A, The method used for feeding larval ticks on human volunteers. B, Larval Amblyomma americanum tick attached to a human volunteer after 15 minutes of exposure.
A, Macular lesions 15 minutes after being bitten by larval Amblyomma americanum ticks. B, Pruritic erythematous papule 48 hours after larval tick attachment. C, Papulovesicular lesions 48 hours after larval tick attachment. D, Vesicular lesions 48 hours after larval tick attachment.
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Goddard J, Portugal JS. Cutaneous Lesions Due to Bites by Larval Amblyomma americanum Ticks. JAMA Dermatol. 2015;151(12):1373–1375. doi:10.1001/jamadermatol.2015.2388
The lone star tick (LST), or Amblyomma americanum, is a notorious human-biting pest. Almost all people living in rural areas of the southern United States have been bitten by this species, especially by the larvae, which are referred to as seed ticks. Tick feeding leads to vascular injury, triggering hemostasis, which relies on blood coagulation, platelet aggregation, and vasoconstriction,1 and ticks use various proteins in their saliva to modulate these host defenses.1,2 Accordingly, humans may develop a variety of allergic responses, cutaneous and otherwise, to these salivary proteins,3,4 including the newly recognized systemic red meat allergy.5 There is a report3 of larval LST bites causing pruritic papules in a patient 5 days after exposure, but, to our knowledge, there are no systematic controlled studies of human bite reactions. Here we demonstrate the development of itchy erythematous papules and vesicles within 48 hours of larval LST attachment to research participants.
Larval LSTs were obtained from the Centers for Disease Control and Prevention and were certified as specific-pathogen free. Study approval was waived by the Mississippi State University Institutional Review Board, and written patient consent was obtained for all patients. Ten adult participants, 5 of each sex, were recruited, and all participants were briefed on the procedures and associated risks. Ten larval ticks were placed in a plastic bottle cap that was secured to the participant’s forearm with cloth first-aid tape (Figure 1A). This application was duplicated on the other arm. The ticks were left in place for 15 minutes, allowing time to attach but not sufficient time for transmission of most tick-borne pathogens. When the caps were removed from the participant’s forearm, unattached (crawling) ticks were collected using masking tape. Any ticks that had attached themselves to the forearm were photographed (Figure 1B) and then removed using fine-tipped forceps. Bite sites were then monitored for 48 hours for the development of cutaneous lesions.
Twenty-three of 200 (11.5%) LST larvae attached to 8 of the 10 participants during the 15-minute period. Tick attachment could easily be verified by observing the splayed palps and inserted hypostome (Figure 1B). On 1 research participant, there was immediate lesion development—two 1- to 2-mm erythematous macules (Figure 2A)—while 5 other participants developed erythematous pruritic papules within 48 hours (Figure 2B). In the participant who developed immediate lesions, these 2 macules became papulovesicular within 48 hours (Figure 2C), as did 3 other lesions on the same person on the other arm (Figure 2D).
We show here that tissue damage from insertion of LST mouthparts and degranulating mast cells may be evident in as little as 15 minutes and may manifest as macules, papules, or vesicles. A previous study6 showed that A americanum was the predominant species found attached to humans in Mississippi during a 10-year time span, and 10 of 36 (27.8%) LST larvae found on humans were either partially or completely engorged. That study, as well as these new data, indicate that the LST is an aggressive human-biting tick species that may readily produce cutaneous lesions in humans.
Accepted for Publication: June 15, 2015.
Corresponding Author: Jerome Goddard, PhD, Department of Biochemistry, Molecular Biology, Entomology, and Plant Pathology, Mississippi State University, PO Box 9775, Mississippi State, MS 39762 (email@example.com).
Published Online: August 26, 2015. doi:10.1001/jamadermatol.2015.2388.
Author Contributions: Dr Goddard and Mr Santos Portugal had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design: Goddard.
Acquisition, analysis, and interpretation of data: All authors.
Drafting of the manuscript: All authors.
Critical revision of the manuscript for important intellectual content: Goddard.
Administrative, technical, or material support: All authors.
Study supervision: All authors.
Conflict of Interest Disclosures: None reported.
Additional Information: This article has been approved for publication as Journal Article No. J-12667 of the Mississippi Agricultural and Forestry Experiment Station, Mississippi State University.
Additional Contributions: Michael Levin, PhD, Centers for Disease Control and Prevention, provided the ticks used in this study. Dr Levin was not financially compensated.