Date of Award
Bachelor of Science
Ticks, Stable Isotope Analysis, Lyme
Lyme disease is a pervasive illness caused by the transmission of the spirochete Borrelia burgdorferi from the bite of an infected black-legged tick, Ixodes scapularis. Ticks initially obtain the spirochete by feeding on an infected animal host. Ticks feed on a broad range of hosts, but some of these hosts are more competent carriers of Lyme disease and more readily transmit B. burgdorferi to feeding ticks. Thus, knowing what host a tick has fed on could provide valuable information in studying the transmission of Lyme disease. However, studying the relationships between ticks and their hosts has proved to be a challenging task.
One possible option for determining a tick’s host could be found in Stable Isotope Analysis (SIA), a technique often used for food web studies that provides unique signatures based on the concentration of stable isotopes found in the analyzed subject. The animal being tested and the diet they consumed, largely determines these signatures.
I build on previous SIA work by testing how ticks isotopic signatures vary when Eastern chipmunk hosts, Tamias striatus, are fed different diets. Past work in our lab suggests that incorporation of carbon stable isotope signatures is quick and sensitive. This leads to concern that individual diets may significantly distort the isotopic signatures of carbon in tick hosts and may not be a valuable indicator.
Chipmunks were captured in Reist Sanctuary and held in the animal care facility. Upon their arrival nymphal ticks were placed on the chipmunks to feed. Meanwhile the chipmunks were fed a variety of regimented diets (corn, insect, sunflower seed, and meat). Ticks that engorged and dropped were collected and animals were released. Adult ticks were processed and submitted for SIA along with samples of each diet the chipmunks were fed for comparison.
The results from the stable isotope analysis showed no significant variation among diet groups. The signatures from ticks did not match the corresponding host diets. These results imply that nitrogen signatures are not as readily incorporated in ticks as carbon is, suggesting that nitrogen could provide valuable insight in regards to understanding tick-host interactions without being sensitive to sudden dietary changes.
Gernat, Kiprian, "Exploring Stable Isotope Analysis for the Identification of Prior Tick Hosts" (2018). Honors Theses. 1685.
Available for download on Saturday, March 30, 2019