Toxoplasma gondii exposure affects neural processing speed as measured by acoustic startle latency in schizophrenia and controls

Molecular Mimicry between Toxoplasma gondii B-Cell Epitopes and Neurodevelopmental Proteins: An Immunoinformatic Approach

Epidemiological studies and meta-analyses have shown a strong association between high seroprevalence of Toxoplasma gondii (T. gondii) and schizophrenia. Schizophrenic patients showed higher levels of anti-Toxoplasma immunoglobulins M and G (IgM and IgG) when compared to healthy controls. Previously, in a rat model, we demonstrated that the progeny of mothers immunized with T. gondii lysates before gestation had behavioral and social impairments during adulthood. Therefore, we suggested that T. gondii infection can trigger autoreactivity by molecularly mimicking host brain proteins. Here, we aimed to identify the occurrence of antigenic mimicry between T. gondii epitopes and host brain proteins. Using a bioinformatic approach, we predicted T. gondii RH-88 B cell epitopes and compared them to human cell-surface proteins involved in brain development and differentiation (BrainS). Five different algorithms for B-cell-epitope prediction were used and compared, resulting in 8584 T. gondii epitopes. We then compared T. gondii predicted epitopes to BrainS proteins by local sequence alignments using BLASTP. T. gondii immunogenic epitopes significantly overlapped with 42 BrainS proteins. Among these overlapping proteins essential for brain development and differentiation, we identified HSP90 and NOTCH receptors as the proteins most likely to be targeted by the maternally generated pathogenic antibodies due to their topological overlap at the extracellular region of their sequence. This analysis highlights the relevance of pregestational clinical surveillance and screening for potential pathogenic anti-T. gondii antibodies. It also identifies potential targets for the design of vaccines that could prevent behavioral and cognitive impairments associated with pre-gestational T. gondii exposure.

Effects of Toxoplasma gondii infection on cognition, symptoms, and response to digital cognitive training in schizophrenia

Studies indicate that neuroscience-informed digital cognitive training can remediate cognitive impairments in schizophrenia, but the factors contributing to these deficits and response to treatment remain unclear. Toxoplasma gondii is a neuroinvasive parasite linked to cognitive decline that also presents a higher prevalence in schizophrenia. Here, we compared the cognition and symptom severity of IgG seropositive (TOXO+; n = 25) and seronegative (TOXO-; n = 35) patients who participated in a randomized controlled trial of digital cognitive training. At baseline, TOXO+ subjects presented lower global cognition than TOXO- (F = 3.78, p = 0.05). Specifically, TOXO+ subjects showed worse verbal memory and learning (F = 4.48, p = 0.03), social cognition (F = 5.71, p = 0.02), and higher antibody concentrations were associated with increased negative (r = 0.42, p = 0.04) and total (r = 0.40, p = 0.04) schizophrenia symptoms. After training, the TOXO+ group showed higher adherence to the intervention (X² = 9.31, p = 0.03), but there were no differences in changes in cognition and symptoms between groups. These findings highlight the association between seropositivity to T. gondii and deteriorated cognition and symptoms in schizophrenia. Further research is needed to assess the specific efficacy of digital cognitive training on this population.

The emerging paradigm of calcium homeostasis as a new therapeutic target for protozoan parasites

Calcium channels (CCs), a group of ubiquitously expressed membrane proteins, are involved in many pathophysiological processes of protozoan parasites. Our understanding of CCs in cell signaling, organelle function, cellular homeostasis, and cell cycle control has led to improved insights into their structure and functions. In this article, we discuss CCs characteristics of five major protozoan parasites Plasmodium, Leishmania, Toxoplasma, Trypanosoma, and Cryptosporidium. We provide a comprehensive review of current antiparasitic drugs and the potential of using CCs as new therapeutic targets. Interestingly, previous studies have demonstrated that human CC modulators can kill or sensitize parasites to antiparasitic drugs. Still, none of the parasite CCs, pumps, or transporters has been validated as drug targets. Information for this review draws from extensive data mining of genome sequences, chemical library screenings, and drug design studies. Parasitic resistance to currently approved therapeutics is a serious and emerging threat to both disease control and management efforts. In this article, we suggest that the disruption of calcium homeostasis may be an effective approach to develop new anti-parasite drug candidates and reduce parasite resistance.

