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Fact Sheet
West
Nile Virus
 West
Nile virus (WNV) has been known to science since 1937,
but its appearance in Europe and North America is a relatively
recent development. Public health officials are especially
concerned about this disease because it can affect humans,
horses, and certain other animals.
The most serious manifestation of WNV infection
is severe and potentially fatal encephalitis, which is
an inflammation of the brain. This occurs mainly in human
beings and horses. In contrast, most birds are simply killed
outright.
What about dogs and cats?
Are dogs and cats in danger from
West Nile Virus?
Technically, yes, but practically speaking, the danger seems remote. There
is one published report from 1982 of West Nile virus infection in a dog from
Botswana, in southern Africa. West Nile virus was also isolated from one dead
cat in 1999. But, scientists examining the blood of dogs in WNV endemic areas
have found only a very low level of infection among dogs. Like humans, dogs
and cats infected with WNV rarely display obvious symptoms and the mortality
rate seems low.
How do dogs or cats become infected
with West Nile virus?
All mammals acquire WNV infection in the same way: from the bite of an infected
mosquito. Mosquitoes themselves become infected when they feed on WNV infected
birds, which may circulate the virus in their blood for a few days before they
die. That’s why public health officials are often so keen to examine dead birds.
Inside infected mosquitoes the virus localizes
itself in the salivary glands. When the mosquito next takes
a blood meal, the virus passes from the mosquito into the
new host. The virus then multiplies in the new host and
may either be contained and eliminated or may cause infection.
It is theoretically possible that dogs and
cats could become infected by eating dead infected birds
or other infected dead animals, but this remains unproven.
Can dogs or cats serve as carriers
of West Nile Virus?
Dogs and cats can, rarely, become infected with WNV. But it seems unlikely
that they could serve as carriers or reservoirs of infection for either humans
or other animals. West Nile virus is transmitted by the bite of infected mosquitoes.
At present, there is no conclusive evidence of person-to-person or animal-to-person
transmission of West Nile virus.
Can a dog or cat infected with West
Nile virus infect other dogs or cats?
There is no documented evidence that West Nile virus is transmitted from mammal
to mammal.
What is the treatment for a dog or
cat infected with West Nile Virus?
Again, it appears that dogs and cats only rarely become infected. Among those
that do become infected, the symptoms are generally mild and probably often
go unrecognized. For the small proportion of infected dogs and cats that do
become ill, full recovery is likely. Treatment is supportive in nature and
may involve hospitalization, hand feeding, and general nursing care. No particular
antibiotics or antiviral drugs have been shown to be effective against WNV,
but they may still be of use in infected dogs and cats because of the potential
for other secondary or concurrent infections.
There is no reason to destroy an animal just
because it has been infected with West Nile virus.
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