Biology Reference
In-Depth Information
the virus grew, the system was opened up to any zoo, regardless of accredita-
tion. Eventually, the system began accepting samples from other groups with
wildlife under their care. In addition to free diagnostic testing, the system
was designed to increase communication between zoological institutions
and their local public health departments, a benefit to both parties.
The WNV surveillance system included sampling for both active and
passive surveillance components. Active surveillance consisted of obtain-
ing blood samples from healthy collection animals during routine physical
exams, preshipment quarantine, or other situations in which the animal was
already being handled (e.g., banding, examination for injury).
For the passive surveillance component, samples were taken from sick or
deceased outdoor birds and mammals that were part of the zoological col-
lection. This piece of the surveillance methodology also included sampling
of deceased wild birds found on zoo grounds. This was an important part of
the system since the most sensitive surveillance tool for tracking the spread
WNV had been the examination of dead wild birds (McLean et al. 2001).
Zoos are in a unique position to test wild birds as many free-ranging ani-
mals utilize zoo grounds for seasonal or permanent habitat. This testing not
only offers additional information regarding the presence of WNV but also
provides zoological institutions with important information about health
risks to the animals in their collection. For many outdoor exhibits, it is nearly
impossible to prevent all free-ranging wildlife from accessing the interior.
In order to sample wild birds found on zoo grounds, permits must
be acquired from the U.S. Fish and Wildlife Services (USFWS) under the
Migratory Bird Treaty Act (MBTA).* In addition to this federal permit, some
states require further permits in order to handle migratory birds. The MBTA,
which was originally enacted into law in 1918, establishes broad restrictions
to protect more than 800 species of migratory birds, their feathers, eggs, and
nests. Even birds that are already deceased are protected under the MBTA.
Originally, each institution had to acquire their own permits in order to test
injured, sick, or dead wild birds found on zoo grounds. However, as WNV
continued to spread and anxiety rose, a unique blanket permit was granted
that allowed all participating institutions to sample deceased wild birds
found on their grounds.
An additional component of the surveillance system consisted of a retro-
spective serosurvey for healthy outdoor animals that were part of the zoo-
logical collection. Participating institutions were asked to bank sera from
healthy at-risk animals for later testing. These longitudinal data allowed an
examination of seroconversion rates and susceptibility to WNV. Additionally,
WNV-positive animals could be followed up to evaluate any potential long-
term sequelae of infection.
The National Animal Health Laboratory Network (NAHLN) laboratory
at Cornell University served as the primary diagnostic laboratory for the
*
The Migratory Bird Treaty Act: http://www.fws.gov/laws/lawsdigest/migtrea.html.
