Predictors of Toxoplasma gondii infection in Czech and Slovak populations: the possible role of cat-related injuries and risky sexual behavior in the parasite transmission.

The protozoan Toxoplasma gondii infects about one-third of the world's population. The consumption of raw meat, contact with cats, contact with soil, and ingestion of food or water contaminated with soil are considered to be the most important sources of infection. Still in most women who were infected during pregnancy, no definitive source of infection is found. In 2014-2016, independent sources of T. gondii infection were searched for by gathering epidemiological data from 1865 (519 infected) responders. Touching garden soil (odds ratio (OR) 3·14, 95% confidence interval (CI) 1·3-6·35), sustaining cat-related injuries (OR 2·16, 95% CI 1·25-3·74), and eating improperly washed root vegetables (OR 1·71, 95% CI 1·02-2·87), but not risky sexual behavior (OR 1·22, 95% CI 0·79-1·90), were the predictors of infection. The seroprevalence of T. gondii infection had been increasing up to ages 35-50 in men and ages 50-54 in women. Past those ages, seroprevalence of toxoplasmosis has been decreasing. This suggests that the natural decrease of anamnestic antibodies concentrations over time leads to positivity-to-negativity seroconversion in many subjects. If this is true, then the prevalence of T. gondii infection in a general population and its potential impacts on public health could be much larger than generally believed.

Impaired health status and increased incidence of diseases in Toxoplasma-seropositive subjects - an explorative cross-sectional study.

The global seroprevalence of latent toxoplasmosis is estimated to be higher than 30%. The presence of slowly dividing parasites in tissue cysts located mainly in immunoprivileged organs was long considered asymptomatic. Recently, many studies have shown that latent Toxoplasma infections could have serious impacts on human health. Here we ran a cross-sectional study in a population of 1486 volunteers. The results showed that 333 infected subjects scored worse than 1153 controls in 28 of 29 health-related variables. Similarly, they reported higher rates of 77 of a list of 134 disorders reported by at least 10 participants of the study. Toxoplasmosis was associated most strongly with musculoskeletal (τ = 0·107, P < 0·0005), followed by neurological (τ = 0·088, P < 0·0005), immune (τ = 0·085, p < 0·0005), metabolic (τ = 0·079, P < 0·0005), respiratory (τ = 0·068, P = 0·0001), allergic (τ = 0·053, P = 0·004), digestive system (τ = 0·052, P = 0·004) and mental health disorders (τ = 0·050, P = 0·008). Results of the present cohort study, along with the previous data from many case-control studies or ecological studies suggest that latent toxoplasmosis represents a large and so far underrated public health problem.

Differences in onset of disease and severity of psychopathology between toxoplasmosis-related and toxoplasmosis-unrelated schizophrenia.

OBJECTIVE: Toxoplasmosis is a lifelong parasitic disease that appears to be associated to schizophrenia. However, no distinguishing attributes in Toxoplasma-infected schizophrenia patients have been described as yet. METHOD: We searched for differences in symptom profile, cognitive performance and treatment response between 194 Toxoplasma-free and 57 (22.7%) Toxoplasma-infected schizophrenia patients treated in Prague Psychiatric Centre between 2000 and 2010. RESULTS: Infected and non-infected patients differed in severity of symptoms (P = 0.032) measured with the Positive and Negative Symptom Scale (PANSS). Infected patients scored higher in positive subscale of PANSS, but not in the general and negative subscales. Infected men scored higher also in Total PANSS score, and negative, reality distortion, disorganisation and cognitive scores. Higher PANSS scores of positive, negative and disorganised psychopathology were associated with the lower titres of anti-Toxoplasma antibodies suggesting that psychopathology deteriorates with duration of parasitic infection. Infected patients remained about 33 days longer in hospital during their last admission than uninfected ones (P = 0.003). Schizophrenia started approximately 1 year earlier in infected men and about 3 years later in infected women, no such difference was observed in uninfected subjects. CONCLUSION: Latent toxoplasmosis in schizophrenia may lead to more severe positive psychopathology and perhaps less favourable course of schizophrenia.

