The economics of managing infectious wildlife disease

We use a two-state linear control model to examine the socially optimal management of disease in a valuable wildlife population when diseased animals cannot be harvested selectively. The two control variables are nonselective harvests and supplemental feeding of wildlife, where feeding increases both in situ productivity and disease prevalence. We derive a double singular solution which depends on the initial state and does not require bang-bang controls. The case of bovine tuberculosis among Michigan white-tailed deer is analyzed. In the base model, the disease is optimally maintained at low levels, with intermittent investments (via feeding) in deer productivity. Key words: bovine tuberculosis, double singular solution, linear control, nonselective harvests, white-tailed deer. The spread of infectious disease among and between wild and domesticated animals has become a major problem worldwide, with ex-amples involving wildlife as the primary vector of disease transmission almost too numerous to count (see the Journal of Wildlife Diseases). The economic costs of wildlife-to-livestock dis-ease transmission can be substantial. For in-stance, a foot and mouth disease outbreak in the U.S., which could easily spread through a wildlife vector such as deer, could cost billions of dollars the first year alone (USDA-APHIS 2002). For this and other diseases, farmers incur losses when infected livestock die or become less productive due to the disease, because the demand for livestock products is diminished, and because of strict regulations imposed when a herd becomes infected (e.g., depopulating a herd). But the costs are not lim-ited to infected farms, as trade sanctions are of-ten imposed on entire counties, states, or even countries where the disease is present. Human Richard D. Horan and Christopher A. Wolf are associate pro