Toxoplasma gondii Effects on the Relationship of Kynurenine Pathway Metabolites to Acoustic Startle Latency in Schizophrenia vs. Control Subjects

Background: Chronic infection with Toxoplasma gondii (TOXO) results in microcysts in the brain that are controlled by inflammatory activation and subsequent changes in the kynurenine pathway. TOXO seropositivity is associated with a heightened risk of schizophrenia (SCZ) and with cognitive impairments. Latency of the acoustic startle response, a putative index of neural processing speed, is slower in SCZ. SCZ subjects who are TOXO seropositive have slower latency than SCZ subjects who are TOXO seronegative. We assessed the relationship between kynurenine pathway metabolites and startle latency as a potential route by which chronic TOXO infection can lead to cognitive slowing in SCZ. Methods: Fourty-seven SCZ subjects and 30 controls (CON) were tested on a standard acoustic startle paradigm. Kynurenine pathway metabolites were measured using liquid chromatography-tandem mass spectrometry were kynurenine (KYN), tryptophan (TRYP), 3-hydroxyanthranilic acid (3-OHAA), anthranilic acid (AA), and kynurenic acid (KYNA). TOXO status was determined by IgG ELISA. Results: In univariate ANCOVAs on onset and peak latency with age and log transformed startle magnitude as covariates, both onset latency [F(1,61) = 5.76; p = 0.019] and peak latency [F(1,61) = 4.34; p = 0.041] were slower in SCZ than CON subjects. In stepwise backward linear regressions after stratification by Diagnosis, slower onset latency in SCZ subjects was predicted by higher TRYP (B = 0.42; p = 0.008) and 3-OHAA:AA (B = 3.68; p = 0.007), and lower KYN:TRYP (B = -185.42; p = 0.034). In regressions with peak latency as the dependent variable, slower peak latency was predicted by higher TRYP (B = 0.47; p = 0.013) and 3-OHAA:AA ratio (B = 4.35; p = 0.010), and by lower KYNA (B = -6.67; p = 0.036). In CON subjects neither onset nor peak latency was predicted by any KYN metabolites. In regressions stratified by TOXO status, in TOXO positive subjects, slower peak latency was predicted by lower concentrations of KYN (B = -8.08; p = 0.008), KYNA (B = -10.64; p = 0.003), and lower KYN:TRYP ratios (B = -347.01; p = 0.03). In TOXO negative subjects neither onset nor peak latency was predicted by any KYN metabolites. Conclusions: KYN pathway markers predict slowing of startle latency in SCZ subjects and in those with chronic TOXO infection, but this is not seen in CON subjects nor TOXO seronegative subjects. These findings coupled with prior work indicating a relationship of slower latency with SCZ and TOXO infection suggest that alterations in KYN pathway markers may be a mechanism by which neural processing speed, as indexed by startle latency, is affected in these subjects.

Association between exposure to toxoplasmosis and major psychiatric disorders: a systematic review

Objective:

To assess the association between exposure to toxoplasmosis and major psychiatric disorders through a systematic review of the literature.

Methods:

The literature review was performed in the MEDLINE, SciELO, and PsycINFO databases. To evaluate the quality of the studies included in the review, the Newcastle-Ottawa Scale was used.

Results:

Thirty-one studies were included, and the majority found an association between exposure to toxoplasmosis and schizophrenia or bipolar disorder (58.3 and 54.5% of the included papers, respectively), but not major depressive disorder. We found no significant difference in mean quality scores between studies that corroborated and contradicted the association hypothesis for either schizophrenia or bipolar disorder. All included papers were considered at least satisfactory according to the Newcastle-Ottawa Scale (total scores ≥ 6 out of 9).

Conclusion:

Although there was no association between exposure to toxoplasmosis and major depressive disorder, the results indicate an association with both bipolar disorder and schizophrenia, despite their heterogeneity. Further studies should be performed with more specific variables so that the nature of these relationships can be elucidated.

