Abstract
The intracellular protozoal parasite Toxoplasma gondii has been associated with worsened cognitive function in animal models and in humans. Despite these associations, the mechanisms by which Toxoplasma gondii might affect cognitive function remain unknown, although Toxoplasma gondii does produce physiologically active intraneuronal cysts and appears to affect dopamine synthesis. Using data from the UK Biobank, we sought to determine whether Toxoplasma gondii is associated with decreased prefrontal, hippocampal, and thalamic gray-matter volumes and with decreased total gray-matter and total white-matter volumes in an adult community-based sample. The results from adjusted multivariable regression modelling showed no associations between Toxoplasma gondii and prefrontal, hippocampal, and thalamic brain gray-matter volumes. In contrast, natural-log transformed antibody levels against the Toxoplasma gondii p22 (b = -3960, 95-percent confidence interval, -6536 to -1383, p < .01) and sag1 (b = -4863, 95-percent confidence interval, -8301 to -1425, p < .01) antigens were associated with smaller total gray-matter volume, as was the mean of natural-log transformed p22 and sag1 titers (b = -6141, 95-percent confidence interval, -9886 to -2397, p < .01). There were no associations between any of the measures of Toxoplasma gondii and total white-matter volume. These findings suggest that Toxoplasma gondii might be associated with decreased total gray-matter in middle-aged and older middle-aged adults in a community-based sample from the United Kingdom.
Highlights
Infecting approximately one-third of the world’s population [1], the neurotropic intracellular apicomplexan protozoal parasite Toxoplasma gondii can remain in the brain for the life of the host [2]
There were no associations between Toxoplasma gondii seropositivity and serointensity and gray-matter volume in five regions of the prefrontal cortex we evaluated, the hippocampus, and the thalamus
The finding of a negative association between Toxoplasma gondii and total gray-matter volume suggests that changes in gray-matter volume could be a mechanism of the relationship between Toxoplasma gondii and previously reported evidence of abnormal brain function, including worse cognitive functioning
Summary
Infecting approximately one-third of the world’s population [1], the neurotropic intracellular apicomplexan protozoal parasite Toxoplasma gondii can remain in the brain for the life of the host [2]. The definitive hosts for Toxoplasma gondii are members of the cat family, which release oocysts into the environment, from where they can infect humans via contact with cat feces, ingestion of undercooked meat containing Toxoplasma gondii oocysts, or congenital transmission [3]. Some research fails to identify associations of Toxoplasma gondii seropositivity and serointensity with cognitive impairment [4,5,6], and one study even found an association between. Toxoplasma gondii and brain volume been conducted using the UK Biobank Resource under Application Number 41535
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