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Researchers Use Live Ticks to Diagnose Persistent Lyme Disease

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Scientists at the National Institute of Allergy and Infectious Diseases (NIAID) have used live larval ticks in an attempt to determine whether Borrelia burgdorferi-- the bacteria that cause Lyme disease -- remain in the body of people who continue to experience symptoms after completing antibiotic therapy. In this small study, most patients did not have detectable bacterial spirochetes.

Some patients treated for Lyme disease -- caused by bacteria carried by ticks that live on deer and other hosts -- continue to have symptoms long after completing standard antibiotic treatment (known as post-treatment Lyme disease syndrome, or PTLDS). Some believe this is due to ongoing infection, while others think immune system dysfunction triggered by the infection or other causes are to blame.

As described in the February 11 advance edition of Clinical Infectious Diseases, Adriana Marquesfrom NIAIDand colleagues evaluatedthe safety of "xenodiagnosis" using Ixodes scapularistick larvae to diagnose ongoing B. burgdorferiinfection. The idea behind this method is that bacteria, if present, will gravitate to their natural host when the ticks feed.

The xenodiagnosis procedure, using disease-free ticks raised in the laboratory, was well-tolerated with no severe adverse consequences. The most common adverse event was mild itching at the tick attachment site.

Ticks from most patients with PTLDS or high antibody levels and from those who completed antibiotic treatment after showing the characteristic "bull's eye" Lyme rash tested negative for B. burgdorferi; 1 person during the early stage of treatment and 1 with PTLDS tested positive. But the researchers concluded, "There is insufficient evidence, however, to conclude that viable spirochetes were present in either patient."

Below is an edited excerpt from a NIAID press release describing the study and its findings in more detail.

Test for Persistent Lyme Infection Using Live Ticks Shown Safe in Clinical Study

Recruitment Continues in Trial at NIH, Tufts Medical Center

February 12, 2014 -- In a first-of-its-kind study for Lyme disease, researchers have used live, disease-free ticks to see if Lyme disease bacteria can be detected in people who continue to experience symptoms such as fatigue or arthritis after completing antibiotic therapy. The technique, called xenodiagnosis, attempts to find evidence of a disease-causing microbe indirectly, through use of the natural disease-carrier -- in this case, ticks. It was well tolerated by the volunteers, but investigators could not find evidence of Lyme disease bacteria in most of the cases where enough ticks were collected to make testing possible.

Larger studies are needed, the scientists say, to determine the significance of positive xenodiagnosis results in cases where Lyme disease symptoms persist following antibiotic therapy.

Adriana Marques, MD, of the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health, and Linden Hu, MD, of Tufts Medical Center, Boston, led the pilot study. Findings appear online in Clinical Infectious Diseases.

The most common tick-borne illness in the United States, Lyme disease is caused by Borrelia burgdorferi bacteria that are transmitted to people by ticks of the Ixodes genus.

"Most cases of Lyme disease are cured by antibiotics, but some patients continue to experience symptoms despite the absence of detectable Lyme bacteria," said NIAID Director Anthony S. Fauci, MD. "This poses a mystery that requires continued research into new or improved ways to diagnose Lyme disease and determine the cause of unresolved symptoms."

"Xenodiagnosis using ticks to detect B. burgdorferi has been used previously in animal studies, but this is the first time it has been tried in people," said Dr. Marques. "Our primary goals in this initial trial were to develop procedures for tick xenodiagnosis and to determine its safety in humans."

Thirty-six adult volunteers enrolled in the study at locations in Maryland, Connecticut, and Massachusetts. Participants included 10 people with post-treatment Lyme disease syndrome (PTLDS); 10 who had high levels of an antibody against B. burgdorferi after antibiotic treatment; five who had erythema migrans (a bull’s-eye rash) and had received antibiotic treatment in the past; one person with erythema migrans who began antibiotic therapy at the time of tick placement; and 10 healthy volunteers.

Participants consented to have up to 30 laboratory-bred, pathogen-free, larval ticks (each smaller than a poppy seed) placed under a dressing. When possible, the ticks were placed near areas where a rash had been observed or near affected joints. After four to six days, investigators removed the ticks and processed them to detect whether any Lyme disease bacteria were present.

The investigators found that xenodiagnosis was well tolerated. "The most common adverse event experienced by volunteers was mild itching at the site of tick attachment," said Dr. Marques.

Not all of the placements yielded enough blood-engorged ticks to perform xenodiagnosis. Twenty-three volunteers with Lyme disease had at least one tick tested; of these, 19 people tested negative. Two people had indeterminate results, thought to be due to laboratory contamination. Xenodiagnosis was positive for B. burgdorferi DNA in the person with erythema migrans who underwent xenodiagnosis early during therapy and in a volunteer with PTLDS.

The researchers note that a limitation of the study is the relatively small number of people on which xenodiagnosis was attempted. "Future studies are necessary to determine the incidence of positive xenodiagnostic results for B. burgdorferi after antibiotic treatment, if these results represent viable organisms or remnants of infection, and whether these results can be related to ongoing symptoms in patients after therapy for Lyme disease," they write.

The study, Searching for Persistence of Infection in Lyme Disease, is continuing to recruit participants. Additional information is available at ClinicalTrials.gov using the identifier NCT01143558.

The research was funded by the NIAID Intramural Research Program and by NIAID grants R21AI082436 and 2R44AI077156.

2/14/14

References

A Marques, SR Telford, S-P Tur, et al. Xenodiagnosis to Detect Borrelia burgdorferi Infection: A First-in-Human Study. Clinical Infectious Diseases. February 11, 2014 (Epub ahead of print).

LK Bockenstedtand JD Radolf. Xenodiagnosis for Posttreatment Lyme Disease Syndrome: Resolving the Conundrum or Adding to It? (Editorial commentary) Clinical Infectious Diseases. February 11, 2014 (Epub ahead of print).

Other Source

National Institutes of Allergy and Infectious Diseases. Test for Persistent Lyme Infection Using Live Ticks Shown Safe in Clinical Study. NIH News press release. February 12, 2014.