Effects of Malaysian strains of Toxoplasma gondii on behaviours and their possible risk in schizophrenia-like rat model

Toxoplasma gondii (T. gondii) is a protozoan parasite that reside majorly in the brain of its intermediate host. T. gondii infected rodents shows some degree of behaviour deficits, while T. gondii infection in humans is associated with psychiatric problems such as schizophrenia. The present study aimed to evaluate the effects of Malaysian strains of T. gondii on rats. Forty five, four weeks old, male Wistar rats were used. The rats were assigned into five groups: two control groups (CG1 and CG2) and three experimental groups (EG1, EG2, EG3). CG1 rats received phosphate buffered saline (PBS), CG2 received MK-801 (as a model for schizophrenia), EG1, EG2, EG3 received orally 5 x 103 single T. gondii oocysts strain of type I, type II and type III respectively. After infection, all the five groups of rats were tested for T. gondii antibodies at two weeks post-infection (PI). Behavioural tests of exploratory activity (open field) and spatial learning and memory retention (Morris water maze) were performed on the ninth and tenth weeks PI followed by histological staining of rat brain. T. gondii IgM antibodies were detected in EG1, EG2 and EG3, but not in CG1 and CG2. The behaviour results demonstrated that rats from CG2, EG1, EG2 and EG3 had increased in their locomotor activities and memory deficits compared to control, while learning remain intact. Moreover, tissue cysts were found widely distributed exclusively in the whole brain of EG1, EG2 and EG3 without tropism. These findings taken together, implies that Malaysian strains of T. gondii are implicated in some causes of behaviour changes that are responsible for schizophrenia-like conditions if humans were infected.