Date of Award
2025
Document Type
Thesis
Degree Name
Master of Science (M.S.)
Department
Biological Sciences
First Advisor
Tara Thiemann, Ph.D.
First Committee Member
Sarah Wheeler, Ph.D.
Second Committee Member
Ryan Hill, Ph.D.
Abstract
Vector-borne diseases are an increasingly relevant threat to public health as climate change alters the ecology of vector populations in relation to humans. One key to combating vector-borne disease is using pyrethroid insecticides against mosquito populations. However, wild mosquito populations have exhibited resistance to those key pyrethroids. One resistance mechanism under investigation is the altering of the voltage-gated sodium channel, which is associated with the genetic mutations known as kdr. The prevalence and history of kdr mutations has been investigated in some populations of Culex pipiens, however, it is unknown in northern California Culex tarsalis populations. This study aims to evaluate the prevalence of the kdr L1014F mutation at two points in time, 2007-2009 and 2021-2022, with three populations (Sacramento-Yolo, Lake County, and Sutter-Yuba) and selective pressure from insecticides. By investigating these two time points, we gain insight into the changes in phenotypic resistance observed in these populations. Using Quantitative Polymerase Chain Reaction and allele-specific primers, individual samples were tested for the kdr L1014F and L1014S mutations. In 2007-2009 populations, there were relatively low (2.4-3.5%) occurrences of L1014F. In 2021-2022 populations, there were high (>85%) occurrences of L1014F, a strong increase when compared to 2007 populations. These data have concerning implications for the levels of pyrethroid resistance in their respective populations. Data from the California Department of Pesticide Regulation shows that agricultural and structural pest control industries were key players in the application of pyrethroid insecticides in the study areas. Implementation of the principles of Integrated Vector Management, such as novel control methods and pesticide rotation, will be vital in combating vector-borne disease in the face of this widespread pyrethroid resistance.
Pages
53
Recommended Citation
Blankenship-Cutshall, Esther. (2025). Knocking on Resistance’s Door: Investigating the Spread and Drivers of kdr Mutations in Northern California Culex tarsalis. University of the Pacific, Thesis. https://scholarlycommons.pacific.edu/uop_etds/4313
