Deciphering the Tools of Nature’s Zombies
Deciphering the Tools of Nature’s Zombies
December 9, 2012 7:21 AM Subscribe
Deciphering the Tools of Nature’s Zombies: The ability of parasites to alter the behaviour of their hosts fascinates both scientists and non-scientists alike. One reason that this topic resonates with so many is that it touches on core philosophical issues such as the existence of free will. If the mind is merely a machine, then it can be controlled by any entity that understands the code and has access to the machinery. This special issue of The Journal of Experimental Biology highlights some of the best-understood examples of parasite-induced changes in host brain and behaviour, encompassing both invertebrate and vertebrate hosts and micro- and macro-parasites. Full issue annotated inside:
HOW PERNICIOUS PARASITES TURN VICTIMS INTO ZOMBIESALTERATION OF HOST BEHAVIOR
Parasites come in all shapes and forms. From skinny tapeworms that infest intestines to the microscopic infectious agent of malaria (Plasmodium), parasites are usually inconvenient and sometimes lethal. But there is one group of parasites that is particularly pernicious – they are the parasites that hijack their host’s nervous system, turning their victims into zombies. ‘The fact that parasites can so efficiently alter host behaviour is fascinating’, says JEB 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. However, the community tackling the thorny question of how parasites take possession of their hosts by manipulating their nervous systems, and the large-scale implications of these behavioural changes, is tiny. Shelley Adamo – an insect behavioural physiologist from Dalhousie University, Canada – adds that working with parasitic systems is particularly challenging because of the necessity of raising two different organisms in the lab. ...
Parasites: evolution’s neurobiologistsNEUROIMMUNOLOGY
For millions of years, parasites have altered the behaviour of their hosts. Parasites can affect host behaviour by: (1) interfering with the host’s normal immune–neural communication, (2) secreting substances that directly alter neuronal activity via non-genomic mechanisms and (3) inducing genomic- and/or proteomic-based changes in the brain of the host. Changes in host behaviour are often restricted to particular behaviours, with many other behaviours remaining unaffected. Neuroscientists can produce this degree of selectivity by targeting specific brain areas. Parasites, however, do not selectively attack discrete brain areas. Parasites typically induce a variety of effects in several parts of the brain. Parasitic manipulation of host behaviour evolved within the context of the manipulation of other host physiological systems (especially the immune system) that was required for a parasite’s survival. This starting point, coupled with the fortuitous nature of evolutionary innovation and evolutionary pressures to minimize the costs of parasitic manipulation, likely contributed to the complex and indirect nature of the mechanisms involved in host behavioural control. Because parasites and neuroscientists use different tactics to control behaviour, studying the methods used by parasites can provide novel insights into how nervous systems generate and regulate behaviour. Studying how parasites influence host behaviour will also help us integrate genomic, proteomic and neurophysiological perspectives on behaviour.
An overview of parasite-induced behavioral alterations – and some lessons from bats
An animal with a parasite is not likely to behave like a similar animal without that parasite. This is a simple 