Transcript The Effects of Antibiotic Introduction on the Feeding of the Tick

The Effects of Antibiotic
Introduction on the
Feeding of the Tick
Dermacentor variabilis.
Stephanie Pratt, Jenny Sandler, Kristi Teal
Science Division, Truman State University
Kirksville, Missouri
The American Dog Tick:
Dermacentor variabilis
http://images.google.com/images?q=Tick-%20life%20cycle&hl=en&lr=&sa=N&tab=wi
Background
Several bacteria isolated from tick
species
– Includes pathogenic and symbiotic
bacteria
• Micrococcus luteus, Bacillus subtilis,
Escherischia coli, and Borrelia burgdorferi
(Sonenshine et al. 2005)
– Role of symbiotic bacteria is
unknown
• Possible roles in digestion and reproduction
Hypothesis
• Symbiotic bacteria may play a role in
blood feeding and digestion.
• Antibiotics would destroy possible
symbiotic bacteria living in the gut of
Dermacentor variabilis.
• Ticks treated with antibiotics would be
less likely to feed successfully.
Objectives
• Treat adult female ticks with antibiotic
• Assess feeding efficiency
• Assess reproductive success
Antibiotic Background
Chlortetracycline
• Tetracycline is used to fight tick-borne
diseases
• Readily available
• Commonly used
Capillary Feeding
The use of capillary tubes allows for reliable
introduction of foreign substances into ticks
(Rechav et al. 1999)
•
http://images.google.com/images?q=tick-%20mouth%20parts&hl=en&lr=&sa=N&tab=wi
Material and Methods
Introduce antibiotic into
unfed adult female ticks
Feed on host ± 7 days
Measure feeding efficiency
and reproduction (Clarke et
al. 1989)
 Completion of feeding
 Engorgement weight
 Egg production
Materials and Methods
Double sided tape and clay
placed on a glass slide
Glass capillary tube
• Allow to feed for 12 hours
Materials and Methods
• Put on host (rabbits) for 5-7 days
• Weighed after detachment
• Weighed eggs after 2 weeks.
Results: Feeding Success
Successful Completion of Engorgement
Ticks that Completed
Feeding Cycle
Percentage of Completion
(Total=110)
No
Capillary
Capillary,
Serum
Capillary,
Chlortetracycline
86
55
55
78%
50%
50%
Highest success in ticks that did not receive capillary tubes.
The capillary interferes with successful feeding completion.
•
• Equal completion between groups that did receive capillary
tubes. Chlortetracycline introduction did not impact the ability to
successfully feed
Results: Feeding Success
Weight of Engorged Ticks
700
• Introduction of
600
Chlortetracycline
has no effect on the
feeding efficiency
Average Weight (mg)
500
400
ANOVA: F=0.817;
d.f.=2,190; p=0.44
300
200
100
0
No Capillary
Capillary, Serum
Capillary, Chlortetracycline
Treatment Group
Mean Post-feeding Weight (± SD) of Dermacentor variabilis
Results: Reproductive
Success
Egg Production (Mass of Eggs Produced during two weeks)
450
• Chlortetracycline
400
shows no significant
increase in egg
production.
Average Weight (mg)
350
300
250
ANOVA: F.=1.96;
d.f.=2,47; p=0.152
200
150
100
50
0
No Capillary
Capillary, Serum
Capillary, Chlortetracycline
Treatment Groups
Mean Egg Production (± SD) in Dermacentor variabilis
Conclusions
• Artificial feeding methods decreased
the success of engorgement
• Antibiotic introduction did not effect
the completion of feeding.
• Chlortetracycline did not significantly
impact the weight of engorged ticks or
egg production.
Future Studies
• Isolate and culture microbes within the
digestive tract of ticks
• Repetition of same experiment with
different antibiotics
Acknowledgements
• Dr. Laura J. Fielden, Faculty Sponsor,
Truman State University
• Dr. John Rutter, Dr. Michael Lockhart,
Dr. Jose Herrera and Dr. Yigal Rechav,
Truman State University
• Truman State University for funding this
research.
References
• Clarke, F.C., Els, D.A., Heller-Haupt, A., Rechav, Y. 1989.
Expression of acquired immunity to immature stages of
the tick Rhipicephalus evertsi evertsi by rabbits and
guinea-pigs. Medical and Veterinary Entomology, Vol. 3,
35-39.
• Rechav, Y., Zyzak, M., Fielden, L.J., Childs, J.E., 1999.
Comparison of Methods for Introducing and Producing
Artificial Infection of Ixodid Ticks (Acari: Ixodidae) with
Ehrlichia chaffeensis. Journal of Medical Entomology,
Vol. 36, 414-419.
• Sonenshine, D. E., Hynes, W. L., Ceraul, S. M., Mitchell, R.,
and Benzine, T. 2005. Host Blood Proteins and
Peptides in the Midgut of the tick Dermacentor variabilis
Contribute to Bacterial Control. Experimental and Applied
Acarology. Vol 36, 207-223.