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 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

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 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

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

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

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.