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Katharine S. Walter, Giovanna Carpi, Adalgisa Caccone | Nature Ecology & Evolution | (2017)
Primary Link Pubmed DOI Openalex

Key Takeaways

Plain English Takeaway

Lyme disease has been around in North America for thousands of years, and its recent rise is mostly due to changes in the environment, not because the bacteria itself has changed.

Study Aim

The study aims to uncover the evolutionary history of Borrelia burgdorferi sensu stricto (the main bacteria causing Lyme disease) in North America. The authors seek to determine how genetic diversity in the bacteria is created and maintained, where and how the bacteria spread across the continent, and how old this diversity is. They want to find out if the recent increase in Lyme disease is due to new bacterial strains or if it reflects much older patterns. Simply put: The study wants to find out how and when the Lyme disease bacteria spread and changed in North America.

Study Design

The researchers collected and sequenced the genomes of 146 Borrelia burgdorferi-infected ticks from the Northeast, Midwest, and southern Canada, covering samples from 1984 to 2013. They used a special DNA capture method to get bacterial DNA directly from ticks, then compared these genomes with previously published ones from North America and Europe. They analyzed genetic differences, recombination events, and built evolutionary trees to trace the bacteria's history and movement. They also examined tick and co-infecting parasite DNA to look for patterns of co-evolution. Simply put: The team studied the DNA of Lyme disease bacteria from many ticks across North America to see how the bacteria changed and spread over time.

Findings

The research demonstrates that Borrelia burgdorferi has a deep and ancient genetic diversity in North America, with its most recent common ancestor dating back about 60,000 years—long before the recent Lyme disease epidemic or the last ice age. The study reveals that the bacteria's spread is shaped by both mutation and recombination, especially in genes that help it infect hosts. There is ongoing gene flow between regions, likely due to animal movement, and no evidence that the bacteria and tick vectors evolved together. The recent rise in Lyme disease cases is attributed to ecological changes, such as reforestation, deer population growth, and climate change, rather than the emergence of new bacterial strains. The authors recommend focusing public health efforts on monitoring areas where ticks are established, as these are likely sites for future Lyme disease spread. Simply put: The study found that Lyme disease bacteria have been in North America for a very long time, and the recent increase in cases is because of changes in the environment, not because the bacteria are new.

Abstract

No abstract available

Referenced In

Lee Johnson
16 days ago
A Scientific Review of Claims made by RFK Jr.

Claim: Ticks Weren’t a Problem Until the 1980s... and They Came From Plum Island

Verdict: False and misleading

“We didn't really have a tick problem in this country until the 1980s. [...] As those deer have proliferated and become very common, the ticks have also proliferated.”

WATCH LIVE: RFK Jr. announces new actions on Lyme disease during NH visit RFK Jr., May 29th, 2026

“[Lyme disease is] highly likely to have been a military weapon. We cannot say 100% for sure, but we do know that they were experimenting with ticks there, and the ticks - as you show - are [an] epidemic because of what happened in Plum Island and the other labs.”

Bioweapons and Lyme Disease with Kris Newby (from 8:00)

RFK Jr., January 19th, 2024

RFK Jr. spoke carefully during a recent announcement about new actions to combat Lyme disease, but just two years ago his opinions were far more extreme. But is RFK Jr. right about ticks not being a problem until the 1980s? How do his recent comments connect to his views from just two years ago?

Ticks Were Around Long Before the 1980s, Lyme Just Wasn’t Identified

Whether RFK Jr. was saying that there were very few ticks before the 80s or that the ticks just weren’t a “problem” until then, he is incorrect.

Ticks were first shown to transmit disease in 1893, when scientists showed Texas cattle fever spread through tick bites. Rocky Mountain spotted fever and tularemia were linked to ticks in the early 20th century, and Lyme disease to the blacklegged tick in the 1970s.

However, he is correct to link the rise of tick populations to deer.

Did Ticks (or Lyme) Become a Problem Because of Plum Island?

So why did RFK Jr. suggest that ticks were only a problem from relatively recently? It’s possibly because it fits with a theory he touted on his podcast in 2024, just a year before starting his current role.

The Plum Island Animal Disease Center was at the centre of RFK’s theorizing. It’s proximity to Lyme, Connecticut and the secretive nature of the facility has spurred conspiracy theories. However, what we know about the facility suggests foot and mouth disease and swine fever were the main focuses of research, not Lyme disease.

Most damning of all, a study on the ancient history of Lyme disease traced the bacterial DNA back and suggested the disease is 60,000 years old. So neither Lyme nor tick issues began at Plum Island.

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