Is there any association between Toxoplasma gondii infection and depression? A systematic review and meta-analysis

Association of neurobiological and immune serum biomarkers with Toxoplasma gondii infection in patients with schizophrenia

Some studies suggest that Toxoplasma gondii infection may increase the risk of developing schizophrenia. Determining changes in blood biomarker concentrations may provide new insights into the underlying mechanisms associated with Toxoplasma gondii infection in schizophrenia. The aim of the study was to evaluate the concentrations of several serum neurobiological and immune parameters and to identify changes in their concentrations that could potentially be indicators of psychopathologic changes in infection. The concentration of biomarkers was determined in serum from patients with schizophrenia (uninfected n = 50, infected n = 30) and from mentally healthy volunteers (uninfected n = 51, infected n = 29) using multiplex analysis. A number of psychometric scales have been applied to assess the cognitive functioning. No significant associations were between schizophrenia and Toxoplasma gondii infection (p = 0.54; OR = 1.18; 95% CI = 0.69-2.01). However, infected patients with schizophrenia had more severe cognitive impairment compared to uninfected schizophrenia patients (PDQ-20). The group of biomarkers has been identified whose concentration changes were observed only between Toxoplasma gondii-infected healthy individuals and individuals with schizophrenia (neurobiological indicators KLK6, UCHL1, Amyloid beta 1-42 and neurogranin; anti-inflammatory cytokine IL-10; chemokines IL-8 and MIP-1 beta), but not between uninfected groups. The hypothesis was proposed that it is possible to use these indices as indicators of the development of schizophrenic psychopathology in Toxoplasma gondii infection. The associations of blood biomarker concentrations with IgA and IgM antibody levels (chemokine RANTES) and with schizophrenia symptoms (hormone-like messenger KLK6; chemokines IP-10 and GRO alpha) were found. Toxoplasma gondii reactivation leads to a decrease in negative symptomatology and reduced FGF-21 levels in patients with schizophrenia, and increased CNTF and NGF beta levels compared to the latent form.

An inexpensive method to measure latent toxoplasmosis and its behavioral consequences

An estimated 2.4 billion humans are affected by the protozoan Toxoplasma gondii, which causes one of the most common infections influencing human behavior and cognition. The infection and its effects are severely underresearched, because the diagnosis is costly and time-intensive, preventing widespread testing, in particular in less-than-wealthy regions. Psychological methods such as response time analysis could circumvent these problems and facilitate more intensive research. We propose a psychological diagnostic method for latent toxoplasmosis using response times, hence enabling large-scale tests of psychological, psychiatrical, and behavioral effects. A clinical trial (N = 119) showed that the method is sensitive (92 %) and specific (97 %) compared to testing for Toxoplasma IgG Antibodies (p < 0.0001, w = 0.85). A representative UK survey (N = 2020) using this method confirmed previously-hypothesized behavioral effects and uncovered previously-unknown effects of latent toxoplasmosis infections which are relevant and pervasive, both psychologically (increase in risky behaviors, depression, anxiety, and stress) and economically (decrease in yearly income of 2500 GBP; decrease in employment of 11 %).

Association between latent toxoplasmosis and bipolar disorder: a case-control seroprevalence study

BACKGROUND

Toxoplasma gondii (T. gondii) is the most successful obligate protozoan that can infect warm-blooded vertebrate hosts. Some researchers suggest that the presence of Toxoplasma cysts in the brain can lead to mental disorders. Bipolar disorder (BD) is one of the serious neuropsychiatric disorders. Several studies have shown a high seroprevalence of T. gondii in bipolar patients. Therefore, this study aims to determine the prevalence of this infection in patients with BD.

METHODS

In this case-control study, anti-Toxoplasma immunoglobulin (Ig) G and IgM antibodies were measured in serum samples from 115 patients with BD and 115 subjects without this disorder from the general population using commercially available enzyme-linked immunosorbent assay. Demographic characteristics of the patient and control groups, information about T. gondii infection and BD, and their potential risk factors were analyzed. We utilized the Mann-Whitney U test for continuous variables, the chi-square test for categorical data, and multivariate logistic regression to assess T. gondii infection and BD, with significance set at P < 0.05.

RESULTS

Twenty-eight (24.34%) of 115 patients with BD and 10 (8.7%) of 115 controls had anti-T. gondii IgG antibodies. IgM antibodies against T. gondii were not reported to be positive in any participants. Furthermore, there was a statistically significant difference in the results [odds ratio (OR) = 2.89: 95% confidence interval (CI) = 1.08-7.73. P = 0.03]. Within the study population, various factors were identified as significant risk factors for BD: sex (OR 8.10, 95% CI 3.16-20.75), age 20-50 (OR 5.11, 95% CI 1.81-14.45), age over 50 (OR 19.54, 95% CI 4.02-94.89), education level (OR 0.24, 95% CI 0.09-0.60), working status (non-employment, OR 4.12, 95% CI 1.65-10.30), and income (middle, OR 0.29, 95% CI 0.10-0.89; high, OR 0.12, 95% CI 0.01-0.77), all with P-values less than 0.05. In addition, in the group of patients, there was no statistically significant relationship between T. gondii infection with the type of bipolar disease (P = 0.93), the severity of the disease (P = 0.61), and the history of suicide attempts (P = 0.63).

CONCLUSION

This study showed that toxoplasmosis is a risk factor for BD and increases the chance of developing BD. However, more studies with a larger sample size are recommended to clarify the development pathways of this disorder and provide new strategies for the prevention and treatment of this disease.

CLINICAL TRIAL

Not applicable.

Association Between Toxoplasma gondii Infection and Serum Neurotransmitter Levels in Major Depressive Disorder Patients: A Case-Control Study in Bangladesh

Toxoplasma gondii (T. gondii) is an obligate, intracellular, neurotropic protozoan parasite. After primary infection, T. gondii parasite undergoes stage conversion from fast-replicating tachyzoites to slow-replicating dormant bradyzoites, particularly in the brain, and persists for a lifetime of an individual. In this study, the impact of T. gondii infection in individuals with psychological disorder, that is, major depressive disorder (MDD) has been studied. Ninety-five MDD (n = 95) patients were enrolled with age and sex-matched healthy controls (HCs, n = 90). The seroprevalence of T. gondii infection among these individuals was determined using the TOXO IgM/IgG Rapid Test Cassette that determines the anti-T. gondii IgM and IgG antibodies in the serum samples. Furthermore, to understand the impact of T. gondii in developing major depression, the serum level of neurotransmitters (i.e., dopamine, adrenaline, and noradrenaline) was determined using an enzyme-linked immunosorbent assay (ELISA). Our data suggest that anti-T. gondii IgG was slightly higher in MDD patients than in HCs. The level of dopamine was significantly lower in T. gondii-infected MDD patients than in HCs. However, adrenaline and noradrenaline levels showed increasing levels in T. gondii-infected MDD patients. The level of neurotransmitters was correlated with the DSM-D scores of MDD patients. These data, nevertheless, confirm that T. gondii might affect the level of neurotransmitters in MDD patients. However, whether the reduced level of dopamine and increased level of adrenaline and noradrenaline act as contributing factors for the development of MDD is yet to be known.

Diseases Caused by and Behaviors Associated with Toxoplasma gondii Infection

Toxoplasma gondii is an Apicomplexan parasite that is estimated to infect at least one-third of the global human population. T. gondii infection may be transmitted horizontally or vertically. The main risk factors for transmission to humans are related to diet, especially the consumption of undercooked meat, along with soil contact. In immunocompetent persons, the acute infection may go undetected as it typically produces minor, non-specific symptoms that are self-limited. After infection is established, recurrent retinochoroiditis is the most common clinical disease. In contrast, severe systemic or cerebral toxoplasmosis may be life-threatening for immunocompromised individuals. Furthermore, congenital toxoplasmosis acquired in utero may have devastating consequences if not recognized and promptly treated. A growing body of research has identified associations between latent T. gondii infection, and personality traits and risk-taking behaviors. Other studies have documented associations between latent infection and psychiatric conditions that include schizophrenia and bipolar affective disorder. With no current treatment regimens being curative of T. gondii infection, effective prevention measures at both the public health and individual levels are vitally important.

