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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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