Correlation of toxoplasmosis with small­for­gestational­age newborns.

BACKGROUND: Toxoplasma gondii infection in pregnant women could lead to significant changes during the pregnancy, affect the outcomes of pregnancy and the timing of labour. Small­for­gestational­age (SGA) newborns are defined by birthweight below the 10th percentile for gestational age. We tested an association between latent toxoplasmosis in pregnant women and deliveries of SGA babies. MATERIAL AND METHODS: For testing, we included 1,647 women who gave birth to a singleton baby at ≥ 37 weeks of gestation. The complement-fixation test (CFT) and enzyme-linked immunosorbent assay (ELISA) tests for IgG and IgM were used. The latent form of toxoplasmosis was defined as a CFT titre of 1:8 or higher, together with index positivity IgG ELISA > 1.1 and negative IgM. RESULTS: There were 406 (24.7 %) women positive, and 1,241 (75.3 %) women negative for latent toxoplasmosis. Of all deliveries. 190 were SGA­positive and 1,457 were SGA­negative. Our study found a statistically significant association between latent toxoplasmosis and SGA foetuses born at term. The Pearson chi-square model was statistically significant (χ2(1) = 7.365, p = .007). The odds ratio was 1.567. CONCLUSION: Pregnant women with latent toxoplasmosis giving birth at ≥ 37 weeks of gestation have a 1.567 times higher risk of delivering an SGA baby (Tab. 2, Fig. 1, Ref. 30).

Serological Diagnostics of Lyme Borreliosis: Comparison of Universal and Borrelia Species-Specific Tests Based on Whole-Cell and Recombinant Antigens.

The study compares diagnostic parameters of different commercial serological kits based on three different antigen types and correlates test results with the status of the patient's Borrelia infection. In total, 8 IgM and 8 IgG kits were tested, as follows: enzyme-linked immunosorbent assay (ELISA) (Euroimmun) based on whole-cell antigen, 3 species-specific enzyme immunoassays (EIAs) (TestLine), Liaison chemiluminescence (DiaSorin), ELISA-Viditest (Vidia), EIA, and Blot-Line (TestLine) using recombinant antigens. All tests were performed on a panel of 90 samples from patients with clinically characterized borreliosis (53 with neuroborreliosis, 32 with erythema migrans, and 5 with arthritis) plus 70 controls from blood donors and syphilis patients. ELISA based on whole-cell antigens has superior sensitivity and superior negative predictive value and serves as an excellent screening test, although its specificity and positive predictive values are low. Species-specific tests have volatile parameters. Their low sensitivity and low negative predictive value handicap them in routine diagnostics. Tests with recombinant antigens are characterized by high specificity and high positive predictive value and have a wide range of use in diagnostic practice. Diagnostic parameters of individual tests depend on the composition of the sample panel. Only a small proportion of contradictory samples giving both negative and positive results is responsible for discrepancies between test results. Correlation of test results with the patient's clinical state is limited, especially in the erythema migrans group with high proportions of negative and contradictory results. In contrast, IgG test results in the neuroborreliosis group, which are more concordant, show acceptable agreement with Borrelia status.

Oral Sex as a Potential Route for Toxoplasma Gondii Transmission: Experiment with Human Semen and Laboratory Mice Model.

PURPOSE: Toxoplasma gondii is one of the most widespread parasites in the human population globally. Several modes of its transmission have been proposed: some are well-researched and confirmed, others remain unconfirmed. One unconfirmed hypothesis pertains to potential transmission of Toxoplasma gondii via oral sex (fellatio) in humans. A recent study found tissue cysts in the semen of men with latent toxoplasmosis. Therefore, we aimed to test the hypothesis of Toxoplasma gondii transmission through oral sex experimentally. METHODS: Eighty-two laboratory mice were orally administered semen samples from 41 men with latent toxoplasmosis. These semen samples were examined for the presence of Toxoplasma gondii DNA using PCR. RESULTS: We detected Toxoplasma gondii DNA in three of the 41 semen samples from men with latent toxoplasmosis. Oral administration of semen samples to laboratory mice did not result in parasite transmission. CONCLUSION: We have not demonstrated the transmission of Toxoplasma to mice by oral exposure to semen from infected men. While this does not conclusively rule out the possibility of such transmission in humans, the results suggest that, if it does occur, this mode of transmission is likely infrequent.

Cognitive Effects of Toxoplasma and CMV Infections: A Cross-Sectional Study of 557 Young Adults Considering Modulation by Sex and Rh Factor.

