Behavioral changes induced by Toxoplasma infection of rodents are highly specific to aversion of cat odors
- 10 April 2007
- journal article
- research article
- Published by Proceedings of the National Academy of Sciences in Proceedings of the National Academy of Sciences of the United States of America
- Vol. 104 (15), 6442-6447
- https://doi.org/10.1073/pnas.0608310104
Abstract
The protozoan parasite Toxoplasma gondii blocks the innate aversion of rats for cat urine, instead producing an attraction to the pheromone; this may increase the likelihood of a cat predating a rat. This is thought to reflect adaptive, behavioral manipulation by Toxoplasma in that the parasite, although capable of infecting rats, reproduces sexually only in the gut of the cat. The “behavioral manipulation” hypothesis postulates that a parasite will specifically manipulate host behaviors essential for enhancing its own transmission. However, the neural circuits implicated in innate fear, anxiety, and learned fear all overlap considerably, raising the possibility that Toxoplasma may disrupt all of these nonspecifically. We investigated these conflicting predictions. In mice and rats, latent Toxoplasma infection converted the aversion to feline odors into attraction. Such loss of fear is remarkably specific, because infection did not diminish learned fear, anxiety-like behavior, olfaction, or nonaversive learning. These effects are associated with a tendency for parasite cysts to be more abundant in amygdalar structures than those found in other regions of the brain. By closely examining other types of behavioral patterns that were predicted to be altered we show that the behavioral effect of chronic Toxoplasma infection is highly specific. Overall, this study provides a strong argument in support of the behavioral manipulation hypothesis. Proximate mechanisms of such behavioral manipulations remain unknown, although a subtle tropism on part of the parasite remains a potent possibility.Keywords
This publication has 35 references indexed in Scilit:
- Maternal presence serves as a switch between learning fear and attraction in infancyNature Neuroscience, 2006
- Implications of increased susceptibility to predation for managing the sylvatic cycle ofEchinococcus multilocularisParasitology, 2006
- Parasites as causative agents of human affective disorders? The impact of anti-psychotic, mood-stabilizer and anti-parasite medication on Toxoplasma gondii 's ability to alter host behaviourProceedings. Biological sciences, 2006
- Parasite manipulation of host behavior: mechanisms, ecology, and future directionsBehavioural Processes, 2005
- The Neuroscience of Mammalian Associative LearningAnnual Review of Psychology, 2005
- Basolateral Amygdala Interacts with Other Brain Regions in Regulating Glucocorticoid Effects on Different Memory FunctionsAnnals of the New York Academy of Sciences, 2004
- Regional dissociations within the hippocampus—memory and anxietyNeuroscience & Biobehavioral Reviews, 2004
- Decreased predator avoidance in parasitized mice: neuromodulatory correlatesParasitology, 1995
- Construction of Permutation TestsJournal of the American Statistical Association, 1990
- Construction of Permutation TestsJournal of the American Statistical Association, 1990