Tick Test for Persistent Lyme Disease Tried in Humans

tick test

Lyme disease is an illness that has garnered a lot of controversy over time.  Not only is it challenging to diagnose, it is also challenging to treat because of the host of neurological, musculoskeletal and cardiac issues that can go along with it.  A new test for the condition in humans has been developed using an insect most commonly linked to the disease – the tick.

Ticks often carry the bacterium responsible for causing Lyme disease because they feed on mice and other rodents that carry the bacterium.  Tick bites, being painless, are very rarely noticed by humans, which is why so many aren’t aware they are carrying a tick with them.  Ticks tend to bite and then feed off the blood of the animal they are feeding off.  The blacklegged tick is the insect most often linked to the disease.

In this case, ticks that are not carrying the illness were used for the tick test on humans.  This is the first time where xenodiagnosis was used on humans.  Xenodiagnosis is sometimes used in animal studies and is when another animal is used to reach a diagnosis in a patient.  Essentially, the uninfected tick would then bite the human believed to be infected with the condition and if the tick presented with the bacterium, then a diagnosis could be reached.

For the study, researchers had 36 subjects, 26 of whom had a history of Lyme disease.  The remaining 10 were healthy with no prior connection to the disease.  In order to see if this initial tick test for persistent Lyme disease to work in humans, the 26 subjects with a history of the illness had 25 to 30 ticks placed on their arm under a special dressing, and these ticks were recovered a few days later to see if Lyme disease would ultimately incubate.

This initial tick test was designed to see if this form of xenodiagnosis would work in humans without any undue harm or discomfort.  Given that all subjects reported a mild itchiness after the tick bites, the test was deemed to be safe.

None of the ticks that were on healthy subjects demonstrated evidence of Lyme disease after incubation was conducted for two weeks.  Usable ticks from 23 of the participants tested positive for Lyme disease and 21 had no ticks positive for signs of bacteria.  Two others demonstrated unclear results from the tick test.

Justin D. Radolf of the University of Connecticut Health Center in Farmington, CT noted in an editorial he wrote about the study that the tests proved interesting but that they did nothing to enhance scientists’ understanding of post-treatment Lyme disease.  Generally, symptoms of Lyme disease will ease following treatment, but there are cases where symptoms can last six months or more.

Scientists involved with the tick test study say that the xenodiagnostic test was simply a first step .  Now, before tick tests are approved for human use in the diagnosis of persistent Lyme disease, further study needs to be done in order to make the connection between the ticks involved in diagnosis and actual evidence of having the disease.

By Christina St-Jean



National Geographic

University Herald

Public Health Agency of Canada

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