The Role of Inflammation in Depression and Beyond: A Primer for Clinicians

PURPOSE OF REVIEW

We evaluate available evidence for the role of inflammation in depression. We reappraise literature involving systemic inflammation, neuroinflammation and neurotransmission and their association with depression. We review the connection between depression, autoimmunity and infectious diseases. We revise anti-inflammatory treatments used in depression.

RECENT FINDINGS

Peripheral inflammatory markers are present in a subset of patients with depression and can alter common neurotransmitters in this population but there is no clear causality between depression and systemic inflammation. Infectious conditions and autoimmune illnesses do not have a clear correlation with depression. Certain medications have positive evidence as adjunctive treatments in depression but studies are heterogenic, hence they are sparsely used in clinical settings. The current evidence does not fully support inflammation, infections or autoimmunity as possible etiologies of depression. The available studies have numerous confounders that obscure the findings. Anti-inflammatory agents may have potential for treatment of depression, but further research is needed to clarify their usefulness in routine clinical practice.

Population-based cohort study of Toxoplasma gondii P22 antibody positivity correlation with anxiety

BACKGROUND

Accumulating evidence suggests that latent infection with Toxoplasma gondii (T. gondii) is associated with a variety of neuropsychiatric and behavioral conditions. This research aims to explore the potential correlation between T. gondii antibody positivity and neuropsychiatric disorders through a comprehensive prospective cohort study.

METHODS

The cohort study utilized the UK Biobank database to recruit 8814 individuals with no prior diagnosis of neuropsychiatric disorders. Cox proportional hazards models were employed to investigate the associations between T. gondii P22 antibody seropositivity (P22+) and the development of various types of neuropsychiatric disorders.

RESULTS

Of the population, 14.65 % tested positive for T. gondii P22 antibody. The presence of T. gondii P22 antibody showed a slight inverse association with epilepsy (HR: 0.28; 95 % CI: 0.10-0.77), while it was positively associated with an increased risk of developing anxiety disorders (HR: 1.38; 95 % CI: 1.04-1.83).

LIMITATIONS

The study sample consisted mostly of white British individuals aged 40 to 69 years old. Although we adjusted for potential confounders, there may be other unmeasured and residual confounding factors that could have influenced our reported associations.

CONCLUSIONS

The findings suggested an increased risk of anxiety and potential evidence of epilepsy associated with T. gondii P22+. However, our analysis did not reveal an increased risk of several other neuropsychiatric conditions including Alzheimer's disease, dementia, substance abuse disorders, depression, and neurodegenerative disorders, associated with P22 antibody seropositivity.

Toxoplasma gondii infection positively associated with schizophrenia: Evidences from UK Biobank cohort and case-controlled studies

Toxoplasma gondii (T. gondii) is an opportunistic pathogen affecting about 1/3 of world population. While often asymptomatic in immunocompetent individuals, it can lead to severe toxoplasmosis in immunocompromised patients. Recent research has unveiled a potential link between T. gondii infection and neuropsychiatric diseases. We implemented both a cohort study and a case control study to further identify this association. In the cohort study, we analyzed data from the UK Biobank database, which included 8814 individuals tested for T. gondii SAG1 antibodies and free of neuropsychiatric disorders at baseline. Among them, 22.52% (n = 1985) tested positive for SAG1 antibody. Over an average follow-up period of 12.26 years, Cox proportional hazards models and logistic regression analysis revealed a significant association between the SAG1 seropositivity at baseline and the incidence of schizophrenia (HR: 5.89; 95% CI: 1.69-20.53). In our case-control study, 239 patients diagnosed with schizophrenia and 455 healthy individuals were involved. Using the modified agglutination test (MAT) to detect T. gondii antibodies, logistic regression analysis showed a higher prevalence of T. gondii infection among schizophrenia patients (10.04%) compared to healthy controls (3.74%). T. gondii infection emerged as a significant risk factor for schizophrenia (OR: 3.33; 95% CI: 1.68-6.61). However, our investigations did not reveal a robust association between T. gondii infection and other neuropsychiatric conditions, including Alzheimer's disease, dementia, anxiety, depression, neurodegenerative disorders, and peripheral neurological disorders such as neurological and plexus disorders.

Systematic Review on the Relationship between Toxoplasmosis and Mental Disorders

BACKGROUND

Toxoplasmosis is a worldwide parasitic zoonosis caused by the protozoan Toxoplasma gondii. In cases of vertical infection, and in immunosuppressed people by the human immunodeficiency virus (HIV) serious clinical conditions may appear, while immunocompetent people do not present symptoms. However, T. gondii infection has been linked to several mental disorders for decades.

OBJECTIVE

To substantiate the possible relationship between T. gondii and mental disorders and suggest control and prevention strategies.

MATERIAL AND METHODS

A systematic review has been carried out to analyze the relationship between T. gondii exposure (presence of IgG) and the onset of mental disorders in minors and adults. The etiopathogenic mechanisms described by the authors have also been included and the systems of surveillance, prevention and control of infection have been evaluated.

RESULTS

Several processes linked to the presence of cysts and the reactivation of the parasite in certain situations produce an immune and inflammatory response. Also, direct and indirect actions on different neurotransmitters. These mechanisms, together with other environmental and genetic factors, would predispose to different psychiatric pathologies.

CONCLUSIONS

Due to the limits of the study, no conclusions can be drawn in childhood and adolescence. However, the results of this systematic review show a possible association of schizophrenia, bipolar disorder and compulsive disorder with T. gondii infection in adults. There is a need to improve control, integrated surveillance and extend prevention measures to the entire population.

Associations between Toxoplasma gondii seropositivity and psychopathological manifestations in schizophrenic patients: A single-center study from Ecuador

BACKGROUND

Schizophrenia, a complex neuropsychiatric disorder, is believed to be influenced by various factors including environmental exposures. A potential environmental factor is the infection by the obligate intracellular parasitic protozoan, Toxoplasma gondii which affects neurotransmitter levels, which could potentially exacerbate, trigger symptoms of schizophrenia or make them worst.

OBJECTIVE

To investigate the association between Toxoplasma gondii seropositivity and psychopathological presentation in persons with schizophrenia in Ecuador.

METHODS

This study was conducted at the Neuroscience Institute of Guayaquil, Ecuador. Among 368 inpatients, 104 were selected based on specific inclusion and exclusion criteria. Descriptive statistics captured patient characteristics and mental health outcomes. Logistic regression models estimated the effect of toxoplasmosis on various mental health outcomes, controlling for demographic and health-related variables.

RESULTS

86.5% of participants were seropositive for toxoplasmosis. Toxoplasma-seropositive schizophrenic patients had a lower risk of depression but a significantly higher risk of disorientation. The most prevalent mental health outcomes were Language Impairments (70.2%) and Bizarre Behavior (76.0%).

CONCLUSION

Our findings suggest that Toxoplasma gondii seropositivity may have specific effects on mental functions in schizophrenic patients, particularly reducing the risk of depression but increasing the risk of disorientation. Further studies are required to clarify these associations and the potential underlying mechanisms.

A systematic review and meta-analysis of protozoan parasite infections among patients with mental health disorders: an overlooked phenomenon

BACKGROUND

Patients with mental disorders have a high risk of intestinal parasitic infection due to poor hygiene practices. Hence, to better clarify this overlooked phenomenon, the current study is conducted to determine the global prevalence of protozoan parasite infections in patients with mental disorders and investigate the associated risk factors.