Increased pregnancy weight gain in women with latent toxoplasmosis and RhD-positivity protection against this effect.

OBJECTIVE: RhD-positive subjects are protected against toxoplasmosis-associated impairment of psychomotor performance. Here we searched for RhD-positivity-associated maternal protection against the effects of toxoplasmosis. METHODS: In the present retrospective cohort study, we analysed data from 785 (139 RhD-negative) Toxoplasma-free and 194 (27 RhD-negative) Toxoplasma-infected pregnant women. We searched for effects of toxoplasmosis and Rhd-phenotype on maternal weight before pregnancy, pregnancy weight gain, fetal ultrasound data (biparietal diameter, abdominal circumference, femur length) and on birth length and weight. RESULTS: At pregnancy week 16, the RhD-negative mothers with toxoplasmosis gained more weight than others (P < 0.001). The difference of about 1600 g remained approximately constant from pregnancy week 16 until the end of pregnancy. Neither toxoplasmosis nor RhD phenotype had any effect on fetal bioparameter data or birth length and weight. CONCLUSION: The most parsimonious explanation for the observed data is that the RhD-positive phenotype might protect infected subjects against a broad spectrum of detrimental effects of latent toxoplasmosis, including excessive gestational weight gain.

Oral sex: A new, and possibly the most dangerous, route of toxoplasmosis transmission.

Toxoplasmosis is a parasitic disease widespread in the temperate zone. The definitive hosts of Toxoplasma gondii, which causes the disease, are cats. All warm-blooded vertebrates, including humans, can be intermediate hosts. A person is usually infected by ingesting oocysts, e.g. by consuming along with vegetables some contaminated soil, by drinking contaminated water, or by ingesting tissue cysts contained, for instance, in poorly cooked meat. Less common is congenital transmission or transmission via organ transplant from an infected donor. Recently, it has been suggested that toxoplasmosis could also be transmitted sexually from infected men to uninfected women. In this article, we discuss and present evidence for an alternative hypothesis, which suggests that toxoplasmosis could be transmitted by oral sex (via fellatio) from an infected man to an uninfected person (male or female), especially if the uninfected individual swallows the infected ejaculate. This hypothesis finds support in the following facts and findings: (1) Toxoplasma has been found in male ejaculate. (2) In several animal species, presence of the parasite in the seminal fluid of infected males can lead to infection of uninfected females during mating. (3) A higher prevalence of toxoplasmosis has been reported in both homosexuals and promiscuous individuals, i.e. in populations which practice a broader spectrum of sexual activities, including oral sex. (4) In heterosexual couples, a partner's infection seems to be a risk factor for infection in women but not in men. (5) A higher prevalence of toxoplasmosis in females compared to males has been observed in adolescents aged 10 to 14, where oral sex, including fellatio, is highly prevalent among those who have not yet engaged in penetrative intercourse. (6) On a theoretical level, one could expect that when an uninfected person swallows ejaculate containing Toxoplasma tissue cysts, this results in a similar infection pattern to ingestion of Toxoplasma-contaminated undercooked meat. (7) Approximately two-thirds of Toxoplasma infections in pregnant women cannot be explained by any of the known risk factors. (8) In both women and men who report practicing fellatio with men, there is a higher prevalence of toxoplasmosis than in corresponding controls. If our hypothesis is correct, an effective public health campaign with emphasis on early sexual education about the risks of unprotected oral sex will be necessary, especially in pregnant women and HIV-positive people. This route of toxoplasmosis transmission could be experimentally verified by force-feeding laboratory mice with the ejaculate of infected men.

Sex-dependent toxoplasmosis-associated differences in testosterone concentration in humans.

Several lines of indirect evidence suggest that subjects with latent infection of the coccidian parasite Toxoplasma gondii have a higher concentration of testosterone than uninfected controls. Here, we searched for direct evidence of latent toxoplasmosis-associated differences in testosterone concentration among a population of 174 female and 91 male students screened for Toxoplasma infection. We have found Toxoplasma-infected men to have a higher concentration of testosterone and Toxoplasma-infected women to have a lower concentration of testosterone than Toxoplasma-free controls. The opposite direction of the testosterone shift in men compared to women can explain the observed gender specificity of behavioural shifts in Toxoplasma-infected subjects.

