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

Tick Tick Dermacentor Dermacentor variabilis.variabilis.

Stephanie Pratt, Jenny Sandler, Kristi Teal

Science Division, Truman State University

Kirksville, Missouri

The American Dog Tick:The American Dog Tick:Dermacentor variabilisDermacentor variabilis

http://images.google.com/images?q=Tick-%20life%20cycle&hl=en&lr=&sa=N&tab=wi

BackgroundBackgroundSeveral 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

HypothesisHypothesis

• 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.

ObjectivesObjectives

• Treat adult female ticks with antibiotic

• Assess feeding efficiency• Assess reproductive success

Antibiotic BackgroundAntibiotic Background

Chlortetracycline

• Tetracycline is used to fight tick-borne diseases

• Readily available • Commonly used

http://images.google.com/images?q=tick-%20mouth%20parts&hl=en&lr=&sa=N&tab=wi

Capillary FeedingCapillary Feeding

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

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

Material and MethodsMaterial and Methods

Materials and MethodsMaterials and Methods

• Allow to feed for 12 hours

Glass capillary tube

Double sided tape and clay placed on a glass slide

Materials and MethodsMaterials and Methods

• Put on host (rabbits) for 5-7 days

• Weighed after detachment

• Weighed eggs after 2 weeks.

Results: Feeding SuccessResults: Feeding SuccessSuccessful Completion of Engorgement

No Capillar

y

Capillary,

Serum

Capillary, Chlortetracycli

ne

Ticks that Completed Feeding Cycle

86 55 55

Percentage of Completion(Total=110)

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 SuccessResults: 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

0

100

200

300

400

500

600

700

No Capillary Capillary, Serum Capillary, Chlortetracycline

Treatment Group

Ave

rage W

eig

ht (

mg)

Results: Reproductive Results: Reproductive SuccessSuccess

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

ConclusionsConclusions

• 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 StudiesFuture Studies

• Isolate and culture microbes within the digestive tract of ticks

• Repetition of same experiment with different antibiotics

AcknowledgementsAcknowledgements

• 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.

ReferencesReferences• 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.