METHODS

Several databases (PubMed, Scopus, Web of Science, ProQuest, and Google Scholar) were searched for papers published until December 2022. The fixed effect meta-analysis was used to estimate the overall odds ratio (OR) and pooled prevalence was estimated using a random-effects model with a 95% confidence interval (CI).

RESULTS

Totally, 131 articles (91 case-control and 40 cross-sectional studies) met the eligibility criteria. Patients with mental disorders were significantly at higher risk for protozoan parasites than healthy controls (OR: 2.059, 1.830-2.317). The highest pooled OR (2.485, 1.413-4.368) was related to patients with neurodevelopmental disorders, and the highest pooled prevalence was detected in patients with neurodevelopmental disorders (0.341, 0.244-0.446), followed by bipolar and related disorders (0.321, 0.000-0.995). Toxoplasma gondii was the most prevalent protozoan parasite (0.343, 0.228-0.467) in cross-sectional studies and the highest pooled OR was related to Cyclospora cayetanensis (4.719, 1.352-16.474) followed by Cryptosporidium parvum (4.618, 2.877-7.412).

CONCLUSION

Our findings demonstrated that individuals afflicted with mental disorders are significantly more susceptible to acquiring protozoan parasites in comparison to healthy individuals. Preventive interventions, regular screening, and treatment approaches for parasitic diseases should be considered for patients with mental disorders.

High unrecognized SARS-CoV-2 exposure of newly admitted and hospitalized psychiatric patients

BACKGROUND

Patients with pre-existing mental disorders are at higher risk for SARS-CoV-2 infection and adverse outcomes, and severe mental illness, including mood and psychosis spectrum disorders, is associated with increased mortality risk. Despite their increased risk profile, patients with severe mental illness have been understudied during the pandemic, with limited estimates of exposure in inpatient settings.

OBJECTIVE

The aim of this study was to describe the SARS-CoV-2 seroprevalence and antibody titers, and pro-inflammatory cytokine concentrations of newly admitted or hospitalized psychiatric inpatients without known history of COVID-19 infection, using robust quantitative multi-antigen assessments, and compare patients' exposure to that of hospital staff.

METHODS

This multi-centric, cross-sectional study compared SARS-CoV-2 seroprevalence and titers of 285 patients (University Psychiatric Centre Duffel [UPCD] N = 194; Assistance-Publique-Hopitaux de Paris [AP-HP] N = 91), and 192 hospital caregivers (UPCD N = 130; AP-HP N = 62) at two large psychiatric care facilities between January 1st and the May 30th 2021. Serum levels of SARS-CoV-2 antibodies against Spike proteins (full length), spike subunit 1 (S1), spike subunit 2 (S2), spike subunit 1 receptor binding domain (S1-RBD) and Nucleocapsid proteins were quantitatively determined using an advanced capillary Western Blot technique. To assess the robustness of the between-group seroprevalence differences, we performed sensitivity analyses with stringent cut-offs for seropositivity. We also assessed peripheral concentrations of IL-6, IL-8 and TNF-a using ELLA assays. Secondary analyses included comparisons of SARS-CoV-2 seroprevalence and titers between patient diagnostic subgroups, and between newly admitted (hospitalization ≤ 7 days) and hospitalized patients (hospitalization > 7 days) and correlations between serological and cytokines.

RESULTS

Patients had a significantly higher SARS-CoV-2 seroprevalence (67.85 % [95% CI 62.20-73.02]) than hospital caregivers (27.08% [95% CI 21.29-33.77]), and had significantly higher global SARS-CoV-2 titers (F = 29.40, df = 2, p < 0.0001). Moreover, patients had a 2.51-fold (95% CI 1.95-3.20) higher SARS-CoV-2 exposure risk compared to hospital caregivers (Fisher's exact test, P < 0.0001). No difference was found in SARS-CoV-2 seroprevalence and titers between patient subgroups. Patients could be differentiated most accurately from hospital caregivers by their higher Spike protein titers (OR 136.54 [95% CI 43.08-481.98], P < 0.0001), lower S1 (OR 0.06 [95% CI 0.02-0.15], P < 0.0001) titers and higher IL-6 (OR 3.41 [95% CI 1.73-7.24], P < 0.0001) and TNF-α (OR 34.29 [95% CI 5.00-258.87], P < 0.0001) and lower titers of IL-8 (OR 0.13 [95% CI 0.05-0.30], P < 0.0001). Seropositive patients had significantly higher SARS-COV-2 antibody titers compared to seropositive hospital caregivers (F = 19.53, df = 2, P < 0.0001), while titers were not different in seronegative individuals. Pro-inflammatory cytokine concentrations were not associated with serological status.

CONCLUSION

Our work demonstrated a very high unrecognized exposure to SARS-CoV-2 among newly admitted and hospitalized psychiatric inpatients, which is cause for concern in the context of highly robust evidence of adverse outcomes following COVID-19 in psychiatric patients. Attention should be directed toward monitoring and mitigating exposure to infectious agents within psychiatric hospitals.

Relationship between Toxoplasma gondii infection and psychiatric disorders in Iran: A systematic review with meta-analysis

BACKGROUND

Toxoplasma gondii, a ubiquitous parasitic protozoan, may be an important cause of neurological and psychiatric diseases. The present systematic review and meta-analysis, therefore, was conducted to investigate the scientific evidence regarding the potential association between T. gondii infection and psychiatric disorders in Iran.

METHODS

We systematically reviewed articles from world-wide databases, including PubMed, Scopus, Science Direct, Web of Science, Google Scholar, and Iranian national databases up to July 30th, 2021. The Newcastle Ottawa Scale (NOS) was used to assess the quality of included studies. The common odds ratio (OR) was estimated using inverse variance and a random-effects model. Heterogeneity was assessed using the χ2-based Cochrane test (Q) and the I2 index. Also, sensitivity analyses and publication bias were calculated. Moreover, subgroup analysis was performed based on the type of disorder and quality score of different eligible studies.

RESULTS

16 studies were included in this meta-analysis. Our meta-analyses found that the OR of the risk of anti- T. gondii IgG and IgM in psychiatric patients compared to the control group was 1.56 (95% CI; 1.23-1.99) and 1.76 (95% CI: 1.19-2.61), respectively. Subgroup analysis based on the type of disorder showed that the OR of the risk of anti- T. gondii IgG in Iranian schizophrenia patients and other psychiatric disorders compared to the control group were 1.50 (95% CI; 1.09-2.07) and 2.03 (95% CI: 1.14-3.60), respectively, which are statistically significant. Also, the OR of the risk of anti- T. gondii IgM in Iranian schizophrenia and depression patients compared to the control group was 1.54 (95% CI; 0.9-2.64) and 1.03 (95% CI: 0.2-5.24), respectively, which are not statistically significant. Additionally, subgroup analysis based on quality scores showed no significant influence on the results according to the moderate quality studies. However, this association was significant according to the high quality studies. The obtained results of Egger's test were 1.5 (95% CI; -0.62-3.73, P = 0.15) and 0.47 (95% CI; -0.82-1.76, P = 0.45), respectively, indicating publication bias. The significant results of the heterogeneity analysis confirmed a high level of heterogeneity in the IgG test (P = 0.000, I2 = 66.6%). However, no significant results from the test of heterogeneity were detected in the IgM test (P = 0.15, I2 = 27.5%). The results of the sensitivity analysis showed that the impact of each study on the meta-analysis was not significant on overall estimates.

CONCLUSIONS

Despite the limited number of studies, these outcomes supported a possible link between T. gondii infection and psychiatric disorders in Iran. However, more high-quality investigations are needed in the future.