Toxoplasma and reaction time: role of toxoplasmosis in the origin, preservation and geographical distribution of Rh blood group polymorphism.

The RhD protein which is the RHD gene product and a major component of the Rh blood group system carries the strongest blood group immunogen, the D-antigen. This antigen is absent in a significant minority of the human population (RhD-negatives) due to RHD deletion or alternation. The origin and persistence of this RhD polymorphism is an old evolutionary enigma. Before the advent of modern medicine, the carriers of the rarer allele (e.g. RhD-negative women in the population of RhD-positives or RhD-positive men in the population of RhD-negatives) were at a disadvantage as some of their children (RhD-positive children born to pre-immunized RhD-negative mothers) were at a higher risk of foetal or newborn death or health impairment from haemolytic disease. Therefore, the RhD-polymorphism should be unstable, unless the disadvantage of carriers of the locally less abundant allele is counterbalanced by, for example, higher viability of the heterozygotes. Here we demonstrated for the first time that among Toxoplasma-free subjects the RhD-negative men had faster reaction times than Rh-positive subjects and showed that heterozygous men with both the RhD plus and RhD minus alleles were protected against prolongation of reaction times caused by infection with the common protozoan parasite Toxoplasma gondii. Our results suggest that the balancing selection favouring heterozygotes could explain the origin and stability of the RhD polymorphism. Moreover, an unequal prevalence of toxoplasmosis in different countries could explain pronounced differences in frequencies of RhD-negative phenotype in geographically distinct populations.

New and old risk-factors for Toxoplasma gondii infection: prospective cross-sectional study among military personnel in the Czech Republic.

The aims of this study were to evaluate seroprevalence and the importance of various risk-factors for Toxoplasma infection in the Czech Republic. A prospective cross-sectional survey was conducted among military personnel in Prague. Consenting subjects (n = 3250) completed a questionnaire concerning demographics and risk-factors, and blood samples were taken to determine anti-Toxoplasma antibody titres according to complement fixation and ELISA IgG and IgM tests. The seroprevalence of toxoplasmosis was 23%. In multivariate analysis, independent predictors of Toxoplasma seropositivity were age (OR 1.03 / year), consumption of raw meat (OR 1.35), owning a cat (OR 1.25), owning rabbits (OR 1.47), childhood residence in a town with a population of <10 000 inhabitants (OR 1.63) vs. location of the childhood residence in a town with population of >100 000 inhabitants, and blood group type A (OR 1.28), B (OR 1.33) or AB (OR 1.43) vs. O. These results suggested that horizontal toxoplasmosis transmission in the Czech Republic may occur through consumption of raw meat, contact with cat faeces and farming.

Toxoplasma-infected subjects report an Obsessive-Compulsive Disorder diagnosis more often and score higher in Obsessive-Compulsive Inventory.

BACKGROUND: Latent toxoplasmosis, the life-long presence of dormant stages of Toxoplasma in immunoprivileged organs and of anamnestic IgG antibodies in blood, affects about 30% of humans. Infected subjects have an increased incidence of various disorders, including schizophrenia. Several studies, as well as the character of toxoplasmosis-associated disturbance of neurotransmitters, suggest that toxoplasmosis could also play an etiological role in Obsessive-Compulsive Disorder (OCD). METHODS: The aim of the present cross-sectional study performed on a population of 7471 volunteers was to confirm the association between toxoplasmosis and OCD, and toxoplasmosis and psychological symptoms of OCD estimated by the standard Obsessive-Compulsive Inventory-Revised (OCI-R). RESULTS: Incidence of OCD was 2.18% (n=39) in men and 2.28% (n=83) in women. Subjects with toxoplasmosis had about a 2.5 times higher odds of OCD and about a 2.7 times higher odds of learning disabilities. The incidence of 18 other neuropsychiatric disorders did not differ between Toxoplasma-infected and Toxoplasma-free subjects. The infected subjects, even the OCD-free subjects, scored higher on the OCI-R. LIMITATIONS: Examined subjects provided the information about their toxoplasmosis and OCD statuses themselves, which could result in underrating the strength of observed associations. CONCLUSIONS: The results confirmed earlier reports of the association between toxoplasmosis and OCD. They also support recent claims that latent toxoplasmosis is in fact a serious disease with many impacts on quality of life of patients.

