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Tick guts key to Lyme disease spread

Medicine@Yale, 2014 - July August

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The prevalence of Lyme disease varies greatly among locales in the Northeastern U.S., even though the deer ticks that transmit the disease are common throughout the region. Now, scientists may have a better idea why.

A team led by Erol Fikrig, M.D., Waldemar Von Zedtwitz Professor of Medicine, and professor of epidemiology and microbial pathogenesis, and a Howard Hughes Medical Institute investigator, has found clues as to Lyme’s uneven prevalence: when a feeding tick ingests Borrelia burgdorferi, the bacterium that causes the disease, the bacteria’s survival depends on microbes in the ticks’ guts.

To control their gut contents, Fikrig’s team raised Ixodes scapularis tick larvae in germ-free containers. When the mature ticks fed on B. burgdorferi-infected animals, they ingested more blood, but carried less bacteria, than ticks reared in normal conditions. The ticks with altered gut microbes had lower levels of STAT, a protein key to maintaining the gut’s immune system and repair mechanisms. In turn, the gut’s lining was altered, and B. burgdorferi had a harder time colonizing it.

The findings, published Jan. 15 in Cell Host & Microbe, may explain the influence of environment on disease incidence and could lead to new ways to stop the spread of B. burgdorferi.