One-third of humanity harbors a lifelong infection with Toxoplasma gondii, and probably about 80% are infected with human cytomegalovirus (CMV). This study aims to delineate the associations between toxoplasmosis and cognitive abilities and compare these to the associations with CMV. We evaluated the cognitive performance of 557 students, who had been examined for Toxoplasma and CMV infections, using intelligence, memory, and psychomotor tests. The results indicated cognitive impairments in seropositive individuals for both pathogens, with variations in cognitive impact related to sex and the Rh factor. Specifically, Toxoplasma infection was associated with lower IQ in men, whereas CMV was predominantly associated with worse performance by women when testing memory and reaction speeds. Analysis of the antibody concentrations indicated that certain Toxoplasma-associated cognitive detrimental effects may wane (impaired intelligence) or worsen (impaired reaction times) over time following infection. The findings imply that the cognitive impairments caused by both neurotropic pathogens are likely due to pathological changes in the brain rather than from direct manipulative action by the parasites.

Detection of persistent low IgG avidity-an interpretative problem in the diagnosis of acute toxoplasmosis.

OBJECTIVES: For the proper diagnosis of toxoplasmosis it is essential to determine the stage of the infection, for which the most preferred method is IgG avidity test. The avidity index (AI) should initially be low (AI≤0.3) in the acute phase and increase during the infection. However, persistent low avidity can occur in patients with latent toxoplasmosis, which can complicate the interpretation of the results. The aim of the study is to explain the causes of this phenomenon. METHODOLOGY: A retrospective study was carried out with 717 serum samples collected from 442 patients from the categories of pregnant and non-pregnant women, men, and newborns + infants (age < 0.5 year). The trends of AI kinetics were evaluated in repeatedly examined patients. The frequency of cases with low avidity was compared in individual categories of patients and in groups of people with acute and non-acute toxoplasmosis. RESULTS: The proportion of patients with initially low avidity was 42.1% in the acute toxoplasmosis group while it was 13.0% in the non-acute groups. In uninfected newborns with anti-Toxoplasma antibodies transmitted from the mother, a decrease in IgG avidity levels over time was observed, resulting in 29.2% of samples showing low (improper) avidity. While the dynamics of IgG avidity and the frequency of cases of improperly low avidity were similar in men and pregnant and non-pregnant women, the category of newborns and infants differed substantially for these indicators. CONCLUSIONS: Due to acceptable specificity and negative predictive value, high avidity can rule out acute toxoplasmosis, but moderate sensitivity complicates the possibility of its confirmation. The results of the avidity test must be interpreted in the context of the results of other methods.

Toxoplasmosis impact on prematurity and low birth weight.

BACKGROUND: Toxoplasma gondii, one of the most common parasites, causes toxoplasmosis, one of the most frequent zoonotic diseases worldwide. T. gondii infects about one-third of the world's population. T. gondii infection is generally considered a major risk for spontaneous abortion, prematurity and low birth weight in the animal sphere. Less commonly, a toxoplasma serological profile is correlated with the particular data of delivery. Acute T. gondii infection during pregnancy often leads to spontaneous abortion and/or a severe injury of the eyes, brain, and other structures of the foetus. Latent T. gondii infection of pregnant women could lead to less obvious but important changes during pregnancy, including the end product of pregnancy and the timing of labour. This study aimed to contribute to the current knowledge by comparing serological T. gondii profiles of pregnant women with prematurity and low birth weights of newborns. MATERIAL AND METHODS: A retrospective study design was adopted. The study participants included a cohort of 1733 pregnant women who consecutively gave birth to their children and underwent regular antenatal biochemical screening between the 14th and 16th weeks of pregnancy. Prematurity was defined as the liveborn preterm delivery in gestational age of pregnancy <37 weeks. Low birth weight was defined as weight at birth of ≤2499 grams. The complement-fixation test (CFT) provided serological profiles for toxoplasmosis that expresses the overall levels of toxoplasma immunoglobulins of all classes. Enzyme-linked immunosorbent assay (ELISA) tests for IgG and IgM were used simultaneously. IgM positivity helped to differentiate acute from the latent stage of toxoplasmosis. Birth data, especially the week of delivery and fetal weight, were evaluated accordingly. RESULTS: Of the 1733 pregnant women, 25% were diagnosed as latent toxoplasma positive, and 75% as toxoplasma negative. There were 87 premature deliveries versus 1646 timely births. We observed 88 low birth weights and 1645 normal fetal weights. We found a statistically significant association between latent toxoplasmosis and prematurity, χ2(1) = 5.471, p = .019 and between latent toxoplasmosis and low birth weight of newborns, χ2(1) = 7.663, p = .006. There was a 1.707 times higher risk of prematurity for toxoplasma-positive women, while the risk for low birth weight was 1.861 times higher. The strength of both tests of association was mild. We tested the correlation between the levels of CFT titres and week of delivery and weight of newborns. No association was found between the level of latent toxoplasmosis and the week of delivery and fetal weight. CONCLUSION: Latent toxoplasmosis was associated with premature birth rate and lower birth weight of newborns. The odds of premature delivery was 1.7 and low birth weight 1.9 times higher in women with latent toxoplasmosis compared to toxoplasma negative women. Even though the strength of the association in our large sample is relatively mild, the combination of latent toxoplasmosis with other adverse factors could cause serious harm. Whole CFT and specific IgG levels of latent toxoplasmosis are not linked to the severity of prematurity or low birth weight in newborns.

