Prevention of the spread of rabies to wildlife by oral vaccination of raccoons in Massachusetts
Robbins, A.H.; Borden, M.D.; Windmiller, B.S.; Niezgoda, M.; Marcus, L.C.; O'Brien, S.M.; Kreindel, S.M.; McGuill, M.W.; DeMaria, A.; Rupprecht, C.E.; Rowell, S.
Journal of the American Veterinary Medical Association 213(10): 1407-1412
1998
ISSN/ISBN: 0003-1488 PMID: 9828930 Document Number: 486884
Objective: To evaluate the use of bait containing rabies vaccine to create a barrier of rabies-vaccinated raccoons in Massachusetts and to determine the effectiveness of various bait distribution strategies in halting the spread of rabies. Design: Prospective study. Sample Population: Free-ranging raccoons. Procedure: Baits were distributed twice yearly in a 207-km2 (80-mi2) area in the vicinity of the Cape Cod Canal. Bait density and distribution strategy varied among 3 treatment areas. Raccoons were caught in live traps after bait distribution and anesthetized; blood samples were obtained to measure serum antibody titers to rabies virus. Vaccination rates were determined by the percentage of captured raccoons with antibody titers to rabies virus > 1:5. In addition, raccoons with clinical signs of illness inside the vaccination zone and adjacent areas were euthanatized and submitted for rabies testing. Results: The percentage of vaccinated raccoons differed significantly among the following 3 areas with various bait densities: high-density area with uniform bait distribution (103 baits/km2 (267 baits/mi2))= 37%; low-density area with additional targeted bait distribution (93 baits/km2(240 baits/mi2))= 67%; and, high density area with additional targeted bait distribution (135 baits/km2 (350 baits/mill) = 77%. Nineteen animals with rabies (15 raccoons, 3 skunks, 1 cat) were reported in the area just outside of the vaccination zone, but only 1 raccoon with rabies was reported from inside the vaccination zone. Clinical Implications: In this suburban study area, an approximate vaccination rate of 63% was sufficient to halt the spread of rabies in free-ranging raccoons. Compared with uniform bait distribution, targeting raccoon habitats increased vaccination rates.