1. 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

2. The American Dog Tick: Dermacentor variabilis

3. 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

4. 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.

5. Objectives Treat adult female ticks with antibiotic
Assess feeding efficiency
Assess reproductive success

6. Antibiotic Background
Chlortetracycline
Tetracycline is used to fight tick-borne diseases
Readily available
Commonly used

7. Capillary Feeding
The use of capillary tubes allows for reliable introduction of foreign substances into ticks (Rechav et al. 1999)

8. 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

9. Materials and Methods Allow to feed for 12 hours
Double sided tape and clay placed on a glass slide
Glass capillary tube
Allow to feed for 12 hours

10. Materials and Methods Put on host (rabbits) for 5-7 days
Weighed after detachment
Weighed eggs after 2 weeks.

11. Results: Feeding Success Successful Completion of Engorgement
No Capillary
Capillary, Serum
Capillary, Chlortetracycline
Ticks that Completed Feeding Cycle 86 55
Percentage of Completion
(Total=110)
78%
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

12. Results: Feeding Success Weight of Engorged Ticks
Introduction of Chlortetracycline has no effect on the feeding efficiency
ANOVA: F=0.817; d.f.=2,190; p=0.44
Mean Post-feeding Weight (± SD) of Dermacentor variabilis

13. Results: Reproductive Success Egg Production (Mass of Eggs Produced during two weeks)
Chlortetracycline shows no significant increase in egg production.
ANOVA: F.=1.96; d.f.=2,47; p=0.152
Mean Egg Production (± SD) in Dermacentor variabilis

14. 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.

15. Future Studies
Isolate and culture microbes within the digestive tract of ticks
Repetition of same experiment with different antibiotics

16. 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.

17. References
Clarke, F.C., Els, D.A., Heller-Haupt, A., Rechav, Y Expression of acquired immunity to immature stages of the tick Rhipicephalus evertsi evertsi by rabbits and guinea-pigs. Medical and Veterinary Entomology, Vol. 3,
Rechav, Y., Zyzak, M., Fielden, L.J., Childs, J.E., Comparison of Methods for Introducing and Producing Artificial Infection of Ixodid Ticks (Acari: Ixodidae) with Ehrlichia chaffeensis. Journal of Medical Entomology, Vol. 36,
Sonenshine, D. E., Hynes, W. L., Ceraul, S. M., Mitchell, R., and Benzine, T Host Blood Proteins and Peptides in the Midgut of the tick Dermacentor variabilis Contribute to Bacterial Control. Experimental and Applied Acarology. Vol 36,