Human Seroprevalence to 11 Zoonotic Pathogens in the U.S. Arctic, Alaska

Background: Due to their close relationship with the environment, Alaskans are at risk for zoonotic pathogen infection. One way to assess a population's disease burden is to determine the seroprevalence of pathogens of interest. The objective of this study was to determine the seroprevalence of 11 zoonotic pathogens in people living in Alaska. Methods: In a 2007 avian influenza exposure study, we recruited persons with varying wild bird exposures. Using sera from this study, we tested for antibodies to Cryptosporidium spp., Echinococcus spp., Giardia intestinalis, Toxoplasma gondii, Trichinella spp., Brucella spp., Coxiella burnetii, Francisella tularensis, California serogroup bunyaviruses, and hepatitis E virus (HEV). Results: Eight hundred eighty-seven persons had sera tested, including 454 subsistence bird hunters and family members, 160 sport bird hunters, 77 avian wildlife biologists, and 196 persons with no wild bird exposure. A subset (n = 481) of sera was tested for California serogroup bunyaviruses. We detected antibodies to 10/11 pathogens. Seropositivity to Cryptosporidium spp. (29%), California serotype bunyaviruses (27%), and G. intestinalis (19%) was the most common; 63% (301/481) of sera had antibodies to at least one pathogen. Using a multivariable logistic regression model, Cryptosporidium spp. seropositivity was higher in females (35.7% vs. 25.0%; p = 0.01) and G. intestinalis seropositivity was higher in males (21.8% vs. 15.5%; p = 0.02). Alaska Native persons were more likely than non-Native persons to be seropositive to C. burnetii (11.7% vs. 3.8%; p = 0.005) and less likely to be seropositive to HEV (0.4% vs. 4.1%; p = 0.01). Seropositivity to Cryptosporidium spp., C. burnetii, HEV, and Echinococcus granulosus was associated with increasing age (p ≤ 0.01 for all) as was seropositivity to ≥1 pathogen (p < 0.0001). Conclusion: Seropositivity to zoonotic pathogens is common among Alaskans with the highest to Cryptosporidium spp., California serogroup bunyaviruses, and G. intestinalis. This study provides a baseline for use in assessing seroprevalence changes over time.

Driving us mad: the association of Toxoplasma gondii with suicide attempts and traffic accidents - a systematic review and meta-analysis

Unnatural causes of death due to traffic accidents (TA) and suicide attempts (SA) constitute a major burden on global health, which remained stable in the last decade despite widespread efforts of prevention. Recently, latent infection with Toxoplasma gondii (T. gondii) has been suggested to be a biological risk factor for both TA and SA. Therefore, a systematic search concerning the relationship of T. gondii infection with TA and/or SA according to PRISMA guidelines in Medline, Pubmed and PsychInfo was conducted collecting papers up to 11 February 2019 (PROSPERO #CRD42018090206). The random-effect model was applied and sensitivity analyses were subsequently performed. Lastly, the population attributable fraction (PAF) was calculated. We found a significant association for antibodies against T. gondii with TA [odds ratio (OR) = 1.69; 95% confidence interval (CI) 1.20-2.38, p = 0.003] and SA (OR = 1.39; 95% CI 1.10-1.76, p = 0006). Indication of publication bias was found for TA, but statistical adjustment for this bias did not change the OR. Heterogeneity between studies on SA was partly explained by type of control population used (ORhealthy controls = 1.9, p &lt; 0.001 v. ORpsychiatric controls = 1.06, p = 0.87) and whether subjects with schizophrenia only were analysed (ORschizophrenia = 0.87, p = 0.62 v. ORvarious = 1.8, p &lt; 0.001). The association was significantly stronger with higher antibody titres in TA and in studies that did not focus on schizophrenia subjects concerning SA. PAF of a T. gondii infection was 17% for TA and 10% for SA. This indicates that preventing T. gondii infection may play a role in the prevention of TA or SA, although uncertainty remains whether infection and outcome are truly causally related.

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

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.

