PCR unravels Lyme disease-infected ticks

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PCR unravels Lyme disease-infected ticks

Lyme disease can cause long term problems, but often people don’t know they are infected after a tick bite so don’t get treatment. A collaboration between faculty and students at a US university used the polymerase chain reaction (PCR) to find out how many deer ticks (Ixodes scapularis) actually carry Borrelia burgdorferi, the bacterium that causes Lyme disease.

 

Source: ARS-USDA; Credit: Scott Bauer

 

The project, at University of Wisconsin-Eau Claire, started when Lloyd Turtinen, professor of biology, found a tick burrowed in his leg.

“I was a little concerned about getting Lyme disease from the tick, so I brought it back to a clinic in Eau Claire,” Turtinen said. “They told me they couldn’t give an antibiotic for Lyme disease until a rash is present. Well, that concerned me because only 75% of people who get a tick that transmits the Borrelia burgdorferi bacteria actually get a rash. So there are 25% of people who will never get a rash, but still have Lyme disease. I thought it would be nice to know if the tick had the bacteria, so I went back to the lab and started working on a process to detect the bacteria’s presence.”

Turtinen developed a chemical process to extract all of the DNA from a deer tick, including any bacterial DNA it may be carrying, and the team used PCR to analyse the DNA from 341 adult female deer ticks collected from 21 counties in Wisconsin during 2010-13. The ticks used for the research were collected by students in Turtinen’s infectious disease ecology classes, who went into the field and used flannel material to sweep the ticks from grass and bushes.

Overall, an average of 35% of the ticks tested positive for the Borrelia burgdorferi bacteria. The counties with the highest infected tick prevalence rates were Chippewa (66.7%), Dunn (44.4%) and Eau Claire (36.5%) counties. Over the four years of collection, the prevalence of positive ticks significantly increased. In 2010, the prevalence from all counties was 21.6%, which increased to 32.4% in 2011, 40.9% in 2012 and 51.2% in 2013.

Turtinen was surprised by the number of ticks that carried the Lyme disease-causing bacteria.

“When we first started this, I didn’t think it was going to be in the 30% range, but that’s what our results show,” Turtinen said. “It certainly calls attention to the fact that there are a lot of positive ticks out there and you have to be careful.”

The increasing incidence of Lyme disease in humans could be related to a number of different factors, including deer population increases and climate change. The project was a collaboration between Turtinen and two student researchers, Alyssa Kruger and Madeleine Hacker. Meet the team in the supporting video on YouTube.

While this project didn’t use xxpress, the ultra-fast thermal cycler (launched in the UK and Germany in 2013), this would have great potential in a project like this. Its intuitive interface makes it simple to use, even for people new to PCR, and its fast turnaround, with 40 cycles in less than 15 minutes, makes projects with a lot of samples move a lot more quickly.


Suzanne Elvidge is a freelance science, biopharma, business and health writer with more than 20 years of experience. She has written for a range of online and print publications including FierceBiomarkers, FierceDrugDelivery, European Life Science, the Journal of Life Sciences (now the Burrill Report), In Vivo, Life Science Leader, Nature Biotechnology, New Scientist, PR Week and Start-Up. She specialises in writing on pharmaceuticals, biotechnology, healthcare, science, lifestyle and green living, but can write on any topic given enough tea and chocolate biscuits. She lives just beyond the neck end of nowhere in the Peak District with her second-hand bookseller husband and two second-hand cats.

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