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    WNV Vertebrate Ecology and Biology-Birds

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    1 : WNV Vertebrate Ecology and Biology-Birds Nicholas Komar, ScD Arbovirus Diseases Branch, DVBID, CDC Fort Collins, CO
    2 : Experimental infection of WNV in 25 species of birds Komar et al., 2003, EID 9(3): 311-323; www.cdc.gov/ncidod/eid/vol9no3/02-0628.htm Other studies: Senne et al. 2000 Swayne et al. 2000 Langevin et al. 2001 Swayne et al. 2001 McLean et al. 2002
    3 : Very Competent Species Mean Reservoir Days Peak Competence Species (n) Infectious* Viremia Index, ci Blue Jay (4) 4.0 11.0 2.6 Common Grackle (6) 3.0 9.4 2.0 House Finch (2) 5.5 8.5 1.8 American Crow (8) 3.2 10.1 1.6 House Sparrow (6) 3.0 8.9 1.6 *Infectious viremia = log 5 or greater per ml serum
    4 : Mean Reservoir Days Peak Comp. Species (n) Infectious* Viremia Index, ci Ring-billed Gull (2) 4.5 7.4 1.3 Black-billed Magpie (3) 3.0 8.7 1.1 American Robin (2) 3.0 8.5 1.1 Red-winged Blackbird (3) 3.0 8.1 1.0 Killdeer (2) 3.0 8.1 0.9 Great Horned Owl (1) 4.0 7.6 0.9 American Kestrel (2) 3.0 8.4 0.9 Fish Crow (8) 2.8 6.8 0.7 * Infectious viremia = log 5 or greater per ml serum Moderately Competent Species
    5 : Mean Reservoir Days Peak Comp. Species (n) Infectious* Viremia Index, ci Mallard (2) 3.0 6.7 0.5 European Starling (6) 2.0 6.0 0.2 Mourning Dove (3) 1.7 5.3 0.2 Northern Flicker (1) 1.0 5.4 0.1 Canada Goose (3) 0.3 4.7 0.03 * Infectious viremia = log 5 or greater per ml serum Weakly competent species
    6 : Mean Reservoir Days Peak Comp. Species (n) Infectious* Viremia Index, ci American Coot (1) 0 4.6 0 Rock Dove (6) 0 4.3 0 Chicken (11) 0 3.4 0 Northern Bobwhite (3) 0 2.8 0 Ring-necked Pheasant (3) 0 2.5 0 Budgerigar (3) 0 2.5 0 Monk Parakeet (3) 0 2.4 0 Japanese Quail (3) 0 2.2 0 * Infectious viremia = log 5 or greater per ml serum Non-competent species
    7 : Summary of Competence Studies Passerines are most competent jays, crows, sparrows, finches, blackbirds, etc. Not all passerines are equally competent Not all birds are competent pigeons, chickens incompetent Competence does NOT imply Reservoir Status
    8 : Reservoir Host Criteria Competent Naturally Exposed Abundant
    9 : Natural Exposure: Seroprevalence Studies High seroprevalence (typically >30%) in resident birds after epizootic transmission Low seroprevalence (typically <1%) in enzootic foci, in non-resident birds, early in transmission season
    10 : WNV Seroprevalence in Birds Queens, September 1999 Species POS/Total % POS Domestic Goose 6/ 7 86 Turkey 2/ 3 67 Chicken 89/141 63 House Sparrow 12/ 20 60 Pigeon 13/ 49 27 Canada Goose 2/ 7 29 Mallard 1/ 16 6 Ref: Komar et al. 2001. Emerg. Inf. Dis. 7(4): 621-625.
    11 : Relative Abundance of Birds, Queens Relative Relative Infection no. of Species Abundance Rate Infections House Sparrow 6000 0.60 4186 Pigeon 1000 0.27 314 Mallard 60 0.06 4 Canada Goose 60 0.29 20 Chicken 3 0.63 2 Domestic Goose 1 0.86 1 Ref: Komar et al. 2001. Emerg. Inf. Dis. 7(4): 621-625.
