Global change, parasite transmission and disease control: lessons from ecology

Parasitic infections are the norm in wildlife, livestock and human populations, and healthy ecosystems tend to be rich in parasites. Yet, their negative impacts can be extreme. Understanding how both anticipated and cryptic ‘systems change’ might affect parasite transmission at an individual, local and global level, both directly and indirectly, is critical for sustainable control. Here we highlight and synthesise evidence regarding potential effects of global change on parasite transmission in natural host-parasite systems, which could inform more refined and sustainable parasite control programmes in domestic animals or humans. Many examples from diverse terrestrial and aquatic ecological systems show how abiotic and biotic factors can interact additively, multiplicatively or antagonistically to modify effects of global change on parasite transmission, including through altered habitat structure, biodiversity, host demographics and evolution. Despite this, few studies of managed systems explicitly consider higher-order interactions, or the effects of parasite evolution, which might either conceal or exaggerate measured impacts of control actions. We call for a more integrated approach to investigating transmission dynamics, which recognizes these complexities and makes use of new technologies for data capture and monitoring, and to support robust predictions of altered parasite dynamics in a rapidly changing world.