Lower performance of Toxoplasma-infected, Rh-negative subjects in the weight holding and hand-grip tests

BACKGROUND

Toxoplasma, a protozoan parasite of cats, infects many species of intermediate and paratenic hosts, including about one-third of humans worldwide. After a short phase of acute infection, the tissue cysts containing slowly dividing bradyzoites are formed in various organs and toxoplasmosis proceeds spontaneously in its latent form. In immunocompetent subjects, latent toxoplasmosis was considered asymptomatic. However, dozens of studies performed on animals and humans in the past twenty years have shown that it is accompanied by a broad spectrum of specific behavioural, physiological and even morphological changes. In human hosts, the changes often go in the opposite direction in men and women, and are mostly weaker or non-existent in Rh-positive subjects.

METHODS

Here, we searched for the indices of lower endurance of the infected subjects by examining the performance of nearly five hundred university students tested for toxoplasmosis and Rh phenotype in two tests, a weight holding test and a grip test.

RESULTS

The results confirmed the existence of a negative association of latent toxoplasmosis with the performance of students, especially Rh-negative men, in these tests. Surprisingly, but in an accordance with some already published data, Toxoplasma-infected, Rh-positive subjects expressed a higher, rather than lower, performance in our endurance tests.

DISCUSSION

Therefore, the results only partly support the hypothesis for the lower endurance of Toxoplasma infected subjects as the performance of Rh-positive subjects (representing majority of population) correlated positively with the Toxoplasma infection.

Relationship between Toxoplasma gondii seropositivity and acoustic startle response in an inner-city population

Toxoplasma gondii (TOXO) is a neuroinvasive protozoan parasite that induces the formation of persistent cysts in mammalian brains. It infects approximately 1.1million people in the United States annually. Latent TOXO infection is implicated in the etiology of psychiatric disorders, especially schizophrenia (SCZ), and has been correlated with modestly impaired cognition. The acoustic startle response (ASR) is a reflex seen in all mammals. It is mediated by a simple subcortical circuit, and provides an indicator of neural function. We previously reported the association of TOXO with slowed acoustic startle latency, an index of neural processing speed, in a sample of schizophrenia and healthy control subjects. The alterations in neurobiology with TOXO latent infection may not be specific to schizophrenia. Therefore we examined TOXO in relation to acoustic startle in an urban, predominately African American, population with mixed psychiatric diagnoses, and healthy controls. Physiological and diagnostic data along with blood samples were collected from 364 outpatients treated at an inner-city hospital. TOXO status was determined with an ELISA assay for TOXO-specific IgG. A discrete titer was calculated based on standard cut-points as an indicator of seropositivity, and the TOXO-specific IgG concentration served as serointensity. A series of linear regression models were used to assess the association of TOXO seropositivity and serointensity with ASR magnitude and latency in models adjusting for demographics and psychiatric diagnoses (PTSD, major depression, schizophrenia, psychosis, substance abuse). ASR magnitude was 11.5% higher in TOXO seropositive subjects compared to seronegative individuals (p=0.01). This effect was more pronounced in models with TOXO serointensity that adjusted for sociodemographic covariates (F=7.41, p=0.0068; F=10.05, p=0.0017), and remained significant when psychiatric diagnoses were stepped into the models. TOXO showed no association with startle latency (t=0.49, p=0.63) in an unadjusted model, nor was TOXO associated with latency in models that included demographic factors. After stepping in individual psychiatric disorders, we found a significant association of latency with a diagnosis of PTSD (F=5.15, p=0.024), but no other psychiatric diagnoses, such that subjects with PTSD had longer startle latency. The mechanism by which TOXO infection is associated with high startle magnitude is not known, but possible mechanisms include TOXO cyst burden in the brain, parasite recrudescence, or molecular mimicry of a host epitope by TOXO. Future studies will focus on the neurobiology underlying the effects of latent TOXO infection as a potential inroad to the development of novel treatment targets for psychiatric disease.

