Richard Ostfeld gets a burning, itchy welt after a tick bite, but never got sick from it.
Research suggests that histamine in the blood kills ticks long before they can infect them.
He has acquired tick resistance, which could help with the research and development of a tick vaccine.
When ticks bite Richard Ostfeld, they die – not because he’s particularly vigilant about crushing them, but because his immune system attacks as soon as it detects their presence.
He is one of the few individuals to have developed acquired tick resistance.
How does ATR work?
Thanks to his work as a community ecologist, Ostfeld often roams tick-infested areas, and hundreds of ticks have bitten him over the years.
He said all of these bites trained his immune system to recognize and attack certain proteins in the tick’s saliva. (But don’t go after ticks to build immunity, as you could contract a debilitating tick-borne illness.)
When a tick starts sucking blood, white blood cells rush to the crime scene and release an inflammatory chemical called histamine. Researchers aren’t entirely sure how histamine kills ticks, but it does its job quickly.
“I develop an itchy, burning welt at the site of the tick bite shortly after the tick tries to close its mouthparts,” Ostfeld said.
The welt lasts a few days, but is harmless to him. For the tick, not so much.
Why is tick immunity important?
This quick tick death isn’t just karma for stealing Ostfeld’s blood – it also protects him from tick-borne illnesses, such as Lyme disease or babesiosis, which can damage organs and cause long-term disability.
These diseases originate from bacteria and viruses, collectively known as pathogens. Which pathogens local ticks carry depends on the species and where you live.
In the northeastern states, Ostfelt said one-third of ticks carry the bacteria that cause Lyme disease (Lyme borreliosis). He added that about one in five ticks can infect you with babesiosis, and one
in ten can cause anaplasmosis.
Given those odds, one of the hundreds of ticks that bit Ostfeld likely carried pathogens, but the ticks died before their infectious saliva could enter his body.
“It takes hours to a few days for pathogens to leave the tick and enter your body,” Ostfeld said.
Because his immune system kills the ticks so quickly, “they can never transmit pathogens to me.”
Tick diseases are becoming more and more common
Ostfeld is certainly not the only person with ATR, but so few people report it that scientists don’t know how common or uncommon it is.
But many people are still vulnerable to tick bites, and that’s a growing problem.
“There has clearly been an increase in the incidence of tick-borne diseases in the human population in recent decades. That is true across the country,” Ostfeld said.
The most recent data from the U.S. Centers for Disease Control and Prevention reported 50,865 cases of tick-borne illnesses in the U.S. in 2019. Lyme disease in particular was booming, with cases doubling between 1991 and 2018.
“That’s not due to an increase in the number of ticks that are infected,” Ostfeld said. Rather, it’s because tick bites in general are becoming more common, he added.
A major reason for the explosion of tick bites is climate change. Ticks used to avoid colder northern states like Alaska and Maine. But as these areas have warmed, ticks have expanded their hunting grounds.
Tick hunting seasons have also lengthened. “If spring comes earlier in the year and winter comes later, the ticks have more time to find a host,” Ostfeld said.
Even if the tick chooses to feed on a pet or wild animal, they can easily carry the tick to nearby humans. In other words, ticks can still find you, even if you haven’t walked through tall grass in years.
Can we use acquired tick resistance to fight back against disease?
Some people and animals develop tick immunity naturally if they encounter ticks in their lifetime.
Scientists have also induced ATR by feeding ticks to animals such as cattle, mice and guinea pigs until their immune systems gradually learned to kill the ticks.
There have been no studies in which scientists have induced ATR in humans. But Ostfeld said some research labs are looking into the possibility. It’s just a tricky process, as a vaccine can trigger an autoimmune response if it attacks the immune system too broadly.
In addition, some people naturally have severe tick allergies and develop anaphylactic shock after a bite, so researchers are very careful that their vaccine doesn’t replicate that.
Despite the challenges, Ostfeld said ATR is still worth watching. “In my view, a promising direction is to develop a vaccine against the ticks themselves, against the right choice of proteins and antigens in the ticks’ saliva.”
The Lyme disease vaccine currently in development would only protect against the bacteria Lyme borreliosis, meaning you could still get other tick-borne illnesses. But a tick saliva vaccine could theoretically teach your body to kill ticks and protect you against whatever pathogens they contain.
“I think it’s a very important direction for research to protect against all of the tick-borne diseases that are circulating and the new ones that will almost certainly emerge in the coming decades,” Ostfeld said.
Perhaps one day we will all have immune systems as adept at killing ticks as Ostfeld’s.
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