Effect of Canine Distemper on an Urban Raccoon Population: An Experiment

Abstract

Large-scale experiments about the effect of disease on wildlife populations are rare. We examined (1) whether the prevalence of canine distemper (CD) could be reduced in urban raccoons (Procyon lotor) using field vaccination and (2) the extent to which CD might limit raccoon populations. From May 1991 to November 1993, raccoons in a treatment area were trapped, vaccinated, and released at the site of capture. Population responses were monitored in treatment and control areas using information from a municipal animal control agency. During a CD epizootic, the prevalence of infected animals detected at necropsy from a sample of the population was significantly lower in the treated area (1.4%) than in the control area (8.3%). Patterns of population change did not differ between the treatment and control areas before, during, or after the epizootic, indicating that CD did not limit the raccoon population. Thus, field vaccination can result in reduced disease prevalence, but will not necessarily result in increased raccoon abundance.