WestNileVirus-L: Re: Question re: Dead Crow Density as Indicator

From: Connstandinos Theophilides <ctheo_at_geo.hunter.cuny.edu>
Date: January 08 2002

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<DIV>Here at the
CARSI Lab. at the Geography Department at Hunter College have developed in
collaboration with the New York City Department of Health a different
approach on monitoring New York City bird reports. Instead of using densities
we implemented a system using the Knox space-time interaction test in a
Geographic Information System for evaluating significant space-time
correspondence between bird deaths (using all birds but pigeons). For the
2001 season we ended up having significant interaction in  5 areas in
New York City in which human cases occured. We should have this written up by
the end of this month at which time I can give you more specifics on our
work. Constandinos Theophilides Research Associate Center for the
Analysis and Research of Spatial Information (CARSI Lab.) Department of
Geography-Hunter College 695 Park Ave. New York, NY 10021 Tel.
(212)-650-3939 Fax (212)-772-3013 <A
href="mailto:ctheo@geo.hunter.cuny.edu">ctheo@geo.hunter.cuny.edu</A> ----- Original Message ----- From: "Lois Levitan" <<A
href="mailto:lcl3@cornell.edu">lcl3@cornell.edu</A>> To: "WESTNILEVIRUS-L" <<A
href="mailto:WESTNILEVIRUS-L@cornell.edu">WESTNILEVIRUS-L@cornell.edu</A>> Sent: Tuesday, January 08, 2002 1:11 PM Subject: Question re:
Dead Crow Density as Indicator for WNV Action > The following
exchange is excerpted from my response to a question > about 'dead crow
density' as a West Nile Virus human health risk > indicator.  If you
have additional information, insights, and > thoughts about WNV risk
indicators, please post to the listserv. > > Thanks, Lois
Levitan > > QUESTION: > >I am a member of a subcommittee
that is evaluating the risks and benefits of > >various approaches
for mosquito control. Many in our community are wary of > >pesticide
spraying and I saw with interest the guidelines suggested in a > >model
on your web page of 1.5 dead crows per square mile as an indicator of >
>human health risk for the WNV. > > > >In Shaker Heights,
OH, where I live, we had a total of 74 infected dead crows > >found
in the city which has an area of 6.5 sq. miles . There was
one single, > >limited permethrin spraying at the end of the
mosquito season which many of > >us felt was more political than
scientific. Early cold weather ended the > >mosquito season and the
spraying so we gathered together to better plan for > >the coming
season. > > > >You can see that our infected dead crow figure
is 11.4/sq. mile, considerably > >above the figure of 1.5 in the
model on your home page. Out of a population > >of 31,000, we did
not have a single reported [human] case of WNV. > >Since the
dead > >crows were only found in certain areas of the city, the 11.5
figure is > >conservative. > > > >In the model, is
the dead infected crow figure of 1.5 calculated over the > >whole
mosquito breeding season or is it taken over a shorter time period; >
>that is, 1.5 crows/sq. mile/week? > > > >Are there other
and better models for assessing risk of WNV in human > >populations
that we could use to avoid premature spraying and yet better > >predict
the onset and thus the risk to our citizens here in Shaker Heights? >
> > >I would appreciate your answers to my questions and also
appreciate any > >additional information that is relevant to our
challenge of developing an > >action plan that provides for both the
short term and long term health of our >
>residents. > > > RESPONSE: > The 'dead crow model'
as an indicator of potential risk from WNV to > human health was suggested
by Dr. Millie Eidson, NYS Public Health > Veterinarian and Director of the
Zoonoses Program at the NYS Dept of > Health, based upon 'annual dead crow
density' reported in New York > State in 2000.  Data submitted from
NYS counties fell out into 3 > groups: Staten Island (a 'relatively rural'
borough of NYC) had 33.3 > dead crows per square miles and 10 human cases
of WNV; the other > counties in NYC and the metropolitan area had 3-12
dead birds per > square mile and 2 or fewer human cases; while upstate
counties where > there was no human illness reported fewer than 1 dead
crow per square > mile. > > The model was proposed as a rapid
means of identifying potential > areas of greater risk.  The thinking
behind this model is elaborated > in Eidson et al. 2001 (Dead Crow
Densities and Human Cases of West > Nile Virus, New York State,
2000.  Emerging Infectious Diseases. > July-Aug 2001
7(4):662-4).  It is posted on the web at > <A
href="http://www.cdc.gov/ncidod/EID/vol7no4/contents.htm">http://www.cdc.gov/ncidod/EID/vol7no4/contents.htm</A> . > > The article includes the
caveats that future applicability of the > model, and its applicability in
other locales are unknown, possibly > because dead bird densities may not
be observed before disease onset, > perhaps because crows in an area
become immune to the disease, or > because there are not many crows or
because pathology studies/reports > are delayed. > > I am
eagerly awaiting re-analysis of the model using 2001 data re: > how well
it held up in the same geographic area during the 2001 > season. 
While I did not scrupulously follow the week-by-week dead > bird reports
in NYS this year, my cursory observations of the > county-by-county risk
levels posted on the NYS DOH website indicated > that the model was not an
accurate indicator in 2001. NYS did not > have human cases until quite
