Billy Thompson
Research Specialist
Research
An estimated 73,000 human cases of E.
coli O157:H7 infection occur each year in the United States, resulting in
61 deaths on average (1). Cattle are known reservoirs of E. coli
O157:H7, and there is considerable
effort by the food safety industry to minimize its prevalence in herds
(2,3). Infected cattle may defecate in
water sources (such as farm ponds and streams), resulting in transmission to
herd members (4). Moreover, it is
possible that aquatic vertebrates that inhabit watersheds become infected, and
serve as a ‘spill-over’ reservoir (5).
Tadpoles are prime candidates for spill-over hosts of zoonotic
pathogens, because they scavenge on aquatic macrophytes and benthos (6), and
incidentally ingest microorganisms (7).
Pathogenic microorganisms, such as E. coli O157:H7,
may infect the intestines or other organs of tadpoles. If this is true, tadpoles could shed viable E.
coli O157:H7 and function as a source of infection for cattle that drink contaminated water.
Additionally, water contaminated by infected tadpoles could potentially
serve as a source of fruit and vegetable contamination if water is used for
irrigation. Inasmuch as tadpole
densities can exceed 100 individuals m-2, they excrete copious
amounts of feces, and some species develop for more than 12 months resulting in
overlapping cohorts and continuous presence (8), this vertebrate group could
contribute significantly to maintaining E. coli O157:H7 in
aquatic environments.
In 2006, Gray et al. (9) orally
inoculated American bullfrog metamorphs and tadpoles with E. coli O157:H7, and
determined that this species was a suitable host. However, infection by oral inoculation of a pathogen
does not necessarily imply that the host could be naturally infected. To date, natural infection of amphibians by a
zoonotic pathogen via exposure to cattle feces containing an environmentally
relevant concentration of the pathogen has not been tested. These data are fundamental to understanding
the threat of American bullfrogs as sources of E. coli O157:H7 in the
environment.
The objective of this study is:
Quantify infection rates in American bullfrog
tadpoles exposed to cattle feces inoculated with E. coli O157:H7 in
outdoor aquatic mesocosms that simulate a natural environment.
Collaborators: UT
East Tennessee Research and Education Center, UT Departments of Animal Science and Forestry, Wildlife and Fisheries, Tennessee Agricultural Experiment Station, University of Georgia College of Veterinary
Medicine
Lead Scientists: Dr. Matthew Gray, Dr. Alan Mathew, Dr. Sreekumari Rajeev
and Dr. Debra Miller
References
(1) Centers for Disease Control and Prevention (CDC). 2006. Escherichia coli O157:H7.
http://www.cdc.gov/ncidod/dbmd/diseaseinfo/escherichiacoli_t.htm.
(2) Center for Disease Control and Prevention (CDC) Foundation. 2006. Get Smart on the Farm Campaign. http://www.cdc.gov/narms/get_smart.htm.
(3) Looper, M. L., T. S. Edrington, R. Rores, C.
F. Rosenkrans Jr, M. E. Nihsen, and G. E. Aiken. 2006.
Prevalence of Escherichia coli O157:H7 and Salmonella in
beef steers consuming different forage diets.
Lett. Appl. Microbiol. 42:583-88.
(4) Shere, J. A., C. W. Kaspar, K. J. Bartlett,
S. E. Linden, B. Norell, S. Francey, and D. M. Schaefer. 2002. Shedding of Escherichia coli O157:h7 in dairy cattle housed in a confined
environment following waterborne inoculation. Appl. Environ. Microbiol. 68:1947-54
(5) Daszak, P., A. A. Cunningham, and A. D. Hyatt. 2000. Emerging infectious diseases of wildlife—threats to biodiversity and human health. Science 287:443-49.
(6) Hoff, KvS, AR Blaustein, RW McDiarmid and R
Altig. 1999. Behavior. Pp 215-239. In: McDiarmid, RW and R
Altig (eds), Tadpoles. The Biology of Anuran Larvae. The
(7) Seale,
D. B., K. Hoff, and R. Wassersug.
1979. Xenopus laevis larvae as model suspension feeders. Hydrobiologia 87:161-169.
(8) Alford RA.
1999. Ecology: resource use,
competition, and predation. Pages
240-278 in RW McDiarmid and R Altig (eds).
Tadpoles: the biology of anuran larvae.
(9) Gray MJ, S Rajeev, DL Miller, AC Schmutzer, EC Buron, ED Rogers, GJ Hickling. 2007. Preliminary evidence that American bullfrogs (Rana catesbeiana) are suitable hosts for Escherichia coli O157:H7. Applied and Environmental Microbiology 73:4066–4068.
Personal
Hello!
I grew up in Swanton, a
small town in northwestern Vermont. I
completed my undergraduate studies at Castleton
State College, double majoring in Biology and Health
Science with a minor in Chemistry.
While at Castleton, I studied the survivability of Escherichia coli O157:H7 in
pond water. This project focused on how
seasonal temperatures and cattle access influence the survivability of the
bacteria in pond water. Furthermore, I
served as the president of the Sigma Zeta
National Science and Mathematics Honor Society and the Student Science
Association. I was a member of the varsity ice hockey
team at Castleton as well. My future
goals include the pursuit of an MD/PhD.
When I’m not busy with work or school, I enjoy time with my daughter,
playing hockey, running, hiking, hunting and fishing.
Contact Information
Email: wthomp16@utk.edu
Phone: (865)
974-3897
UT Department of Forestry, Wildlife and Fisheries