Publication Date



bloating, functional bowel disorders, malabsorption, small intestinal bacterial overgrowth, SIBO, gastrointestinal symptoms, digestive symptoms, vector-borne illness, tick-borne, Lyme disease


Background: In the clinical setting, it is not common practice to consider a vector bite, such as from a tick or flea, to be a contributing factor to chronic digestive symptoms. This article investigates associations we have observed among symptomatic patients and positive blood tests for vector-borne illness (VBI).

Methods: Patients who visited an urban gastroenterology clinic over a 3-year period were retrospectively reviewed. A total of 270 patients presenting with a constellation of digestive symptoms — and who had no apparent digestive pathology and reported no prior diagnosis or treatments for VBI — were analyzed. Before the initial visit, all patients completed a review of systems medical history form, which comprised 19 gastrointestinal (GI) symptoms and 73 non-GI-related symptoms and conditions. Patients were tested for small intestinal bacterial overgrowth (SIBO) by lactulose breath test. VBI (babesiosis, ehrlichiosis, anaplasmosis, bartonellosis, borreliosis) was established using 1 or more of several blood tests. Odds ratio (OR) analysis determined associations between exposure to VBI, SIBO, and presenting symptoms/conditions. Two age groups (≤ 35 years and ≥ 36 years) were studied using Cochran-Mantel-Haenszel stratum-based test.

Results: A higher OR (2.03, 95% CI: 1.5–3.6) was found between patients with ≥ 3 digestive symptoms and positive blood tests for ≥ 1 VBI. Five of the 19 GI symptoms were independently associated with VBI-positive samples: food intolerance, indigestion, nausea/vomiting, constipation, and heartburn. A similar association in patients with ≥ 3 non-GI symptoms (OR: 2.83, 95% CI: 1.3–6.4) was observed. Five of the 73 non-GI symptoms/conditions were independently associated with VBI-positive samples: chest pain, shortness of breath, extremity or joint pain, anxiety, and night sweats. Having ≥3 of any digestive or nondigestive symptoms generated significant relative risk of being VBI-positive. Presence of SIBO alone did not identify significant relative risk for a VBI, and age was not a confounder.

Conclusions: Findings revealed an association between positive blood tests for vector-borne illness and chronically symptomatic patients regardless of whether symptoms were digestive or nondigestive. The manifestation of 3 or more gastrointestinal and/or extraintestinal symptoms should raise suspicion for a VBI.

Appendix A.pdf (88 kB)
Online Appendix A

Appendix B.pdf (150 kB)
Online Appendix B




September 20th, 2019


June 25th, 2020


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