New tool in the fight against Lyme disease | National
DETROIT – As black-legged ticks crawl across Michigan, scientists hope a new vaccine under development could make their presence less of a threat.
The vaccine would rob the ticks of a trait that makes them extraordinary vectors of Lyme disease: the ability to bite and suck blood without warning and stop long enough to pass bacteria on to their hosts.
“Have you ever heard of someone punching after a tick bite?” said Dr. Erol Fikrig, an infectious disease researcher and professor at Yale School of Medicine who works on vaccine development. “No. A tick is dumb. It feeds on you for a long time.”
Fikrig hopes the vaccine will induce a physical response in a person to bites from a black-legged tick, also known as a deer tick, the species that carries Lyme disease bacteria.
On a vaccinated person, the skin around a black-legged tick bite would be itchy, visible, and inflamed, similar to a mosquito bite. The response would give someone a chance to remove a tick before it has time to transmit Lyme.
“There are very few people who will look at a tick bite, find a tick on it and let it stay,” said Fikrig. “They’ll pull it off pretty quickly.”
The vaccine was inspired by a natural phenomenon called acquired tick resistance. Some animals develop a natural resistance to tick spitting over time; These animals develop sores around tick bites, and ticks that bite them do not eat well, which can cause them to peel off early. The vaccine under development is said to produce a similar response.
A tick bite vaccine has an advantage over a Lyme disease vaccine because black-legged ticks can carry more bacteria than those that cause Lyme disease, said Jean Tsao, associate professor and tick expert at Michigan State University.
There is also anaplasmosis, another disease caused by tick bites, the symptoms of which include fever, headache, chills, and muscle pain, but which is difficult to diagnose because it does not leave a rash. This disease only becomes of concern if not treated early with doxycycline, medical experts said.
“We talked about Lyme because it’s the main vector-borne disease … but you also have anaplasmosis,” Tsao said. “Number two is a bit away, but far more people get anaplasmosis than West Nile, Zika or Dengue. And then there are five other pathogens that Lyme disease tick transmits. The tick is more useful in many ways in my opinion. “
Fikrig and a group of east coast university researchers tested the vaccine on guinea pigs and reported their results in a November issue of Science Translational Medicine, which publishes original, peer-reviewed scientific articles.
Guinea pigs vaccinated in the study developed redness and irritation as early as 18 hours after being bitten. Ticks also fed poorly and for shorter periods of time on the vaccinated guinea pigs, sometimes dying or separating on their own after 48 hours.
“So far, I’m cautiously optimistic” that the vaccine will one day be available to humans, Fikrig said. “From what we’ve seen in the guinea pigs, the results are quite promising.”
A vaccine against Lyme disease is currently being developed by Valneva and Pfizer. It is in human clinical trials.
While the researchers continue their experiments, the ticks march on.
About 35,000 Lyme disease cases are reported annually in the United States, according to the federal centers for disease control and prevention. However, the CDC said that number is likely too low because it relies on doctors actively reporting cases. The CDC estimates that 476,000 Americans are treated for Lyme each year, a number that can be inflated by patients treated for Lyme without actually becoming infected.
In 2020, 305 cases of Lyme were reported to the Michigan Department of Health and Human Services, mostly in the western counties of the state. That’s 66 cases that were reported in 2011.
Black-legged ticks are becoming more common in Michigan, said MSU’s Tsao. When she moved to the state in 2003, the risk of encountering a Lyme disease-carrying tick was very low. Today there is a chance to catch Lyme in almost every county. The disease is usually not far from where the ticks spread.
“In 2010, 2015, they started traversing the southern counties of the Lower Peninsula,” she said. “If you speak to people in Ann Arbor and Ypsilanti, they would say that they probably started seeing more ticks three to four years ago.”
Doctors from Michigan are increasingly seeing Lyme disease in their patients, said Dr. Leonard Johnson, director of the Infectious Disease Department at Ascension St. John Hospital in Detroit.
“It used to be rare that we saw it, and it was only with people who had traveled to the areas” where Lyme is common, like the east coast or the western Upper Peninsula, Johnson said. “But now we see it pretty often in the warm months.”
It usually takes about 36 hours for a tick to spread Lyme disease, he said.
People who become infected with the disease usually develop a porthole-shaped rash around a tick bite. If it’s not treated with antibiotics within a few weeks, Lyme disease can lead to long-term complications like chronic joint inflammation, heart disease, and neurological disorders, Johnson said. These complications require more intensive treatment.
Johnson suggested checking her skin for ticks after being outdoors, especially in wooded areas, and looking for target-shaped rashes.
Most of the patients Johnson treated for Lyme disease did not know they had been bitten by a tick. The vaccine could change that.
“It would allow you to remove the tick before the infection actually occurs,” he said. “I think it could be a valuable tool.”
The vaccine is still in the early stages of development. Fikrig estimates researchers are in the first year of vaccine development, usually a five to ten year process. Although the rapid development of COVID-19 vaccines indicates the possibility for a shorter timeframe, he said.
“COVID showed us something else,” said Fikrig. “COVID vaccines hit the market for about (a year), but maybe that was an exception to the rule. It’s still difficult to say. But maybe the experience with COVID can accelerate the development process in the future.”
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