Epidemiology of rabies in skunks in Texas
Tom J. Sidwa, D.V.M.Zoonosis Control Branch
Texas Department of State Health Services
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
Epidemiologic study
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
RESULTS
Annual variationsnumbers of rabid skunks 1953-2007
0
100
200
300
400
500
600
700
800
900
1953 1955 1957 1959 1961 1963 1965 1967 1969 1971 1973 1975 1977 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 2005 2007
Year
No
. of
rab
id s
ku
nk
s
Annual variationsnumbers of rabid skunks 1985 - 2007
0
200
400
600
800
1000
1200
1400
1600
1800
2000
1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007
Year
No
. of
Sku
nks
Positive Skunks
Total Skunk Submissions
Distribution of rabid skunks Urban vs. Rural
0
500
1,000
1,500
2,000
2,500
3,000
1985 -1989
1990 -1994
1995 -1999
2000 -2004
2005 -2007
Year
No
. o
f ra
bid
sk
un
ks
White = UrbanBlack = Rural
Monthly variation
numbers of rabid skunks
0
200
400
600
800
1,000
1,200
1,400
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Month
No
. o
f ra
bid
sku
nks
Striped SkunkMephitis mephitis
Hooded SkunkMephitis macroura
Hog-Nosed SkunkConepatus leuconotus
Western Spotted Skunk Spilogale gracilis
Eastern Spotted Skunk Spilogale putoris
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.
Rabies virus variants
Domestic animal exposure to rabid skunks
0
200
400
600
800
1000
1200
1400
1987 1989 1991 1993 1995 1997 1999 2001 2003 2005 2007
Year
Nu
mb
er
Rabid Skunks
Exposed Humans
Exposed Animals
Human Exposure to rabid skunks
0
200
400
600
800
1000
1200
1400
1987 1989 1991 1993 1995 1997 1999 2001 2003 2005 2007
Year
Nu
mb
er
Rabid Skunks
Exposed Humans
Exposed Animals
Human Exposure to rabid skunks
0
2
4
6
8
10
12
14
16
18
0-5 6-10 11-15 16-20 21-25 26-30 31-35 36-40 41-45 46-50 51-55 56-60 61-65 66-70 71-75 76-80 >80
Age range (y)
No
. o
f in
div
idu
als
Males
Females
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