Lyme disease is one of the most devastating tick-borne infections in the United States, affecting more than 300,000 people each year. It’s also one of the most mysterious: The creature that spreads it—the black-legged tick—lives throughout the country. Yet the northeastern United States is home to far more cases than anywhere else. Now, researchers have identified an unexpected reason: lizards.
Black-legged ticks (Ixodes scapularis), also known as deer ticks, carry corkscrew-shaped bacteria that cause Lyme disease. The ticks pick up the pathogens—spirochetes that belong to the genus Borrelia—when they suck the blood of animals like mice, deer, and lizards. In the next stage of their life cycle, the ticks may latch onto an unlucky human. But every host transmits the microbes differently. Reptiles are worse transmitters than mammals, so ticks that have lived on reptiles are less likely to make people sick.
The north-south divide in Lyme cases is a fairly sharp line right along the border of Virginia and North Carolina. Researchers have hypothesized that disparity in cases stems from ticks feeding on different hosts in the two regions. (See link for article)