Towards an Immunophenotype of Schizophrenia: Progress, Potential Mechanisms, and Future Directions

The evidence to date, coupled with advances in immunology and genetics has afforded the field an unparalleled opportunity to investigate the hypothesis that a subset of patients with schizophrenia may manifest an immunophenotype, toward new potential diagnostics and therapeutics to reduce risk, alleviate symptoms, and improve quality of life in both at-risk populations and patients with established schizophrenia. In this paper, we will first summarize the findings on immune dysfunction in schizophrenia, including (1) genetic, prenatal, and premorbid immune risk factors and (2) immune markers across the clinical course of the disorder, including cytokines; C-reactive protein; immune cells; antibodies, autoantibodies and comorbid autoimmune disorders; complement; oxidative stress; imaging of neuroinflammation; infections; and clinical trials of anti-inflammatory agents and immunotherapy. We will then discuss a potential mechanistic framework toward increased understanding of a potential schizophrenia immunophenotype. We will then critically appraise the existing literature, and discuss suggestions for the future research agenda in this area that are needed to rigorously evaluate this hypothesis.

Neurological Sequelae Resulting from Encephalitic Alphavirus Infection

The recent surge in viral clinical cases and associated neurological deficits have reminded us that viral infections can lead to detrimental, long-term effects, termed sequelae, in survivors. Alphaviruses are enveloped, single-stranded positive-sense RNA viruses in the Togaviridae family. Transmission of alphaviruses between and within species occurs mainly via the bite of an infected mosquito bite, giving alphaviruses a place among arboviruses, or arthropod-borne viruses. Alphaviruses are found throughout the world and typically cause arthralgic or encephalitic disease in infected humans. Originally detected in the 1930s, today the major encephalitic viruses include Venezuelan, Western, and Eastern equine encephalitis viruses (VEEV, WEEV, and EEEV, respectively). VEEV, WEEV, and EEEV are endemic to the Americas and are important human pathogens, leading to thousands of human infections each year. Despite awareness of these viruses for nearly 100 years, we possess little mechanistic understanding regarding the complications (sequelae) that emerge after resolution of acute infection. Neurological sequelae are those complications involving damage to the central nervous system that results in cognitive, sensory, or motor deficits that may also manifest as emotional instability and seizures in the most severe cases. This article serves to provide an overview of clinical cases documented in the past century as well as a summary of the reported neurological sequelae due to VEEV, WEEV, and EEEV infection. We conclude with a treatise on the utility of, and practical considerations for animal models applied to the problem of neurological sequelae of viral encephalopathies in order to decipher mechanisms and interventional strategies.

The association between antibodies to neurotropic pathogens and schizophrenia: a case-control study

Background:

Exposure to neurotropic pathogens has been proposed as an environmental risk factor for schizophrenia and can be evaluated by measuring pathogen-specific immunoglobulin G (IgG). Seroprevalence of pathogen-specific IgG reflects prior exposure, whereas IgG levels are associated with reactivity or reinfection. Several studies have examined these parameters in schizophrenia. However, results still remain inconclusive, as several previous studies did not correct for important confounding factors.

Aims:

To investigate whether schizophrenia is associated with prior exposure to neurotropic pathogens, or with their reactivation.

Methods:

We examined the seroprevalence and titer of IgG antibodies against herpes simplex virus-1 and -2 (HSV-1/HSV-2), varicella zoster virus (VZV), Epstein–Barr virus (EBV), cytomegalovirus (CMV), and Toxoplasma gondii (TG) in plasma of 368 adult patients with a schizophrenia spectrum disorder and 282 controls using ELISA.

Results:

We did not find evidence for an increased exposure to HSV-1, HSV-2, EBV, and TG in patients. There was a significantly higher seroprevalence of VZV (98.9% vs. 95.6%, P<0.05) and CMV (40.4% vs. 27.7%, P<0.001) in controls as compared with patients, which did not remain statistically significant after adjustment for various potential confounders. We did not find significant differences in antibody titers of seropositive patients and controls for any of the six pathogens.

Conclusions:

Our results do not support the hypothesis that increased exposure to neurotropic pathogens after birth is associated with schizophrenia.

