HISTORY

In June of 2001, Lincoln Park Zoo in conjunction with the CDC hosted the National Zoological West Nile Virus Surveillance Working Group to discuss the design and implementation of a nation-wide surveillance system for WNV in zoological institutions. The meeting brought together zoo professionals with human and veterinary public health experts from local, state, and federal agencies. The result of the workshop was a set of guidelines entitled Surveillance for West Nile Virus in Zoological Institutions and the implementation of a one-year pilot study. The system was endorsed by the CDC, the AZA, and the American Association of Zoo Veterinarians (AAZV).

The pilot began in 2001 with six AZA-accredited zoos and aquariums with outdoor exhibits. However, as WNV continued to move west across the U.S., zoos and other wildlife-related organizations became increasingly concerned about the safety of their animals. While the system was originally designed to serve the AZA community, 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. At its conclusion in 2006, nearly 180 zoological institutions, wildlife sanctuaries, private veterinarians, and animal rehabilitation centers had submitted samples as part of the system.

COMPONENTS

The WNV surveillance system included sampling for both active and passive surveillance components. Active surveillance consisted of obtaining blood samples from healthy collection animals during routine physical exams, pre-shipment 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 collection. This piece of the surveillance methodology also included sampling of deceased wild birds found on zoo grounds. 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. 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. Not only did this testing offer additional information regarding the presence of WNV, it 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.

An additional component of the surveillance system consisted of a retrospective serosurvey for healthy outdoor animals that were part of the zoological collection. Participating institutions were asked to bank sera from healthy at-risk animals for later testing. These longitudinal data allowed an examination of seroconversion rate 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 system. This choice was optimal not only for the interest and willingness to participate by the lab, but also because they had expertise in WNV testing and the ability to provide full-service diagnostic testing. Sample types requested by the diagnostic laboratory included blood (preferably serum) and tissue, including kidney, heart, and brain.

CONFIDENTIALITY

A major concern of participants was the privacy of the information gathered from their institution. When the media reported that WNV was found at the Bronx Zoo, gate receipts fell 30% (McNamara, pers. comm.). As most zoos rely heavily on their gate receipts for funding, it was understandable for institutions to have hesitations about testing for WNV on their grounds. As such, it was crucial to the system that data flow be precisely delineated so participants were ensured their data would remain confidential. The first step to protecting the data came from requiring the diagnostic laboratory to report test results directly to the submitting institution. Those data were also sent to a secure centralized database at LPZ.

The second step was to require the submitting institution to relay results to their local public health agency.  This was meant to strengthen the relationship between zoos and their local public health authorities.  An important aspect of this relationship was the sense of trust that would allow zoos to report results to public health agencies without fear of inappropriate release. This step was also essential as the response to an outbreak is much timelier if initiated at the local level.

The third step was to de-identify any data made available to the public. De-identified data from the LPZ database were summarized and made available to the public. In keeping with the goal of providing additional data to national WNV surveillance, the de-identified results from the surveillance system could be uploaded into ArboNet, a cooperative database for WNV surveillance maintained by the CDC.