Direct evidence of Toxoplasma-induced changes in serum testosterone in mice.

Latent toxoplasmosis is known to influence the morphology of infected persons and also increases the probability of the birth of male offspring in both humans and mice. All these traits can be related to the observed differences in the concentration of testosterone between Toxoplasma-infected and Toxoplasma-free subjects. However, it is not possible to decide, using the Toxoplasma-human model, whether toxoplasmosis influences the level of testosterone in the infected host or whether individuals with different levels of testosterone vary in the probability of toxoplasma infection. Here we studied changes in the testosterone levels in the latent phase of toxoplasmosis in laboratory mice artificially infected with cystogenic but relatively virulent strain T38 of T. gondii. We observed decreased testosterone levels in both female and male mice with latent toxoplasmosis in comparison to uninfected controls (P=0.001). The present results indicate that Toxoplasma infection changes the concentration of serum testosterone in mice and human rather than changed concentration of testosterone influences the probability of the Toxoplasma infection. It is possible that the decrease of testosterone is an adaptive mechanism of infected mice aimed to compensate toxoplasmosis-induced immunosuppression observed during latent Toxoplasma infection.

Modulation of immunity in mice with latent toxoplasmosis--the experimental support for the immunosuppression hypothesis of Toxoplasma-induced changes in reproduction of mice and humans.

The immunosuppression hypothesis suggests that the increased sex ratio in mice and women with latent toxoplasmosis, retarded embryonic growth in the early phases of pregnancy, prolonged pregnancy of Toxoplasma-infected women, and increased prevalence of toxoplasmosis in mothers of children with Down syndrome can be explained by the presumed immunosuppressive effects of latent toxoplasmosis. Here, we searched for indices of immunosuppression in mice experimentally infected with Toxoplasma gondii. Our results showed that mice in the early phase of latent infection exhibited temporarily increased production of interleukin (IL)-12 and decreased production of IL-10. In accordance with the immunosuppression hypothesis, the mice showed decreased production of IL-2 and nitric oxide and decreased proliferation reaction (synthesis of DNA) in the mixed lymphocyte culture in the early and also in the late phases of latent toxoplasmosis. Since about 30% of the world population are latently infected by T. gondii, the toxoplasmosis-associated immunosuppression might have serious public health consequences.

Pattern of money allocation in experimental games supports the stress hypothesis of gender differences in Toxoplasma gondii-induced behavioural changes.

Latent toxoplasmosis has been previously found to cause behavioural and personality changes in humans, which are specific for each gender. Here we tested the stress hypothesis of these gender differences based on the assumption that latent toxoplasmosis causes long-term subliminal stress. In line with this hypothesis, the gender difference will appear specifically in situations with interpersonal context because in contrast to the typical individualistic coping style of men, women have a tendency to express elevated prosocial behaviour under stress. Altogether 295 biology students (29/191 females and 27/104 males infected by T. gondii) played a modified version of the Dictator Game and the Trust Game. As predicted, a gender difference in the effect of latent toxoplasmosis was found for the measure of reciprocal altruism in the Trust Game (p = 0.016), but both genders appeared less generous when infected in the Dictator Game modified to minimize social connotation (p = 0.048).

Monitoring of kynurenine pathway metabolites, neurotransmitters and their metabolites in blood plasma and brain tissue of individuals with latent toxoplasmosis.

