The tick is considered the most dangerous arthropod in the United States because of its ability to transmit diseases such as Lyme disease and Rocky Mountain spotted fever. The most common ticks that vector diseases include the blacklegged tick (or deer tick), brown dog tick, American dog tick, and lone star tick. During late spring and early summer the populations of many tick species peak and both humans and animals are at the greatest risk for contracting tick-borne diseases.

Researchers study ticks to aid in developing prevention and treatments for tick-borne diseases, and also  investigate their insertion mechanics, means of attachment, and mechanics for sucking blood. In contrast to mosquitos that possess mouthparts that resemble a hypodermic needle, the mouthparts of ticks are outfitted with two sets of sharp hooks that pierce skin. These hooks pull the skin apart, allowing ticks to burrow within. Once these hook-like appendages pull back the skin, a tick will insert its hypostome, which looks like a chainsaw with hooks along its edges and keeps ticks secured to the skin.

X-Ray Microscopic Imaging of Ticks

This month we imaged an American dog tick and also captured an isolated high-resolution view of the mouthparts of a lone star tick (Amblyomma Americanum) using the SkyScan 2214 nano-CT. For inspecting microscopic features within small insects, the submicron resolution of the SkyScan 2214 captures the insect with a remarkable level of detail.

Each tick was harvested alive from a dog and sent to the Micro Photonics Imaging Laboratory for examination. Prior to imaging, both ticks were immersed in a 0.3% phosphotungstic acid (PTA) solution for a few hours to improve soft tissue contrast. After contrast enhancement, each was also dried using a hexamethyldisilazine (HMDS) solution following standard chemical drying protocols.

As shown in Figure 2, the SkyScan 2214 nano-CT captured fine details both on the surface level of the sample but more importantly within the musculature and internal viscera of the dog tick. The contrast existing within the soft tissues is the result of the use of both PTA and HMDS in the sample preparation process. Without the addition of this contrast agent and drying agent, the internal structures of the sample would likely remain unresolved from a lack of contrast, even at the 1500nm voxel size used in this acquisition.

Bruker CTVox allows us to move through the dataset visually as a 3D volume and explore the musculature and other internal structures (Figure 3).

The head and especially the mouthparts are of primary interest when examining ticks for scientific purposes, especially when related to biomimicry applications. Using the SkyScan 2214 nano-CT we focused imaging our second sample, the lone star tick, on only the head and moved down to 700 nm for our isotropic voxel size (Figure 4).

When exploring the submicron imaging results for the lone star tick head in CTVox, we see great detail on the eye structures of the insect and in particular the prominent hook structures that are evident when examining the mouth (Figure 5). Ticks use these barbed mouthparts to persistently attach to their host and complicate removal.

Conclusion

The subicron resolution of the SkyScan 2214 nano-CT was a perfect match obtaining high resolution data both throughout a tick sample as well as within a specific region, such as the head.

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Scan Specifications

These scans were completed on our SkyScan 2214 nano-CT system at the Micro Photonics Imaging Laboratory in Allentown, PA. Reconstructions were completed using NRecon while visualization and volumetric inspection of the 2D and 3D results were completed using Dataviewer and CTVox. CTan was utilized to remove noise arising from packing material around the samples.

Would you like your work to be featured in our monthly newsletter? If so, please contact us by calling Seth Hogg at 610-366-7103 or e-mailing seth.hogg@microphotonics.com.