When you’re sick, the most aggressive treatment option sometimes sounds the most appealing. We operate on war metaphors for disease and as patients, we want bombs, missiles and full-blown nuclear artillery attacking our pathogen invaders. What we forget is that aggressive attack, whether in war or in medicine, can also be inflammatory and runs the greatest risk of retaliation. How can pathogens retaliate? Enter the realm of research on drug resistance evolution.
In April 2011, a study published in the Proceedings of the National Academy of Sciences (PNAS) explored evidence for the danger of aggressive chemotherapy treatments in the spread of diseases like malaria. The arguments presented by researchers Andrew Read, Troy Day and Silvie Huijben suggest that more aggressive treatments come at the cost of creating stronger selection pressures against mild strains of pathogens, resulting in the survival and persistence of only the most virulent pathogens. Selection for virulence has longer lasting consequences on the evolution of disease than is worth the risk of using aggressive treatments.
In the model system of ants and cacti, aggression may come at the cost of decreased pollination and thus decreased fecundity. In the discussion of drug resistant pathogens, aggression comes at the cost of higher virulence in pathogens and thus lowered fitness in hosts. The trade-off trend seems to be recurrent. Aggression has benefits whether deterring herbivores on plants or treating malaria in ailing patients but we must consider the consequences of potential benefits and bear in mind the complexity of ecological systems when evaluating relationships between ants and plant hosts or pathogens and their unfortunate prey.
Check out the article, “The evolution of drug resistance and the curious orthodoxy of aggressive chemotherapy,” A. Read, T. Day, S. Huijben here: