Age-structured vectorial capacity reveals timing, not magnitude of within-mosquito dynamics is critical for arbovirus fitness assessment

E Handly Mayton; A Ryan Tramonte; Helen J Wearing; Rebecca C Christofferson

doi:10.1186/s13071-020-04181-4

Age-structured vectorial capacity reveals timing, not magnitude of within-mosquito dynamics is critical for arbovirus fitness assessment

Parasit Vectors. 2020 Jun 15;13(1):310. doi: 10.1186/s13071-020-04181-4.

Authors

E Handly Mayton¹, A Ryan Tramonte¹, Helen J Wearing², Rebecca C Christofferson^{3

4}

Affiliations

¹ Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA, USA.
² Departments of Biology and Mathematics & Statistics, University of New Mexico, Albuquerque, NM, USA.
³ Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA, USA. rcarri1@lsu.edu.
⁴ Center for Computation and Technology, Louisiana State University, Baton Rouge, LA, USA. rcarri1@lsu.edu.

Abstract

Background: Transmission dynamics of arboviruses like Zika virus are often evaluated by vector competence (the proportion of infectious vectors given exposure) and the extrinsic incubation period (EIP, the time it takes for a vector to become infectious), but vector age is another critical driver of transmission dynamics. Vectorial capacity (VC) is a measure of transmission potential of a vector-pathogen system, but how these three components, EIP, vector competence and vector age, affect VC in concert still needs study.

Methods: The interaction of vector competence, EIP, and mosquito age at the time of infection acquisition (Age_acquisition) was experimentally measured in an Aedes aegypti-ZIKV model system, as well as the age-dependence of probability of survival and the willingness to bite. An age-structured vectorial capacity framework (VC_age) was then developed using both EIP_Min and EIP_Max, defined as the time to first observed minimum proportion of transmitting mosquitoes and the time to observed maximum proportion of transmitting mosquitoes.

Results: The within-mosquito dynamics of vector competence/EIP were not significant among treatments where mosquitoes were exposed at different ages. However, VC_age revealed: (i) age-dependence in vector-virus interactions is important for transmission success; (ii) lower vector competence but at shorter EIPs was sufficient for transmission perpetuation; and (iii) R₀ may be overestimated by using non-age-structured VC.

Conclusions: The results indicate that ultimately the temporal component of the virus-vector dynamics is most critical, especially when exposure occurred at advanced mosquito age. While our study is limited to a single virus-vector system, and a multitude of other factors affect both vector competence and mosquito mortality, our methods can be extrapolated to these other scenarios. Results indicate that how 'highly' or 'negligibly' competent vectors are categorized may need adjustment.

Keywords: Aedes aegypti; Arbovirus; Biting rate; EIP; Extrinsic incubation period; Mortality; Vector competence; Vectorial capacity; Zika.

MeSH terms

Aedes / genetics*
Aedes / virology*
Age Factors*
Animals
Female
Genetic Fitness*
Host-Pathogen Interactions
Humans
Mosquito Vectors
Zika Virus
Zika Virus Infection / transmission*
Zika Virus Infection / virology

Abstract

MeSH terms

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