Registered Replication Report: Rand, Greene, and Nowak (2012).

In an anonymous 4-person economic game, participants contributed more money to a common project (i.e., cooperated) when required to decide quickly than when forced to delay their decision (Rand, Greene & Nowak, 2012), a pattern consistent with the social heuristics hypothesis proposed by Rand and colleagues. The results of studies using time pressure have been mixed, with some replication attempts observing similar patterns (e.g., Rand et al., 2014) and others observing null effects (e.g., Tinghög et al., 2013; Verkoeijen & Bouwmeester, 2014). This Registered Replication Report (RRR) assessed the size and variability of the effect of time pressure on cooperative decisions by combining 21 separate, preregistered replications of the critical conditions from Study 7 of the original article (Rand et al., 2012). The primary planned analysis used data from all participants who were randomly assigned to conditions and who met the protocol inclusion criteria (an intent-to-treat approach that included the 65.9% of participants in the time-pressure condition and 7.5% in the forced-delay condition who did not adhere to the time constraints), and we observed a difference in contributions of -0.37 percentage points compared with an 8.6 percentage point difference calculated from the original data. Analyzing the data as the original article did, including data only for participants who complied with the time constraints, the RRR observed a 10.37 percentage point difference in contributions compared with a 15.31 percentage point difference in the original study. In combination, the results of the intent-to-treat analysis and the compliant-only analysis are consistent with the presence of selection biases and the absence of a causal effect of time pressure on cooperation.

Concordance between genetic relatedness and phenotypic similarities of Trichomonas vaginalis strains.

BACKGROUND: Despite the medical importance of trichomoniasis, little is known about the genetic relatedness of Trichomonas vaginalis strains with similar biological characteristics. Furthermore, the distribution of endobionts such as mycoplasmas or Trichomonas vaginalis virus (TVV) in the T. vaginalis metapopulation is poorly characterised. RESULTS: We assayed the relationship between 20 strains of T. vaginalis from 8 countries using the Random Amplified Polymorphic DNA (RAPD) analysis with 27 random primers. The genealogical tree was constructed and its bootstrap values were computed using the program FreeTree. Using the permutation tail probability tests we found that the topology of the tree reflected both the pattern of resistance to metronidazole (the major anti-trichomonal drug) (p < 0.01) and the pattern of infection of strains by mycoplasmas (p < 0.05). However, the tree did not reflect pattern of virulence, geographic origin or infection by TVV. Despite low bootstrap support for many branches, the significant clustering of strains with similar drug susceptibility suggests that the tree approaches the true genealogy of strains. The clustering of mycoplasma positive strains may be an experimental artifact, caused by shared RAPD characters which are dependent on the presence of mycoplasma DNA. CONCLUSIONS: Our results confirmed both the suitability of the RAPD technique for genealogical studies in T. vaginalis and previous conclusions on the relatedness of metronidazol resistant strains. However, our studies indicate that testing analysed strains for the presence of endobionts and assessment of the robustness of tree topologies by bootstrap analysis seem to be obligatory steps in such analyses.

Correlation of duration of latent Toxoplasma gondii infection with personality changes in women.

