Oral Rabies Vaccination of Raccoons (Procyon lotor) across a Development Intensity Gradient in Burlington, Vermont, USA, 2015–2017

Authors

Emily M. Beasley, Université de MontréalFollow
Kathleen M. Nelson, USDA APHIS WS NRMP New Hampshire
Dennis Slate, Chippewa Bay Wildlife Art and Science LLC
Amy T. Gilbert, USDA APHIS WS NWRC ColoradoFollow
Frederick E. Pogmore, USDA APHIS WS VermontFollow
Richard B. Chipman, USDA APHIS WS NRMP New HampshireFollow
Amy J. Davis, USDA APHIS WS NWRC ColoradoFollow

Date of this Version

2024

Citation

Journal of Wildlife Diseases (2024) 60(1): 1–13

doi: 10.7589/JWD-D-22-00117

Comments

United States government work

Abstract

Management of the raccoon rabies virus variant in North America is conducted primarily using oral rabies vaccination (ORV). When a sufficient proportion of the population is vaccinated (60%), rabies transmission can be eliminated. To date, ORV programs have successfully controlled and eliminated raccoon rabies in rural areas, but there has been less success in urban areas. We studied the proportions of rabies virus neutralizing antibodies (RVNA) in a raccoon (Procyon lotor) population during a 3-year ORV trial in developed areas of Burlington, Vermont, United States. We used a modified N-mixture model to estimate raccoon abundance, RVNA seroprevalence, and capture rates jointly to examine factors that relate to ORV success to better inform management. We found that raccoon abundance was lower in less-developed areas compared to urban centers. Raccoon RVNA seroprevalence decreased as population abundance increased; it increased as the average age of the population increased. Nontarget opossum (Didelphis virginiana) captures correlated with a decrease in raccoon RVNA seroprevalence in low-development areas, suggesting that they may be competing for baits. The target bait density across the entire study area was 150 baits/km², but a hand baiting strategy was heavily concentrated on roads, resulting in uneven bait densities within sampling sites (0–484 baits/km²). Uneven bait distribution across the study area may explain low RVNA seroprevalence in some locations. Our results suggest that increases in bait density across the study area may improve RVNA seroprevalence and support annual ORV to account for raccoon population turnover.