WEST NILE VIRUS-RELATED TRENDS IN AVIAN MORTALITY IN CALIFORNIA, USA, 2003-12.
West Nile virus (WNV) is an arbovirus transmitted enzootically by Culex mosquitoes among avian hosts. Since 2000, the California Dead Bird Surveillance Program (DBSP) has tracked avian mortality reported by the public on a telephone hotline and website and measured the prevalence of WNV infection in dead birds. We summarize herein WNV prevalence in dead birds tested and variation of WNV transmission over time and space with the use of DBSP data from 2003 to 2012. Prevalence among dead birds was highest in 2004, 2008, and 2012. This pattern was similar to peak WNV infection years for mosquitoes but not to human WNV incidence. Although American Crows (Corvus brachyrhynchos) were most frequently reported and tested, this species ranked third in infection prevalence (44%) after Yellow-billed Magpies (Pica nuttalli; 62%) and Western Scrub-Jays (Aphelocoma californica; 48%). Overall prevalence in American Robin (Turdus migratorius), House Finch (Haemorhous mexicanus), and House Sparrow (Passer domesticus) carcasses ranged from 18% to 22%. Corvid WNV prevalence was highest in South Coast, Bay/Delta, Sacramento, and San Joaquin valleys, and Klamath/North Coast bioregions, overlapping areas of elevated WNV activity in other surveillance measurements. Bioregional analysis revealed the avian species most likely to be reported and found positive in each bioregion. Our results may be useful to WNV surveillance and control efforts and provide insight into bird population trends in California.
1  California Department of Public Health, Vector-Borne Disease Section, 850 Marina Parkway, Richmond, California 94804, USA.
Leslie
L
Foss
1  California Department of Public Health, Vector-Borne Disease Section, 850 Marina Parkway, Richmond, California 94804, USA.
Kerry
K
Padgett
2  Center for Vectorborne Diseases, Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, VetMed3A, Room 5329, University of California, Davis, California 95616, USA.
William K
WK
Reisen
3  California Department of Public Health, Vector-Borne Disease Section, 1616 Capitol Avenue, MS-7307, PO Box 997377, Sacramento, California 95899, USA.
Anne
A
Kjemtrup
4  California Department of Public Health, Vector-Borne Disease Section, 8633 Bond Road, Elk Grove, California 95624, USA.
Joshua
J
Ogawa
3  California Department of Public Health, Vector-Borne Disease Section, 1616 Capitol Avenue, MS-7307, PO Box 997377, Sacramento, California 95899, USA.
Vicki
V
Kramer
D000818:Animals; D000835:Animals, Wild / Q000821:virology; D001715:Bird Diseases / Q000401:mortality* / Q000821:virology; D002140:California / Q000453:epidemiology; D046368:Crows / Q000382:microbiology; D046109:Passeriformes / Q000821:virology; D011159:Population Surveillance; D014901:West Nile Fever / Q000453:epidemiology / Q000662:veterinary*; D014902:West Nile virus
American Crow; West Nile virus; Yellow-billed Magpie; bioregion; corvid; passerine; raptor; surveillance