A while ago I posted about some claims that a snake species had evolved an “unbeatable” predation tactic.
I also posted about a claim that an antibiotic had been invented to which bacteria could not evolve resistance.
Here is the most recent in this series of “I can’t imagine how evolution could occur in this circumstance” silliness.
Insecticides are one of the cheapest, most effective, and best proven methods of controlling malaria, but mosquitoes can rapidly evolve resistance. Such evolution, first seen in the 1950s in areas of widespread DDT use, is a major challenge because attempts to comprehensively control and even eliminate malaria rely heavily on indoor house spraying and insecticide-treated bed nets. Current strategies for dealing with resistance evolution are expensive and open ended, and their sustainability has yet to be demonstrated. Here we show that if insecticides targeted old mosquitoes, and ideally old malaria-infected mosquitoes, they could provide effective malaria control while only weakly selecting for resistance. This alone would greatly enhance the useful life span of an insecticide. However, such weak selection for resistance can easily be overwhelmed if resistance is associated with fitness costs. In that case, late-life–acting insecticides would never be undermined by mosquito evolution. We discuss a number of practical ways to achieve this, including different use of existing chemical insecticides, biopesticides, and novel chemistry. Done right, a one-off investment in a single insecticide would solve the problem of mosquito resistance forever.
Ok readers, go see their paper, then post ideas regarding how evolution might still occur either in the mosquitoes or Plasmodium to make this not so very “evolution-proof” after all.
Hint: Note the following specifics:
The population genetics model makes the following assumptions:
1. Adult mosquito population size is constant.
2. Mosquitoes do not complete more than ten gonotrophic cycles.
3. The genetic make-up of mating males in any cycle is the same as that calculated for newly hatched mosquitoes in that cycle.
4. Males of all resistant/susceptibility genotypes are equally likely to mate successfully.
5. Females mate once only, in their first cycle, as is the norm.
6. Number of eggs produced per laying female is unaffected by egg paternal genotype.
7. Genotypes of emerging adults joining the population are in the same proportions as the genotypes of the generation of eggs from which they hatch.
8. Resistance is dominant, as can be the case.
9. Costs of resistance are dominant.
10. The proportion of infectious humans is constant.
The feeding cycle model makes the following assumptions.
1. Mosquitoes bite humans randomly and uniformly.
2. Malaria-infected mosquitoes never become uninfected.
3. The proportion of humans who are infectious is constant.
4. A variety of parameters do not change over successive gonotrophic cycles: (i) the background mosquito mortality rate (what Smith and McKenzie call “force of mortality”), which is considered as a constant per-capita daily death rate (i.e. there is no senescence), (ii) the probability of taking a blood meal and (iii) the probability of feeding on a human.
5. Conventional insecticides are instant kill.
I’ll point out again what Orgel’s second rule says: Evolution is cleverer than you are.