Graduate Program

Biological Sciences

Degree Name

Master of Science (MS)

Semester of Degree Completion

Spring 2024

Thesis Director

Thomas Canam

Thesis Committee Member

Gary A. Bulla

Thesis Committee Member

Yordan S. Yordanov

Abstract

Some of the most prominent vectors for West Nile Virus are mosquitoes of the genus Culex. As a result, efforts have been made to monitor the spread of Culex species as climate change has allowed them to travel to places that they never inhabited before. Since Cx. restuans is a less prevalent vector, most studies for prevention focus on Cx. pipiens, which is the primary vector for the spread of West Nile Virus in the Midwestern United States, especially in the late summer and early fall seasons. As both species share many morphological characteristics and are present at approximately the same times of the year in shared habitats, differentiating the two species is imperative to prevent and predict widespread outbreaks. However, the primary identifier of Cx. restuans is the presence of white spots on the thorax that are frequently lost in the capturing process, making visual identification between Cx. restuans and Cx. pipiens extremely challenging. The purpose of this study was to examine additional morphological features (e.g. wing veination) as possible species identifiers while also examining molecular methods of identification. Mosquitoes for this study were captured indiscriminately in Oblong, Illinois, and taken to the laboratory for morphological identification. Once identified based on visual cues, genomic DNA was extracted and subjected to PCR targeting an ITS-28S rDNA region. The same samples also served as template for qPCR with primers and probes specific for either Cx. pipiens or Cx. restuans. The species-specific primers of the PCR method of identification were generally inconsistent, while the qPCR method that targeted the acetylcholinesterase (Ace2) gene was more reliable. Of the 155 individual mosquito samples, the morphological and qPCR identifications were in agreement just 16.8% of the time, suggesting that the morphological identifiers used were not sufficient for accurate species identification between Cx. pipiens and Cx. restuans. The qPCR technique also led to 20% of samples showing positive signals for both species, which indicates that the qPCR method may not have the specificity required for accurate identification. In the future, modern genomic resources coupled with inexpensive sequencing techniques could allow for a routine sequence-based identification strategy instead of indirect molecular methods.

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