Infection of male rats with Toxoplasma gondii induces effort-aversion in a T-maze decision-making task

• Rats with Toxoplasma gondii infection show greater effort aversion.
• This effect is restricted to chronic phase of the infection.
• This effect is congruent with atrophy of basolateral amygdala previously reported.

Rats chronically infected with protozoan Toxoplasma gondii exhibit greater delay aversion in an inter-temporal task. Moreover T. gondii infection also results in dendritic atrophy of basolateral amygdala neurons. Basolateral amygdala is reported to bias decision making towards greater effortful alternatives. In this context, we report that T. gondii increases effort aversion in infected male rats. This host–parasite association has been widely studied in the context of loss of innate fear in the infected males. It is suggested that reduced fear towards predators reflects a parasitic behavioral manipulation to enhance trophic transmission of T. gondii. Observations reported here extend this paradigm away from a monolithic change in fear and towards a multi-dimensional change in decision making.