Chronic infection by atypical Toxoplasma gondii strain induces disturbance in microglia population and altered behaviour in mice

Toxoplasma gondii chronic infection is characterized by the establishment of tissue cysts in the brain and increased levels of IFN-γ, which can lead to brain circuitry interference and consequently abnormal behaviour in mice. In this sense, the study presented here sought to investigate the impact of chronic infection by two T. gondii strains in the brain of infection-resistant mice, as a model for studying the involvement of chronic neuroinflammation with the development of behavioural alterations. For that, male BALB/c mice were divided into three groups: non-infected (Ni), infected with T. gondii ME49 clonal strain (ME49), and infected with TgCkBrRN2 atypical strain (CK2). Mice were monitored for 60 days to establish the chronic infection and then submitted to behavioural assessment. The enzyme-linked immunosorbent assay was used for measurement of specific IgG in the blood and levels of inflammatory cytokines and neurotrophic factors in the brain, and the cell's immunophenotype was determined by multiparametric flow cytometry. Mice infected with ME49 clonal strain displayed hyperlocomotor activity and memory deficit, although no signs of depressive- and/or anxiety-like behaviour were detected; on the other hand, chronic infection with CK2 atypical strain induced anxiety- and depressive-like behaviour. During chronic infection by CK2 atypical strain, mice displayed a higher number of T. gondii brain tissue cysts and inflammatory infiltrate, composed mainly of CD3⁺ T lymphocytes and Ly6C^hi inflammatory monocytes, compared to mice infected with the ME49 clonal strain. Infected mice presented a marked decrease of microglia population compared to non-infected group. Chronic infection with CK2 strain produced elevated levels of IFN-γ and TNF-ɑ in the brain, decreased NGF levels in the prefrontal cortex and striatum, and altered levels of fractalkine (CX3CL1) in the prefrontal cortex and hippocampus. The persistent inflammation and the disturbance in the cerebral homeostasis may contribute to altered behaviour in mice, as the levels of IFN-γ were shown to be correlated with the behavioural parameters assessed here. Considering the high incidence and life-long persistence of T. gondii infection, this approach can be considered a suitable model for studying the impact of chronic infections in the brain and how it impacts in behavioural responses.

Reduced numbers of naïve CD4 + T cells and an altered CD4/CD8 balance in depressed common variable immune deficiency (CVID) patients. Is thymosin-α1 a possible treatment?

In the 1990's the macrophage-T-cell-theory of depression was posed stating that low grade inflammation and an abnormal T cell system destabilize the development and function of the emotional brain in such a way, that individuals become ultrasensitive to stress. Recently we gathered evidence that indeed higher frequencies of CD4+ memory T cells, lower frequencies of naive CD4 + T cells, higher frequencies of CD8 + T cells (the latter two in part elicited by Cytomegalovirus, CMV, infection) are a characteristic of Major Depressive Disorder (MDD). In MDD patients with a history of childhood trauma and severe depression monocytes are inflammatory activated. Low grade inflammation and T cell system defects have also been reported in patients with Common Variable Immune Deficiency (CVID) (next to antibody production defects). CVID patients show a higher prevalence of mild depression. The aim of this study was to determine T cell frequencies and monocyte inflammatory activation in CVID patients with and without depression. This study confirms that CVID patients have CMV independent decreases in the frequency of naïve CD4 + T cells and it de novo shows a CMV dependent increase in the expression of inflammatory genes in monocytes. CVID patients with depression are additionally characterized by a CMV independent increase in the frequency of naïve CD8 + T cells, while lacking monocyte inflammatory activation. In conclusion, depressed CVID patients have T cell abnormalities comparable to that of patients with regular MDD. These abnormalities are presently targeted by thymosin α1 in an open-label proof of concept trial.

From the immune system to mood disorders especially induced by Toxoplasma gondii: CD4+ T cell as a bridge

Toxoplasma gondii (T. gondii), a ubiquitous and obligatory intracellular protozoa, not only alters peripheral immune status, but crosses the blood-brain barrier to trigger brain parenchymal injury and central neuroinflammation to establish latent cerebral infection in humans and other vertebrates. Recent findings underscore the strong correlation between alterations in the peripheral and central immune environment and mood disorders. Th17 and Th1 cells are important pro-inflammatory cells that can drive the pathology of mood disorders by promoting neuroinflammation. As opposed to Th17 and Th1, regulatory T cells have inhibitory inflammatory and neuroprotective functions that can ameliorate mood disorders. T. gondii induces neuroinflammation, which can be mediated by CD4+ T cells (such as Tregs, Th17, Th1, and Th2). Though the pathophysiology and treatment of mood disorder have been currently studied, emerging evidence points to unique role of CD4+ T cells in mood disorder, especially those caused by T. gondii infection. In this review, we explore some recent studies that extend our understanding of the relationship between mood disorders and T. gondii.

Estimations of the number people with mental diseases associated with toxoplasmosis and identification of risk factors by continent

Strong evidence exists based on metanalysis of the relationship between toxoplasmosis and many psychiatric diseases: schizophrenia, bipolar disorder, and suicidal behavior. Herein, we estimate the number of cases based on the attributable fraction due to toxoplasmosis on these diseases. The population attributable fraction of mental disease associated with toxoplasmosis was 20,4% for schizophrenia; 27,3% for bipolar disorder; and 0,29% for suicidal behavior (self-harm). The lower and upper estimated number of people with mental disease associated with toxoplasmosis was 4'816.491 and 5'564.407 for schizophrenia; 6'348.946 and 7'510.118,82 for bipolar disorder; and 24.310 and 28.151 for self-harm; for a global total lower estimated number of 11'189.748 and global total upper estimated number of 13'102.678 people with mental disease associated with toxoplasmosis for the year 2019. According to the prediction through the Bayesian model of risk factors for toxoplasmosis associated with mental disease, these varied in importance geographically; thus, in Africa, the most important risk factor was water contamination and in the European region, the cooking conditions of meats. Toxoplasmosis and mental health should be a research priority given the enormous potential impact of reducing this parasite in the general population.

Are bipolar disorder, major depression, and suicidality linked with Toxoplasma gondii? A seromolecular case-control study

OBJECTIVE

The existence of predisposing effects of latent Toxoplasma gondii (T. gondii) infection in bipolar disorder (BD), major depression (MD), and even suicide attempt (SA) has long been debatable. This conjecture remains unclear because there is a lack of evidence regarding how T. gondii manipulates the brain and behavior.

METHODS

We investigated the influence of T. gondii infection on BD and MD patients with or without SA compared to age-, sex-, and province-matched healthy controls (HCs) concurrently with serology and molecular-based evaluations. We prospectively assessed 147 volunteers with BD, 161 with MD, and 310 HCs.

RESULTS

T. gondii seropositivity rates were 57.1% for BD, 29.2% for MD, 64.8% for SA, and 21.3% for HC. Binary logistic regression analyses revealed that T. gondii positive Immunoglobulin G (IgG) status may be a prominent tendentious agent for BD (OR = 3.52; 95% CI [2.19-5.80]; p < 0.001) and SA (OR = 17.17; 95% CI [8.12-36.28]; p < 0.001), but not for MD (OR = 1.21; 95% CI [0.74-1.99]; p = 0.45). Nevertheless, the T. gondii DNA ratios determined by polymerase chain reaction (PCR) were linked to BD and MD.

CONCLUSION

Our findings strongly support the burgeoning interest in the possibility that latent T. gondii infection may be relevant to the etiology of BD and SA, although this connection remains ambiguous.

