Genetic analysis of northeastern populations of Ixodes scapularis using RAPD and FRLP-PCR techniques
In the northeastern United States, Ixodes scapularis has been shown to transmit the causative agents of at least four diseases, Lyme disease, human babesiosis, human granulocytic ehrlichiosis and a tick-borne encephalitis-like virus. Genetic differences between tick populations are of evolutionary significance as well as having implications for the management of the species. To ascertain the relatedness of I. scapularis populations, female blacklegged ticks were collected throughout coastal New England from Massachusetts to New Jersey. In addition, I. scapularis from Wisconsin, I. ricinus from Europe, and I. persulcatus from China were sampled. These populations were compared using randomly amplified polymorphic DNA (RAPD) and restriction fragment length polymorphism (RFLP) analysis of a region of their rDNA. A total of 20 arbitrary primers was screened on the samples. Phylogenetic analysis of the RAPD profiles showed that although there were some relationships between genetic distance and geographic distance, these populations of I. scapularis were not geographically or genetically isolated. Also, four restriction enzymes (Cfo I, Hind III, Rsa I, and Taq I) were screened on the samples. A 1.5 kb fragment of the rDNA of I. scapularis was amplified and digested with each of the enzymes. The fragment contained the 5.8S gene and its two flanking internal transcribed spacers (ITS-1 and ITS-2). RFLP analysis of the amplified ITS fragment showed very few polymorphisms in the I. scapularis populations. Only one of the 24 samples contained polymorphic markers. These analyses indicate low levels of variation between populations of I. scapularis in the northeastern United States. These results support the hypothesis that I. scapularis has migrated into new areas via two primary means of dispersal. Host-mediated dispersal, primarily on avian hosts, is suggested to be responsible for the long-range expansion of I. scapularis into new habitats throughout the northeast. Also, short-range migration of these ticks on hosts, including birds and mammals, is evident from the similarity of many of the Rhode Island sites. Finally, finding that the tick populations are not geographically isolated suggests that the elimination of I. scapularis from any specific area is improbable. ^
Biology, Molecular|Biology, Entomology|Biology, Genetics
Daniel Mark Markowski,
"Genetic analysis of northeastern populations of Ixodes scapularis using RAPD and FRLP-PCR techniques"
Dissertations and Master's Theses (Campus Access).