Final Post

Classes have now begun and my summer or research has come to an end. Over the course of the past couple of months I have learned a lot about what it means to be involved in biological research, both in the lab and out in the field. From mountain biking and hiking in 100 degree weather in order to collect ticks, to running PCR’s and gel electrophoresis, my summer was an exciting learning experience. I gained quite a lot from this journey both academically and mentally. Spending several hours every day in pants and long sleeved shirts on mountain bikes and through brambles and thick underbrush is not the easiest thing I have ever done. Despite the physical challenges that this presented though, I woke up each day feeling excited for the day to come.

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Problem solving with contamination and data entry

Since my last post, I have completed more PCR and gel electrophoresis with the adult ticks. Everything was going very smoothly until a couple of days ago when I ran a gel and found every single tick came out as positive for the pathogen Ehrlichia chaffeensis. This seemed abnormal and quite frankly, alarming. If all of the tick extracts that were used in that agarose gel were in fact positive, that would have put the prevalence for 2016 above 20% which is much higher than 2017 and 2018. A difference that high did not seem right to me so I knew the odd results must have been due to contamination that occurred along the way. So, I began trying to figure out what to do and after working with my professor we came up with the solution to use new primers. These new primers that I have begun using are longer in base pairs. Therefor, any contamination that could have occurred with the old primers gets discounted as the new primers attach to a longer section of the DNA. I re-ran the contaminated agarose gels and they came out normal again, giving me only 2 positives instead of 32.

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DNA analyses on Amblyomma americanum adults

Since my last blog post, I have been conducting analyses on adult ticks to check for zoonotic pathogens. Specifically, I have been testing for Ehrlichia chaffeensis, which can be transmitted to humans. To conduct the DNA analyses, I first start by identifying the adult ticks and cutting each on in half using a sterile razor blade. Each tick is placed in a sterile tube for DNA extraction. Following a series of elutions, a polymerase chain reaction is carried out to amplify the DNA. After the reaction is complete, gel electrophoresis is completed to determine the presence or absence of Ehrlichia chaffeensis. 

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Research on Amblyomma americanum adults and nymphs

So far this summer, I have spent the majority of my time conducting field work around the Virginia and Middle Peninsula areas in order to collect ticks that will be analyzed for pathogens. To do this, we drove, mountain biked, and hiked into the woods at various locations where transects were then established at points that have been utilized for the past several years for tick collection. For the tick collection itself, I dragged a 1 meter squared tarp along each transect, checking for ticks every three meters and putting any ticks in 70% ethanol. After returning to campus each day, I stored the ticks in freezers to preserve them until DNA analysis could be conducted. Below is an example photo of over 200 Amblyomma americanum nymphs in a collection tube with ethanol. In just one three meter stretch, we found 202 ticks, which is a record for this project.

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Seasonal Influence on the Prevalence of Ehrlichia chaffeensis in Amblyomma americanum Adults

As the years have passed, tick-borne illnesses have posed a growing threat to human health. Many studies have looked into the increasing prevalence of the agent causing Lyme disease in blacklegged ticks, but few have looked into the lone star tick (Amblyomma americanum) and its related risks including the bacterial pathogen Ehrlichia chaffeensis. (Goddard et al. 2009). In order to understand the extent to which E. chaffeensis threatens human health, its prevalence and distribution must be studied. Previous research done in the Applied Conservation and Ecological Research (ACER) lab has described E. chaffeensis  prevalence on the nymph population of A. americanum and how weather changes might be related to pathogen prevalence. I am conducting parallel research this summer to investigate E. chaffeensis prevalence in the adult tick population and how its prevalence is affected by weather patterns and related environmental factors. In addition to my upcoming sampling effort this summer, I am compiling ticks collected in past years from 130 plots in the Virginia Middle Peninsula and will use these five years’ data to conduct DNA and data analyses to determine any correlations between pathogen prevalence and weather patterns.