    12 : Reservoir Potential of Birds, Queens A x B = C Relative no. Competence Reservoir Species infections Index Inoculation Index House Sparrow 4186 1.6 11,000 Pigeon 314 0 0 Mallard 4 0.5 3 Canada Goose 20 0.03 1 Chicken 2 0 0 Read: “For every one WNV-infectious Culex pipiens infected by a Canada goose, there were 3 infected by mallards and more than 11000 infected by house sparrows”
    13 : Birds affected by WNV – 162 spp.
    14 : Avian Mortality: Disease Impact Studies Surveillance data lack attack rates, mortality rates Preliminary observations were made in 2002 of three marked crow populations: Stillwater, OK; Ithaca NY; Chicago, IL
    15 : Species n mortality rate controls American Crow 20 100 8 Black-billed Magpie 5 100 1 Blue Jay 6 83 0 House Finch 3 67 3 Fish Crow 11 64 5 Ring-billed Gull 2 50 1 Common Grackle 10 40 2 House Sparrow 12 25 5 These birds infected by natural means (mosquito, oral, bird-bird) Experimental WNV Mortality -1 Komar et al., 2003, EID 9(3): 311-322; www.cdc.gov/ncidod/eid/vol9no3/02-0628.htm
    16 : Experimental WNV Mortality -2 Species n mortality rate controls European Starling 6 0 2 Rock Dove 6 0 6 Chicken 18 0 24 Ring-necked Pheasant 3 0 0 Canada Goose 3 0 0 American Robin 3 0 3 Red-winged Blackbird 3 0 0 Mourning Dove 3 0 3 Budgerigar 3 0 3 Monk Parakeet 3 0 3 Japanese Quail 3 0 3 Northern Bobwhite 3 0 3 Komar et al., 2003, EID 9(3): 311-322; www.cdc.gov/ncidod/eid/vol9no3/02-0628.htm
    17 : Alternative Transmission in Birds
    18 : WNV Cage Mate Transmission Species No. of cages No. of transmissions American Crow 4 4 Black-billed Magpie 3 2 Blue Jay 2 2 Ring-billed Gull 1 1 Chicken 18 1 Other species (n=13) 30 0 Komar et al., 2003, EID 9(3): 311-322; www.cdc.gov/ncidod/eid/vol9no3/02-0628.htm
    19 : WNV Oral Transmission Species n dose no. viremic Common Grackle 4 1000 pfu 4 House Finch 1 mosquito 1 House Sparrow 6 107 pfu 6 American Crow 6 sparrow 5 American Crow 3 107 pfu 3 Great Horned Owl 1 mice 1 Komar et al., 2003, EID 9(3): 311-322; www.cdc.gov/ncidod/eid/vol9no3/02-0628.htm
    20 : Cloacal shedding in crows Threshold of infectiousness ?????
    21 : Persistence of WNV in Tissues Viral Days Species Tissue Load post-viremia Killdeer 1 Skin 110 pfu/0.5 cm3 9 Killdeer 2 Spleen 550 10 Killdeer 2 Skin 20,000 10 Mourning Dove Kidney 100 11 Budgerigar Heart 130 13 Blue Jay Eye 360 9 Common Grackle Skin 380 11 Common Grackle Eye 150 11 House Sparrow 1 Skin 370 8 House Sparrow 2 Spleen 120 10 House Sparrow 2 Lung 590 10 House Sparrow 3 Brain 300 8 Komar et al., 2003, EID 9(3): 311-322; www.cdc.gov/ncidod/eid/vol9no3/02-0628.htm
    22 : Birds as Dispersal Vehicles No hard evidence yet Laboratory studies pending Field studies unsuccessful to date Significance of prolonged viral persistence in organs?
    23 : Ecological Factors Affecting Transmission
    24 : Pigeons seroconverted 270% more frequently in the canopy in New York City: 32 vs 12 in 2002
    25 : Acknowledgments
    26 : West Nile Virus: Primary Passerine-Culex Transmission Cycle

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