Citizen Science Research Demonstrates Value in Identifying Tick Prevalence in the US

A citizen science sampling study published in PLoS One highlights the value of citizen participation in research, particularly in regard to identifying tick prevalence in North America.

Using citizen participation data collected from 49 states, researchers from Northern Arizona University (NAU) found that tick exposure is highest during the spring months, with Ixodes scapularis, Dermacentor variabilis, and Amblyomma americanum representing the most prevalent tick species affecting individuals in the United States. Additionally, researchers found that human hosts are the most common host types, with many of these hosts more often bitten by adult ticks.

"Utilizing citizen science could be a broadly efficient way of filling a large gap that currently exists in our understanding of tick-borne disease risk,” Nathan C. Nieto, PhD, of NAU, explained in a recent statement. “This study offers a unique perspective, as it looks at risk to humans that goes beyond the physician-reported infection rates and involved ticks that were found on or near people.”

Additionally, the descriptions of disease incidence and local risk as well as data on “where and when people come into contact with ticks...could be useful to reconcile information on local tick risk and incidence," the authors of the study wrote.

Researchers from Northern Arizona University publicized a free tick detection service that was available for the general public via a website. A total of 16,080 tick submissions (mean, 1.33 ticks/submission) by the general public provided information regarding the location where a tick was encountered, the type of host (human or pet/animal), the date the tick was encountered, and the individual's activity during the encounter. The de-identified submission data as well as the tick itself (if available) were mailed to researchers for identification of species, sex, and life stage. Researchers then tested ticks for Borrelia burgdorferi, B. miyamotoi, Anaplasma phagocytophilum, and Babesia microti.

The largest peak for tick submissions was in the spring, followed by the second largest submission in the autumn. Human hosts comprised the majority of tick submissions at 71.4%, whereas dogs comprised 17.1% of affected hosts. The remaining hosts included various domesticated animals, as well as wildlife and livestock. In 73.9% of cases, ticks were found to have bitten the host, yet 23.4% of submitted ticks were recorded as questing/crawling. Approximately 80.0% of ticks were in the adult stage, with nymphs (17.7%) and larvae (0.9%) representing the additional tick stages in the analyzed submissions.

Of 49 stages from where ticks were submitted, a total of 13 species were identified. The B. burgdorferi, B. miyamotoi, Anaplasma phagocytophilum, and Babesia microti pathogens were detected in ticks of the I. scapularis, D. variabilis, and A. americanum species. In 0.98% of ticks tested in the analysis, co-infections were found. Approximately 1.7% of ticks presented with the most common co-infection of A. phagocytophilum and B. burgdorferi, which represented a 0.5% overall prevalence in the tested ticks.

A primary limitation of a citizen science-based sampling study includes the variability in motivation among participants to submit tick samples; however, samples obtained for this type of study are the best representative of the overall tick prevalence in the population.

“We believe that utilizing the citizen science potential in a local area could be broadly effective at providing public health managers with a relatively cheap (reduced labor and travel costs) and effective (greater scope) way of determining the risk of particular tick species in a region,” the authors conclude. “These data can also be used at a more local scale to examine the phenology of human-tick encounters, geographical diversity of tick and pathogen genetics and so on.”