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.

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.

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.

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.

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.

Toxoplasmosis can be a sexually transmitted infection with serious clinical consequences. Not all routes of infection are created equal.

Toxoplasma gondii infects about 30% of the human population. Common sources of infection are oocysts in cat faeces contaminating drinking water or unwashed vegetables, undercooked meat containing tissue cysts, and organ transplants from infected donors containing tissue cysts. However, very often, it is not possible to identify any potential source of infection in mothers of children with congenital toxoplasmosis. Here we present a hypothesis suggesting that toxoplasmosis is transmitted from infected men to noninfected women during unprotected sexual intercourse, which can result in the most serious form of disease, congenital toxoplasmosis. Arguments for the hypothesis: (1) Toxoplasma tachyzoites are present in the seminal fluid and tissue of the testes of various animals including humans. In some species infection of females by artificial insemination with semen from infected males has been observed. (2) Up to two thirds of Toxoplasma infections in pregnant women cannot be explained by the known risk factors. (3) Prevalence of toxoplasmosis in women in child-bearing age covaries with the incidence of sexually transmitted diseases in particular countries. (4) In some countries, an increased incidence of toxoplasmosis has been reported in women (but not men) aged 25-35 years. This second peak of infection could be associated with women having regular unprotected sex after marriage. (5) Toxoplasmosis triggers schizophrenia in predisposed subjects. Onset of schizophrenia is about 2-3 years earlier in men than in women. However, this difference in the onset can be found only between Toxoplasma-infected patients. The increased onset of schizophrenia in infected women could be associated with the already mentioned second peak of toxoplasmosis incidence. (6) The prevalence of toxoplasmosis decreases in developed countries in last 20 years. This trend could be a result of decrease in promiscuity and increase in safe sex practices, both associated with the AIDS pandemics. (7) In women, probability of being Toxoplasma-infected correlates positively with the amount of unprotected sex with the child's father before the conception. Evidence against the hypothesis: Questionnaire study showed negative association between Toxoplasma infection and the number of earlier partners with whom the woman had unprotected sex. If our hypothesis turns out to be true, then sexual route of transmission, even if rare, could be responsible for a large part of cases of congenital toxoplasmosis. Women should be warned that having unprotected sex with men of positive or unknown toxoplasmosis status should be avoided during pregnancy.

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.

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.

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.

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.

Influence of latent toxoplasmosis on the secondary sex ratio in mice.

The sex ratio may be influenced by many factors, such as stress and immunosuppression, age of parents, parity and sex of preceding siblings. In animal systems, parasitism often changes the sex ratio of infected hosts, which can increase the probability of their transmission. The most common human protozoan parasite in developed countries, Toxoplasma gondii (prevalence 20%-80%), is known to change the behaviour of its intermediate hosts, thereby increasing the probability of transmission to its definitive host (the cat) by predation. The intermediate hosts, which under natural conditions are rodents, serve as the vector for Toxoplasma. Therefore, we speculate that Toxoplasma can alter the secondary sex ratio (i.e. male to female ratio in the offspring) of infected females to increase the proportion of (congenitally infected) male offspring, which are the more migratory sex in most rodent species. Here we studied the sex ratio of experimentally infected laboratory mice, expressed here as the proportion of males in the litter. In accordance with our hypothesis and results of previous retrospective cohort studies on human subjects, mice with toxoplasmosis produced a higher sex ratio than controls, in the early phase of latent infection. In the later phase of infection, mice with congenital toxoplasmosis had a lower sex ratio than controls, which is in accord with the Trivers-Willard hypothesis of sex ratio manipulation, suggesting that females in poor physical condition give birth to more female offspring.

Poorer results of mice with latent toxoplasmosis in learning tests: impaired learning processes or the novelty discrimination mechanism?