Beyond the association. Toxoplasma gondii in schizophrenia, bipolar disorder, and addiction: systematic review and meta-analysis

OBJECTIVE

To perform a meta-analysis on studies reporting prevalence of Toxoplasma gondii (T. gondii) infection in any psychiatric disorder compared with healthy controls. Our secondary objective was to analyze factors possibly moderating heterogeneity.

METHOD

A systematic search was performed to identify studies into T. gondii infection for all major psychiatric disorders versus healthy controls. Methodological quality, publication bias, and possible moderators were assessed.

RESULTS

A total of 2866 citations were retrieved and 50 studies finally included. Significant odds ratios (ORs) with IgG antibodies were found in schizophrenia (OR 1.81, P < 0.00001), bipolar disorder (OR 1.52, P = 0.02), obsessive-compulsive disorder (OR 3.4, P < 0.001), and addiction (OR 1.91, P < 0.00001), but not for major depression (OR 1.21, P = 0.28). Exploration of the association between T. gondii and schizophrenia yielded a significant effect of seropositivity before onset and serointensity, but not IgM antibodies or gender. The amplitude of the OR was influenced by region and general seroprevalence. Moderators together accounted for 56% of the observed variance in study effects. After controlling for publication bias, the adjusted OR (1.43) in schizophrenia remained significant.

CONCLUSION

These findings suggest that T. gondii infection is associated with several psychiatric disorders and that in schizophrenia reactivation of latent T. gondii infection may occur.

Toxoplasma gondii infection: seroprevalence and associated risk factors among primary school children in the capital area of the Republic of the Marshall Islands

Although Toxoplasma gondii infection is commonly prevalent in the tropical/subtropical regions, the prevalence of toxoplasmosis in the Republic of the Marshall Islands (RMI) remains unclear. A seroepidemiological survey was undertaken for investigating T. gondii infection in primary school children (PSC) using the latex agglutination (LA) test in the capital area of RMI. Information on demographic characteristics and environmental risk factors was collected via a structured questionnaire. Logistic regression model was applied for multivariate analysis. The overall infection rate of T. gondii was found to be 54.8%. Significant gender differences were found at different urbanization levels. PSC with LA titers of ≥ 1:1,024, indicating high responders, were found to be younger age group than others (8.7 years vs. 10.3 years, P = 0.003); moreover, infection rates among both age groups as well as high responders showed a decreasing trend with age. Multivariate analysis revealed that residing in urban rather than suburban settings was associated with increased risk of infection (P = 0.04). No associations were found between raw meat consumption, drinking unboiled water, and cleaning of cat hutch using gloves. This is the first serological survey of T. gondii infection among PSC in RMI and could help in the development of strategies in the future for disease prevention and control of T. gondii transmission.

Seropositivity and serointensity of Toxoplasma gondii antibodies and DNA among patients with schizophrenia

The aim of this cross sectional case control study was to examine the serofrequency and serointensity of Toxoplasma gondii (Tg) IgG, IgM, and DNA among patients with schizophrenia. A total of 101 patients with schizophrenia and 55 healthy controls from Sungai Buloh Hospital, Selangor, Malaysia and University Malaya Medical Center (UMMC) were included in this study. The diagnosis of schizophrenia was made based on the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV). The presence of Tg infection was examined using both indirect (ELISA) and direct (quantitative real-time PCR) detection methods by measuring Tg IgG and IgM and DNA, respectively. The serofrequency of Tg IgG antibodies (51.5%, 52/101) and DNA (32.67%, 33/101) among patients with schizophrenia was significantly higher than IgG (18.2%, 10/55) and DNA (3.64%, 2/55) of the controls (IgG, P=0.000, OD=4.8, CI=2.2-10.5; DNA, P=0.000, OD=12.9, CI=2.17-10.51). However, the Tg IgM antibody between patients with schizophrenia and controls was not significant (P>0.005). There was no significant difference (P>0.005) in both serointensity of Tg IgG and DNA between patients with schizophrenia and controls. These findings have further demonstrated the strong association between the active Tg infection and schizophrenia.

