Semester of Graduation

Fall 2024

Degree

Master of Science (MS)

Department

Entomology

Document Type

Thesis

Abstract

Culex quinquefasciatus Say is a medically important peridomestic mosquito species due to its ability to transmit West Nile virus (WNV). Its preference to oviposit in organically polluted water makes it a targeted vector in St. Tammany Parish, Louisiana. St. Tammany Parish, LA has tens of thousands of onsite wastewater treatment systems (OWTSs) that fail inspection nearly 50% of the time releasing untreated sewage wastewater into roadside drainage ditches. In this study, we examined failed OWTSs impact on water quality, the presence of larval Cx. quinquefasciatus and larvivorous fish—a predator of mosquito larvae. In addition, we investigated the effects of ammonium hydroxide’s acute toxicity to third instar Cx. quinquefasciatus in 24 hours toxicity assays and effects on life history traits in development assays recording life stage duration, mortality, total development time, and effects on female to male ratio. Finally, we looked at how ammonium hydroxide affects oviposition choice of Cx. quinquefasciatus in bucket oviposition assays and behavior in Y-tube olfactory assays.

Total dissolved solids (TDS) were significantly higher for failed OWTSs. TDS levels were significantly lower at sites with fish present. Both fish and larval Cx. quinquefasciatus presences were independent of OWTS status. The 24-hour LC50 of ammonium hydroxide for third instar Cx. quinquefasciatus was 3.058 mM [2.839 to 3.250 mM, 95% CI]. While ammonium hydroxide significantly increased the total development time of Cx. quinquefasciatus, mortality, emergence rates, and female to male ratio in treated groups were similar to the control. For oviposition assays, we observed a consistent preference for the control or lower concentrations of ammonium hydroxide with one exception.

Overall, this research provides a better understanding of factors that influence the presence of Cx. quinquefasciatus in St. Tammany Parish. It also helps us to see how ammonium may impact the survival and life history traits of Cx. quinquefasciatus. Future studies need to be done to better mimic the conditions using wild-type Cx. quinquefasciatus to better determine the extent to which they are contributing to the presence of an important vector for WNV in St. Tammany Parish.

Date

11-1-2024

Committee Chair

Healy, Kristen

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Available for download on Monday, November 01, 2027

Included in

Entomology Commons

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