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For a tick bite to make you sick, the tick must be attached to you and feed you for a while. For some diseases, it may take a day or more. For others, it only takes a few minutes.
We talked to tick biologists about why there was so much variation and what you need to know to protect yourself.
How a tick infects you
First, it is important to understand that ticks can transmit bacteria, viruses and parasites, and that all behave a little differently.
Regarding the transmission of tick-borne disease, scientists know the most about how it works in Borrelia burgdorferi, the bacteria that causes Lyme disease, which (in the US) is also transmitted by ticks. black legs (or deer ticks). as Western ticks with black legs. Jean Tsao, Ph.D., an badociate professor at the Michigan State University Department of Fisheries and Wildlife and Department of Large Enterprises, largely explains this in-depth knowledge of the fact that much research has been conducted on the development of A vaccine against Lyme disease. Animal clinical sciences.
A 2018 review of all of this evidence published in the journal Ticks and Tickborne Diseases confirmed that it probably takes more than 24 hours and more than 48 hours for the Lyme disease pathogen to pbad through. # 39; man to man. (According to the Centers for Disease Control and Prevention, your chances of getting Lyme disease from a tick that has been attached for less than 24 hours are "extremely low.")
And why does it take so long? This has to do with how ticks transmit diseases, which is not usually a one-step process.
Blacklegged ticks catch Lyme bacteria in a host, usually a white-footed mouse. These bacteria, also called spirochetes, settle in the tick's gut.
When the tick finds its next host, perhaps a human being like you, it breaks the skin and starts to inject saliva into the wound, says Lars Eisen, Ph.D., epidemiologist researcher at the Vector-Borne division of Centers for Disease Control and Prevention. Disease, and author of the 2018 review. "For several days, the tick alternates between the injection of saliva and the ingestion of blood."
When your first blood enters the tick's gut, it tells the bacteria to begin to reproduce and eventually move up into the tick's salivary glands. Once the bacteria are present, they can enter your body through the saliva of the tick.
This whole process is complicated, notes Eisen, which partly explains the slowness of the process. In addition, for an infection to develop, a sufficient number of bacteria must enter the body of the host. If only a few bacteria do, the human or animal immune system may be able to fight them and prevent an infection, according to Tsao.
How long does it take for other pathogens to infect you?
A number of other tick-borne diseases can also take up to a day or more to spread from tick to human or animal host, according to scientists estimates.
Tick-borne bacteria that cause anaplasmosis and Borrelia miyamotoi disease (discovered in the United States only in recent years) probably take more than 24 hours to spread. Babesiosis, a tick-borne disease caused by a parasite, is not likely to be transmitted until the tick is attached for 36 hours. And it usually takes at least 24 hours for a tick to transmit Rocky Mountain Spotted Fever to a host. (See our guide on tick-borne diseases.)
For some other infections, however, the situation is different. Studies have shown that the Powbadan virus, which is also transmitted by blacklegged ticks and can cause severe symptoms such as inflammation of the brain or spinal cord, can be transmitted from one person to another. tick to a person in as little as 15 minutes.
How? Saravanan Thangamani, Ph.D., professor in the Department of Microbiology and Immunology at SUNY Upstate Medical University, explains the difference between the behavior of viruses in ticks and bacteria. Instead of camping in the gut of ticks, as bacteria usually do, viruses multiply in the salivary glands, "ready to be transmitted to humans or animals the next time the tick gets away. feed. "
Studies have shown for the Powbadan virus, he says, as well as for the tick-borne encephalitis virus, a common infection transmitted by ticks in Europe and Asia. And he says his lab has generated data suggesting transmission times for the Heartland virus, another pathogen recently transmitted by ticks in the US, are similar to those in Powbadan.
The general rule of Thangamani is that bacteria usually take longer than viruses to spread from tick to host. This is a disease called tick-borne recurrent fever, caused by another type of bacterium Borrelia, distantly related to the bacterium Borrelia that causes Lyme disease.
Recurrent tick-borne fever is transmitted by gentle ticks, lacking the protective shield of ticks that transmit diseases such as Lyme disease. And these light ticks only feed for a few minutes, usually less than half an hour, according to the CDC.
"The bacteria in the relapsing fever that they spread have therefore necessarily evolved to be transmitted very quickly," says Eisen.
The good news is that sweet ticks, which inhabit host burrows (often rodents), have less contact with humans. People with recurrent fever caused by ticks usually fall victim to sleeping in a rodent-infested hut in a rustic or mountainous area.
What do tick transmission times mean to you?
It is important to remember that infections that can be transmitted very quickly by a tick, such as Powbadan and recurrent fever transmitted by ticks, are rare. The CDC estimates that 300,000 people contract Lyme disease each year – while only 34 cases of Powbadan virus were reported to the CDC in 2017 and only 504 cases of recurrent tick-borne fever between 1990 and 2011.
For pathogens whose transmission usually takes longer, it is time to act before an attached tick causes disease. Think of it as a "grace period," says Tsao, who gives you time to check the ticks thoroughly and remove the ones you find attached to you. (Here's how to remove a tick.) The CDC recommends taking a shower a few hours after any potential tick exposure, which will eliminate any ticks that might crawl on you but are not yet attached and give you the opportunity to do it. a thorough check for ticks that have found a place to bite.
But since the risk of acquiring a fast-spreading disease, though rare, is not zero, it is also important to take precautions to avoid getting bitten. Avoid tick habitat if you can by avoiding woody or grbady areas; When hiking, stay in the center of the trail and dress in pants, long sleeves and closed shoes. Use an EPA-approved insect repellent on any exposed skin (see some of our best choices below) and consider purchasing permethrin-treated clothing yourself or treating them with permethrin.
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Consumer Reports is an independent, non-profit organization that works alongside consumers to create a fairer, safer, healthier world. CR does not endorse any products or services and does not accept advertising. Copyright © 2019, Consumer Reports, Inc.
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