Therapeutic Implications of the Microbial Hypothesis of Mental Illness

There is increasingly compelling evidence that microorganisms may play an etiological role in the emergence of mental illness in a subset of the population. Historically, most work has focused on the neurotrophic herpesviruses, herpes simplex virus type 1 (HSV-1), cytomegalovirus (CMV), and Epstein-Barr virus (EBV) as well as the protozoan, Toxoplasma gondii. In this chapter, we provide an umbrella review of this literature and additionally highlight prospective studies that allow more mechanistic conclusions to be drawn. Next, we focus on clinical trials of anti-microbial medications for the treatment of psychiatric disorders. We critically evaluate six trials that tested the impact of anti-herpes medications on inflammatory outcomes in the context of a medical disorder, nine clinical trials utilizing anti-herpetic medications for the treatment of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) or schizophrenia, and four clinical trials utilizing anti-parasitic medications for the treatment of schizophrenia. We then turn our attention to evidence for a gut dysbiosis and altered microbiome in psychiatric disorders, and the potential therapeutic effects of probiotics, including an analysis of more than 10 randomized controlled trials of probiotics in the context of schizophrenia, bipolar disorder (BD), and major depressive disorder (MDD).

Association between Toxoplasma gondii infection and psychiatric disorders: a cross-sectional study in China

Psychiatric patients have become the focus of public attention, and current research suggests a possible link between Toxoplasma gondii (T. gondii) infection and mental illness. To understand the current situation of T. gondii infection in psychiatric patients in the study area, the relationship between T. gondii infection and mental diseases, and the influence of T. gondii infection on psychiatric patients, this study examined 3101 psychiatric inpatients from 2015 to 2020. All people included in the study were tested for anti-Toxoplasma IgM antibody and anti-Toxoplasma IgG antibody. Additionally, 4040 individuals from the general population were included as controls. The chi-square test and logistic regression analysis were carried out to determine the association between psychiatric disorders and T. gondii infection. The seroprevalence of anti-Toxoplasma IgM antibody was 0.23% (7/3101) in psychiatric inpatients and 0.11% (2/1846) in the general population, and there was no significant difference (p > 0.05). The seroprevalence rate of anti-Toxoplasma IgG antibodies was 3.03% (94/3101) in psychiatric inpatients and 1.05% (23/2194) in the general population, and there was a significant difference (p < 0.01). The seroprevalence of anti-Toxoplasma IgG antibody in psychiatric inpatients was significantly different between different age groups (p < 0.01). The positivity rate of anti-Toxoplasma IgG antibodies was 5.17% (3/58) in patients with mania, 3.24% (8/247) in patients with recurrent depressive disorder, 3.54% (13/367) in patients with depression, 3.22% (39/1213) in patients with schizophrenia, 2.41% (18/748) in patients with bipolar disorder and 2.25% (2/89) in patients with dissociative disorder. Compared to the general population, patients with mania (OR = 5.149 95% CI 1.501–17.659 p = 0.009), schizophrenia (OR = 3.136 95% CI 1.864–5.275 p = 0.000), depression (OR = 3.466 95% CI 1.740–6.906 p = 0.000), recurrent depressive disorder (OR = 3.160 95% CI 1.398–7.142 p = 0.006) and bipolar disorder (OR = 2.327 95% CI 1.249–4.337 p = 0.008) were found to be significantly associated with the seroprevalence of anti-Toxoplasma IgG antibody. This study suggests that the seroprevalence of T. gondii infection in psychiatric patients was higher and that age was an influencing factor of T. gondii infection in psychiatric patients. T. gondii infection was associated with mania, schizophrenia, depression, recurrent depressive disorder and bipolar disorder.

Latent Toxoplasmosis is Associated with Depression and Suicidal Behavior

OBJECTIVE

Neuroinflammation is implicated in the pathophysiology of depression. Toxoplasma gondii (T. gondii) causes chronic brain inflammatory process and may thus contribute to both depression and its most serious complication, suicidal behavior. In this study, we hypothesized that latent toxoplasmosis may underlie current depression and/or suicidal behavior.

METHOD

Currently depressed individuals (N = 384) and age, sex, and residence-matched healthy controls (HC) (N = 400) were tested for latent toxoplasmosis (i.e., positive serum T. gondii IgG antibodies). Exclusions included positive IgM and negative IgG antibodies indicating acute T. gondii infection and history of cognitive problems. Depression severity and history of lifetime suicide attempts were assessed using Beck Depression Inventory (BDI) and Columbia Suicide Severity Rating Scale, respectively.

RESULTS

Participants with seropositive anti-T. gondii IgG antibody had a significantly higher odds of being depressed compared with seronegative participants (OR = 2.9, 95% CI: 1.9-4.3; p < 0.001). BDI score was significantly different between depressed seropositive and depressed seronegative individuals (IgG＋: mean (SD)= 39.65 (11.83) vs. IgG-: mean (SD)= 33.44(9.80); t = 5.03, p < 0.001). Further, seropositive depressed participants were more likely to have prior history of actual suicide attempts compared with seronegative participants (OR= 6.2, 95% CI: 3.4-11.2, p < 0.001).

CONCLUSIONS

Latent toxoplasmosis may represent be a risk factor for depression and suicidal behavior. Screening for, and treatment of, underlying T. gondii infection may help improve depression and curb the increasing suicide rates. Future studies should prospectively test these hypotheses to be adequately implemented.HIGHLIGHTSLatent toxoplasmosis has been linked to history of psychiatric disorders.Depressed individuals have higher positivity rate of T. gondii IgG antibody than healthy controls.Depressed T. gondii seropositive individuals have increased likelihood to have history of suicidal behavior.

Impact of Plant-Based Foods and Nutraceuticals on Toxoplasma gondii Cysts: Nutritional Therapy as a Viable Approach for Managing Chronic Brain Toxoplasmosis

Toxoplasma gondii is an obligate intracellular parasite that mainly infects warm-blooded animals including humans. T. gondii can encyst and persist chronically in the brain, leading to a broad spectrum of neurological sequelae. Despite the associated health threats, no clinical drug is currently available to eliminate T. gondii cysts. In a continuous effort to uncover novel therapeutic agents for these cysts, the potential of nutritional products has been explored. Herein, we describe findings from in vitro and in vivo studies that support the efficacy of plant-based foods and nutraceuticals against brain cyst burden and cerebral pathologies associated with chronic toxoplasmosis. Finally, we discuss strategies to increase the translatability of preclinical studies and nutritional products to address whether nutritional therapy can be beneficial for coping with chronic T. gondii infections in humans.

Toxoplasma gondii Infection in Patients with Psychiatric Disorders from Western Romania

Background and Objectives: High rates of infection with Toxoplasma gondii were found in psychiatric patients globally. In this study, we assessed for the first time the prevalence of T. gondii infection in psychiatric patients and healthy individuals with no known psychiatric disorders in Western Romania. Materials and Methods: The presence of specific IgG anti-T. gondii antibodies was evaluated in 308 psychiatric patients and 296 control subjects using a chemiluminescence assay. Results: Overall, the seroprevalence of IgG antibodies was higher in psychiatric patients (67.86%; 209/308), compared with the control group (54.05%; 160/296) (p < 0.001). Our results revealed a significantly higher prevalence of T. gondii antibodies among patients with schizophrenia (69.77%), organic (personality and behaviour) disorders (76.74%), and mental disorders concerning alcohol abuse (84.62%), compared with the control group (p = 0.009, p = 0.005, p = 0.043, respectively). Conclusions: This study provides new and important information on the seroprevalence of T. gondii in Romanian psychiatric patients and may serve for further scientific research regarding the status of T. gondii infection in patients with psychiatric disorders.

Toxoplasmosis: Targeting neurotransmitter systems in psychiatric disorders

The most common form of the disease caused by Toxoplasma gondii (T. gondii) is latent toxoplasmosis due to the formation of tissue cysts in various organs, such as the brain. Latent toxoplasmosis is probably a risk factor in the development of some neuropsychiatric disorders. Behavioral changes after infection are caused by the host immune response, manipulation by the parasite, central nervous system (CNS) inflammation, as well as changes in hormonal and neuromodulator relationships. The present review focused on the exact mechanisms of T. gondii effect on the alteration of behavior and neurotransmitter levels, their catabolites and metabolites, as well as the interaction between immune responses and this parasite in the etiopathogenesis of psychiatric disorders. The dysfunction of neurotransmitters in the neural transmission is associated with several neuropsychiatric disorders. However, further intensive studies are required to determine the effect of this parasite on altering the level of neurotransmitters and the role of neurotransmitters in the etiology of host behavioral changes.

