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Lyme Disease Tick Hotspots

lyme disease mapNew research suggests Lyme disease ticks are endemic in the Northeast and Northern Midwest of the United States, prompting calls for further education programs on prevention and awareness of Lyme disease. In the most extensive and meticulous mapping project to date on Lyme disease, researchers at the Yale School of Public Health, in Connecticut, worked at more than three hundred sites to assess the presence of ticks infected with borrelia bacteria. Their results could influence Lyme disease policies across America.

Unreliable Tick Reports

Led by Maria A. Diuk-Wasser, an assistant professor of epidemiology at Yale, eighty field operatives spent hours traversing the country armed with 1m² flags of corduroy. Flagging for ticks can help identify high-risk areas and warn people accordingly but, up until now, the reports available on tick-endemic areas were largely unreliable. The ticks responsible for spreading Lyme disease, Ixodes scapularis in the US, were trapped by the researchers and then tested for evidence of bacterial infection.

Two Main Foci of Lyme-Infected Ticks

The Yale team developed a map showing that the Northeast and upper-Midwest of the US were the main areas in which ticks infected with Lyme disease bacteria were endemic. Publishing their findings in this month’s issue of the American Journal of Tropical Medicine and Hygiene, the researchers note that they identified areas where infected ticks were present but where there were still not reported cases of Lyme disease. This could demonstrate limited human exposure to these tick populations or it could signify misdiagnosis or asymptomatic infection in people in the tick-endemic area.

Ticks Preferring Non-Human Hosts

One other reason for low reported numbers of Lyme disease infection in humans in areas where infected ticks are now known to be endemic is the preference of these ticks to choose non-human hosts. Ixodes scapularis nymphs appear to choose lizards and skinks as their hosts in the more southern states, unlike in their northern counterparts. Cases reported in the south are thought likely due to misdiagnosis or an infection picked up whilst travelling.

Checking for Ticks

For three years, between 2004 and 2007, field assistants checked for nymph ticks an average of five times at each study site. The checks occurred in late spring and summer, during the most active time of the year for nymphal ticks. Thirty-seven states were included in the study, all east of the 100th meridian, as this is the area in which nymphal ticks have been identified previously. A number of factors appear to influence the presence of ticks in an area, namely low elevation, low humidity, and seasonal temperatures. One specific area in which infected ticks are rife is between southern Maine and northern Virginia; the other main focus is Wisconsin, northern Minnesota, and in part of northern Illinois. Continued migration of deer in these areas, as well as tree-planting schemes and other alterations to the urban and rural landscape will all likely effect the resident populations of ticks infected with Lyme disease bacteria.

Preventing Lyme Disease

A key outcome of this research is the scrutiny applied to current tick awareness procedures. As it stands, tick bite prophylaxis, i.e. use of tick repellents and use of Lyme disease antibiotics after a bite, is recommended only when 20% or more of nymphs in an area are infected with Lyme disease bacteria. The scientists at the Yale School of Public Health conclude that the presence of any nymphs infected with Borrelia burgdorferi is sufficient for postexposure preventative measures to be taken. The knowledge that an area has infected ticks present, even in the absence of reported Lyme disease cases, allows local authorities to improve prevention, diagnosis, and treatment protocols in such Lyme disease-infected tick endemic areas.


Diuk-Wasser MA, Hoen AG, Cislo P, Brinkerhoff R, Hamer SA, Rowland M, Cortinas R, Vourc’h G, Melton F, Hickling GJ, Tsao JI, Bunikis J, Barbour AG, Kitron U, Piesman J, Fish D., Human Risk of Infection with Borrelia burgdorferi, the Lyme Disease Agent, in Eastern United States.
Am J Trop Med Hyg. 2012 Feb;86(2):320-327.

Lyme map. The map shows an elevated risk of Lyme disease from Maine south to Maryland, Northern Virginia, and the Washington DC area. Investigators found a separate region of increased risk in the upper Midwest. The 3 sites marked with red crosses indicate the only sites where investigators collected high numbers of infected tics, but where the statistical model did not accurately predict them as high risk.

{ 5 comments… add one }
  • Stoner February 22, 2012, 12:36 pm

    HEY,,,I have figured it out for mtself,I have had lymes for 20 years,was tested in early 1990’s test said I didn’t have it,I’ve suffered threw 20 years of hell with this.My cat came in the other day Feb. warm day,Ipicked 3 tic’s off the cat in plainview,have picked as many as 34 just this past 6 months,worst I ever seen.I live neer greensburg,penna.out in the farm land. The map is not very precise,as to where these things are.how many people are out their,not nowing what they have being sick and miserable,with no one to turn too. Doctors just laughed at me and my syco.symtoms,all in my head approch,saying (What do you want me to do give you some magic pill or something) wake up people they don’t want you to know what you got,they just keep guessin, My experances with lymes??? thanks stoner

  • doug February 22, 2012, 6:48 pm

    Northern Idaho is also evolving a concentration of lyme infection. Forest service workers have had it in big numbers.

  • fisherman February 23, 2012, 1:06 am

    Here in southern Maine Lymes disease has become a near epidemic this past summer, worst year I’ve ever seen for Deer ticks, I have a feeling that the warmer, wetter weather we have been getting the past several years has something to do with the increase in tick population.

  • Andrew McGovern February 24, 2012, 9:52 am

    Believe it or not but I know in 1n 1985 at 32, years old, in north central Kansas, while out large mouth fishing, in tall grass and dead timber scattered all over, I got the bulls eye bite verfied by a medical journal of the day. Later, by a Dr. Wycoff in Hastings, Ne. My stiff neck started in 1989 and all the other symtoms I read about in the Journal came on. As years have gone by the suffering has been great. I had a regular test for Lyme Disease at the VA Med clinic, which came out positive and later the Western Blot test which came out probable postive twenty years later. I am 58 now and can’t do a darn thing because of the pain all over my skeletal system. I would’nt wish this disease on anyone.

  • scott ference March 27, 2012, 3:44 pm

    On march 26th 2012 me Scott Ference went into the woods by my house and I was looking for fish. And yes I did find some.But when I came home I was telling my step dad about what kind of fish I found when I scratched my head and guess what fell off my head when I scratched my head ”CORRECT” a tick. I new it was a tick because I’m in boy scouts and I learned what they looked like because my friend who was in the troop got bit by one and when he came home I guess he told his mom his leg was light and he was felling light headed so his mom took him to the hospital and the doctor told him it was a tick bite and his mom freaked out and took him out of the troop. When he came to the next meeting he showed me and my troop his tick bite it looked like a lump and after that my scout master showed us what a tick looks like so we can be aware of a tick looks like. And when that tick fell off my head onto the ground I saw the circle back and the 8 eight legs I freaked out I’m just glade it did’int bite me and it was getting ready to bite me.And after that I took a shower just to make sure. I think that was the scary’est thing I had ever had on me.

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