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Omitting age-dependent mosquito mortality in malaria models underestimates the effectiveness of insecticide-treated nets

Iacovidou, Melissa A., Barreaux, Priscille, Spencer, Simon E. F., Thomas, Matthew B., Gorsich, Erin E. and Rock, Kat S. (2022) 'Omitting age-dependent mosquito mortality in malaria models underestimates the effectiveness of insecticide-treated nets'. PLoS Computational Biology, Vol 18, Issue 9, e1009540.

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Abstract

Mathematical models of vector-borne infections, including malaria, often assume age-independent mortality rates of vectors, despite evidence that many insects senesce. In this study we present survival data on insecticide-resistant Anopheles gambiae s.l. from experiments in Côte d’Ivoire. We fit a constant mortality function and two age-dependent functions (logistic and Gompertz) to the data from mosquitoes exposed (treated) and not exposed (control) to insecticide-treated nets (ITNs), to establish biologically realistic survival functions. This enables us to explore the effects of insecticide exposure on mosquito mortality rates, and the extent to which insecticide resistance might impact the effectiveness of ITNs. We investigate this by calculating the expected number of infectious bites a mosquito will take in its lifetime, and by extension the vectorial capacity. Our results show that the predicted vectorial capacity is substantially lower in mosquitoes exposed to ITNs, despite the mosquitoes in the experiment being highly insecticide-resistant. The more realistic age-dependent functions provide a better fit to the experimental data compared to a constant mortality function and, hence, influence the predicted impact of ITNs on malaria transmission potential. In models with age-independent mortality, there is a great reduction for the vectorial capacity under exposure compared to no exposure. However, the two age-dependent functions predicted an even larger reduction due to exposure, highlighting the impact of incorporating age in the mortality rates. These results further show that multiple exposures to ITNs had a considerable effect on the vectorial capacity. Overall, the study highlights the importance of including age dependency in mathematical models of vector-borne disease transmission and in fully understanding the impact of interventions.

Item Type: Article
Subjects: QX Parasitology > QX 20 Research (General)
QX Parasitology > Insects. Other Parasites > QX 510 Mosquitoes
QX Parasitology > Insects. Other Parasites > QX 600 Insect control. Tick control
WC Communicable Diseases > Tropical and Parasitic Diseases > WC 750 Malaria
WC Communicable Diseases > Tropical and Parasitic Diseases > WC 765 Prevention and control
Faculty: Department: Biological Sciences > Vector Biology Department
Digital Object Identifer (DOI): https://doi.org/10.1371/journal.pcbi.1009540
SWORD Depositor: JISC Pubrouter
Depositing User: JISC Pubrouter
Date Deposited: 10 Nov 2022 16:25
Last Modified: 13 Jun 2023 11:23
URI: https://archive.lstmed.ac.uk/id/eprint/21235

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