Association between Toxoplasma gondii Infection and Headache: A Systematic Review and Meta-Analysis

BACKGROUND

The impact of infectious agents, such as Toxoplasma gondii (T. gondii), on human behavior and mental disorders, has recently attracted the attention of researchers. T. gondii has emerged as a suitable candidate for such disorders due to its neutral nature. Therefore, the current study aimed at investigating the possible relationship between T. gondii infection and headache.

METHODS

Five databases were thoroughly searched (up to October 4, 2019) for articles on the prevalence of T. gondii in headache sufferers. In this study, the odds ratio (OR) and corresponding 95% confidence interval (CI) were estimated using a random effect model and forest plot to gauge effect size and effect of each study.

RESULTS

A total number of four articles, including one cross-sectional and three case-control studies 2517 participants, entered the meta-analysis, out of whom, 1205 subjects were afflicted with headache or migraine (17.67% positive for toxoplasmosis) and 1312 participants were not (18.29% for toxoplasmosis). The results of the meta-analysis indicated a common OR of 1.59 (95% CI: 1.03-2.47) by the random effect model.

CONCLUSION

The obtained results of several studies have linked toxoplasmosis and headache. Therefore, more quality studies with larger sample sizes are needed to determine the detailed association between headache and T. gondii infection for the prevention and control of toxoplasmosis among headache sufferers.

New role of sertraline against Toxoplasma gondii-induced depression-like behaviours in mice

Toxoplasma gondii (T. gondii) is a neurotropic protozoan parasite, which can cause mental and behavioural disorders. The present study aimed to elucidate the effects and underlying molecular mechanisms of sertraline (SERT) on T. gondii-induced depression-like behaviours. In the present study, a mouse model and a microglial cell line (BV2 cells) model were established by infecting with the T. gondii RH strain. In in vivo and in vitro experiments, the underlying molecular mechanisms of SERT in inhibiting depression-like behaviours and cellular perturbations caused by T. gondii infection were investigated in the mouse brain and BV2 cells. The administration of SERT significantly ameliorated depression-like behaviours in T. gondii-infected mice. Furthermore, SERT inhibited T. gondii proliferation. Treatment with SERT significantly inhibited the activation of microglia and decreased levels of pro-inflammatory cytokines such as tumour necrosis factor-alpha, and interferon-gamma, by down-regulating tumour necrosis factor receptor 1/nuclear factor-kappa B signalling pathway, thereby ameliorating the depression-like behaviours induced by T. gondii infection. Our study provides insight into the underlying molecular mechanisms of the newly discovered role of SERT against T. gondii-induced depression-like behaviours.

Association between Toxoplasma gondii Infection in Brain and a History of Depression in Suicide Decedents: A Cross-Sectional Study

We assessed the association between Toxoplasma gondii (T. gondii) infection of the central nervous system and suicide correlates in suicide decedents. Eighty-seven decedents who died by suicide received in a forensic setting for medico-legal autopsies in Mexico City were studied. Two samples of brain (amygdala and prefrontal cortex) from each decedent were examined for detection of T. gondii using immunohistochemistry. Correlates of suicide including a history of previous suicide attempts, co-morbid mental disorder, consumption of alcohol or tobacco, irritability and aggression, economic problems, presence of drugs or alcohol in blood and suicide method were obtained and analyzed for their association with T. gondii infection. T. gondii immunohistochemistry was positive in prefrontal cortex sections in 6 decedents and in an amygdala section in one decedent. Thus, the prevalence of T. gondii infection in brain in suicide victims was 8.0% (7/87). Bivariate and logistic regression analysis of suicide correlates showed that only a history of depression was associated with T. gondii infection of the brain in suicide victims (OR: 12.00; 95% CI: 2.26–63.46; p = 0.003). Our results provide evidence that T. gondii infection in brain is associated with a history of depression in suicide decedents.

Scoping Review of Toxoplasma Postinfectious Sequelae

Previous economic estimates of infection with Toxoplasma gondii and chronic sequelae following infection lack sufficient data to establish the true burden of disease and its chronic sequelae. This scoping review aims to fill this gap by updating existing literature regarding the development of postinfectious sequelae following T. gondii infection. Literature published between January 1, 2000, and November 6, 2018, in PubMed, EMBASE, and Scopus was searched for a wide range of postinfectious sequelae and economic estimate terms. This scoping review includes summaries from the 108 articles covering 5 main groupings of outcomes (categories are not exclusive) including vision disorders (n = 58), psychological and mental health disorders (n = 27), neurological disorders (n = 17), fetal death and infection (n = 15), and hearing loss (n = 6), as well as a description of other outcomes reported. While the majority of the included studies assessed the incidence of these outcomes postinfection, very few followed participants long-term. These prospective studies are needed to understand the true burden of postinfectious sequelae over the life course, particularly because congenital infection with Toxoplasma can lead to severe outcomes for newborns. This scoping review can be used as an important resource for other researchers wishing to conduct future systematic reviews and meta-analyses, as well as for policy makers interested in developing guidance for public and health care partners.

Relationship between Latent Toxoplasmosis and Depression in Clients of a Center for Assisted Reproduction

Latent infection of the globally spread parasite Toxoplasma gondii in humans has been associated with changes in personality and behavior. Numerous studies have investigated the effect of toxoplasmosis on depression, but their results are inconsistent. Our study focused on the effect of latent toxoplasmosis on depression in men and women in association with their fertility. In 2016-2018, we recruited clients (677 men and 664 women) of the Center for Assisted Reproduction and asked them to complete a standardized Beck Depression Inventory-II. In women without fertility problems, we found higher depression scores in Toxoplasma-positive than in Toxoplasma-negative (p = 0.010, Cohen's d = 0.48). Toxoplasma-positive infertile men, on the other hand, had lower depression scores than Toxoplasma-negative infertile men (p ≤ 0.001, Cohen's d = 0.48). Our results are consistent with the previously described effects of latent toxoplasmosis, which seem to go in opposite directions regarding the effect on personality and behavior of men and women. Our results could be explained by gender-contrasting reactions to chronic stress associated with lifelong infection. This suggests that due to gender differences in the impact of latent toxoplasmosis, future studies ought to perform separate analyses for women and men.

Implications of Zoonoses From Hunting and Use of Wildlife in North American Arctic and Boreal Biomes: Pandemic Potential, Monitoring, and Mitigation

The COVID-19 pandemic has re-focused attention on mechanisms that lead to zoonotic disease spillover and spread. Commercial wildlife trade, and associated markets, are recognized mechanisms for zoonotic disease emergence, resulting in a growing global conversation around reducing human disease risks from spillover associated with hunting, trade, and consumption of wild animals. These discussions are especially relevant to people who rely on harvesting wildlife to meet nutritional, and cultural needs, including those in Arctic and boreal regions. Global policies around wildlife use and trade can impact food sovereignty and security, especially of Indigenous Peoples. We reviewed known zoonotic pathogens and current risks of transmission from wildlife (including fish) to humans in North American Arctic and boreal biomes, and evaluated the epidemic and pandemic potential of these zoonoses. We discuss future concerns, and consider monitoring and mitigation measures in these changing socio-ecological systems. While multiple zoonotic pathogens circulate in these systems, risks to humans are mostly limited to individual illness or local community outbreaks. These regions are relatively remote, subject to very cold temperatures, have relatively low wildlife, domestic animal, and pathogen diversity, and in many cases low density, including of humans. Hence, favorable conditions for emergence of novel diseases or major amplification of a spillover event are currently not present. The greatest risk to northern communities from pathogens of pandemic potential is via introduction with humans visiting from other areas. However, Arctic and boreal ecosystems are undergoing rapid changes through climate warming, habitat encroachment, and development; all of which can change host and pathogen relationships, thereby affecting the probability of the emergence of new (and re-emergence of old) zoonoses. Indigenous leadership and engagement in disease monitoring, prevention and response, is vital from the outset, and would increase the success of such efforts, as well as ensure the protection of Indigenous rights as outlined in the United Nations Declaration on the Rights of Indigenous Peoples. Partnering with northern communities and including Indigenous Knowledge Systems would improve the timeliness, and likelihood, of detecting emerging zoonotic risks, and contextualize risk assessments to the unique human-wildlife relationships present in northern biomes.

