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Monitoring population effects of an emergent disease in wild birds. Shannon L. LaDeau Postdoctoral fellow Smithsonian Institution National Zoo-Migratory Bird Center Advisor: Peter Marra. Disease emergence in U.S. avifauna:. Avian tuberculosis (1986) Newcastle disease (1992)

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monitoring population effects of an emergent disease in wild birds

Monitoring population effects of an emergent disease in wild birds.

Shannon L. LaDeau

Postdoctoral fellow

Smithsonian Institution

National Zoo-Migratory Bird Center

Advisor: Peter Marra

slide2

Disease emergence in U.S. avifauna:

Avian tuberculosis (1986)

Newcastle disease (1992)

House Finch conjunctivitis (1994)

West Nile virus (1999)

H5N1-Avian flu (??)

STEPHEN JAFFE/AFP

US Army specialist Steve Richards captures mosquitos

“Ready or not, here it comes. It is being spread much faster than first predicted from one wild flock of birds to another, an airborne delivery system that no government can stop. “ from coverage of M. Leavitt speech. March 2006

slide3

© Peter Weber.

© Chan Robbins.

Objective

Identify impacts of West Nile virus in wild bird populations.

slide4

1999

2000

2001

2004

2002

2003

West Nile virus

1999 emergence in Queens, NY.

Primary avian host. Mosquito vector

284 avian species in 48 states

Positive bird surveillance: by county

From CDC/USGS

slide5

North American Breeding Bird Survey

(BBS)

  • Citizen scientists
  • 1966 to current
  • Over 4100 survey routes
  • 24.5 mile along secondary roads

Sauer, J. R., J. E. Hines, and J. Fallon. 2005. The North American Breeding Bird Survey, Results and Analysis 1966 - 2004. Version 2005.2. USGS Patuxent Wildlife Research Center, Laurel, MD

slide6

Route selection

  • Mid-Atlantic states
  • Temporal coverage: At least 80% data coverage from
  • 1980 – 2005 with observations in 5 of 6 years after 1999.

2004 Population

(people/per sq Mile

< 3500

3500-8850

8851-20850

20851 - 55775

slide7

http://www.mbr-pwrc.usgs.gov

West Nile Footprint

  • Crows experience high mortality.
  • Komar et al. 2003
  • Eidson et al. 2001
slide8

Data

Mean of OBSERVED counts

Average count

WNV emergence in NY

slide9

1999

2000

2001

2004

2002

2003

Spread of West Nile virus

slide10

http://www.mbr-pwrc.usgs.gov

West Nile Footprint

  • Crows experience high mortality.
  • Komar et al. 2003
  • Eidson et al. 2001

2. Population effects will be patchy and greater near urban areas.

Kilpatrick et al. unpub

Hochachka et al. 2004

Caffrey and Peterson 2003

slide11

Data model

For a given species, individual counts are conditionally Poisson

where subscripts i and j refer to observer and route identity, respectively, and t denotes year.

The expected value for a given annual count after accounting for

route and observer effects is

with random effects for variation among routes, years and observers.

slide12

Data

Mean of OBSERVED counts

WNV exposure?

Average count

slide13

Data versus Predicted

Mean of PREDICTED counts

Mean of OBSERVED counts

Average count

slide14

Mid-Atlantic states

Observations > Predicted

Observations < Predicted

Unusual routes after 2000

slide15

Observations > Predicted

Observations < Predicted

Unusual routes before 1999

slide16

Summary

  • 1. Monitoring disease in wildlife populations demands analyses that can accommodate natural stochasticity, census data and unplanned experiments without replication.
  • We may not be collecting data at scales useful for monitoring avian disease. [Consistent sampling across rural to urban]
  • Modeling/Analyses future:
      • other species
      • state-space approach
      • using human or crow data as prior information regarding spatial exposure.
slide17
Special thanks to….
  • USGS and BBS volunteers
  • Wayne Thogmartin, Bill Link, John Sauer, Michael Lavine, and Jim Clark for discussion and modeling input.
slide19

Monitoring wildlife disease is difficult:

Can’t see the disease - Follow mortality

Often there is no population data prior to disease

How disease regulates/limits wildlife is largely unknown.

Disease emergence in U.S. avifauna:

Avian tuberculosis (1986)

Newcastle disease (1992)

House Finch conjunctivitis (1994)

West Nile virus (1999)

H5N1-Avian flu (??)

slide20

Do we have the data we need?

WNV exposure rates

WNV-related mortality rates

Population size prior to disease emergence

Monitoring of populations at scale of disease ecology

slide21

Average count

HOFI

©Gerhard Hofmann

AMRO

Average count

© Chan Robbins.

MODO

© Peter LaTourrette

Data

slide22

Trend Analysis

Identify routes where trend before WNV emergence differs from post 2000 trend.

slide23

Trend analysis

Change in trend from 20 year mean

Increase in trend

Decrease in trend

slide24

1999

2000

2001

2004

2002

2003

Spread of West Nile virus

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