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Successful conditions for the early spread of a TE in a disease vector population

John Marshall, Department of Biomathematics, UCLA. Successful conditions for the early spread of a TE in a disease vector population. IR. effector gene. transposase gene. IR. Requirements for a successful control strategy:. Element loss probability: < 1%

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Successful conditions for the early spread of a TE in a disease vector population

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  1. John Marshall, Department of Biomathematics, UCLA Successful conditions for the early spread of a TE in a disease vector population IR effector gene transposase gene IR

  2. Requirements for a successful control strategy: • Element loss probability: < 1% • Rate of element spread: reach 10% prevalence in < 1 year Question: What conditions satisfy these requirements? • Replicative transposition rate • Reduction of transposition rate with additional TE copies • Fitness cost of TE copies • Rate of population growth/decline • Release size • Time of release • TE copy number of released mosquitoes

  3. Transposition and deletion (i = 2) TE TE Diploid cell: Element deletion Replicative transposition TE TE TE TE No transposition or deletion TE TE

  4. Repression of transposition Host fitness costs Transposition rate Host death rate TE copy number TE copy number Sources: • Insertional mutagenesis • Ectopic recombination • Act of transposition Sources: • Self repression • Host repression

  5. Production of gametes (i = 2) TE TE Diploid cell: Gametes: TE TE TE 0.5 - 1 TE 0.25 - 2 TEs 0 -

  6. Population size changes of An. gambiae in Mali, West Africa

  7. What this means mathematically Use to calculate: • TE extinction probabilities • Mean and variance of host counts over time

  8. Optimal release time is end of dry season/beginning of rainy season • Optimal release at beginning of population growth phase • Bias towards release later rather than earlier

  9. vs. transposition rate TE loss probabilities vs. release size vs. release copy no. • Release size has the greatest influence on TE loss probability • Loss probability is < 1% for release size > 25

  10. No. transgenic hosts vs. time • Transposition rate has the greatest influence on rate of TE spread • TE reaches 10% prevalence in < 1 year for transposition rate > 0.087 • Almost all An. gambiae only have a single TE copy in the early stages of spread 1 2 3

  11. Model conclusions Transposition rate: • Most efficient way to increase rate of element spread • Recommend transposition rate > 0.1 per element per generation Release size: • Most efficient way to reduce loss probability • Recommend release size > 50 Fall off of transposition rate with increasing copy number: • Recommend focus on transposition rate and fitness cost when there is only a single element in the genome

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