Parasites are unpleasant lodgers at the best of times, but there is one group of parasites that is particularly pernicious. These are the parasites that hijack their victims' nervous systems, reducing them to helpless zombies. 'The fact that parasites can so efficiently alter host behaviour is fascinating', says The Journal of Experimental Biology Editor Michael Dickinson, from the University of Washington, USA, adding, 'There is something horrifying and wondrous about a tiny "implant" being able to control such a large animal machine'. What is more, it appears that these minute manipulators can have a significant, and often under-appreciated, impact on ecology, physiology and evolution, orchestrating the behaviour of vertebrates and invertebrates alike. 'Neuroparasitology is a science where science meets science fiction', Dickinson observes.
In a special collection of Review articles edited by Shelley Adamo, Dickinson, Joanne Webster and Janis Weeks, the journal covers many branches of the newly emerging field of Neuroparasitology, from the behavioural changes exhibited by hijacked hosts to the complex neurological mechanisms that allow parasites to control their victims and the high-tech approaches that are essential for studying them. Featuring case studies of timid animals that are manipulated by their parasites to become more bold and insects that have lost the ability to move independently – allowing hijackers to use the victims' bodies as incubators and food supplies for their young – the collection also features an entire section dedicated to Toxoplasma gondii, a parasite of rodents and cats that can be picked up by humans and may be a contributory factor in some cases of human schizophrenia. In addition, the collection features a section dedicated to our current understanding of the complex neurological mechanisms that allow parasites to take control of their host's nervous system by co-opting the victim's own immune response to alter its behaviour.