Case #490 - April, 2019
A 55-year old man from Massachusetts removed a tick attached to his forearm after returning from a weekend camping trip. He then took it to his county health clinic from where it was subsequently sent to the State Public Health laboratory for identification. Figure A shows a dorsal view of the tick, while Figure B shows the ventral side. Figure C and D shows a close-up of the mouthparts while Figure E is a close-up of the lower ventral side. What is your identification? Based on what criteria? What is the public health importance, if any, of this genus in North America?
These images were kindly provided by Amanda Castonguay from Brigham and Women’s Hospital, Boston, MA
This was an adult Ixodes spp. tick (most likely Ixodes scapularis), commonly referred to as the black legged deer tick. Diagnostic morphologic features shown included:
- Inornate scutum (dorsal shield) partially covering the upper body surface (blue arrow, Figure A)
- Absence of festoons (yellow arrow, Figure A)
- Large spiracular plates (pink arrow, Figure B)
- Long palps and hypostome (red bracket) in relation to the basis capituli (black arrow) (Figure C)
- Inverted anal groove extending anteriorly around the anus (green arrow, Figure E)
Ixodes spp. ticks are arthropod vectors that can transmit Borrelia burgdorferi (Lyme disease), tick-borne encephalitis (TBE), and Babesia spp. Identification of ticks to the species level can be difficult and best deferred to a trained entomologist.
More on ticks: https://www.cdc.gov/dpdx/ticks/index.html
Images presented in the monthly case studies are from specimens submitted for diagnosis or archiving. On rare occasions, clinical histories given may be partly fictitious.
DPDx is an educational resource designed for health professionals and laboratory scientists. For an overview including prevention, control, and treatment visit www.cdc.gov/parasites/.