Assessing Wolbachia Releases in an Age-Structured Population
Authors:Jorly Chatouphonexay, Marie Encarnacion, Breanne Hollie
- Alun Lloyd, Professor of Mathematics, North Carolina State University
- Tim Antonelli, Graduate Student Mentor for NCSU REU program, North Carolina State University
- Michael Robert, Graduate Student Mentor for NCSU REU program, North Carolina State University
Dengue fever affects 50-100 million people each year and can lead to serious complications, such as dengue hemorrhagic fever or dengue shock syndrome. The dengue virus is transmitted primarily by the bite of the mosquito, Aedes aegypti. Current measures for reducing population size of Aedes aegypti have had limited success in controlling the disease and are expensive to maintain long-term. Thus, novel control strategies for reducing the mosquito’s ability to transmit the virus have been proposed. One such strategy is to introduce mosquitoes infected with the bacterium Wolbachia, which shortens mosquito lifespan and interferes with dengue replication within the mosquito host. Wolbachia is a maternally inherited bacterium whose spread is facilitated by cytoplasmic incompatibility, which causes unviable offspring to be produced when a Wolbachia-infected male mosquito mates with an uninfected female. This leads to infected females producing more viable offspring than uninfected females when infected males are present.
We developed two age-structured population models, based on a population genetics model by Huang et al. (2009) and a Leslie matrix model by Rasgon and Scott (2004), to study the spread of Wolbachia-infected mosquitoes in a native population. We studied the effectiveness of releases of different age classes (e.g. immatures vs. young adults vs. older adults) to determine which age class would require the minimum number of releases to increase the number of Wolbachia-infected mosquitoes in the population. By calculating the release threshold, we can find the minimum initial release frequency of each age class where Wolbachia would become fixed in the population. We considered different fecundity values, degrees of assortative mating, and releases of both sexes as opposed to females-only to understand how these release scenarios affects the release threshold. We found that female-only releases and the release of young adults are best for spreading Wolbachia through the population.