Recipient Organization
STATE UNIV OF NEW YORK
(N/A)
SYRACUSE,NY 13210
Performing Department
Environmental & Forest Biology
Non Technical Summary
Lyme disease, caused by the spirochete Borrelia burgdorferi, is estimated to infect 300,000 people in the United States annually. While the ecology of Lyme disease and its associated tick vector is well documented in areas where the tick is present in large number and the disease has plagued humans for decades, little is known regarding what facilitates establishment of the tick and disease in new geographical areas. This study will investigate the role that tick utilization of various small mammal hosts plays in the emergence of the tick-borne pathogen and causative agent of Lyme disease. To do this we will trap small mammals and their collect their associated Ixodes scapularis ticks, from sites identified in previous work as either historically Lyme and tick endemic or newly Lyme and tick emergent. Ticks collected off specific small mammal species will be genotyped by next-generation Illumina based genotyping-by-sequencing (GBS), and tick genotypes associated with specific animal species will be compared within and between endemic and newly emergent sites. Additionally, B. burgdorferi genotypes will be determined via ampliseq in both tick and small mammals and investigated for associations with specific tick genotypes or small mammal species. Based on previous research in habitats where Ixodes scapularis is highly abundant the tick is presumed to practice broad host feeding behaviors. Yet, we lack specific knowledge if this behavior is consistent in habitats where the ticks are found in very low numbers and disease is emergent. The work proposed in this study will test whether tick host utilization differs between tick abundant and tick poor sites using highly sophisticated molecular techniques and analyses. Knowledge gained from these studies will provide researchers insight into the role different small mammal's play in the establishment and emergence of the black-legged tick and its associated agent of human Lyme disease. This is important as currently the only fail proof method to prevent Lyme disease is tick avoidance, however tick avoidance often leads lead to a negative view of wooded habitats and may ultimately deters individuals from visiting public forests. Moreover methods such as environmental application of acaricides is documented to have negative effects on non-target species, specifically pollinators such as honey bees while having little effect on tick encounter rates (thus not reducing disease risk). Findings from this study may influence how land managers employ specific targeted control tick control measures in newly established areas and areas under threat of establishment. Understanding the nuances that allow for successful establishment of both the tick vector and Lyme disease bacterium in novel forested lands is the first step in truly having the ability to predict and ultimately control human disease risk in an ever-changing world. Better understanding these processes will lead to informed action by stakeholders to protect the health of animals, humans and their environment.
Animal Health Component
(N/A)
Research Effort Categories
Basic
100%
Applied
(N/A)
Developmental
(N/A)
Goals / Objectives
The overarching goal of this study is to investigate the role that host utilization plays in the emergence of the tick-borne pathogen and causative agent of Lyme disease, Borrelia burgdorferi. To answer this question the proposed study will use to following objectives:Compare I. scapularis parasitism rates on multiple small mammal host species at sites where ticks andB. burgdorferi have been historically abundant (tick-rich) and sites of recent colonization (tick-poor).Determine if a non-random associations exist between tick genotype and parasitized host species both within and between study sites using Illumina based genotyping-by-sequencing.Investigate B. burgdorferi genotypes infecting specific small mammal species. Using Illumina based amplicon sequencing; B. burgdorferi genotypes infecting small mammals, the ticks collected off them, as well as host seeking ticks will be determined and tested for non-random associations.
Project Methods
This project will take place over a 2 year period. During year one all of the field work and data will be collected. A season of small mammal trapping will provide suffcient samples for the second half of the porject which will consits of the molecular analyses.Field WorkSmall mammal trapping and tick collection. Small mammals and their associated ticks will be collected from sites previously identified as historically endemic (tick-rich) and newly established (tick-poor) during spring-fall of 2018. Sites will be visited at least one night biweekly throughout this period resulting in a minimum of 3600 traps nights per site (9 months X 2 visits x 200 traps). Trapping will be consist of setting 200 Sherman live traps placed 10 meters apart in twenty-100 meter transects over night at each site. Captured small mammals will be weighed, measured and identified to species, sex and approximate age. To facilitate the counting and collection of host associated ticks and ear punch biopsies, small mammals will be anesthetized via isoflurane. Animals will be allowed to recover and be released at the site of capture. Tick counts will be utilized to detect any non-random parasitism rates on specific small mammal species between tick-rich and tick-poor sites.Molecular AnalysesIllumina Genotype-by-sequencing (GBS). With the significant advancement of next-generation sequencing technologies, the field of population genetics has quickly evolved and now utilizes an organism's genome to understand complex phylogeographic and demographic scenarios.In this study we will investigate the association of specific tick genotypes and the small mammals they parasitize. To do this, we will use the high-throughput, low-cost per sample genotype-by-sequencing (GBS) approach described by Elshire et al.GBS utilizes the activity of specific restriction enzymes (e.g., PstI that has been optimized for two tick species) to fragment an organism's genome, resulting in a reducedrepresented genetic library. This "reduced sized genome" is then sequenced, and single nucleotide polymorphic (SNP) sites are used to interrogate phylogenetic questions.To determine if an association between tick genotype and host mammal species exists, high quality SNPs will be analyzed for genetic structure via principal components analyses (PCA) using the EIGENSOFT package, Bayesian population inference implemented in the program STUCTURE and analysis of molecular variance (AMOVA) in the program ARLEQUIN.Borrelia burgdorferi genotyping. Recent studies have associated B. burgdorferi genotypes with specific small mammal species.These finding may be explained by cryptic B. burgdorferi transmission cycles driven by the propensity for a specific tick genotype to feed exclusively on one mammal species. In this study we will investigate B. burgdorferi genotypes in small mammals and the ticks associated with them. Initial screening for B. burgdorferi infected samples will be accomplished by testing DNA extracted from ticks and small mammal ear punch biopsies with traditional PCR targeting the outer surface protein C (ospC). Samples that are found to be positive for B. burgdorferi infection by this traditional PCR will be subjected to Illumina based-amplicon sequencing (ampliseq), which is a novel strategy used to overcome the limitation of traditional Sanger based sequencing especially when genotype coinfections are common, to determine the prevalence and proportion of infecting bacterial genotypes.