Ticks at High Altitudes: Expanding Lyme Disease Risk
Ticks are now being found at higher elevations
Mountain regions once considered low risk may harbor tick-borne pathogens
Climate and habitat changes may expand exposure
Investigators examined ticks living in the Alps over a 4-year period to better understand how altitude may influence tick survival and the spread of tick-borne pathogens.
The study focused on Ixodes ricinus, a European tick species similar to Ixodes scapularis in the United States. Researchers evaluated both questing ticks collected from vegetation and ticks identified on wildlife carcasses in the Piedmont region of the Alps.
A total of 6,492 I. ricinus ticks were collected. Investigators also examined ticks found on red deer, roe deer, and chamois between 2017 and 2019.
The authors reported that tick numbers were significantly associated with altitude, habitat type, and signs of animal activity, particularly roe deer presence.
Although tick density decreased with increasing altitude, Ixodes ricinus ticks were still identified at elevations reaching 1,884 meters above sea level.
Ticks collected included larvae, nymphs, and adult ticks. The presence of all three life stages is important because the Centers for Disease Control and Prevention considers a tick population established when all life stages are identified in a region.
The findings were notable because these higher-altitude environments had traditionally been considered unsuitable for tick survival due to colder temperatures, limited vegetation, and drier soils.
Molecular analysis identified multiple pathogens within the ticks, including Borrelia burgdorferi sensu lato, Rickettsia helvetica, and Anaplasma phagocytophilum. Investigators also detected Borrelia miyamotoi.
The authors suggested that climate and environmental changes may be contributing to the expansion of ticks into mountainous regions.
While fewer ticks were found in open alpine areas and coniferous woods, public exposure remains a concern because these recreational regions are frequently visited by hikers and tourists.
The authors also noted that Lyme disease cases in the Piedmont region may be underdiagnosed or underreported.
Frequently Asked Questions
Can ticks live at high elevations?
Yes. Investigators identified ticks at elevations approaching 1,884 meters above sea level in the Alps.
Can ticks survive in mountainous regions?
Yes. Although colder temperatures may reduce tick density, some tick species are adapting to mountain environments previously considered unsuitable.
Why are ticks moving into higher altitudes?
Researchers believe climate change, habitat shifts, and animal movement patterns may contribute to the spread of ticks into higher elevations.
Do high-altitude ticks carry Lyme disease bacteria?
Yes. Investigators detected Borrelia burgdorferi sensu lato and other tick-borne pathogens in ticks collected from mountainous regions.
Are hikers at risk for tick exposure in mountain regions?
Potentially. Even areas with lower tick density may still pose exposure risks when heavily used for recreation and tourism.
Clinical Takeaway
This study highlights how tick habitats may be expanding into higher elevations once considered low risk for tick exposure. The presence of multiple tick life stages and several pathogens suggests that mountainous environments may increasingly support established tick populations.
As environmental conditions continue to change, clinicians and travelers may need to consider tick exposure even in higher-altitude recreational regions.
Related Articles
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Diseases from ticks
Prevention of Lyme disease
References
- Garcia-Vozmediano A, Krawczyk AI, Sprong H, Rossi L, Ramassa E, Tomassone L. Ticks climb the mountains: Ixodid tick infestation and infection by tick-borne pathogens in the Western Alps. Ticks Tick Borne Dis. 2020;11(5):101489.
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
