Relationship between toxoplasmosis and obsessive compulsive disorder: A systematic review and meta-analysis

Toxoplasma gondii infection and testosterone alteration: A systematic review and meta-analyses

BACKGROUND

Toxoplasma gondii (T. gondii) is a worldwide distributed protozoan parasite which has infected a wide range of warm-blooded animals and humans. The most common form of T. gondii infection is asymptomatic (latent); nevertheless, latent toxoplasmosis can induce various alterations of sex hormones, especially testosterone, in infected humans and animals. On the other hand, testosterone is involved in behavioral traits and reproductive functions in both sexes. Hence, the purpose of this systematic review is to summarize the available evidence regarding the association between T. gondii infection and testosterone alteration.

METHODS

In the setting of a systematic review, an electronic search (any date to 10 January 2023) without language restrictions was performed using Science Direct, Web of Science, PubMed, Scopus, and Google Scholar. The PRISMA guidelines were followed. Following the initial search, a total of 12,306 titles and abstracts were screened initially; 12,281 were excluded due to the lack of eligibility criteria or duplication. Finally, 24 articles met the included criteria. A mean±standard deviation (SD) was calculated to assess the difference of testosterone between T. gondii positive and T. gondii negative humans. The possibility of publication bias was assessed using Egger's regression. P-value < 0.05 was considered statistically significant.

RESULTS

This systematic review identified 24 articles (18 studies in humans and six studies in animals). Most human studies (13 out of 19) reported an increased level of testosterone following latent toxoplasmosis in males, while three studies reported decreased levels and two studies reported an insignificant change. Eleven articles (seven datasets in males and seven datasets in females) were eligible to be included in the data synthesis. Based on the random-effects model, the pooled mean± SD of testosterone in T. gondii positive than T. gondii negative was increased by 0.73 and 0.55 units in males and females, respectively. The Egger's regression did not detect a statistically significant publication bias in males and females (p = value = 0.95 and 0.71), respectively. Three studies in male animals (rats, mice, and spotted hyenas) and two studies in female animals (mice and spotted hyenas) reported a decline in testosterone in infected compared with non-infected animals. While, one study in female rats reported no significant changes of testosterone in infected than non-infected animals. Moreover, two studies in male rats reported an increased level of testosterone in infected than non-infected animals.

CONCLUSIONS

This study provides new insights about the association between T. gondii infection and testosterone alteration and identifies relevant data gaps that can inform and encourage further studies. The consequence of increased testosterone levels following T. gondii infection could partly be associated with increased sexual behavior and sexual transmission of the parasite. On the other hand, declining testosterone levels following T. gondii infection may be associated with male reproductive impairments, which were observed in T. gondii-infected humans and animals. Furthermore, these findings suggest the great need for more epidemiological and experimental investigations in depth to understand the relationship between T. gondii infection and testosterone alteration alongside with future consequences of testosterone alteration.

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.

Positive Toxoplasma IgG Serology Is Associated with Increased Overall Mortality - A Propensity Score-Matched Analysis

Toxoplasma gondii is a prevalent parasitic disease with significant morbidity and mortality in immunocompromised populations. We lack long-term outcomes for latent infections. We aimed to elucidate the relationship between latent T. gondii infection and mortality risk. We queried TriNetX, a international multicenter network, to validate mortality risk differences among patients with positive or negative toxoplasma IgG through propensity score matching (PSM). We excluded patients with toxoplasmosis disease by International Classification of Diseases codes or polymerase chain reaction testing. We found 28,138 patients with available toxoplasma IgG serology. Seropositive patients were older and had a male preponderance. More seropositive patients identified as Hispanic, Latino, or Black persons. Patients who were positive for T. gondii IgG serology were slightly more likely to have underlying heart failure, a transplanted organ or tissue, malignant neoplasms of lymphoid or hematopoietic tissues, and diseases of the nervous system than seronegative controls. After PSM of patients with positive (N = 6,475) and negative (N = 6,475) toxoplasma IgG serologies, toxoplasmosis-positive patients were more likely to have long-term drug use but less likely to suffer from behavioral disorders. The overall PSM 1- and 5-year mortality was higher among patients with a positive toxoplasma IgG serology. The risk of schizophrenia was increased at 5 years. We found a prevalence of toxoplasma IgG positivity of 0.03% during the last 3 years. Latent T. gondii associates with a higher overall mortality risk. The study of social determinants of health and follow-up studies are necessary to corroborate the findings and find possible causal mechanisms.