Many parasites induce characteristic changes in behavior of their hosts. In humans latent toxoplasmosis is associated with changes in personality profiles. It has been already shown that a decrease in superego strength is correlated with duration of toxoplasmosis in men. Here we studied changes in personality profiles with Cattell's 16 PF questionnaire in Toxoplasma-infected women. The changes were measured as differences in personality factors between Toxoplasma-infected subjects and uninfected controls of the same age. The low-rate changes were studied in 230 women diagnosed with acute toxoplasmosis during past 14 years. The results showed the correlation between duration of toxoplasmosis and level of factors G (high superego strength) and Q3 (high strength of self sentiment). The high-rate changes were estimated by measuring the correlation between level of Toxoplasma-antibody titers (which rapidly decline after the end of acute phase of toxoplasmosis) and personality factors in an experimental set of 55 young mothers with latent toxoplasmosis. Again, certain factors, namely A (affectothymia), F (surgence), G (high superego strength), H (parmia), and L (protension), correlated with the length of the infection. We suggest that the parasite induced the changes in the personality profiles of the women because of our observation of an increasingly different personality profile over time between women with latent infection and controls. The same evidence questions the view that women with a particular personality profile are more prone to acquisition of T. gondii infection.

Does a cell perform isoelectric focusing?

A model of intracellular electrical sorting of enzymes and organelles in the cytosol, based on isoelectric focusing, is proposed. The focusing is suggested to take place over a centrally symmetric pH gradient which in the cytosol of the yeast Saccharomyces cerevisiae is known to be 7.2-6.4. From published data on the energetic capacity and from the computed electric resistance of the S. cerevisiae cell, the maximum value of the electric field that can be maintained in the cytosol was estimated. The results showed that the strength of a centrally symmetric intracytosolic electric field could be as high as 90 mV/cm, which is sufficient to account for sorting of cytosolic proteins according to their isoelectric points. Although direct experimental evidence for intracellular isoelectric focusing is still missing, several phenomena of physiological importance can be understood on the assumption of its real existence.

Transient nature of Toxoplasma gondii-induced behavioral changes in mice.

Many parasites induce specific changes in host behavior that promote the transmission of their infective stages between hosts. Toxoplasmosis in rodents is known to be accompanied by specific behavioral changes (shift in activity level, learning capacity, and novelty discrimination) that can theoretically increase the chance of infected animals being eaten by the definitive host, the cat. However, toxoplasmosis is also accompanied by many pathological symptoms. It is not known whether the behavioral changes are products of manipulation activity of the parasite or only nonspecific by-products of pathological symptoms of toxoplasmosis. Here, we compared the dynamics of development of behavioral and pathological changes in Toxoplasma gondii-infected mice. The results showed that the maximum reduction of mouse activity corresponded with the peak of pathological symptoms, and also that maximum increase of reaction times corresponded with the peak of development of tissue cysts in the brains of infected mice. Behavioral changes were only transient and disappeared before the 12th wk postinoculation. The results suggest that the behavioral changes in infected mice reported by many authors and observed in our experiments could be nonspecific by-products of pathological symptoms of toxoplasmosis rather than specific products of manipulation activity by the parasite.

Free-Tree--freeware program for construction of phylogenetic trees on the basis of distance data and bootstrap/jackknife analysis of the tree robustness. Application in the RAPD analysis of genus Frenkelia.

The Win95 program for computation of distance matrixes and construction of phylogenetic or phenetic trees on the basis of RAPD, RFLP and allozyme data was presented. In contrast with other presently available software, the program FreeTree can also assess the robustness of the tree topology by bootstrap, jackknife or OTU-jackknife analysis. Moreover, the program can be used also for an analysis of data obtained in several independent experiments performed with nonidentical subsets of taxa. The function of the program was demonstrated by an analysis of RAPD data from 22 strains of Frenkelia. The program is available as an autoextractive archive containing the installation files of FreeTree and TreeView, manual in MS Word format and a sample of the input file at http://www.natur.cuni.cz/flegr/programs/+ ++freetree.

Influence of chronic toxoplasmosis on some human personality factors.

