The Duration of the Effects of Repeated Widespread Badger Culling on Cattle Tuberculosis Following the Cessation of Culling

Background: In the British Isles, control of cattle tuberculosis (TB) is hindered by persistent infection of wild badger (Meles meles) populations. A large-scale field trial—the Randomised Badger Culling Trial (RBCT)—previously showed that widespread badger culling produced modest reductions in cattle TB incidence during culling, which were offset by elevated TB risks for cattle on adjoining lands. Once culling was halted, beneficial effects inside culling areas increased, while detrimental effects on adjoining lands disappeared. However, a full assessment of the utility of badger culling requires information on the duration of culling effects. Methodology/Principal Findings: We monitored cattle TB incidence in and around RBCT areas after culling ended. We found that benefits inside culled areas declined over time, and were no longer detectable by three years post-culling. On adjoining lands, a trend suggesting beneficial effects immediately after the end of culling was insignificant, and disappeared after 18 months post-culling. From completion of the first cull to the loss of detectable effects (an average five-year culling period plus 2.5 years post-culling), cattle TB incidence was 28.7% lower (95% confidence interval [CI] 20.7 to 35.8% lower) inside ten 100 km2 culled areas than inside ten matched no-culling areas, and comparable (11.7% higher, 95% CI: 13.0% lower to 43.4% higher, p = 0.39) on lands #2 km outside culled and no-culling areas. The financial costs of culling an idealized 150 km2 area would exceed the savings achieved through reduced cattle TB, by factors of 2 to 3.5. Conclusions/Significance: Our findings show that the reductions in cattle TB incidence achieved by repeated badger culling were not sustained in the long term after culling ended and did not offset the financial costs of culling. These results, combined with evaluation of alternative culling methods, suggest that badger culling is unlikely to contribute effectively to the control of cattle TB in Britain.

Infant Mortality as a Potential Measure of Community Health in Urban Growth

This document is one of a series which contains the results of research carried out during a 1969 Summer Study of Urban Decentralization at the Oak Ridge National Laboratory, sponsored by the Department of Housing and Urban Development and the U.S. Atomic Energy Commission. The summary of the Summer Study is contained in "An Introduction to Urban Decentralization Research," ORNL-HUD-3.

Wildlife Risk Management at Vancouver International Airport

The Vancouver International Airport (YVR) is the second busiest airport in Canada. YVR is located on Sea Island in the Fraser River Estuary - a world-class wintering and staging area for hundreds of thousands of migratory birds. The Fraser Delta supports Canada’s largest wintering populations of waterfowl, shorebirds, and raptors. The large number of aircraft movements and the presence of many birds near YVR pose a wide range of considerable aviation safety hazards. Until the late 1980s when a full-time Wildlife Control Program (WCP) was initiated, YVR had the highest number of bird strikes of any Canadian commercial airport. Although the risks of bird strikes associated with the operation of YVR are generally well known by airport managers, and a number of risk assessments have been conducted associated with the Sea Island Conservation Area, no quantitative assessment of risks of bird strikes has been conducted for airport operations at YVR. Because the goal of all airports is to operate safely, an airport wildlife management program strives to reduce the risk of bird strikes. A risk assessment establishes the current risk of strikes, which can be used as a benchmark to focus wildlife control activities and to assess the effectiveness of the program in reducing bird strike risks. A quantitative risk assessment also documents the process and information used in assessing risk and allows the assessment to be repeated in the future in order to measure the change in risk over time in an objective and comparative manner. This study was undertaken to comply with new Canadian legislation expected to take effect in 2006 requiring airports in Canada to conduct a risk assessment and develop a wildlife management plan. Although YVR has had a management plan for many years, it took this opportunity to update the plan and conduct a risk assessment.