late in the season, all in NYC and Long > Island.  For the most part,
the risk level in these counties based on > dead bird densities was listed
as "low" even through the periods that > human illnesses were
reported. > > Several factors may be at work: > Attention to
dead bird reports in different counties varied > considerably. 
Anecdotal reports I heard from around the state > indicated to me that in
some counties records were kept of all dead > birds, while calls were
dismissed in other counties if the bird > didn't seem to be a good
candidate for pathology testing.  Knowledge > about WNV, and
resources for tracking or preventing it have not been > high priorities in
many counties outside the NYC metro area.  While > this may well be
an appropriate allocation of scarce resources, it > also means that data
are skewed, with much more data provided from > and to places where risk
is perceived to be greater. > > I have heard from some of the
entomologists and ornithologists > involved in WNV surveillance that crows
in upstate NY did not seem to > be responding with same level of
susceptibility as those in the NYC > metro area. > > These and
other sources concur that other less obvious bird species > may be equally
or more susceptible, but not as easily noticed by > people (smaller birds,
living further from human habitation...). > > I would expect that
base populations of crows might well differ in > urban, suburban and rural
areas.  According to Dr Kevin McGowan of > Cornell's Laboratory of
Ornithology, whose research is on behavioral > ecology (and population
demographics) of crows, this information is > simply not known for most
areas. > > Ie: crows may not be an equally sensitive indicator in
all areas of > NYS.  And data from different sources and areas of the
state vary in > terms of reliability and completeness. > > I
suggest you read the Eidson et al article, then perhaps contact Dr. >
Eidson (<A href="mailto:mxe04@health.state.ny.us">mxe04@health.state.ny.us</A>) for her current thinking about the >
utility of the model and/or revisions of it.  (I expect and hope
that > the epidemiologists thinking about WNV are working on refining a
risk > indicator(s).  The data you provide may be useful in this
process.) > As the range of WNV in the US is increasing, there is
tremendous > interest in the questions you raise. > > With
regard to the other side to your questions--re: what communities > can do
vis-a-vis mosquito control:  I believe they can do a lot by >
encouraging residents to follow the guidelines listed on my WNV > webpage
and in many of the informational brochures of NYS > municipalities (ie:
clean gutters, aerate small pools, clean or > eliminate containers of
standing water...).  And that the government > agencies themselves
can do a lot within established programs of, > e.g., roadside and park
maintenance.  Ie: Mosquito hygiene can become > better integrated
into the way we conduct personal and government > business.  By
taking proactive steps for prevention and source > reduction, and putting
a good spin on these activities, one would > hope that politicians could
gain the same political advantage that > some have thought they could only
gain by using mosquito adulticides. > The word I have been hearing from
most of the mosquito entomologists > at the NYS DOH, as well as the tune
of official publications defining > prevention and control protocols, is
strong emphasis on prevention > and caution against considering use of
pesticides unless there is > immediate threat to human health.  What
defines this threat, and what > to do when it exists, are of course not
clear cut.  Hence the > interest in risk
indicators... > > ... > > I applaud the fact that your
community is having this discussion > before a time of community crisis
and hope the discussion will also > be broadened to look into other uses
of pesticides.  The reality is > that much more pesticidal chemicals
are used for other purposes > around homes and communities, exposing
people, pets and wildlife to > harmful toxins, often simply for cosmetic
reasons (e.g., dandelion > control).  In fact, Ward Stone, the NYS
pathologist at the Department > of Environmental Conservation, has
preliminary data indicating > greater bird die-off due to pesticides than
to the disease of WNV! > These pesticides were typically granular rat
poisons, etc., not the > pesticides used to control WNV. > >
... > -- > Lois Levitan, PhD      
Program Leader > Environmental Risk Analysis Program > Center for
the Environment > 213 Rice Hall, Cornell University > Ithaca, New
York USA 14853-5601 > > Phone:   (607)
255-4765     Fax: (607) 255-0238 > Email: <A
href="mailto:LCL3@cornell.edu">LCL3@cornell.edu</A> > > Program Email: <A
href="mailto:envrisk@cornell.edu">envrisk@cornell.edu</A> > Web:http://www.cfe.cornell.edu/ERAP > >
-------------------------------------------------------------------------- ------------------------------ >
WESTNILEVIRUS-L is an email discussion group for communication > and
discussion about West Nile Virus, particularly regarding policy, > risk
reduction and public education issues. It is moderated by > Dr. Lois
Levitan at Cornell University's Center for the Environment. > To subscribe
(or unsubscribe), send an email request to <<A
href="mailto:envrisk@cornell.edu">envrisk@cornell.edu</A>>. > Subscribers can post to the group by sending an email
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Received on Tue Jan 08 14:53:25 2002

Re: Question re: Dead Crow Density as Indicator for WNV Action