Latent toxoplasmosis and olfactory functions of Rh positive and Rh negative subjects

Abstract

Backgrounds: The prevalence of toxoplasmosis is higher in schizophrenics than in the general population. It has been suggested that certain symptoms of schizophrenia, including changes in olfactory functions, are in fact symptoms of toxoplasmosis that can be easily detected in schizophrenics only due to the increased prevalence of toxoplasmosis in this population. Schizophrenics have impaired identification of odors and lower sensitivity of odor detection, however, no information about these parameters of non-schizophrenic Toxoplasma-infected subjects is available.

Methods: Here we searched for differences in olfactory functions between 62 infected and 61 noninfected non-schizophrenic subjects using the case-controls experimental design.

Results: The infected men scored better than the non-infected controls in the standard odor-identification test. The infected women rated all smells as more intensive while the infected men rated nearly all smells as less intensive. Infected women rated the pleasantness of the smell of the cat urine as higher than the non-infected women and the opposite was true for the men-in contrast, higher pleasantness of odor in infected men and lower in infected women were observed and described in the 2011 study. Toxoplasmosis, Rh, and toxoplasmosis-Rh interaction were not associated with the rated pleasantness of the smell of other stimuli. However, our sample contained only 17 Rh negative men and 30 Rh negative women. Therefore, all results concerning the main effects of Rh factor and the interaction with Rh factor must be considered only preliminary.

Conclusions: Our results suggest that latent toxoplasmosis is associated with changes in the olfactory functions in humans; however, the observed changes differ from those observed in schizophrenics.

Fig 1. Differences of abilities to recognize odors in the Toxoplasma-free and Toxoplasma-infected subjects.

The error bars show 95% confidence intervals, the numbers the results of ANCOVA test–the association between toxoplasmosis and performance of subjects in particular tests.

Fig 2. Difference in the intensities of smells attributed by women and men to particular odors.

The error bars show 95% confidence intervals, the numbers the results of ANCOVA test–the p-value of the association of toxoplasmosis with the reported intensity of smell of particular samples. No result remained significant after the correction for multiple tests.

Fig 3. Difference in pleasantness attributed to particular odors by Toxoplasma-free and Toxoplasma-infected raters.

The figure shows mean pleasantness of odors in arbitrary units measured as the responses of the raters to the question “How pleasurable would it be to use perfume containing this ingredient and to smell like this?” (graphic scale, 9 cm). The spreads shows 95% confidence interval, the numbers the results of ANCOVA test–the p-value of the association of toxoplasmosis with the reported pleasantness of smell of particular samples. No result remained significant after the correction for multiple tests.

Fig 4. Pleasantness of odors estimated by the chromassociation method.

The figure shows mean pleasantness of color (scale 1–12) attributed by the individual raters to particular odor. The spreads shows 95% confidence interval, the numbers the results of ANCOVA test–the p-value of the association of toxoplasmosis with the pleasantness of smell of particular samples measured with the chromassociation method. No result remained significant after the correction for multiple tests.