95] and WNV titers in California condors have been long lasting, up to 416 days post-vaccination [93] . Thus, it is not surprising that older condors are more likely to be seropositive for WNV as a result of strong antibody responses to WNV upon natural exposure.