The aim of the presented work was to develop a highly sensitive, accurate and rapid analytical method for the determination of concentration levels of tryptophan and its metabolites of kynurenine catabolic pathway, as well as neurotransmitters and their metabolites in complex biological matrices (brain tissue and blood plasma). The developed analytical method consists of analytes separation from the biological matrices by protein precipitation (blood plasma) or solvent extraction (brain tissue), derivatization of the analytes and their detection by high-performance liquid chromatography combined with mass spectrometry. Individual steps of the whole process were optimized and the method was validated in the terms of selectivity, linearity (R2≥0.980), precision (RSD ≤ 13.3%), recovery (≥82.0%), limit of detection (1.8 ng/mL of blood plasma, 2.2 pg/mg of brain tissue) and limit of quantification (2.5 ng/mL of blood plasma, 2.8 pg/mg of brain tissue). The method was subsequently verified by an animal study, where the concentration levels of the analytes in biological matrices (blood plasma and brain tissue) of T. gondii - infected rats and control animals were compared. All the data obtained from the animal study were statistically evaluated. Increased concentration levels of kynurenine catabolic pathway metabolites (e.g. kynurenine, 3-hydroxykynurenine, quinolinic acid) were observed in the case of T. gondii - infected rats in contrast to the control group. The opposite effect was determined in the case of serotonin and its metabolite 5-hydroxyindoleacetic acid, where higher concentration levels were found in blood plasma of healthy subjects. Finally, Principal Component Analysis (PCA) was utilized for a score plot formation. PCA score plots have demonstrated the similarities of individuals within each group and the differences among the groups.

Universality of indeterminate growth in lizards rejected: the micro-CT reveals contrasting timing of growth cartilage persistence in iguanas, agamas, and chameleons.

Squamate reptiles are considered to exhibit indeterminate growth. Nevertheless, current literature disputes the available definitions of this growth type, presents new theoretical models, and questions its universality in cold-blooded vertebrates. We have followed up on our previous research employing micro-CT to explore growth plate cartilage (GPC) in the epiphysis of long bones, which is responsible for longitudinal skeletal growth by the endochondral ossification process. We focused on numerous and highly diversified group of the Iguania clade comprising Acrodonta (agamas and chameleons) and Pleurodonta ("iguanas"). We recorded the absence of GPC in most of the examined adult Pleurodonta specimens and interpret it as an irreversible arrest of skeletal growth. This finding clearly rejects the universality of indeterminate growth in lizards. On the other hand, we found apparent GPC preservation in most of the adult specimens belonging to Acrodonta. This suggests a preserved ability to continue body growth throughout most of their life. We discuss the uncovered disparity between Acrodonta and Pleurodonta and emphasize the importance of GPC degradation timing.

Triploid Colubrid Snake Provides Insight into the Mechanism of Sex Determination in Advanced Snakes.

The advanced snakes (Caenophidia), the important amniote lineage encompassing more than 3,000 living species, possess highly conserved female heterogamety across all families. However, we still lack any knowledge on the gene(s) and the molecular mechanism controlling sex determination. Triploid individuals spontaneously appear in populations of diploid species and can provide an important insight into the evolution of sex determination. Here, we report a case of spontaneous triploidy in a male of the twin-spotted ratsnake (Elaphe bimaculata) with ZZW sex chromosomes. We speculate that as both ZZ and ZZW individuals develop male gonads, the ratio between the number of Z chromosomes and autosomes, and not the presence of the W chromosome in the genome, drives sex determination in the advanced snakes.

A serological study of antibodies to Anaplasma phagocytophilum and Borrelia burgdorferi sensu lato in the sera of healthy individuals collected two decades apart.

Sera collected from healthy individuals from the general population in the Czech Republic during repeated cross-sectional surveys were analyzed. Samples collected in the same six districts in two time periods, 1978-1989 and 2001, were compared. The study subjects were divided into six age categories between 10 and 59 years. Overall, 434 samples from 1978-1989 and 270 samples from 2001 were screened for Anaplasma phagocytophilum (AP) and Borrelia burgdorferi sensu lato (BB). The anti-AP positivity rates were 13.1% and 11.5% in the first and second period, respectively, and did not differ significantly between the periods (P = 0.559). The anti-BB antibodies were detected in 33.9% and 14.8% of study subjects, respectively. The positivity rates were significantly lower in the second period (P<0.001). No considerable changes were observed in the sex distribution of positive findings between the two periods. The highest positivity rates of anti-AP antibodies were found in the 10-14 year age group: 16.0% in 1978-1989 and 16.7% in 2001. The age distribution of the anti-AP antibody positivity rates did not change substantially (P = 0.872). In 1978-1989, the lowest anti-BB antibody positivity rate (26.7%) was found in the 10-14 year age group, with a gradual increase with age to 41.1% in 50-59 year-olds. In 2001, the positivity rate in the 10-14 year age group was 26.2% and was not significantly different from that in the first period (P = 0.955). However, the positivity rates in the older age groups 15-59 years decreased significantly (P<0.001) and varied between 8.3% and 15.1%.

