Why Tick-Borne Illnesses Persist for Decades
Tick-borne illnesses such as Lyme disease behave differently from many infectious diseases. Instead of appearing suddenly and disappearing quickly, these infections circulate quietly between ticks and wildlife reservoirs, allowing them to persist in nature for decades.
This ecological pattern helps explain
why Lyme disease tests the limits of medicine
. Because Lyme disease circulates between ticks and wildlife reservoirs, treating infected patients alone cannot eliminate the infection from the environment.
Wildlife reservoirs sustain infection
Lyme disease is maintained in nature through a complex ecological cycle involving ticks and wildlife. Small mammals such as the white-footed mouse can carry Borrelia burgdorferi, the bacteria responsible for Lyme disease, without becoming severely ill.
When ticks feed on infected animals, they acquire the bacteria and may later transmit it to other hosts, including humans. Because these reservoir hosts are widespread and abundant, the infection can remain established in an ecosystem for long periods.
Ticks may also carry multiple pathogens, meaning a single tick bite can transmit more than one infection, including Lyme disease, Babesia, or Anaplasma.
The tick life cycle promotes persistence
The multi-stage life cycle of the deer tick (Ixodes scapularis) contributes to the persistence of tick-borne illnesses. Ticks pass through larval, nymphal, and adult stages, feeding on different animals at each stage.
This feeding pattern allows infection to circulate continuously among wildlife hosts. Humans become infected when a tick carrying the pathogen feeds on them during one of these stages.
Geographic spread is gradual but continuous
Unlike rapidly spreading viral outbreaks, tick-borne diseases expand slowly over time. Changes in climate, wildlife populations, and land use have allowed ticks to expand into new regions.
As tick populations move into new habitats, infections such as Lyme disease, Babesia, and Anaplasma may gradually appear in areas where they were previously uncommon.
READ MORE:
Ticks and Lyme disease bacteria have been with us since the Ice Age
Why eliminating tick-borne illnesses is difficult
Unlike many infectious diseases that spread primarily from person to person, Lyme disease and other tick-borne infections persist because they are maintained in complex ecological cycles.
The bacteria circulate between ticks and wildlife reservoirs such as mice and birds. Humans are typically accidental hosts. Treating human infections therefore does not remove the bacteria from the natural environment.
These ecological dynamics help explain why Lyme disease continues to expand geographically and why controlling tick-borne illnesses remains an ongoing challenge.
A slow but persistent pattern
Some researchers have compared the spread of tick-borne illnesses to Aesop’s fable of the tortoise and the hare. Tick-borne diseases may expand gradually, but their steady persistence makes them difficult to control.
Understanding this ecological pattern is essential for recognizing why Lyme disease remains an important and evolving public health concern.
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References:
- Mohan KVK, Leiby DA. Emerging tick-borne diseases and blood safety: summary of a public workshop. Transfusion. 2020.
- Poinar G. Spirochete-like cells in a Dominican amber Amblyomma tick. Journal of Historical Biology. 2015.
- Nuwer R. Lyme Disease’s possible bacterial predecessor found in ancient tick. Nature News.
- Kean WF, Tocchio S, Kean M, Rainsford KD. The musculoskeletal abnormalities of the Similaun Iceman (“Ötzi”). Inflammopharmacology. 2013.
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
Might we then eventually grow along the lines of TBD and eventually our systems will adjust to live comfortably with these infections?
Typically Lyme disease patients don’t die. Instead, they often find themselves alive with a poor quality of life.