Toxoplasmosis: A pathway to neuropsychiatric disorders

•Toxoplasma gondii is a pervasive human pathogen and alters host behaviour.•Neuro-immune interaction is an emerging field that has widespread public health implications.•The effect of pathogenic infections on mental health can be varied and subtle.•Molecular links need to be established to develop effective therapies in clinic. Toxoplasma gondii is an obligate intracellular parasite that resides, in a latent form, in the human central nervous system. Infection with Toxoplasma drastically alters the behaviour of rodents and is associated with the incidence of specific neuropsychiatric conditions in humans. But the question remains: how does this pervasive human pathogen alter behaviour of the mammalian host? This fundamental question is receiving increasing attention as it has far reaching public health implications for a parasite that is very common in human populations. Our current understanding centres on neuronal changes that are elicited directly by this intracellular parasite versus indirect changes that occur due to activation of the immune system within the CNS, or a combination of both. In this review, we explore the interactions between Toxoplasma and its host, the proposed mechanisms and consequences on neuronal function and mental health, and discuss Toxoplasma infection as a public health issue.