The heteroxenous protozoan parasite Toxoplasma gondii is transmitted from the intermediate host (any warm-blooded animal) to the definitive host (members of the felidae) by carnivory. The infected intermediate hosts develop several specific behavioural changes that are usually considered products of manipulative activity of the parasite aimed to increase the probability of its transmission to the definitive host. Among other changes, the infected rodents were shown to have impaired learning capability. All previous studies were done 2-6 weeks after the infection. Therefore, it was difficult to resolve whether the observed impairment of learning processes was a result of acute or latent toxoplasmosis, i.e. whether it was a side-effect of the disease or a product of manipulation activity. Here we studied the learning capability of Toxoplasma-infected mice in the static rod test and 8-arm radial maze test and their spontaneous activity in the wheel running test 10 weeks after the infection. The infected mice achieved worse scores in the learning tests but showed higher spontaneous activity in the wheel running test. However, a detailed study of the obtained results as well as of the data reported by other authors suggested that the differences between infected and control mice were a result of impaired ability to recognize novel stimuli rather than of impaired learning capacity in animals with latent toxoplasmosis.

Women infected with parasite Toxoplasma have more sons.

The boy-to-girl ratio at birth (secondary sex ratio) is around 0.51 in most populations. The sex ratio varies between societies and may be influenced by many factors, such as stress and immunosuppression, age, primiparity, the sex of the preceding siblings and the socioeconomic status of the parents. As parasite infection affects many immunological and physiological parameters of the host, we analyzed the effect of latent toxoplasmosis on sex ratios in humans. Clinical records of 1,803 infants born from 1996 to 2004 contained information regarding the mother's age, concentration of anti-Toxoplasma antibodies, previous deliveries and abortions and the sex of the newborn. The results of our retrospective cohort study suggest that the presence of one of the most common parasites (with a worldwide prevalence from 20 to 80%), Toxoplasma gondii, can influence the secondary sex ratio in humans. Depending on the antibody concentration, the probability of the birth of a boy can increase up to a value of 0.72, C.I.95 = (0.636, 0.805), which means that for every 260 boys born, 100 girls are born to women with the highest concentration of anti-Toxoplasma antibodies. The toxoplasmosis associated with immunosuppression or immunomodulation might be responsible for the enhanced survival of male embryos. In light of the high prevalence of latent toxoplasmosis in most countries, the impact of toxoplasmosis on the human population might be considerable.

The role of dopamine in Toxoplasma-induced behavioural alterations in mice: an ethological and ethopharmacological study.

Toxoplasma gondii, a cosmopolitan protozoan parasite, is known to induce behavioural alterations in rodents and may exert an effect on human personality and behaviour. The mechanism of parasite-induced alterations in host behaviour has not been described, but it was hypothesized that development of Toxoplasma tissue cysts in the brain could affect the dopaminergic neuromodulatory system. In this study, we tested the effect of latent Toxoplasma infection on mouse behaviour associated with activity of the dopaminergic system, i.e. locomotion in a novel environment and exploration test. Additionally, we examined the behavioural response of Toxoplasma-infected mice to a selective dopamine uptake inhibitor, GBR 12909. In both genders, Toxoplasma infection decreased locomotion in the open field. Infected females displayed an increased level of exploration in the holeboard test. GBR 12909 induced suppression in holeboard-exploration in the infected males, but had an opposite effect on the controls. These results suggest an association between Toxoplasma gondii infection and changes in the dopaminergic neuromodulatory system.

Tetratrichomonads from the oral cavity and respiratory tract of humans.

