Date of Graduation

8-2024

Document Type

Thesis

Degree Name

Master of Science in Entomology (MS)

Degree Level

Graduate

Department

Entomology and Plant Pathology

Advisor/Mentor

McDermott, Emily

Committee Member

Kariyat, Rupesh

Second Committee Member

Loftin, Kelly

Third Committee Member

McGregor, Bethany

Keywords

Competence; Culicoides; Insecticide; Sublethal; Vector

Abstract

Culicoides biting midges are common pests around the world of humans, livestock, and wildlife. In addition to nuisance blood feeding, they are also able to transmit pathogens to their hosts like bluetongue virus (BTV) and African horse sickness virus, which can be damaging in terms of both production economics and animal welfare. In order to protect humans and livestock from biting pests like Culicoides, a wide array of interventions is recommended, but chemical insecticides and repellent use are ubiquitous. For a multitude of reasons ranging from natural weathering of applied insecticides to the increase in resistance-associated mutations and behaviors in exposed populations, it is common for insects like Culicoides midges to come into contact with chemicals at concentrations which do not kill them. These sublethal exposures have been shown to cause a variety of changes in vector physiology and behavior, sometimes affecting their ability to transmit the pathogens they carry. The converse is also true: it has been found that arboviral infection can alter vector responses to commonly employed chemicals like permethrin and DEET. To investigate the interactive effects of anthropogenic chemical use and arboviral infection, we studied Culicoides sonorensis in several experimental scenarios. By exposing C. sonorensis midges to sublethal concentrations of insecticide and offering them a BTV-infected bloodmeal, we discovered a potential effect of permethrin on viral dissemination 7 days after infection and a pronounced reduction in blood feeding following permethrin exposure. In a follow-up study, we tested the effects of three insecticides on midge blood feeding and confirmed that sublethal exposure of permethrin can significantly reduce blood feeding in midges for up to 12 hours. Similarly, Fluralaner can reduce blood feeding for up to 6 hours after exposure. In the last experiment, we tested the effects of BTV on C. sonorensis blood feeding behavior and found that infection did not change engorgement rates when midges were exposed to two common repellents: DEET and permethrin.

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