A model for the origins and spread of drug-resistant malaria

TLDR

Host immunity is the primary biological factor controlling malaria infection. The study presents a general method for parasite population genetics to investigate drug‑resistance evolution in *Plasmodium*, focusing on pre‑drug allele frequencies, post‑drug dynamics, and threshold frequencies below which resistance will not arise. Two immunity models—generalized immunity regulating overall infection level and specific immunity regulating each clone—are used within this method to analyze the evolution of resistance. The analyses reveal implicit assumptions in earlier models, reconcile conflicting conclusions, and support a more informed discussion on practical drug use.

Abstract

A general method of investigating parasite population genetics is presented and used to investigate the evolution of drug resistance in Plasmodium . The most important biological factor is the nature of the control, presumably through host immunity, of the malarial infection. Two models are examined: a ‘generalized immunity’ (GI) model in which immunity regulates the overall level of infection, and a ‘specific immunity’ (SI) model in which each clone within the infection is regulated independently. These models are used to investigate 3 critical factors in the evolution of resistance: (i) the frequency of resistant alleles in the population prior to drug use, (ii) the dynamics of resistance following drug application and (iii) the magnitude of threshold frequencies below which resistance will not evolve. These analyses also identify the implicit assumptions made in several previous models, reconcile their differing conclusions and allow a more informed debate about the practical application of drugs.