The global status and genetic characterization of hydatidosis in camels (Camelus dromedarius): a systematic literature review with meta-analysis based on published papers

Hydatidosis is a potential zoonotic helminthic disease affecting a broad spectrum of mammals, including humans, worldwide. The current review was conducted to investigate the genotypic status and prevalence of hydatid disease in camels across the world. For the purpose of the study, the articles addressing the worldwide prevalence of hydatidosis in camels were searched in several English language databases. The search process resulted in the inclusion of 122 papers. Based on the data presented in the reviewed articles, the pooled prevalence of hydatid disease in camels across the world was measured at 23.75% (95% CI 20.15-27.55). Moreover, the subgroup analysis demonstrated significant differences in the overall prevalence of hydatidosis among camels based on year, geographic area, climate parameters, camel population, gender, infected organ, fertility rate of the cyst and laboratory diagnostic technique. Furthermore, the Echinococcus granulosus genotypes identified in camels with hydatidosis included G1, G2, G3, G1-G3, G5, G6, G7, G6-G7 and G6-G10, with G6 being the most common genotype throughout the world. The data obtained from the current study are central to the better conceptualization of the biological and epidemiological characteristics of E. granulosus s.l. genotypes around the world, which can be helpful in the planning and adoption of more comprehensive control strategies.

Infections, inflammation, and risk of neuropsychiatric disorders: the neglected role of "co-infection"

Neuropsychiatric disorders (NPDs) have multiple etiological factors, mainly genetic background, environmental conditions and immunological factors. The host immune responses play a pivotal role in various physiological and pathophysiological process. In NPDs, inflammatory immune responses have shown to be involved in diseases severity and treatment outcome. Inflammatory cytokines and chemokines are involved in various neurobiological pathways, such as GABAergic signaling and neurotransmitter synthesis. Infectious agents are among the major amplifier of inflammatory reactions, hence, have an indirect role in the pathogenesis of NPDs. As such, some infections directly affect the central nervous system (CNS) and alter the genes that involved in neurobiological pathways and NPDs. Interestingly, the most of infectious agents that involved in NPDs (e.g., Toxoplasma gondii, cytomegalovirus and herpes simplex virus) is latent (asymptomatic) and co-or-multiple infection of them are common. Nonetheless, the role of co-or-multiple infection in the pathogenesis of NPDs has not deeply investigated. Evidences indicate that co-or-multiple infection synergically augment the level of inflammatory reactions and have more severe outcomes than single infection. Hence, it is plausible that co-or-multiple infections can increase the risk and/or pathogenesis of NPDs. Further understanding about the role of co-or-multiple infections can offer new insights about the etiology, treatment and prevention of NPDs. Likewise, therapy based on anti-infective and anti-inflammatory agents could be a promising therapeutic option as an adjuvant for treatment of NPDs.

Relationship between toxoplasmosis and autism: A systematic review and meta-analysis

Toxoplasma gondii (T. gondii) is a foodborne parasite that is investigated in many psychiatric diseases, such as autism spectrum disorders (ASD). Therefore, a systematic literature review was conducted searching seven electronic databases on the prevalence of T. gondii antibodies among autism patients. The current study involved sensitivity analysis, meta-regression, subgroup analysis, publication bias test, and quality assessment of studies. On the basis of the findings, the odds ratio (OR) of latent Toxoplasma infection 1.93 (95% confidence intervals (CI): 1.01-3.66) was associated with ASD risk. However, there was no relationship between acute infection and ASD 0.39 (95% CI: 0.18-0.87). The obtained results of Begg's and Egger's tests showed no publication bias (P = 0.851 and P = 0.297, respectively). The sensitivity analysis confirmed robust and stable estimates with a significant level of heterogeneity (I2 = 78.1%, P < 0.000). Of the investigated patients' characteristics, only the gender variable was analyzed, indicating the combined ORs of 2.63 (95% CI: 0.29-23.63) in females and 2.62 (95% CI: 0.94-7.30) in male participants. This study showed that toxoplasmosis plays an important role as a risk factor for autism. However, further prospective investigations are highly recommended to illuminate the developmental pathways to this disorder and provide new strategies for the prevention and treatment of this disease.

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.

Sarcocystosis in Ruminants of Iran, as Neglected Food-Borne Disease: A Systematic Review and Meta-analysis

PURPOSE

Sarcocystis is a zoonotic parasitic pathogen which endangers the safety of meat and meat products. This systematic review and meta-analysis aimed to evaluate the prevalence rate and status of Sarcocystis spp. in ruminants as important food sources in Iran.

METHODS

Data were collected from papers indexed in five English language electronic databases (PubMed, Scopus, Web of Science, Science Direct, and Google Scholar) and four Persian electronic databases (IranMedex, SID, IranDoc, and Magiran) from January to April 2019. Papers were selected based on inclusion criteria. Data analysis was performed in StatsDirect statistical software, version 2.7.2.

RESULTS

The searching process resulted in the identification of 73 studies. Data analyses revealed that the total prevalence (95% confidence intervals) of Sarcocystis spp. in Iranian ruminants was 74.40% (64.01-83.56). In addition, a significant association was also observed between sarcocystosis infection in Iranian ruminants and year, host, location, and diagnostic technique (P < 0.001).

CONCLUSIONS

According to our data, the prevalence of Sarcocystis infection in ruminants is relatively high. High pathogenicity of some Sarcocystis spp. and the negative impact that the spread of some parasites among ruminants can have on human and animal health necessitate the direction of more attention toward monitoring, controlling, and preventing sarcocystosis.

Aggravation of symptom severity in adult attention-deficit/hyperactivity disorder by latent Toxoplasma gondii infection: a case-control study

Toxoplasma gondii (T. gondii) has a high worldwide prevalence and an underestimated impact on neuropsychiatric disorders. Previous studies related T. gondii to disorders associated with the dysfunctional dopaminergic system. However, an association between T. gondii infection and adult attention-deficit/hyperactivity disorder (ADHD) has not yet been studied. In a sex- and age-matched case-control study, we investigated the seropositivity, serointensity, and avidity of latent T. gondii infection in adult ADHD patients and examined the influence of those variables on the symptomatology of ADHD. Of 140 participants, 20.0% were seropositive for anti-T. gondii IgG and 0% for anti-T. gondii IgM. T. gondii seropositivity was associated with 2.8-fold increase in the odds of ADHD in a confounder-adjusted multivariable analysis. Age and consumption of raw/undercooked meat were confirmed as significant predictors of T. gondii seropositivity. Multiple linear regression analysis of self-rated ADHD-related symptom severity in all participants revealed a significant association with T. gondii seropositivity, elevated IgG titers (serointensity), and stronger anti-T. gondii IgG avidity. Overall symptom severity was increased in seropositive ADHD patients compared to seronegative subjects with ADHD. In particular, hyperactivity was significantly associated with serointensity. We conclude that there is a high rate of T. gondii seropositivity in adults with ADHD. Additionally, our results suggest a clinical impact of latent T. gondii infection on ADHD-related symptoms in a serointensity- and avidity-dependent manner.

