Lyme disease patterns tied to tick behavior and host choice

In a new study published by PLOS, researchers investigated the geographical patterns of Lyme disease. The experts have discovered that a tick’s host-seeking behavior, as well as their preferred hosts, can explain why Lyme disease is more prevalent in the northeastern region of the United States compared to the southeast.

Ticks contract Lyme disease by biting animals that are infected with Borrelia bacteria. Infected ticks can pass the disease along to humans. While it was known that Lyme disease is more commonly diagnosed in the northeast, the causes of this discrepancy are unclear. 

To investigate, a team led by Dr. Howard Ginsberg of the U.S. Geological Survey Patuxent Wildlife Research Center conducted an extensive study of tick-host interactions at eight field sites throughout the eastern U.S.

The researchers found that southern ticks have a tendency to select lizards as their hosts, rather than small mammals. This is significant because lizards infected with Borrelia bacteria are less likely to pass it along to other ticks compared to mammals. 

The tendency of southern ticks to bite lizards instead of mammals may explain why fewer ticks, and fewer people, develop Lyme disease in the South. 

“Northern blacklegged ticks attach mostly to mice and other mammals, while southern ticks love lizards, especially skinks,” said Dr. Ginsberg. “It’s interesting that this quirk in tick ecology can have such an important effect on human health.”

Dr. Ginsberg’s team previously reported that southern ticks tend to stay below leaf litter when seeking hosts, while northern ticks usually climb to leaf tops and twigs. This increases the likelihood that northern ticks will encounter and bite humans. 

Furthermore, variations in tick densities from north to south could help explain the Lyme-disease gradient. Future research is needed to explore how climate change may affect ticks and their hosts, potentially altering Lyme disease patterns in the U.S. and Canada.

The study is published in the journal PLOS Biology.

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By Chrissy Sexton, Earth.com Staff Writer