Lyme disease is caused by the bacterium Borrelia burgdorferi which is transmitted to humans and other animals through the bites of infected ticks. It is currently the most common vector-borne disease in the United States, infecting approximately 476,000 individuals each year and sometimes causing severe disease and even death.
A team of scientists led by the New England Center of Excellence in Vector-Borne Diseases (NEWVEC) has recently discovered that the blood of white-tailed deer efficiently kills the bacteria causing this frequently debilitating illness, a finding that could lead to new strategies of prevention and treatment.
“Deer are vitally important to the survival of deer ticks, but they are not involved with transmitting the Lyme bacteria, Borrelia burgdorferi,” explained study senior author Stephen Rich, the director of NEWVEC and a professor of Microbiology at the University of Massachusetts Amherst.
“We’ve known for some time that ticks taken from white-tailed deer are not infected, and we speculated that something about the deer prevented those ticks from becoming infected. But until publication of our paper, no one had done the experiment to show that deer blood – specifically the serum component of white-tailed deer blood – kills Lyme.”
The Lyme disease bacterium is passed to juvenile blacklegged deer ticks (Ixodes scapularis) from the mice these arthropods feed on, with the infected ticks then passing on the bacterium to humans. “We are the accidental host. The ticks that bite us are actually looking for a deer because that’s where they breed. Without the deer, you don’t have ticks. But if you had only deer, you wouldn’t have any Lyme,” Rich said.
The experts added the bacteria in blood serum samples collected from a semi-captive white-tailed deer herd that had no previous exposure to the parasite, and found that this serum efficiently neutralized the bacteria. While the Lyme bacterium has proteins on its surface that protect it from the human innate immune system, deer blood appears to have properties that make the bacteria unable to protect themselves and multiply.
“Whatever it is in the deer that’s killing the germ is part of the innate immune system, a part of the immune system that precedes antibodies,” Rich explained.
In future research, the scientists aim to determine the precise mechanisms in the deer blood which kill the Lyme-causing bacteria, and test whether such defense mechanisms could be induced in humans too.
The study is published in the journal Vector-Borne and Zoonotic Diseases.
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By Andrei Ionescu, Earth.com Staff Writer
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