Illinois Natural History Survey Reports

              1
ILLINOIS
NATURAL
HISTORY
SURVE Y R e p o r t s
Winter 2003
No. 374
I N S I D E
One Botanist's View
of the Landscape
2
Insect-weed Interac-tions
in Snap Bean
Crops
3
Creel Surveys in
Illinois
4
New INHS
Publications
5
Species Spotlight:
Mistletoe
6
Naturalist's Apprentice:
Parasitic Plants and
Animals Crossword
7
Continued on last page
As of December 23, 2002, Illi-nois
had the highest number of
human cases (778) of West Nile
virus (WNV) in the United
States, including 52 deaths.
Cook County, which contains
about 40% of the population
of Illinois, was the hardest
hit with 565 human cases and
32 deaths. In some areas of
Cook County during August,
almost 75% of the pooled
batches of Culex mosquitoes
sent to the Illinois Natural
History Survey Medical En-tomology
Program by col-laborators
tested positive for
WNV. Preliminary bird sur-veys
around Chicago indi-cated
a reduction in the num-bers
of Crows, Bluejays, rap-tors
(especially owls), and
some songbirds. However,
transmission of WNV was
not limited to Cook County.
Since May 2002, a total of
513 birds, 528 mosquito
pools, and 1,084 horses in 98
Illinois counties tested positive
for the virus. Eastern gray squir-rels
(from northern and central
Illinois), a dog (from central Illi-nois),
and a young zoo-raised
wolf (northern Illinois) also
tested positive for WNV. Hu-man
cases occurred in 48 coun-ties
in Illinois by October.
Considering the relatively low
clinical case rate of WNV in hu-mans
(about 3,900 cases and 241
deaths in the U.S. this year),
WNV might be considered of
minor public health importance,
but there is ample evidence that
West Nile Virus in Illinois
this arbovirus may have consider-able
impact on both human and
animal health.
First, clinical cases and deaths
are just the tip of the epidemic
iceberg. Several studies suggest
that for every clinical case there
are from 30 to 150 infections.
Thus, about 16,000 to 117,000
people may have contracted the
West Nile virus in Illinois. The
statistical extremes of infection,
like serious neurological sequelae
and death, start to become appar-ent
when increasing numbers of
people become infected.
Second, West Nile virus has
become a potential human risk
beyond the mosquito route.
Transmission may also occur
through blood transfusion or or-gan
transplantation from an in-fected
donor. Breast milk
samples of infected mothers have
also been found to contain
WNV, although no infants have
contracted encephalitis via this
route. However, transplacental
infection of an infant by an in-fected
mother was recently re-ported
by the Centers for Disease
Control and Prevention. The
long-term implications of these
nonvector transmission routes
are unknown. There are simply
too few scientific data at present
to answer some important ques-tions
about human and animal
health, so it is only prudent to be
cautious when addressing issues
of risk.
Third, many suggest that
WNV will burn out its reservoir
Bob Novak of INHS talks with Macon County Mosquito Abatement District
personnel about the introduction of the Asian tiger mosquito to Decatur in
tires. Photo by Richard Lampman, INHS Center for Economic Entomology
A dry ice light trap
used to collect mos-quitoes
in southern
Illinois. Photo by Richard
Lampman, INHS Center for
Economic Entomology