Toxoplasma gondii induced shift in decision making and impulsive behaviours in infected male rats (Rattus novergicus)

• Main Author: Tan, Donna
• Other Authors: Ajai Vyas
• Format: Theses and Dissertations
• Language: English
• Published: 2015
• Subjects: DRNTU::Science::Biological sciences::Zoology::Animal behavior
• Online Access: https://hdl.handle.net/10356/65721
• Institution: Nanyang Technological University

Rats infected with Toxoplasma gondii lose their innate aversion to cat odours and instead develop an atypical attraction to cat urine. This phenomenon has been used widely as a model system for behavioural manipulation hypothesis. This hypothesis posits a naturally selected ability of the parasites to change host behaviour in ways that are beneficial for parasite transmission but detrimental to the host itself. The dominant narrative in this regard posits that Toxoplasma gondii changes fear response of the host, in order to increase parasite transmission to its definitive felid hosts. Yet, fear of predators is not a monolithic behavioural construct. It instead exists in a continuum with approach behaviours due to constant weighing of options required in an ambivalent and probabilistic environment. In this framework, I demonstrate that Toxoplasma gondii infection alters decision making in infected rats by instituting more impulsive, delay-averse and risk-seeking choices. In addition, I show concomitant changes in mesolimbic dopamine system that might underlie this behavioural shift. Finally, I extend these observations by linking observed behavioural changes to the endocrine environment akin to those observed during Toxoplasma gondii infection. These observations suggest that changes in host behaviour post-infection are part of a wider behavioural syndrome that targets negotiation of trade-offs between the current and residual fitness of animals.