Gender differences in behavioural changes induced by latent toxoplasmosis.

There is growing evidence that the protozoan Toxoplasma gondii modifies behaviour of its intermediate hosts, including humans, where it globally infects about 20-60% of the population. Although it is considered asymptomatic in its latent stage, it was previously found to have remarkable and gender different effects on the personality factors A (warmth), G (rule consciousness), L (vigilance, mistrust) and Q3 (self-control, self-image) from Cattell's 16PF Questionnaire. We performed a double blind experiment testing 72 and 142 uninfected men and women, respectively, and 20 and 29 infected men and women, respectively, in order to verify these gender differences using behavioural experiments. Our composite behavioural variables Self-Control and Clothes Tidiness (analogue to the 16PF factors G--conscientiousness and Q3--self-control) showed a significant effect of the toxoplasmosis-gender interaction with infected men scoring significantly lower than uninfected men and a trend in the opposite direction in women. The effect of the toxoplasmosis-gender interaction on our composite behavioural variable Relationships (analogue to factor A--warmth) approached significance; infected men scored significantly lower than uninfected men whereas there was no difference in women. In the composite behavioural variable Mistrust (analogue to factor L), the pattern was affected by environment (rural versus urban). Possible interpretations of the gender differences are discussed.

Short-term stability of Borrelia garinii in cerebrospinal fluid.

The aim of our study was to find out the optimal conditions for short-term storage of cerebrospinal fluid (CSF) samples for direct diagnosis of Lyme disease. A mixture of Borrelia-negative CSFs spiked with a defined amount of cultured Borrelia garinii was used. Borrelia stability was investigated over 7 days at four different temperatures [room temperature (RT), +4, -20 and -70 °C]. Quantitative changes in CSF Borrelia were measured by quantitative PCR (qPCR), and morphological changes in the spirochetes were observed by transmission electron microscopy (TEM). These qPCR results were statistically evaluated. We found +4 °C to be an optimal temperature for short-term storage of CSF samples intended for TEM observation. There was no significant difference between the temperatures tested in the average quantity of Borrelia measured by qPCR. On the contrary, electron optical diagnosis of frozen samples and samples stored at RT showed destructive morphological changes and decreased spirochete counts. Our results show that optimal conditions for the pre-analytical phase of investigation of one type of material can differ depending on the diagnostic method employed.

Influence of latent 'asymptomatic' toxoplasmosis on body weight of pregnant women.

The latent toxoplasmosis is usually considered to be asymptomatic, however, this paradigm has never been rigorously tested. Here we searched for symptoms of deterioration of physical health (decrease of weight) in infected people by analysis of clinical records of 758 women tested for toxoplasmosis in the 16th week of gravidity. Toxoplasma-positive women have a lower body weight in the 16th week of gravidity (p = 0.02) than Toxoplasma-negative women. Moreover, a negative correlation between weight and the duration of toxoplasmosis was found in a subset of 174 Toxoplasma-positive women (p = 0.04), suggesting that slow and cumulative effects of latent toxoplasmosis, rather than a transient effect of acute toxoplasmosis, are responsible for the decreased weight of infected subjects. Longer duration of gravidity estimated from the date of last menstruation in the set of Toxoplasma-positive women in the 16th week of gravidity estimated with ultrasonography (p = 0.04) suggests a possibility of retarded foetal growth in Toxoplasma-positive women. The prevalence of latent toxoplasmosis is extremely high. Therefore, even its mild symptoms such as the decreased body weight in Toxoplasma-positive pregnant women might in fact indicate an unrecognized serious public health problem.

The Effect of Latent Toxoplasma gondii Infection on the Immune Response in HIV-Infected Patients.

