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CONTINUING STUDIES OF TRYPANOSOMA CRUZI IN GEORGIA RACCOONS
Kevin Tyler Ward, Department of Biology
Faculty Sponsor: Dr. J. Mitchell Lockhart, Department of Biology
Figure 2. Representative gel
from T. cruzi PCR. Note ladder
on bottom and positive control
on top.
Figure 3. Seasonal prevalence of T. cruzi in Raccoons
Prevalence of Trypanosoma cruzi in Raccoons
100
90
80
70
60
Females
50
40
Males
Total
30
20
Apr-05
Feb-05
Dec-04
Oct-04
Aug-04
Jun-04
Apr-04
Feb-04
Dec-03
Oct-03
Aug-03
10
0
Jun-03
An increasingly persistent parasite, Trypanosoma cruzi, is the source of
Chagas’ disease, a condition accountable for over 50,000 deaths per year (Tanowitz
et. al. 1992). The principal location of these deaths are several Latin American
countries. Although T. cruzi is more established in these countries, it infects 16-18
million people worldwide every year (World Health Organization, 1993). There have
been five reported cases in the United States all of which occurred in Tennessee,
Texas, or California (reviewed by Herwaldt et. al., 2000). A probable explanation for
the extreme disparity between cases in the United States and Latin American
countries involves living conditions. It is now believed that there may be up to one
hundred thousand immigrants living within the United States that are infected with T.
cruzi (Kirchhoff, 1993).
Upon reaching maturity and with the aid of a blood sucking invertebrate host,
T. cruzi can be transmitted to various mammals including deer, armadillos,
opossums, raccoons, and also reptiles and birds. T. cruzi inhabits the intestines of
the invertebrate host and is transmitted after the host bites a mammal, where it then
resides in the blood and/or tissues (Figure 1).
Raccoons and opossums are thought to be frequent carriers of T. cruzi in the
United States. Recent research demonstrates that 15% of raccoons tested in North
Carolina (Karsten et. al., 1992) and 22.2% in Georgia (Pung, 1995) were infected
with T. cruzi, whereas 16% of opossums tested in Georgia and northwest Florida
were positive for T.cruzi (McKeever et al., 1958).
From 2003-2005, a total of 423 raccoons were evaluated for
the presence of T. cruzi. In 2003, 36/150 (24.0%) raccoons
tested positive; in 2004, 50/202 (24.7%) raccoons tested
positive; and in 2005 15/66 (22.7%) raccoons have tested
positive for the presence of T. cruzi (Figure 2). No significant
trends were noted with regard to seasonal prevalence (Figure
3). 58/284 male raccoons (20.4%) were positive for T. cruzi
versus 43/133 (32.3%) of females raccoons (Figure 5). This
difference was statistically significant (p > 0.005). We theorize
that reproductive status may influence prevalence of T. cruzi,
but we would like to investigate this hypothesis further. This
study represents the first three years of a four year study. We
will analyze the final years data and incorporate specific age
data in the future.
Apr-03
INTRODUCTION
RESULTS and DISCUSSION
Feb-03
Trypanosoma cruzi, a parasite known to cause Chagas’ disease occupies several
mammalian hosts including canids, opossums, and raccoons. Although most cases of
Chagas’ disease are found in Central and South America, the parasite is present in
wildlife populations in North America and warrant further investigation. More than 200
raccoons were obtained in 2005 from south Georgia and north Florida as part of a USDAWildlife Services bobwhite quail predator removal study and were evaluated for the
presence of T. cruzi by PCR. For 2005, roughly 25.0% of 100 samples tested so far have
been positive. This data will be compared with data collected in 2003 and 2004 and will
be analyzed using various natural history variables. Collectively, data from these 3 years
suggests that there are considerable levels of T. cruzi in wildlife populations in these
locations.
Percent Infected
ABSTRACT
Month/Year
Figure 1. Life cycle of Trypanosoma cruzi.
METHODS
Animals were collected from Tall Timbers Research
Station and the Eastern and Western section of Pinbebloom
Plantation. The locations are found in the Red Hills region
of south Georgia and north Florida. Animals were
euthanized, frozen, and transported to Valdosta State
University. Animals were necropsied and various tissue
samples and morphometric data was collected.
From 2003-2005, 423 raccoons have been evaluated for
the presence of T. cruzi using polymerase chain reaction.
Frozen tissue samples were thawed and DNA isolations
were performed using Qiagen DNeasyTM tissue kits
following manufacturer’s protocol.
PCR, utilizing T. cruzi specific primers MCS-35 and MCS36 found in a 330 base pair region of the kinetoplast DNA
minicircle of T. cruzi, was performed. PCR products were
electrophoresed in 2% agarose gels and visualized using
ethidium bromide and photographed. Positive and negative
controls were run for each set of samples and strict
protocols were followed to avoid contamination.
Acknowledgements
We would like to thank the USDA-WS for trapping animals, all
other principals associated with the Predator Removal Study, and
the Valdosta State University Faculty Research Fund for providing
funds to complete this project.
REFERENCES
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Fifth reported U. S. case of autochthonous transmission of Trypanosoma cruzi, in Tennessee, 1998.
Journal of Infectious Diseases 181: 395-399.
John, D. T., and K. L. Hoppe. 1986. Trypanosoma cruzi from wild raccoons in Oklahoma. American Journal
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Kirchhoff, L. V. 1993. American Trypanosomiasis (Chagas’ disease)- A Tropical disease now I the United
States. The New England Journal of Medicine 329: 639-644.
McKeever, S., G. W. Gorman, and L. Norman. 1958. Occurrence of a Trypaosoma cruzi-like organism in
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