Ridecamp: [RC] WNV infection in other species

<http://www.promedmail.org>
Date: Wed 9 Oct 2002
From: Bill Johnston <wjohnston@xxxxxxxxxxxxxxxx>

Recent media reports have prompted many questions regarding West Nile virus
(WNV) infection in species other than birds, horses, and humans. As an
"emerging disease" in the United States, WNV has clinical and health effects
on various animal species and populations that have yet to be described or
fully reported. The following information is offered on the current
knowledge of WNV infection in other species.
It is currently believed that any type of bird or mammal may be susceptible
to WNV infection, but very few species appear to develop clinical illness
due to infection. Since entering North America in 1999, WNV has been
reported in thousands of birds, horses, and humans (over 2768 people and 146
deaths, as of Wed 9 Oct 2002). Before this year, WNV infection had been
reported in several bat species, chipmunks, gray squirrels, striped skunks,
a rabbit, and 3 cats. Laboratory trials had indicated that cats would become
viremic and ill, but that dogs were relatively resistant to infection with
WNV.
Serosurveys in New York following the 1999 outbreak revealed that 8-11
percent of dogs had antibody titers to WNV, but had not become ill. As WNV
has moved across the country this summer, infection and illness have now
been reported in a domestic sheep, a mountain goat, a dog, a 7-month-old
wolf pup, a llama, and an alpaca. Serologically positive black bears and
white-tailed deer have also been detected, but these animals did not develop
clinical illness.
Some of the animals that became ill had another underlying health condition
and/or a compromised immune system predisposing them to development of
clinical disease. For instance, the one 8-year-old dog in Illinois was
immune-compromised. From what is currently known, WNV does not appear to
pose a significant health risk for species other than birds, horses, and
humans. The extremely small number of cases in other species, the active
surveillance conducted for the last 4 years, and reports from 42 states that
have detected WNV suggest that most of these species are extremely resistant
to developing clinical illness from infection. There is also no current
evidence that any of these species are capable of serving as a reservoir for
the virus.
It is likely more cases in other hosts will be found as WNV enters and
becomes established in new areas. As additional information becomes
available, the relative health significance of WNV infection in these
populations will become more clearly established.
Bill Johnston, DVM, DACVPM
State Public Health Veterinarian
Alabama Department of Public Health
P.O. Box 303017
Montgomery, AL 36130-3017
<wjohnston@xxxxxxxxxxxxxxxx>


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