How is Lyme Transmitted?

In the United States, Lyme Borreliosis is primarily transmitted through the bite and attachment of hard-shelled ticks from the Ixodesgenus – most notably Ixodes Scapularis (the blacklegged, or deer tick) and Ixodes Pacificus (the Western blacklegged tick).

Source: TickEncounter Resource Center

The highest concentrations of the deer tick can be found on east coast (especially the Northeast and South Atlantic regions) and the Upper Midwest of the United States, while the Western blacklegged tick is mostly found on the nation’s west coast.

However, recent research has found that both populations are growing beyond these areas into Mountain and Central regions. The deer tick can now be found in at least 1,420 (45.7%) of the 3,110 counties in the continental United States, while the Western blacklegged tick can be found in 111 (3.6%) of the nation’s counties.

Taken together, these Lyme–carrying ticks are present in nearly half (49.2%) of the counties, across 43 states. To put this in perspective, when the previous map documenting these tick populations was presented in 1998, they were shown to be present in 1,058 (34%) of U.S. counties, across 41 states.

So, in the 18 years between research maps, there has been a 44.7% increase in the number of counties that have documented the presence of these Lyme vectors – from 1,058 to 1,420 counties.

For information about the presence of the blacklegged ticks in Indiana, please visit our Ticks In Indiana page.

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What Habitats Do These Ticks Prefer?

You will find Lyme-carrying ticks most readily in shady wooded areas with leaf litter, near low brush, and in tall grasses. People living in or near such areas are much more likely to come into contact with ticks in their homes and yards, and on their livestock and, especially, their household pets.

In fact, owning pets in or near tick habitat areas increases the likelihood of a tick attachment by ticks to people or other animals inside the home. The simple reason for this is that pets are more likely to stray into tick habitats on or around the property. And, while some ticks may attach to the pet, others will not be able to find an attachment site in the animal’s fur, and will, instead, “ride” the animal into the home and possibly attach itself to the next host it finds – whether it is a human or another pet.

In the human population, children are at the highest risk for infection mainly because they are outdoors more often in the warmer months, when ticks are most prevalent. But most children either do not do a conscious tick check after being outdoors, or they simply cannot see or feel the tick attachment. And, if they do find a tick attached, they may remove it improperly. So, establishing a tick removal protocol in your home will be most beneficial to your children.

For more information on this protocol, please visit our After Coming Back Indoors page.

Remember, though, that ticks are not limited to densely wooded areas or “out in the country”. Just because you are not living in the middle of the wilderness, it does not mean that you, your family, and your pets are not at risk for encountering ticks.

These vectors will settle wherever they can survive and find hosts, such as parks, vegetation near highway shoulders and underpasses, and gardens and patches of forest in cities and suburbs. And, the fact that tick populations in these areas are smaller than those in thickly wooded regions does not completely eliminate the possibility of infection.

For more information on tick habitats and how to minimize both human and pet exposure to them on your property, please visit our Create A Tick-Safe Environment page.

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How Long Does It Take For A Tick To Transmit Lyme Borreliosis (Or Another Infection)?

While research suggests that the amount of time that a tick is attached plays a role in the transmission of Lyme Borreliosis, those studies do not consider:

  • Whether the tick was previously attached to other hosts
  • Any other potential co-infections that the patient might have in his or her system (which either actually facilitate the movement of borrelia or suppress the immune system to help it take hold)
  • The differences between the immune systems of humans and the animal hosts that were tested
  • The differences between individual human immune systems

Even though attachment time could be a factor, using it as a primary reason for delaying or refusing to consider a Lyme disease diagnosis may pose an unnecessary risk to the patient’s health. It would be helpful to take the entire picture into account (e.g. a patient’s signs, symptoms, and concerns) when evaluating a possible diagnosis, without giving attachment time too much weight.