A relationship between latent toxoplasmosis and the immune system during HIV disease is poorly understood. Therefore, the aim of this follow-up study was to characterize immunological parameters in HIV-infected patients with latent toxoplasmosis and noninfected individuals. A total of 101 HIV-infected patients were enrolled in the study. The patients were classified into two groups based on anti-Toxoplasma gondii antibodies: a group of 55 toxoplasma-positive persons (TP) and a group of 46 toxoplasma-negative persons (TN). Absolute counts of several lymphocyte subsets decreased in the TP group, namely, T cells (p = 0.007), B cells (p = 0.002), NK cells (p = 0.009), CD4 T cells (p = 0.028), and CD8 T cells (p = 0.004). On the other hand, the percentage of CD8 T cells expressing CD38 and HLA-DR significantly increased during the follow-up in the TP group (p = 0.003, p = 0.042, resp.) as well as the intensity of CD38 and HLA-DR expression (MFI) on CD8 T cells (p = 0.001, p = 0.057, resp.). In the TN group, analysis of the kinetics of immunological parameters revealed no significant changes over time. In conclusion, the results suggest that latent T. gondii infection modulates the immune response during HIV infection.

Increased risk of traffic accidents in subjects with latent toxoplasmosis: a retrospective case-control study.

BACKGROUND: The parasite Toxoplasma gondii infects 30-60% of humans worldwide. Latent toxoplasmosis, i.e., the life-long presence of Toxoplasma cysts in neural and muscular tissues, leads to prolongation of reaction times in infected subjects. It is not know, however, whether the changes observed in laboratory influence the performance of subjects in real-life situations. METHODS: The seroprevalence of latent toxoplasmosis in subjects involved in traffic accidents (N=146) and in the general population living in the same area (N=446) was compared by a Mantel-Haenszel test for age-stratified data. Correlation between relative risk of traffic accident and a level of anti-Toxoplasma antibody titre was evaluated with the Cochran-Armitage test for trend. RESULTS: A higher seroprevalence was found in the traffic accident set than in the general population (Chi2MH=21.45, p<0.0001). The value of the odds ratio (OR) suggests that subjects with latent toxoplasmosis had a 2.65 (C.I.95= 1.764.01) times higher risk of an accident than the toxoplasmosis-negative subjects. The OR significantly increased with level of anti-Toxoplasma antibody titre (p<0.0001), being low (OR=1.86, C.I.95=1.14-3.03) for the 99 subjects with low antibody titres (8 and 16), higher (OR=4.78, C.I.95=2.39-9.59) for the 37 subjects with moderate titres (32 and 64), and very high (OR=16.03, C.I.95=1.89-135.66) for the 6 subjects with titres higher than 64. CONCLUSION: The subjects with latent toxoplasmosis have significantly increased risk of traffic accidents than the noninfected subjects. Relative risk of traffic accidents decreases with the duration of infection. These results suggest that 'asymptomatic' acquired toxoplasmosis might in fact represent a serious and highly underestimated public health as well as economic problem.

Decreased level of psychobiological factor novelty seeking and lower intelligence in men latently infected with the protozoan parasite Toxoplasma gondii Dopamine, a missing link between schizophrenia and toxoplasmosis?

Toxoplasma gondii, a parasitic protozoan, infects about 30-60% of people worldwide. The latent toxoplasmosis, i.e. life-long presence of cysts in the brain and muscular tissues, has no effect on human health. However, infected subjects score worse in psychomotor performance tests and have different personality profiles than Toxoplasma-negative subjects. The mechanism of this effect is unknown; however, it is supposed that presence of parasites' cysts in the brain induces an increase of the concentration of dopamine. Here we search for the existence of differences in personality profile between Toxoplasma-positive and Toxoplasma-negative subjects by testing 857 military conscripts using a modern psychobiological questionnaire, namely with Cloninger's Temperament and Character Inventory (TCI). ANCOVA showed that Toxoplasma-positive subjects had lower Novelty seeking (NS) scores (P=0.035) and lower scores for three of its four subscales, namely Impulsiveness (P=0.049), Extravagance (P=0.056) and Disorderliness (P=0.006) than the Toxoplasma-negative subjects. Differences between Toxoplasma-negative and positive subjects in NS was inversely correlated with duration of toxoplasmosis estimated on the basis of concentration anti-Toxoplasma antibodies (P=0.031). Unexpectedly, the infected subjects had also lower IQ (P(2)=0.003) and lower probability of achieving a higher education (P(2)<0.0000). Decrease of NS suggests that the increase of dopamine in brain of infected subjects can represent a missing link between toxoplasmosis and schizophrenia.