Abstract
The Alaskan population of Steller's Eiders (Polysticta stelleri) has undergone drastic declines in nesting ranges in recent decades and was listed as threatened under the U.S. Endangered Species Act in 1997. A virus survey to detect and characterize viruses from Steller's eiders and other declining sea duck populations in Alaska is ongoing. Using molecular, cell culture and serological methods, the survey will determine the identity and prevalence of sea duck viruses and characterize patterns of exposure in wild populations.
Cloacal swabs and serum samples were collected from Steller's eiders at molting and wintering sites in Alaska during 2003-2004. Cloacal swabs were cultured on Muscovy duck embryonic fibroblasts1 and evaluated for a cytopathic effect indicating the presence of viruses. A potentially novel virus was isolated from a male Steller's eider captured in 2003 at the Alaska Peninsula. The cytopathic effect was suggestive of an adenovirus and molecular analyses were performed to further characterize the virus isolate 553V. PCR using viral DNA and primers from conserved regions of the fowl adenoviral hexon gene3 produced an approximately 900 base pair fragment and preliminary analysis of the amplified DNA sequence suggests a novel adenovirus. A PCR assay using 553V-specific oligonucleotide primers designed to screen for viruses in field samples is under development.
To determine the prevalence of exposure to the newly isolated virus, serum samples from Steller's eiders captured at molting and wintering locations were screened in a virus microneutralization assay.2 Birds previously exposed to the virus in the wild were identified by the presence of 553V-specific neutralizing antibodies. In a serological study of Steller's eiders molting at the Alaska Peninsula in 2003 and 2004 as well as from 3 wintering locations (Alaska Peninsula, Unalaska and Kodiak) (winter 2003-2004), 0-28% of Steller's eiders showed a titer of 1:64 or greater of virus-specific antibodies.
Further molecular and serological characterization of 553V, in conjunction with isolation and characterization of additional sea duck virus isolates will allow genetic and antigenic comparisons among isolates. This preliminary study will be expanded to include additional years, as well as additional sea duck species from the same locations.
References
1. Docherty DE, Slota PG. 1988. Use of Muscovy Duck Embryo Fibroblasts for the Isolation of Viruses from Wild Birds. Journal of Tissue Culture Methods. Vol. 11, No. 3, Pp. 165-170
2. Hollmen TE, Franson CF, Flint PL, Grand JB, Lanctot RB, Docherty DE, Wilson HM. 2003. An Adenovirus Linked to Mortality and Disease in Long-Tailed Ducks (Clangula hyemalis) in Alaska. Avian Diseases. Vol. 47, No. 4, Pp. 1434-1440.
3. Meulemans G, Boschmans M, van den Berg TP, Decaesstecker M. 2001. Polymerase Chain Reaction Combined with Restriction Enzyme Analysis for Detection and Differentiation of Fowl Adenoviruses. Avian Pathology. Vol. 30 Pp. 655-660.