To clarify the taxonomy of trichomonads associated with human respiratory diseases, we examined a collection of axenic trichomonad strains isolated from the oral cavity and bronchi of patients from pulmonary diseases clinics in Tallin, Estonia. The oral and bronchial strains were compared mutually as well as with a reference strain of Trichomonas tenax, a common inhabitant of the human oral cavity, and other trichomonad species from humans and animals. Unexpectedly, the morphological studies, as well as DNA sequencing of ITS1-5.8S rRNA-ITS2 regions revealed that the Estonian strains belong to the genus Tetratrichomonas, with a high similarity to the avian species Tetratrichomonas gallinarum. None of the strains belonged to Trichomonas tenax. DNA fingerprinting using the RAPD method separated Estonian strains into 2 distinct groups: 'bronchial' consisting of 5 and 2 strains isolated from bronchi and 'oral' cavity, respectively, and oral consisting of 3 oral strains. Consistent differences between 'bronchial' and 'oral' groups were confirmed by analysis of ITS1-5.8S rRNA-ITS2 sequences. Our results have revealed novel trichomonad species of the human oral cavity and bronchi.

Body height, body mass index, waist-hip ratio, fluctuating asymmetry and second to fourth digit ratio in subjects with latent toxoplasmosis.

Between 20% and 60% of the population of most countries are infected with the protozoan Toxoplasma gondii. Subjects with clinically asymptomatic life-long latent toxoplasmosis differ from those who are Toxoplasma free in several behavioural parameters. Case-control studies cannot decide whether these differences already existed before infection or whether they were induced by the presence of Toxoplasma in the brain of infected hosts. Here we searched for such morphological differences between Toxoplasma-infected and Toxoplasma-free subjects that could be induced by the parasite (body weight, body height, body mass index, waist-hip ratio), or could rather correlate with their natural resistance to parasitic infection (fluctuating asymmetry, 2D : 4D ratio). We found Toxoplasma-infected men to be taller and Toxoplasma-infected men and women to have lower 2D : 4D ratios previously reported to be associated with higher pre-natal testosterone levels. The 2D : 4D ratio negatively correlated with the level of specific anti-Toxoplasma antibodies in Toxoplasma-free subjects. These results suggest that some of the observed differences between infected and non-infected subjects may have existed before infection and could be caused by the lower natural resistance to Toxoplasma infection in subjects with higher pre-natal testosterone levels.

Comparison of european Trichobilharzia species based on ITS1 and ITS2 sequences.

Schistosomes are parasites of considerable medical and veterinary importance and, therefore, all aspects of their biology have been intensively studied. In contrast, our knowledge of species of the largest genus, Trichobilharzia, is insufficient. Because morphological characterization of Trichobilharzia species provides a limited number of criteria for species determination, molecular data are required. In the present paper, we sequenced internal transcribed spacers ITS1 and ITS2, and 5.8S ribosomal RNA (rRNA) genes of 3 European Trichobilharzia species (T. regenti, T. szidati and T. franki). We showed that ITS1 and ITS2 sequences can be used in species identification. Repetitive elements were found in ITS1 of all 3 Trichobilharzia species; their number and length varied depending on the species. Phylogenetic analysis showed that the visceral T. franki is more related to the nasal T. regenti, than to the visceral T. szidati. The newly designed primer, which is specific for T. regenti, might be used as a tool for diagnosis of this potential pathogen.

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.

Decrease of psychomotor performance in subjects with latent 'asymptomatic' toxoplasmosis.

Toxoplasma gondii is known to induce specific behavioural changes in its intermediate hosts. This is usually considered to be an evolutionary adaptation aimed to increase the probability of transmission of the parasite into its definitive host, the cat, by predation. In rodents an increase of reaction time as well as many other specific behavioural patterns have been observed. Here we report the results of our double blind study showing the significantly longer reaction times of 60 subjects with latent toxoplasmosis in comparison with those of 56 controls. Moreover, the existence of a positive correlation between length of infection and mean reaction time suggested that slow and cumulative effects of latent toxoplasmosis rather than a one-step (and possibly transient) effect of acute toxoplasmosis disease are responsible for the decrease of psychomotor performance of infected subjects. To our knowledge, this is the first study confirming the existence of such parasite-induced changes in human behaviour that could be considered in evolutionary history of the human species as adaptive from the point of view of parasite transmission.