Abstract

In June 2001, the National Zoological Surveillance Working Group was formed incorporating both human and veterinary health experts from the Centers for Disease Control and Prevention, local and state public health agencies, the United States Department of Agriculture, the American Zoo and Aquarium Association and the American Association of Zoo Veterinarians. A nationwide surveillance system for detection of West Nile virus (WNV) in zoos was outlined in a set of guidelines entitled Surveillance for West Nile Virus in Zoological Institutions. A 1-year pilot study was initiated in September 2001 and is being implemented in two phases. Phase I consists of the collection and testing of samples from ill or dead at-risk animals on zoo grounds; at-risk animals are defined as animals (from any taxa) housed outside for at least part of the time that may be regularly exposed to mosquitoes. Phase II consists of a serosurvey of archived samples from at-risk animals from selected institutions. The Cornell University Veterinary Diagnostic Lab is performing all virus isolation, serologic and RT-PCR tests for the system. Preliminary results from the first 6 months include data from over 1,500 animals from 64 participating institutions in 30 states and the District of Columbia representing all regions of the country. To date, there have been 33 WNV antibody-positive birds, 29 virus-positive birds, one bird that was antibody-negative but virus-positive, and the first antibody-positive reptile in the United States. In addition, four birds were found to be antibody-positive for St. Louis encephalitis virus (SLE). Thirteen additional animals screened positive for antibodies to WNV and are currently undergoing confirmatory testing, and five animals have been confirmed as flavivirus antibody-positive but could not be classified further. All WNV antibody-, PCR, or culture-positive animals were from known WNV-epizootic areas in the United States. These initial results show promise for both increasing the effectiveness of existing national surveillance systems by providing data from previously untapped sources, and for increasing the quality of health monitoring in zoos in the face of a rapidly spreading emerging disease.