Mathematical Modelling of Insecticide Resistance Management Strategies for the Control of Vector Borne Diseases.

Hobbs, Neil (2023) Mathematical Modelling of Insecticide Resistance Management Strategies for the Control of Vector Borne Diseases., Thesis (Masters), Liverpool School of Tropical Medicine.

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Abstract

The use of insecticides as long-lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS) for vector control has, while providing disease control simultaneously applied high levels of insecticide selection to vector populations. The consequence has been the evolution of insecticide resistance and there are concerns insecticide resistance will inhibit effective disease control. Insecticide resistance management (IRM) strategies are intended to slow the progression of insecticide resistance within and between populations. There remains debate regarding which IRM strategies are effective and when. With the imminent arrival of new insecticides for vector control there is an urgent need to evaluate their use in IRM strategies. Laboratory and field trials of IRM strategies are impractical due to the long timescales required. Computer simulations and mathematical modelling is therefore used to provide insight into the effectiveness of proposed IRM strategies. Previous models have assumed resistance is monogenic.
Where the modelling presented in this thesis differs is the assumption of polygenic resistance. This thesis includes the description, calibration, and application of three quantitative genetics models which allow for insecticide resistance to be modelled as a polygenic trait. The first model “polyres”, allows for cross resistance and mixtures. This model is extended to the “polytruncate” and “polysmooth” models which further allow the inclusion of insecticide dosing and insecticide. Finally, “polysmooth” is extended for multiple gonotrophic cycles allowing for the more complex IRM strategies
of household level mosaics (“micro-mosaics”) and combinations of LLINs and IRS. The models are applied over a range of scenarios allowing the IRM strategies to be compared.
The results from these scenarios indicate the difference between the rotation and sequence strategy is typically small. The impact of insecticide decay was explored mechanistically, highlighting this is a key issue in IRM. Mixtures are found to be most effective when both insecticides are at full-dose, with minimal initial resistance to either partner insecticide. Household deployments as “micro-mosaics” were found to be equivalent to rotations and perform worse than full-dose mixtures. Combinations of LLINs and IRS were found to perform worse than mixture LLINs for IRM, even with multiple IRS insecticides available. The findings from these models in general support the results from previous models which assumed a monogenic basis of resistance. Due to the inclusion of two key parameters (cross resistance and insecticide decay), additional new insight into IRM is provided.

Item Type:	Thesis (Masters)
Subjects:	W General Medicine. Health Professions > W 82 Biomedical technology (General) QX Parasitology > QX 20 Research (General) QX Parasitology > Insects. Other Parasites > QX 600 Insect control. Tick control QX Parasitology > Insects. Other Parasites > QX 650 Insect vectors
Faculty: Department:	Biological Sciences > Vector Biology Department
Depositing User:	Lynn Roberts-Maloney
Date Deposited:	18 Sep 2024 09:16
Last Modified:	18 Sep 2024 09:19
URI:	https://archive.lstmed.ac.uk/id/eprint/25357

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