This research was supported by the Intramural Research Program of the NIH, National Institute of Allergy and Infectious Diseases. We thank Linden T. Hu, Sam R. Telford III, Kenneth Dardick, Carla Williams, Erin Chung, and Christina Brandeburg for their participation in the development of the procedures.

Exposing volunteers to tick bites is an experimental method and must be conducted under a clinical research protocol approved by the relevant regulatory authorities. The clinical studies (NCT01143558, NCT02446626, and NCT05036707) were approved by the respective institutional review boards, conducted under investigational device exemptions granted by the US Food and Drug Administration, and carried out in accordance with Good Clinical Practice guidelines. Additionally, these studies were registered with ClinicalTrials.go...

Human Exposure to Larval Ticks for Tickborne Disease Research

<ol>
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J., Spielman, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Duration+of+tick+attachment+and+Borrelia+burgdorferi+transmission.">Duration of tick attachment and Borrelia burgdorferi transmission.</a> J Clin Microbiol. 25 (3), 557-558 (1987).</li><li>Vora, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ticks+elicit+variable+fibrinogenolytic+activities+upon+feeding+on+hosts+with+different+immune+backgrounds.">Ticks elicit variable fibrinogenolytic activities upon feeding on hosts with different immune backgrounds.</a> Sci Rep. 7, 44593 (2017).</li><li>Narasimhan, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Immunity+against+Ixodes+scapularis+salivary+proteins+expressed+within+24+hours+of+attachment+thwarts+tick+feeding+and+impairs+Borrelia+transmission.">Immunity against Ixodes scapularis salivary proteins expressed within 24 hours of attachment thwarts tick feeding and impairs Borrelia transmission.</a> PLoS One. 2 (5), 451 (2007).</li><li>Nazario, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Prevention+of+Borrelia+burgdorferi+transmission+in+guinea+pigs+by+tick+immunity.">Prevention of Borrelia burgdorferi transmission in guinea pigs by tick immunity.</a> Am J Trop Med Hyg. 58 (6), 780-785 (1998).</li><li>Krause, P. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dermatologic+changes+induced+by+repeated+Ixodes+scapularis+bites+and+implications+for+prevention+of+tick-borne+infection.">Dermatologic changes induced by repeated Ixodes scapularis bites and implications for prevention of tick-borne infection.</a> Vector Borne Zoonotic Dis. 9 (6), 603-610 (2009).</li><li>Anderson, J. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ticks,+Ixodes+scapularis,+feed+repeatedly+on+white-footed+mice+despite+strong+inflammatory+response:+an+expanding+paradigm+for+understanding+tick-host+interactions.">Ticks, Ixodes scapularis, feed repeatedly on white-footed mice despite strong inflammatory response: an expanding paradigm for understanding tick-host interactions.</a> Front Immunol. 8, 1784 (2017).</li><li>Rosenberg, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vital+signs:+trends+in+reported+vectorborne+disease+cases+-+United+States+and+Territories,+2004-2016.">Vital signs: trends in reported vectorborne disease cases - United States and Territories, 2004-2016.</a> MMWR Morb Mortal Wkly Rep. 67 (17), 496-501 (2018).</li><li>Paules, C. I., Marston, H. D., Bloom, M. E., Fauci, A. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tickborne+diseases+-+confronting+a+growing+threat.">Tickborne diseases - confronting a growing threat.</a> N Engl J Med. 379 (8), 701-703 (2018).</li><li>Tardy, O., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanistic+movement+models+to+predict+geographic+range+expansions+of+ticks+and+tick-borne+pathogens:+Case+studies+with+Ixodes+scapularis+and+Amblyomma+americanum+in+eastern+North+America.">Mechanistic movement models to predict geographic range expansions of ticks and tick-borne pathogens: Case studies with Ixodes scapularis and Amblyomma americanum in eastern North America.</a> Ticks Tick Borne Dis. 14 (4), 102161 (2023).</li><li>Molaei, G., Eisen, L. M., Price, K. J., Eisen, R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Range+expansion+of+native+and+invasive+ticks:+a+looming+public+health+threat.">Range expansion of native and invasive ticks: a looming public health threat.</a> J Infect Dis. 226 (3), 370-373 (2022).</li><li>Marques, A. R., Strle, F., Wormser, G. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+Lyme+disease+in+the+United+States+and+Europe.">Comparison of Lyme disease in the United States and Europe.</a> Emerg Infect Dis. 27 (8), 2017-2024 (2021).</li><li>Kugeler, K. J., Schwartz, A. M., Delorey, M. J., Mead, P. S., Hinckley, A. 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A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Economic+burden+of+reported+Lyme+disease+in+high-incidence+areas,+United+States.">Economic burden of reported Lyme disease in high-incidence areas, United States.</a> Emerg Infect Dis. 28 (6), 1170-1179 (2022).</li><li>Eisen, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tick+species+infesting+humans+in+the+United+States.">Tick species infesting humans in the United States.</a> Ticks Tick Borne Dis. 13 (6), 102025 (2022).</li><li>Embers, M. 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While animal studies involving exposures to ticks4,5,6,7,21 have been invaluable in increasing our understanding of host response to tickborne diseases and tick bites, these models have limitations in how well they predict the human host response. This model, which describes the methodology for exposing humans to tick bites in a controlled manner, can be easil...

