What Percentage of Ticks Carry Lyme Disease?
Many deer ticks carry more than one pathogen
Co-infections may increase the severity and complexity of illness
Ticks on Long Island showed high rates of Lyme disease infection
As the authors point out, “Concurrent polymicrobial infections in humans can have a synergistic effect and result in a more severe course of illness.”1
In an effort to investigate what percentage of ticks carry Lyme disease, researchers examined three tick species, including the deer tick (Ixodes scapularis), found in Suffolk County, Long Island.1
Their study revealed that over half of the deer ticks (63%) were infected with at least one pathogen.1
For a broader overview of overlapping tick-borne infections, visit our Lyme Coinfections hub.
How Common Was Lyme Disease in Deer Ticks?
“Borrelia burgdorferi was the most prevalent pathogen (57% in adults; 27% in nymphs), followed by Babesia microti (14% in adults; 15% in nymphs), Anaplasma phagocytophilum (14% in adults; 2% in nymphs), Borrelia miyamotoi (3% in adults), and Powassan virus (2% in adults),” writes Sanchez-Vicente.1
This study highlights the growing complexity of tick-borne disease exposure in endemic regions.
Multiple Pathogens Were Common
Dual infections were detected in 19% of the I. scapularis ticks, while triple infections were detected in 3% of the ticks.1
“Of note is that nearly one-quarter of the I. scapularis ticks tested had polymicrobial infections,” writes Sanchez-Vicente, “and this justifies the modification of the clinical approach to tick-borne diseases to cover all infection possibilities.”1
Polymicrobial infections represent another aspect of tick-borne diseases that can complicate diagnosis and augment disease severity.
Blood-Borne Co-Infections Raise Additional Concerns
Three pathogens detected in this study—Anaplasma, Babesia, and Ehrlichia—infect blood cells and can potentially be transmitted through blood transfusions.1
This warrants concern given that the ratio of Lyme disease cases to babesiosis cases has been approximately 4 to 1 for many years.
“This ratio also holds for the ratio of B. burgdorferi to B. microti in ticks in this study, i.e., 3.8 to 1,” the authors write.1
Why Co-Infections Matter Clinically
Patients bitten by infected ticks may acquire more than one pathogen simultaneously.
Co-infections can complicate diagnosis, broaden symptom presentations, and potentially worsen disease severity.
Some co-infections may also respond differently to antibiotics commonly used for Lyme disease.
For example, Babesia is a parasitic infection and is not treated with doxycycline alone.
For more on Babesia, visit our Babesia and Lyme Disease guide.
Frequently Asked Questions
What percentage of ticks carry Lyme disease?
In this Long Island study, 57% of adult deer ticks and 27% of nymph deer ticks carried Borrelia burgdorferi, the bacterium associated with Lyme disease.1
Do ticks carry more than one disease?
Yes. Some deer ticks carry multiple pathogens simultaneously, including Lyme disease, Babesia, Anaplasma, and Powassan virus.1
What are Lyme disease co-infections?
Co-infections are additional tick-borne infections transmitted alongside Lyme disease, often from the same tick bite.
Can one tick bite transmit multiple infections?
Yes. Some ticks contain more than one pathogen and may transmit multiple infections during a single bite.
Are all deer ticks infected with Lyme disease?
No. Infection rates vary by geographic region, tick life stage, and environmental conditions.
Why are tick co-infections important?
Co-infections may complicate diagnosis, increase illness severity, and require different treatment approaches.
Clinical Takeaway
Many deer ticks carry more than one pathogen, and co-infections may complicate both diagnosis and treatment.
This Long Island study demonstrated high rates of Lyme disease, Babesia, Anaplasma, and other pathogens within the same tick population.
Patients with persistent or atypical symptoms after a tick bite may warrant evaluation for multiple tick-borne infections.
Related Articles
These related articles explore co-infections, polymicrobial illness, delayed diagnosis, and complex tick-borne disease presentations.
Delayed Lyme Disease Diagnosis
Tick-Borne Co-Infections Are the Norm, Not the Exception
One Bite, Six Diseases, All From the Same Tick
Lyme Disease Symptoms Guide
Prevention of Lyme Disease
Reference
Sanchez-Vicente S, Tagliafierro T, Coleman JL, Benach JL, Tokarz R. Polymicrobial Nature of Tick-Borne Diseases. mBio. 2019 Sep 10;10(5).
Dr. Daniel Cameron, MD, MPH
Lyme disease clinician with over 30 years of experience and past president of ILADS.
Symptoms • Testing • Coinfections • Recovery • Pediatric • Prevention
