Sentinel Bird Surveillance for West Nile virus. Nicholas Komar, Sc.D. CDC-Arbovirus Diseases Branch Fort Collins, CO. West Nile Virus Transmission Cycle. Mosquito vector. Incidental infections. WNV. WNV. Incidental infections. Bird reservoir hosts. WNV Surveillance Modalities.
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Sentinel Bird Surveillance for West Nile virus Nicholas Komar, Sc.D. CDC-Arbovirus Diseases Branch Fort Collins, CO
West Nile Virus Transmission Cycle Mosquito vector Incidental infections WNV WNV Incidental infections Bird reservoir hosts
WNV Surveillance Modalities • Dead birds (especially crows) • Mosquitoes • Live wild bird sentinels • Live captive sentinels (e.g. chickens) • Veterinary surveillance • Human surveillance
The success of sentinel bird surveillance depends solely on the effort expended by surveillance workers.
WNV Surveillance Totals, 2000Reported to CDC thru 1/25/01 * Confirmed & Probable cases; ** includes 7 from NYC
WNV seroprevalence, cumulative % Pos for Neut Ab Species NE Queens ’99 S.I.’00 Chicken 63 6 Pigeon 27 54 Mallard 6 8 House sparrow 60 9 Cardinal -- 69 Catbird -- 33 Dog 11 -- Horse 6 -- Human 2.6 0.5
Can Chickens be used as Sentinels? • Highly susceptible (for development of antibodies) • Resistant to mortality • Non-infectious to eachother • Non-infectious to handlers • Non-infectious to mosquitoes
Pathogenicity of WNV in Chickens USDA-APHIS-NVSL: Senne, Pederson, Hutto, Taylor, Schmitt, Panigrahy Avian Dis 44:642-649, 2000
Mean Days Mean PeakSpecies n Infectious* Viremia ** ci***Blue jay 2 4 12.3 2.4Common grackle 6 3 9.4 1.0House sparrow 6 3 8.9 0.9House finch 2 6 8.8 0.8American robin 2 3 8.5 0.6Red-wing. blackbird 3 3 8.1 0.5Mallard 2 3 6.7 0.3European starling 6 2 6.0 0.1Canada goose 3 0 4.7 0American coot 1 0 4.6 0Rock dove 6 0 4.3 0Chicken 16 0 3.2 0Ring-neck Pheasant 3 0 2.7 0 * Infectious viremia = log 5 or greater per ml serum; ** log pfu/ml serum *** ci = susceptibility * mean infectiousness * days infectious Do chickens develop WN viremia?
Features of a Sentinel Chicken Program • Chicken flocks established at known transmission foci • Birds are bled periodically • Serum samples sent immediately for testing • HI or M-ELISA test used for screen • N test for confirmation (3 days) • Positives replaced for accurate monitoring
New York City’s Sentinel Chicken Program • Details provided by Dr. Bryan Cherry • 13 coops (7 birds each) at live poultry markets in 4 boroughs, plus one flock of 15 in Staten Island • 7 of 106 seroconverted (tested at Cornell) • One dead chicken tested WNV+ by NYSDOH
New York State’s Sentinel Chicken Program • Details from Dr. Millie Eidson, Dr. Greg Ebel • Flocks placed in 4 counties: Suffolk (103 birds), Rockland (24), Westchester (70), Onondaga (47) • Sera screened by G-ELISA, confirmed by PRNT • 1 of 244 seroconverted 4 Aug in Westchester
New Jersey’s Sentinel Chicken Program • Details provided by Cheryl Farello, Dr. Bob Eisner • All 21 counties maintained 1-2 flocks of 3 birds each (more flocks in Ocean, Monmouth) • 4 of 102 seroconverted • Sera screened by HI, confirmed by PRNT at USDA-APHIS-VS-NVSL • Dates of seroconversions are 27-29 Sep from Sussex, Middlesex, Morris, Essex counties
Features of a Sentinel Wild Bird Program • Sampling sites established at known transmission foci • Wild birds are captured periodically and banded • Serum samples sent immediately for testing. Virus isolation may be attempted. • HI, ELISA or PRNT used for screen • PRNT for confirmation (3 days) • Hatch-year birds most useful, or recaptured adults, of targeted species
Summary of Wild Bird Surveillance, NYC Species n No. POS % House Sparrow 440 3 0.7% Other 150 1 0.7% Line list:Jul 21 House Sparrow Queens-Floral ParkAug 2 Mockingbird Brooklyn-Sunset ParkAug 9 House Sparrow Bronx-Orchard BeachAug 21House Sparrow Queens-Forest Park
First WNV Surveillance Events, 2000 Sentinel wild bird, Suffolk Horse, Richmond Sentinel Chicken, Westchester Oc. japonicus, Westchester; Cx. pipiens, Richmond Viral activity (inferred) Human, Richmond Crow, Suffolk Crow, Richmond Mar Jun Jul Aug Apr Sep Oct
Culex sp. WN virus infectionsJuly 15-24, 2000 * Minimum Infection Ratio = # infected/1000 tested