Hard ticks (Ixodidae: Acari) are obligate blood-feeding ectoparasites that occur worldwide and are capable of transmitting a broad range of pathogens, including bacteria, viruses, and parasites, of major medical and veterinary importance. Ixodid ticks must remain attached to the host for days to complete a blood meal, and they have the capacity to stay attached to the skin while avoiding recognition, preventing local blood coagulation, and facilitating long-term feeding1,2,3. Animal studies have demonstrated that non-permissive hosts acquire resistance to tick bites with repeated tick exposures, which can lead to a decreased ability to transmit a pathogen, while ticks can repeatedly parasitize permissive hosts. Acquired tick resistance is dependent on the nature of the host immune response4,5,6,7.
Tickborne diseases are an increasing threat in the United States (US), with the number of reported cases more than doubling between 2004 and 20168,9. Due to climate change, the geographic ranges of different ticks continue to expand10,11. The leading tickborne diseases in the US include Lyme disease, anaplasmosis, ehrlichiosis, spotted fever rickettsiosis, babesiosis, tularemia, and Powassan virus disease8. Lyme disease, caused by infection with Borrelia burgdorferi sensu lato, is the most common tickborne disease in the US and Europe12. With approximately 476,000 individuals diagnosed with Lyme disease annually in the US, there is both a public health and economic burden to individuals and to society13,14,15.
Ixodes scapularis (the black-legged or deer tick) is the primary vector for Lyme disease, as well as anaplasmosis, babesiosis, Borrelia miyamotoi disease, and Powassan virus disease in the US. Other medically important tick species in the US include Amblyomma americanum (Lone star tick), Dermacentor variabilis (American dog tick), Ixodes pacificus (Western black-legged tick), Dermacentor andersoni (Rocky Mountain wood tick), Ixodes cookei (Groundhog tick), Dermacentor occidentalis (Pacific Coast tick), Rhipicephalus sanguineus (brown dog tick), and Amblyomma maculatum (Gulf Coast tick)16.
Developing a method to expose research volunteers to tick bites supports studies using the natural vector to search for evidence of infection, a procedure known as xenodiagnosis17,18,19,20,21, and to learn more about immunity induced by exposure to ticks, which can contribute to the discovery of an anti-tick vaccine5,6,7. The procedure described here was developed and used in the first human research study using laboratory-reared Ixodes scapularis larva for xenodiagnosis of B. burgdorferi infection after antibiotic therapy (NCT01143558), published in 201419. The system has been successfully used in a phase 2 study investigating whether a positive xenodiagnosis correlated with the persistence of symptoms after antibiotic treatment of Lyme disease (NCT02446626) and in a study exploring the host response to tick bites (NCT05036707).
This procedure protocol describes the process for creating the containment dressing, the tick placement procedure, and the tick removal procedure, as well as the site care needed to maintain the containment dressing. The details regarding the pathogen-free I. scapularis tick colony and tick exposure procedures used for the above-cited studies have been previously described19,22. This methodology offers a flexible research tool that can be adapted to studying different aspects of the human host response to tick bites, the effectiveness of tick prevention medications, as well as Lyme disease and other tickborne illnesses.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>20 G needle</td>
			<td>Any brand</td>
			<td></td>
			<td>For puncturing the vial cap.</td>
		</tr>
		<tr>
			<td>3&#34; x 3&#34; containment dressing</td>
			<td>Monarch Labs Names</td>
			<td>LeFlap</td>
			<td>https://www.monarchlabs.com/ordering</td>
		</tr>
		<tr>
			<td>4&#34; x 4&#34; extra-thin hydrocolloid dressing</td>
			<td>ConvaTec</td>
			<td>DuoDerm</td>
			<td>https://www.convatec.com/products/advanced-wound-care/brand-names/pc-wound-duoderm-granluflex/duoderm-extra-thin-dressing/</td>
		</tr>
		<tr>
			<td>4&#34; x 4&#34; gauze</td>
			<td>Monarch Labs Names</td>
			<td></td>
			<td>For cleaning skin</td>
		</tr>
		<tr>
			<td>Clean water or saline</td>
			<td></td>
			<td></td>
			<td>For cleaning skin</td>
		</tr>
		<tr>
			<td>Moisture barrier (e.g. 7&#34; x 7&#34;)</td>
			<td>AquaGuard</td>
			<td>TIDI</td>
			<td>For showering, ttps://www.tidiproducts.com/product-listing/aquaguard-shower-cover-sheets&#160;</td>
		</tr>
		<tr>
			<td>Non-adhesive foam dressing</td>
			<td>Coloplast</td>
			<td>Biatain</td>
			<td>https://www.coloplast.us/biatain-non-adhesive-en-us.aspx</td>
		</tr>
		<tr>
			<td>Roll of 2&#34; hypoallergenic tape</td>
			<td>Monarch Labs Names</td>
			<td>Durapore</td>
			<td>For reinforcing containment dressing.</td>
		</tr>
		<tr>
			<td>Roll of adhesive tape</td>
			<td></td>
			<td></td>
			<td>For trapping ticks</td>
		</tr>
		<tr>
			<td>Vials for collection (e.g. cryovials)</td>
			<td>Ependorf</td>
			<td>ECC200</td>
			<td></td>
		</tr>
	</tbody>
</table>

