Precautions for tick-borne disease extend "beyond lyme"

A nymphal blacklegged tick on leaf litter in Tennessee. Credit: Graham Hickling, University of Tennessee

(Medical Xpress)—This year's mild winter and early spring were a bonanza for tick populations in the eastern United States. Reports of tick-borne disease rose fast.

While is the most common in the Northeast and Upper Midwest, new research results emphasize that it is not the greatest cause for concern in most Southeastern states.

The findings are published today in a paper in the journal Zoonoses and Public Health.

The majority of human-biting in the North—members of the blacklegged tick species—cause Lyme disease, but these same ticks do not commonly bite humans south of mid-Virginia.

Biologist Graham Hickling of the University of Tennessee, co-author of the paper, says many patients in Southeastern states, who become sick from a tick-bite, assume they have Lyme disease, but the odds of that being the case are low.

"Ticks in the eastern U.S. collectively carry more than a dozen agents that can cause human disease," says Hickling.

"Here in Tennessee we regularly collect lone star ticks that test positive for Ehrlichia, [a tick-borne ]. Lone stars are an aggressive species that account for most of the human bites that we see in this region. So ehrlichiosis has to be a big concern, yet most people have never heard of it."

In contrast, says Hickling, there have been no confirmed reports to date of the Lyme disease pathogen among the sparse populations of blacklegged ticks found in Tennessee.

"The Southeast is dominated by different tick species than the ones that attack humans in the North," says Ellen Stromdahl, an entomologist at the U.S. Army Public Health Command and lead author of the paper.

"The lone star tick is by far the most abundant tick in the Southeast, and which species of you is critical because different ticks carry different diseases. In the Southeast you are unlikely to be bitten by the blacklegged ticks that spread Lyme disease," Stromdahl says.


A female blacklegged tick converting its blood-meal into thousands of eggs. Credit: Graham Hickling, University of Tennessee

Most bites in the Southeast are from the tick species that spread spotted fever rickettsiosis and ehrlichiosis, but not Lyme disease.

A complicating factor for public health officials is that tick species are on the move, as wildlife populations, forest habitats and weather patterns change across the continent.

This spring the Tennessee Department of Health, for example, reported a 500 percent increase in tick-borne rickettsiosis.

"Identifying health risks in the face of changing climates will be critical in coming years," says Sam Scheiner, National Science Foundation program director for the joint NSF-National Institutes of Health Ecology and Evolution of Infectious Diseases (EEID) program, which funds Hickling's research.

At NSF, the EEID program is co-funded by the Directorates for Biological Sciences and Geosciences.

"This study will inform public health officials about what diseases are found in which areas," says Scheiner, "so they can minimize human health problems."

Hickling's work is also in collaboration with scientist Jean Tsao of the University of Michigan and is part of an EEID project to identify the ecological factors leading to distributions of tick species and pathogens—in particular, where the Lyme disease tick and pathogen are found.

Lyme-infected blacklegged ticks are expanding south through Virginia, and lone star ticks are moving north, the scientists have found.

The bite of the lone star tick can create a bulls-eye rash that appears like that of Lyme disease, but the rash isn't caused by the Lyme bacteria.

The scientists say that this almost certainly leads to misdiagnosis of some patients in mid-Atlantic states, where both tick species are common.

The best way to distinguish Lyme from other tick-borne diseases is to be vigilant for tick bites, and whenever possible save any tick that manages to bite you, the biologists recommend. Store the tick in your freezer or in a vial of alcohol so it can be identified if you become ill.

In the Northeast, Lyme disease awareness campaigns have focused public attention on the nymphal blacklegged tick—which is responsible for most disease transmission and which is tinier than the adult form.

While nymphal blacklegged ticks and nymphal lone star ticks—which also bite humans—can be distinguished, the two are often confused by the public.

In one study, 13 of 20 patients reporting tick bites to physicians were given antibiotics on the assumption that they were at risk for Lyme disease, yet 53 of the 54 ticks removed from those same patients were lone star ticks, which do not spread Lyme disease.

"Where you live determines which tick species is likely to bite you," says Tsao, "and therefore which diseases you're most likely to contract."

The biologists say they are happy that recent treatment recommendations have begun to emphasize the importance of considering the tick species and its infection status as part of the diagnostic process.

Their advice: Stay open-minded about which tick-borne diseases are most common in your area—and save the tick that bites you.

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Doug_Huffman
not rated yet Sep 07, 2012
The image is nearly unique and great. With a scale bar it would have been better. Nymphal Ixodes characteristic dimension is 1.5 mm, only slightly larger than the larval 1 mm that is the same as the egg, of which ~3,000 are produced by a female. There is no evidence of transovarial BB transmission.

Referring only to Ixodes, these ticks are not dependent on climate change for their spread, but on their traveling hosts. Ixodes lifecycle is exquisitely tuned, across years, generations and stages, by diapause and development times. An Empirical Quantitative Framework for the Seasonal Population Dynamics of the Tick Ixodes ricinus by Randolph, Green, Hoodless, Peacey in International Journal for Parisitology 32 (2002)
Willie2011
5 / 5 (1) Sep 07, 2012
As long as articles like this perpetuate that ticks carrying lyme disease do not prevail in the south the longer the authors can pat themeselves on their backs - that they have contributed in the masses in the south being diagnosed with lyme disease. Deer ticks are prevalent in the south and do transmit lyme disease. I am in Texas whereas 3 ticks from my property were all deer ticks and all three harbored borrelia in their guts. Coincidence not! Please research further and practice giving the public what they deserve which is the truth. BTW the lone star tick actually started in the south and moved to the north. Lets not forget about masters disease which is caused by lonestar tick. Nothing is known about the consequences of this disease. Why? Maybe its because articles like this make it all seem confusion - Hence the conflict about lyme disease. A disease that keeps people from having productive great lives because authors of articles continue to give life and breath to
rfw
not rated yet Sep 07, 2012
This article's recommendation, that we save the ticks that bite us for analysis is good as far as it goes. The problem with the idea is that they must first be able to SEE the offending critter. The tick in the photo, if correctly dimensioned (by Doug above) at ~1.5 mm is much larger than its equally aggressive and infectious immature stages which are too small to see. Thus one simply cannot be vigilant enough. Instead, if illness happens, one must do a multi-species blood panel & look for ALL possibilities for the source of the problem.