Tick-Borne Surveillance Patterns in Perceived Non-Endemic Geographic Areas: Human Tick Encounters and Disease Outcomes
*Author to whom correspondence should be addressed.
Academic Editor: Raphael B. Stricker
Received: 12 May 2021 / Revised: 15 June 2021 / Accepted: 16 June 2021 / Published: 21 June 2021
Recent scholarship supports the use of tick bite encounters as a proxy for human disease risk. Extending entomological monitoring, this study was designed to provide geographically salient information on self-reported tick bite encounters by survey respondents who concomitantly reported a Lyme disease (LD) diagnosis in a state perceived as non-endemic to tick-borne illness. Focusing on Texas, a mixed-methods approach was used to compare data on tick bite encounters from self-reported LD patients with county-level confirmed cases of LD from the U.S. Centers for Disease Control and Prevention (CDC), as well as serological canine reports.
A greater proportion of respondents reported not recalling a tick bite in the study population, but a binomial test indicated that this difference was not statistically significant. A secondary analysis compared neighboring county-level data and ecological regions.
Using multi-layer thematic mapping, our findings indicated that tick bite reports accurately overlapped with the geographic patterns of those patients previously known to be CDC-positive for serological LD and with canine-positive tests for Borrelia burgdorferi, anaplasmosis, and ehrlichiosis, as well as within neighboring counties and ecological regions. LD patient-reported tick bite encounters, corrected for population density, also accurately aligned with official CDC county hot-spots. Given the large number of counties in Texas, these findings are notable.
Overall, the study demonstrates that direct, clinically diagnosed patient reports with county-level tick bite encounter data offer important public health surveillance measures, particularly as it pertains to difficult-to-diagnose diseases where testing protocols may not be well established. Further integration of geo-ecological and socio-demographic factors with existing national epidemiological data, as well as increasingly accessible self-report methods such as online surveys, will contribute to the contextual information needed to organize and implement a coordinated public health response to LD.
- Primary care physicians may under-diagnose LD in areas perceived as non-endemic .
- Misdiagnosis was reported in seventy-two percent of respondents in a large survey , indicating the need for improved surveillance beyond entomology that links tick encounters with human disease risk, which can inform diagnostic approaches.
- The need for expanded and improved LD research and knowledge is highly apparent for the benefit of both patients and health practitioners.
- Given that LD is often labeled a “contested illness,” TTS respondents who may be perceived as “faking it” could easily report any random county if their tick bites were indeed a false entry in the TTS survey. In other words, it would be highly unlikely that the totality of respondents’ tick bite reports would map directly to confirmed official CDC cases or canine serological findings through attempted deception. TTS-reported tick bites overlap almost exactly with CDC-confirmed LD cases in county-level and eco-region analyses. In one case, in a county in which TTS respondents did not overlap with human cases, tick encounter reports did overlap with a positive canine county.
You know it’s bad when researchers have to deal with the myth that patients are considered deceivers.