a model for experimental exposure of humans to larval ixodes scapularis ticks

Tickborne diseases are a significant public health problem in the United States and worldwide. Ticks are obligate blood-feeding arthropods; an ixodid tick must remain attached to the skin of the host and complete its multi-day feeding process to acquire its blood meal. Exposing animals to ticks is a common practice for studying host responses to tick bites and tickborne diseases. We developed the procedure, conducted the first human research study, and published the findings on exposing human volunteers to uninfected larval Ixodes scapularis ticks. This article describes the methodology used to construct the containment dressing, how to apply and secure the ticks to the host, how to maintain the dressing, and how to remove the ticks from the host. Exposing volunteers to tick bites is an experimental procedure and must be performed under a clinical research protocol approved by the appropriate regulatory authorities. This method allows for translational research to better understand the human response to tick bites and foster the development of diagnostics, prevention, and therapies for tickborne diseases.

Author Spotlight: Controlled Human Exposure Model for Tick Research and Lyme Disease Studies

A Model for Experimental Exposure of Humans to Larval Ixodes scapularis Ticks

This protocol offers an effective method for a controlled exposure of humans to ticks. For research, the protocol can be used to study the human immune response tick bites, as well as the development of diagnostics and preventions against tick-borne diseases. There were no published procedures for placing ticks on human research volunteers.The challenge was to develop a system that allowed the ticks to feed for days while also being comfortable for the participants. This model contains the ticks for the duration of the feeding and allow the research participants to proceed with their daily activities with minor lifestyle adjustments.

The study demonstrated that the procedure is safe and well-tolerated, with the primary adverse event being mild itching at the site of the bites, observed in 58% of the procedures. There were no serious adverse events related to the procedure when using clean laboratory-reared larval I. scapularis ticks19. In the 43 procedures conducted, the mean percentage of recovery of attached ticks compared to placed ticks was 45% &#177; 27% (SD), with a median percentage of 40% (<strong class="xfig"...

Watch this Scientific Journal Video about A Model for Experimental Exposure of Humans to Larval Ixodes scapularis Ticks at JoVE.com

This article presents the methodology for exposing humans to larval Ixodes scapularis for clinical research. The technique is relatively simple, tolerable by the research volunteers, and can be modified according to experimental needs. Such research involving human subjects must be conducted under clinical study protocols approved by the appropriate regulatory authorities.

Tickborne diseases are a significant public health problem in the United States and worldwide. Ticks are obligate blood-feeding arthropods; an ixodid tick ...

a-model-for-experimental-exposure-humans-to-larval-ixodes-scapularis