2
activity, which means faster
reproduction and maturation of
the virus, and a greater number of
potential bites.
Of all the types of mosquitoes,
the one in the United States which
is the most common carrier of
WNV is
Culex pipiens
. It is most
prevalent in urban environments,
rather than in healthy wetlands
and wild areas. It is the female
mosquito that does the biting,
needing the protein in blood to
ensure proper development of her
eggs.
When the insect bites an
infected animal, the virus is stored
in the mosquito’s salivary glands,
and then can be transmitted to
the next “host" that is bitten.
Mosquito eggs are laid in
bunches, and each bunch can
contain hundreds of eggs, so it’s
easy to see why they can multiply
quickly. In addition, the eggs can
be dormant for years if there is a
drought, then hatch when water
returns.
It is important to remember,
however, that even in places where
the disease has been confirmed,
it is actually carried by a very low
percentage of the mosquitoes in
that area.
At one time crows seemed to be
both the primary sources and
victims of WNV. Now, however, more
than 140 species of birds have
been reported, as well many other
creatures including horses, cats,
dogs, chipmunks, skunks, bats,
squirrels, bears, alligators, and
domestic rabbits.
At this time, many areas still
request that dead birds be
reported to the local health
department. However, these birds
might not be physically collected
by authorities in that jurisdiction
if the presence of WNV has already
been established, since further
testing would not yield any
additional useful information.
Most birds and animals which
are infected will survive. That being
said, the virus is expanding within
many wildlife populations, and can
be expected to affect greater
numbers in the future.
It is also spreading surprisingly
quickly throughout the country,
found now in nearly every state,
just over three years after its
first appearance in NY.
The fact that WNV is not host-
specific is of great concern. Even
exotic wildlife in zoos is being
affected, putting breeding
programs in jeopardy.
In natural areas where certain
species are hit hard by the virus,
the balance of nature can shift.
For example, rodents can
proliferate if the number of
raptors drops.
As native wildlife is stressed
more and more by other factors,
such as habitat destruction,
drought, and pesticide use, it is
more important than ever that we
replace lost habitat and become
educated on what can be done to
attract and help wildlife without
endangering ourselves or our
families..
There are no documented cases
of a person getting WNV from
another person or from an
animal. This is an important
distinction for those who care for
animals, whether wild or
domestic.
Although there is evidence that
birds can now pass the virus
directly to other birds, most
animals don’t seem to transmit
the virus to other animals, so
having an infected pet in contact
with other pets, or encouraging
groups of wildlife to congregate,
doesn’t directly encourage the
spread of the disease.
The main danger is that a
mosquito will bite the infected
animal and then spread WNV by
biting another animal in the same
vicinity. For this reason certain
habitat elements, such as bird
feeders, should be more numerous
and placed farther apart than you
might normally have planned.
At this time, indications are
that the originally-infected animal
is only infectious (through
mosquito transmission) for a few
days. Birds are considered
“reservoir" hosts, since an infected
bird can transfer the virus to
many mosquitoes.
Interestingly, humans and some
other mammals, such as deer, are
called “dead end" hosts. This
means that the virus doesn’t stay
viable in their bodies long enough
for them to transfer it to a lot of
other mosquitoes.
For some reason, while some
dead end hosts (such as humans
and horses) can get sick, others
(like dogs and cats) can be
infected but won’t become ill.
An infected animal or bird can
serve as a valuable warning
system to people, indicating that
there are infected mosquitoes in
the area, and that precautions
should be taken to avoid getting
bitten.
While there is no evidence that a
person can be infected by handling
wildlife, whether it is alive or dead,
that has WNV, it is a reasonable
precaution to wear gloves when
doing so, and to avoid getting any
blood from a suspected infected
animal on an open wound.
There is also no evidence that a
person can contract the virus by
eating an infected bird or animal,
but it is prudent to be sure that
the meat is well-cooked before
being consumed.
It is very important to
emphasize the low risk to humans.
Most people who are infected with
WNV will not actually have any
symptoms.
