Use of Geographic Information Systems to Investigate Disease Transmission in Zoo Animals
Geographic information systems (GIS) are computer-based mapping programs for visualizing and analyzing data. Using GIS to investigate disease in zoo animals can increase knowledge about complex disease transmission patterns. The ability to identify and predict these patterns can help with both research and animal health management. In three studies at Brookfield Zoological Park, a GIS (ArcView) was used to map and analyze spatial patterns to test hypotheses about disease epidemiology. The overall goal of this project was to examine the use of GIS as a visualization tool to study disease transmission within zoos and to develop recommendations to help predict and prevent disease at Brookfield and other zoos.
In the first study, risk factors were studied for seropositivity to canine distemper virus (CDV) among zoo cats. Potential for contact between cats and raccoons was of principal interest, although age, species, origin, and contacts with other animals were also possible risk factors/confounders. Eighty-seven zoo cats were tested for CDV using the serum-neutralizing test. No cats had been previously vaccinated for CDV. Aerial photographs of the zoo were digitized and imported into the GIS. All feline housing and holding enclosures were identified on the GIS coverage. Seropositive and seronegative animals were mapped to their enclosures. Information on each animal’s sex, age, and history was assessed and linked into the GIS database. Based on this information, risk factors were compared between seropositive and seronegative animals using spatial analysis and multivariate logistic regression. Animals in outdoor locations were at significantly higher risk of CDV infection. Other significant covariates included sex, age, and species. Seropositive cats were present in all feline-housing locations at the zoo, regardless of proximity to woods, water, trash bins, and other habitat features.
The second study mapped the movements of eight reptiles diagnosed, postmortem, with mycobacteriosis. Each animal’s enclosure history was tracked from 1978 to the date of death. A map of the interior of the Reptile House was digitized, and temporospatial movements of infected animals were mapped. This information was used to identify other reptiles that shared contact with diseased animals, to quantify the likelihood of potential exposure, and to distinguish high-risk enclosures.
The third study examined the spread of poxvirus lesions among pinnipeds housed in four pools. Eight animals were diagnosed with pox lesions. The objective of the study was to determine the method of viral transmission. Potential means included waterborne spread through a common filtration system, animal-to-animal spread, and fomite transmission. Keeper and veterinary records beginning from 1993 were used to date the first appearance of pox lesions in each affected animal. The four pinniped pools were mapped. Each animal was assigned to its inhabited enclosure, and disease transmission patterns were determined.
Geographic information systems provide an effective way to understand, observe, and summarize patterns of disease transmission in zoos. Disease clustering, transmission, animal movement, and high-risk individuals can be identified with the powerful aid of a GIS. This technology will be useful to animal health researchers, especially as it becomes more widely used in zoos, by departments such as facilities planning and guest services.
The authors wish to thank the keeper staff and laboratory personnel who assisted in the gathering of these data and processing of the serum samples; Mark Jocelyn, at the Illinois Natural History Survey, for GIS assistance; and the Howard Hughes Medical Institute for its support.