Evolution, Malaria, And Mosquitoes

1) Posted by Jacob Best

Article 1

The development of resistance in pests is a problem shared by the disease control and the agricultural fields of research. More pertinent to the disease control sector is the issue of malaria-carrying mosquitoes. With humans lives at risk with every new infection, most organizations advocate the use of instantly lethal insecticides to immediately deal with pests. This course of action may remedy the situation swiftly but its lasting power is null. Indeed, the use of fast acting pesticides puts a high selection pressure on mosquito populations, thus increasing the likelihood that only those individuals which develop resistance will go on to reproduce. Within a few years, the pesticide has no effect.

Read, et al. propose a novel solution to this issue: the development of a pesticide which is “evolution proof,” that is, a pesticide which promotes resistance evolution cannot act on. Without the ability to select for resistance, the likelihood of transmission is lessened. To accomplish this lofty goal, Read, et al. propose a pesticide which acts on mosquitoes after reproduction has already occurred. Thus, if the insect gains resistance, it will not be passed down to its descendants because they will have already been laid. Such an insecticide is called an LLA, or late-life-acting insecticide. Several versions are proposed by Read, et al., each being less tenable then the previous, yet each confers essentially uninheritable resistance by having the benefit of resistance be less than the cost associated with it. There are challenges to developing such a drug, but the least conspicuous may be the most difficult to overcome: funding. One reason immediately lethal insecticides are the most common is because the pesticide industry is linked to  the agriculture field, whose chief goal is not to prevent disease spread, but rather to ensure the most crops possible. Thus, LLAs insecticides do not experience the same financial backing.

Overall, the paper by Read, et al. shows the power of taking evolution into account when dealing with modern problems. Beyond evolution, it exemplifies how scientific concern is focused not only with best practices but also with industrial motivation.

2) Posted by Olivia Barr

This article discussed drug treatments and resistance in malaria. The main drug most people have heard of his Chloroquinine due to its popularity up until the 90s, however resistant strands of malaria have become common leading to many people switching to Sulfadoxine-pyrimethamine (SP). As with most infectious diseases, resistance to this new drug is inevitable so efforts to slow this process are the main focus as of now. The main method to slow resistance evolution we discussed in this module was refuges, having a separate population not treated by the drug to maintain the nonresistant gene at high ratios in the population. For obvious ethical reasons, this is not a possible with a human population so the article discussed more alternatives. Based upon the article’s discussion, the ideal antimalarial drug, to limit selection of resistance, would be very strong, killing both sensitive and partially resistant parasites and the drug would ideally decay rapidly as to minimize the time spent in the system at low potency. The article goes on to discuss genetic signatures associated with drug resistance, the main of which they discussed is selective sweeps which we also discussed in this module. Areas of lower than expected variation are indicative of these selective sweeps and help scientists identify loci where resistance selection may have occurred. This allows scientists to study evolution on a molecular level and learn more about parasitic selection and more potential prevention methods.

Definitely having the context of this chapter made this article much easier to understand and interpret.