An effect of parasites on host behaviour was tested on the toxoplasma-human model. Three hundred and thirty-eight (338) people were assessed with Cattell's personality questionnaire and then tested for Toxoplasma gondii infection with a delayed type hypersensitivity test for Toxoplasma. A highly significant correlation between chronic toxoplasmosis and two personality factors (G-Low Superego Strength and L-Protension) was found (p = 0.0032 and 0.0020, respectively). A correlation of the intensity of the personality factor-shifts with the duration of the infection (estimated from antibody titer) suggests that toxoplasmosis induces the shift in human personality, rather than the personality factors G and L influence an acquisition rate of Toxoplasma gondii infection.

Changes in the personality profile of young women with latent toxoplasmosis.

Latent toxoplasmosis is the most widespread parasite infection in developed and developing countries. The prevalence of Toxoplasma gondii infection varies mostly between 20 to 80% in different territories. This form of toxoplasmosis is generally considered to be asymptomatic. Recently published results, however, suggest that the personality profiles of infected subjects differ from those of uninfected controls. These results, however, were obtained on non-standard populations (biologists or former acute toxoplasmosis patients). Here we studied the personality profiles of 191 young women tested for anti-Toxoplasma immunity during gravidity. The results showed that the differences between Toxoplasma-negative and Toxoplasma-positive subjects exits also in this sample of healthy women. The subjects with latent toxoplasmosis had higher intelligence, lower guilt proneness, and possibly also higher ergic tension. The difference in several other factors (desurgency/surgency, alaxia/protension, naiveté/shrewdness, and self-sentiment integration) concerned changes in the variances, rather than the mean values of the factors.

Multiple populations of double-stranded RNA in two virus-harbouring strains of Trichomonas vaginalis.

The existence of six dsRNA segments of Trichomonas vaginalis virus was confirmed and the molar mass and relative abundance of these segments were determined by agarose gel electrophoresis with reovirus dsRNA serving as a standard. The M's were 3.5, 3.4, 3.2, 2.5, 1.4 and 0.34 Mg/mol for the two strains studied, the relative abundances, however, were 1.0, 1.4, 3.0, 0.3, 2.7, 4.2 and 1.0, 0.6, 1.7, 0.5, 3.4 1.0 for these strains, respectively. Cell homogenate fractionation showed that all dsRNA segments were associated with viral particles. The data appeared to support the hypothesis of a relationship between viruses of the protozoan T. vaginalis and of the yeast Saccharomyces cerevisiae.

The dsRNA of Trichomonas vaginalis is associated with virus-like particles and does not correlate with metronidazole resistance.

Twelve metronidazole-resistant and twelve metronidazole-susceptible strains of Trichomonas vaginalis were tested for the presence of dsRNA. Three resistant and five susceptible strains were found to contain dsRNA which indicated that metronidazole resistance does not correlate with the absence of dsRNA. Electron microscopy showed the homogenates of all dsRNA-positive strains to contain virus-like particles 32-38 nm in diameter, while no such particles were found in the dsRNA-negative strains. A mutual relationship between the dsRNA and virus-like particles seems to exist.

The role of psychological factors in questionnaire-based studies on routes of human toxoplasmosis transmission.

The paper studies impacts of particular toxoplasmosis risk factors (consumption of raw meat and contact with cats), their interactions, and their relationship with the personality of the subjects. Among 243 men and 343 women the frequency of subjects with antitoxoplasma immunity was 26.6% and 21.6%, respectively. The association of antitoxoplasma immunity (assessed by the toxoplasmin skin test) with the two risk factors was estimated by log-linear analysis. Reported contact with cats has no influence on the probability of having antitoxoplasma immunity (P = 0.23) while the consumption of raw meat increased this probability (P = 0.0008). Very strong positive association between the contact with cats and the raw meat consumption was found among subjects without toxoplasmosis (P = 0.0028), suggesting that among these persons some subjects either incorrectly assessed their exposition to the risk factors or provided false data during the interview. The results of logistic regression suggest that the contact with cat and the consumption of raw meat are associated with particular personality traits. However, these traits differ from those associated with antitoxoplasma immunity suggesting that the correlation between antitoxoplasma immunity and consumption of raw meat reflects epidemiological importance of the raw meat rather than a correlation of both factors (raw meat consumption and probability of acquiring toxoplasmosis) with the subjects personality.