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This epidemiologic study provides insights into rabies in skunks in Texas from 1953 to 2007, focusing on seasonal patterns, routes of exposure, and associated costs in human and domestic animals.
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Epidemiology of rabies in skunks in Texas Tom J. Sidwa, D.V.M. Zoonosis Control Branch Texas Department of State Health Services
Epidemiologic study • Objective • To obtain epidemiologic information on rabies in skunks in Texas • Sample Population • Reports of skunks submitted for rabies testing in Texas from 1953 through 2007
Animal Rabies Cases in Texas • Annually >90% of all cases are in wildlife species • skunks and bats usually most affected species • skunks most commonly affected species during 14 of the 20 years from 1988 through 2007
Data Extracted From Reports • seasonality of rabies in skunks • seasonality of human and domestic animal exposures to rabid skunks • commonly reported clinical signs of rabies in skunks • animals frequently exposed to rabid skunks • common routes of exposure of domestic animals to rabid skunks • disposition of domestic animals exposed to rabid skunks • age and gender of humans exposed to rabid skunks • usual routes of exposure of humans to rabid skunks
Materials and Methods • Testing largely due to exposure of humans or domestic animals • Testing done at one of 5 laboratories in State • direct immunofluorescence microscopic examination of brain tissue impressions • Variant typing performed at DSHS Lab • monoclonal antibodies against the viral nucleoprotein to identify rabies virus variants • Nucleoprotein sequencing • Rabies case investigations performed by personnel from • DSHS Regional Zoonosis Control • local health departments • local rabies control authorities.
Materials and Methods • The type and amount of data available for each year of the study varied • earliest years of the study • Data on numbers of rabid skunks were available only from historical copies of yearly summaries of statewide rabies cases • type and amount of information collected during case investigations tended to increase over the years • information on domestic animals and humans exposed to rabid skunks was not entered in the database in full-year increments until 1987 • information on rabies virus variants was available only during the later years of the study
Distribution of rabid skunksUrban vs. Rural White = Urban Black = Rural
Species of rabid skunks • From 1985 through 2007 • 68.56% of confirmed rabies positive skunks were speciated upon receipt at lab • Of these 99.48% were identified as striped skunks • 0.37% were identified as hog-nosed skunks • 0.12% were identified as spotted skunks • 0.02% was identified as a hooded skunk.
Mode of Human Exposure1987 through 2007 • Other than bite exposures • one of the most common methods - person with a break in the skin petting or cleaning a dog that had been in a fight with a rabid skunk • Bite exposure – anatomical location in order of frequency • Feet • arms and hands • trying to separate a dog from a rabid skunk • Face • most often a sleeping person
Skunk Behavior Associated with Human Exposures • most commonly reported behaviors • attacking dogs • appearing outside during the day • attacking humans • entering a dog pen • approaching or entering a house • acting sick • attacking a cat or other animal • entering a tent.
Behavior of Laboratory-Confirmed Rabid Skunks • All 362 rabid skunks - 2007 • most frequent behaviors • entering a dog pen (148 incidents) • appearing outside during the day (140 incidents) • attacking pets (64 incidents) (Multiple behaviors could be exhibited by a single rabid skunk)
Associated Costs • confining and observing exposed domestic animals • Post-exposure prophylaxis in exposed humans and animals • 170 lb. human ~ $2,400 for biologicals alone • costs associated with further preventing disease transmission • Domestic animal vaccination • Enhanced stray animal control • Population reduction • Trap Vaccinate Release • Ultimately Oral Rabies Vaccination Program
Study Limitations • Failure to consistently submit suspect skunks for testing • Limited nature of data available during early years of study period
ACKNOWLEDGEMENT • Coauthors: • Texas Department of State Health Services • Ernest H. Oertli, DVM, PhD, DACVPM • Pamela J. Wilson, MEd • Patrick R. Hunt, BS • Texas State University, San Marcos, Texas • Rodney E. Rohde, MS
APPRECIATION • Technical Assistance • Dena Garrison • Bonny Mayes • Jesse Blanton • Robert Dowler • Jerry Dragoo • David Schmidly • Craig Ramey • Keith Clark