Epidemiology of rabies in skunks in Texas

1. Epidemiology of rabies in skunks in Texas Tom J. Sidwa, D.V.M. Zoonosis Control Branch Texas Department of State Health Services

2. 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

4. 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

5. 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

6. 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.

7. 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

8. RESULTS

9. Annual variationsnumbers of rabid skunks 1953-2007

10. Annual variationsnumbers of rabid skunks 1985 - 2007

11. Distribution of rabid skunksUrban vs. Rural White = Urban Black = Rural

12. Monthly variationnumbers of rabid skunks

13. Striped SkunkMephitis mephitis

14. Hooded SkunkMephitis macroura

15. Hog-Nosed SkunkConepatus leuconotus

16. Western Spotted Skunk Spilogale gracilis

17. Eastern Spotted Skunk Spilogale putoris

18. 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.

19. Rabies virus variants

20. Domestic animal exposure to rabid skunks

21. Human Exposure to rabid skunks

22. Human Exposure to rabid skunks

23. 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

24. 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.

25. 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)

26. 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

27. Study Limitations • Failure to consistently submit suspect skunks for testing • Limited nature of data available during early years of study period

28. 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

29. APPRECIATION • Technical Assistance • Dena Garrison • Bonny Mayes • Jesse Blanton • Robert Dowler • Jerry Dragoo • David Schmidly • Craig Ramey • Keith Clark