Toxoplasma gondii infection in interstate truck drivers: a case-control seroprevalence study

Background

Infection with Toxoplasma gondii can be acquired via the ingestion of undercooked or raw meat containing tissue cysts, or via ingestion of water contaminated with oocysts. Professional long distance truck driving may have epidemiological importance for food-borne infections since drivers eat out of home and in places where hygiene and cooking practices are uncertain. We aimed to determine whether interstate truck drivers in Durango, Mexico have an increased risk of infection with T. gondii as indicated by seropositivity; and to determine the socio-demographic, work, clinical, and behavioral characteristics associated with T. gondii seropositivity in interstate truck drivers.

Methods

Through a case–control study design, 192 truck drivers and 192 controls from the general population of the same region matched by gender and age were examined with enzyme-linked immunoassays for the presence of anti-Toxoplasma IgG and IgM antibodies. Socio-demographic, work, clinical and behavioral characteristics from the truck drivers were obtained.

Results

Anti-T. gondii IgG antibodies were found in 23 (12.0%) of 192 truck drivers and in 13 (6.8%) of 192 controls (OR = 21.0; 95% CI: 1.23-358.38; P = 0.002). Anti-T. gondii IgM antibodies were found in 7 (3.6%) cases and in 7 (3.6%) controls (P = 1.00). The seroprevalence of T. gondii infection was higher in drivers with reflex impairment than in those without this impairment (4/13, 30.8% vs 19/179, 10.6%, respectively; P = 0.05), and in drivers with hearing impairment than in those without this impairment (3/7, 42.9% vs 20/185, 10.8%, respectively; P = 0.03). Multivariate analysis of work and behavioral characteristics of truck drives showed positive associations of T. gondii exposure with trips to the south of Mexico (OR = 3.11; 95% CI: 1.02-9.44; P = 0.04) and consumption of horse meat (OR = 5.18; 95% CI: 1.62-16.55; P = 0.005).

Conclusions

Results suggest that interstate truck drivers may have an increased risk for T. gondii infection, and that T. gondii exposure may be impacting neurological functions in truck drivers. Contributing factors for T. gondii exposure should be taken into account for the design of optimal prevention measures against T. gondii infection.

Contrasting effect of prepulse signals on performance of Toxoplasma-infected and Toxoplasma-free subjects in an acoustic reaction times test

Background

About 30% of people on Earth have latent toxoplasmosis. Infected subjects do not express any clinical symptoms, however, they carry dormant stages of parasite Toxoplasma for the rest of their life. This form of toxoplasmosis is mostly considered harmless, however, recent studies showed its specific effects on physiology, behaviour and its associations with various diseases, including psychiatric disorders such as schizophrenia. Individuals who suffer from schizophrenia have about 2.7 times higher prevalence of Toxoplasma-seropositivity than controls, which suggests that some traits characteristic of schizophrenic patients, including the sex difference in schizophrenia onset, decrease of grey matter density in specific brain areas and modification of prepulse inhibition of startle reaction could in fact be caused by toxoplasmosis for those patients who are Toxoplasma-seropositive.

Methodology/Principal Findings

We measured the effect of prepulse inhibition/facilitation of the startle reaction on reaction times. The students, 170 women and 66 men, were asked to react as quickly as possible to a startling acoustic signal by pressing a computer mouse button. Some of the startling signals were without the prepulse, some were 20 msec. preceded by a short (20 msec.) prepulse signal of lower intensity. Toxoplasma-seropositive subjects had longer reaction times than the controls. Acoustic prepulse shorted the reaction times in all subjects. This effect of prepulse on reaction times was stronger in male subjects and increased with the duration of infection, suggesting that it represented a cumulative effect of latent toxoplasmosis, rather than a fading out after effect of past acute toxoplasmosis.

Conclusions

Different sensitivity of Toxoplasma-seropositive and Toxoplasma-seronegative subjects on effect of prepulses on reaction times (the toxoplasmosis-prepulse interaction) suggested, but of course did not prove, that the alternations of prepulse inhibition of startle reaction observed in schizophrenia patients probably joined the list of schizophrenia symptoms that are in fact caused by latent toxoplasmosis.