Infection with Toxoplasma gondii increases the risk of psychiatric disorders in Taiwan: a nationwide population-based cohort study

This study aimed to evaluate associations between toxoplasmosis and psychiatric disorders in Taiwan based on the National Health Insurance Research Database, Taiwan (1997-2013). Patients newly diagnosed with toxoplasmosis formed the case group (n = 259), and the control group included propensity-score matched patients without toxoplasmosis (n = 1036). The primary outcome was incidence of psychiatric disorders. Cox proportional hazards regression and stratified analyses were performed to examine risk of developing specific psychiatric disorders between patients with and without toxoplasmosis. Patients with toxoplasmosis had significantly higher incidence of psychiatric disorders than those without toxoplasmosis (P = 0.016). A significant difference was found in numbers of psychiatric disorders between the two groups during 14 years of follow-up (log-rank P < 0.001). Those with toxoplasmosis had significantly higher risk of bipolar disorder [adjusted hazard ratio (aHR = 3.60, 95% confidence interval (CI) = 2.07, 7.26), depression (aHR = 4.94, 95% CI = 2.15, 11.80) and anxiety (aHR = 5.36, 95% CI = 2.98, 25.88), but no significant between-group differences were found for schizophrenia and other psychiatric disorders. In conclusion, the present nationwide population-based analysis revealed that Toxoplasma gondii infection in Taiwan significantly increases the risk for developing bipolar disorder, depression and anxiety, but not for schizophrenia and other psychiatric disorders.

Association of exposure to Toxoplasma gondii, Epstein-Barr Virus, Herpes Simplex virus Type 1 and Cytomegalovirus with new-onset depressive and anxiety disorders: An 11-year follow-up study

BACKGROUND

Some prevalent infections have been associated with common mental disorders, but there are few longitudinal studies, and results are inconsistent. We aimed to assess whether serological evidence of exposure to Toxoplasma gondii (T. gondii), Epstein-Barr Virus (EBV), Herpes Simplex virus Type 1 (HSV-1) and Cytomegalovirus (CMV) predict development of new-onset depressive and anxiety disorders.

METHODS

In a nationally representative sample of the Finnish adult population aged 30 and over (BRIF8901, n = 8028), IgG antibodies for T. gondii, EBV, HSV-1 and CMV were measured in plasma samples. The population was followed up for 11 years and new-onset depressive and anxiety disorders were diagnosed with the Composite International Diagnostic Interview. Associations were analysed controlling for sex, age, educational level, region of residence and marital status, and in separate analyses also for C-reactive protein level.

RESULTS

Seropositivity and serointensity of the four infectious agents were not associated with an increased risk of new-onset depressive or anxiety disorders. Seropositivity for CMV at baseline was associated with a lower risk of new-onset generalized anxiety disorder (adjusted OR 0.43, 95% CI 0.22-0.86 for CMV positive persons).

CONCLUSION

The results of this large, nationally representative longitudinal study suggest that common viral infections are not significant risk factors for common mental disorders. The association of CMV with a lower risk of generalized anxiety disorder warrants further investigation.

Toxoplasma gondii infection and risk of attention-deficit hyperactivity disorder: a systematic review and meta-analysis

Toxoplasma gondii (T. gondii), as an opportunistic neurotropic parasite of the Apicomplexa family, was firstly described in 1908. As attention-deficit hyperactivity disorder (ADHD) is one of the most common neuropsychiatric disorders in children and adolescents and often persists into adulthood, the purpose of this systematic review and meta-analysis was to investigate the relationship between T. gondii infection and ADHD.The data were systematically collected from seven electronic databases up to May 1^st 2019 with no language restriction. This study was registered at the International Prospective Register of Systematic Reviews (PROSPERO; code: CRD42020149353). Odds ratios (ORs) and 95% confidence intervals (CI) were estimated using a random effects model. Seven studies involving five cross-sectional and two case-control studies were included in this meta-analysis.Results indicated that there was a statistically non-significant association between exposure to T. gondii infection and increased risk of ADHD based on the detection of immunoglobulin G (IgG) antibody (2.02 [95% CI: 0.97-4.20]; I²=58.7%). However, obtained results of Egger's tests for anti-T. gondii IgG antibody showed publication bias (P=0.014).Sensitivity analysis revealed stable results for the association between anti-T. gondii IgG antibody with ADHD.Given the small number of studies in this field and the obtained results, it cannot be conclusively stated that T. gondii is a risk factor for ADHD.It is important to have reliable information about the relationship between T. gondii and ADHD around the world; as it may lead to better insight to elucidate the possible association of toxoplasmosis and the pathogenesis of ADHD.

Arctigenin ameliorates depression-like behaviors in Toxoplasma gondii-infected intermediate hosts via the TLR4/NF-κB and TNFR1/NF-κB signaling pathways

Toxoplasma gondii (T. gondii) is a known neurotropic protozoan that remains in the central nervous system and induces neuropsychiatric diseases in intermediate hosts. Arctigenin (AG) is one of the major bioactive lignans of the fruit Arctium lappa L. and has a broad spectrum of pharmacological activities such as neuroprotective, anti-inflammatory and anti-T. gondii effects. However, the effect of AG against depressive behaviors observed in T. gondii-infected hosts has not yet been clarified. In the present study, we analyzed the effects of AG against T. gondii-induced depressive behaviors in intermediate hosts using a microglia cell line (BV2 cells) and brain tissues of BALB/c mice during the acute phase of infection with the RH strain of T. gondii. AG attenuated microglial activation and neuroinflammation via the Toll-like receptor/nuclear factor-kappa B (NF-κB) and tumor necrosis factor receptor 1/NF-κB signaling pathways, followed by up-regulating the dopamine and 5-hydroxytryptamine levels and inhibiting the depression-like behaviors of hosts. AG also significantly decreased the T. gondii burden in mouse brain tissues. In conclusion, we elucidated the effects and underlying molecular mechanisms of AG against depressive behaviors induced by T. gondii infection.

Prevalence and Influencing Factors of Anxiety and Depression Symptoms in the First-Line Medical Staff Fighting Against COVID-19 in Gansu

BACKGROUND

The outbreak of novel coronavirus pneumonia (COVID-19) has brought enormous physical and psychological pressure on Chinese medical staff. It is extremely important to understand the prevalence and influencing factors of anxiety and depression symptoms in first-line anti-epidemic medical staff and their coping styles for these negative emotions.

METHODS

A cross-sectional survey was conducted in Gansu (China), with a questionnaire packet which consisted of the self-rating anxiety scale (SAS), self-rating depression scale (SDS), and the simplified coping style questionnaire (SCSQ). A total of 79 doctors and 86 nurses participated in the survey. Correlation analysis was performed to explore the relationship between SAS, SDS, and SCSQ score. A linear regression model was used to determine the influencing factors for anxiety or depression symptoms.

RESULTS

The prevalence rates of anxiety and depression symptoms among doctors was 11.4% and 45.6%, respectively. History of depression or anxiety (T=-2.644, p= 0.010, 95%CI: -10.514~-1.481) was shown to be a risk factor for anxiety symptoms in doctors, while being male (T=2.970, p=0.004, 95%CI: 2.667~13.521) was a protective factor for depression. The prevalence rate of anxiety and depression symptoms among nurses was 27.9% and 43.0%, respectively. History of depression or anxiety was a common risk factor for anxiety symptoms (T=-3.635, p=0.000, 95%CI: -16.360~-4.789) and depression symptoms (T=-2.835, p=0.005, 95%CI:-18.238~-3.254) in nurses. The results of partial correlation analysis (controlled for gender and history of depression or anxiety) indicated that the total score of positive coping was negatively correlated with the total score of anxiety (r=-0.182, p=0.002) and depression (r=-0.253, p=0.001).

CONCLUSIONS

The first-line anti-epidemic medical staff have high anxiety and depression symptoms and adopting positive coping styles will help to improve their negative emotions.