Silent Infections are not So Silent: The Emerging Role of Combined Infections, Inflammation, and Vitamin Levels in OCD

Objective

Recent evidence highlights that different agents may trigger immune-mediated processes involved in the pathophysiology of different neuropsychiatric conditions. Given the limited information on obsessive-compulsive disorder (OCD), the present study aimed at assessing current/past infections and plasma levels of vitamin D, vitamin B12, folic acid, homocysteine and common peripheral inflammatory markers in a group of OCD outpatients.

Method

The sample included 217 adult outpatients with an OCD diagnosis according to the DSM-5 criteria. The Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) was used to assess the clinical phenotype and symptom severity. Laboratory blood tests measured levels of vitamin D, vitamin B12, folic acid, homocysteine, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), blood count and antibodies titers for cytomegalovirus (CMV), Epstein Barr virus (EBV), Toxoplasma gondii and antistreptolysin titer.

Results

Sixty-one patients had a previous EBV infection, 46 were seropositive for CMV IgG, 24 showed positive antistreptolysin titer, 14 were seropositive for Toxoplasma gondii IgG, and four for CMV IgM. More than a half of patients showed vitamin D insufficiency. Compared to seronegative patients, patients with a past EBV infection displayed significantly higher scores on the Y-BOCS total score and compulsion subscale, and other symptoms. Vitamin D was negatively correlated with both the Y-BOCS total score and the subscales scores. Folic acid was negatively correlated with the Y-BOCS total and obsessions subscale score.

Conclusions

The findings of our study show an association between Epstein-Barr infection and hypovitaminosis D and the overall severity and specific symptom patterns of OCD. The laboratory measures used in this study are useful, cheap and easy parameters that should be routinely assessed in patients with OCD. Further studies are needed to clarify their role in OCD pathophysiology and outcomes, as well as the potential therapeutic impact of vitamins and antibiotics/immunomodulatory agents in OCD and other psychiatric conditions.

Toxoplasma infection and Rhesus blood group system: A systematic review and meta-analysis

BACKGROUND

Toxoplasmosis is one of the most common infections in humans and animals, which is caused by an obligate intracellular opportunistic parasite known as Toxoplasma gondii (T. gondii). Some data have shown that both Rhesus (Rh)-positive and Rh-negative individuals differ in response to biological factors, including Toxoplasma infection. Therefore, this systematic review and meta-analysis was conducted to investigate the scientific evidence regarding the possible association between the Rh blood group and Toxoplasma infection and to determine the seroprevalence of T. gondii in the Rh blood group system.

METHODS

The research was conducted on PubMed, ScienceDirect, ProQuest, and Google Scholar databases until January 2023. Twenty-one cross-sectional studies were included with a total of 10910 people. The data were synthesized using a random effect model with 95% confidence intervals (CIs).

RESULTS

The overall prevalence of T. gondii was calculated at 32.34% (CI 95%: 28.23-36.45%) and 33.35% (CI 95%: 19.73-46.96%) in Rh-positive and Rh-negative blood groups. In addition, the pooled OR for the relationship between the Rh blood group and the seroprevalence of T. gondii was 0.96 (95% CI: 0.72-1.28).

CONCLUSIONS

This meta-analysis showed a high prevalence of Toxoplasma infection in both Rh-negative and positive blood groups. This systematic review and meta-analysis revealed that no significant association was found between toxoplasmosis and Rh factor. Because of the limited number of studies in this field, more research is recommended to determine the exact relationship between toxoplasmosis and the Rh factor.

Al-Safar M, Mahmood SA. Men's ND1 gene genetic makeup Toxoplasmosis and Oligospermia affecting couples' infertility

Introduction: Toxoplasma infection was higher in infertile couples than fertile couples, probably due to anti-sperm antibodies that were higher in couples with Toxoplasmosis. Investigations of T. gondii infections in men with infertility showed that among 100 cases of men's infertility, 36% were serologically positive for Toxoplasma-IgG and IgM. It has been concluded that T. gondii can affect men's fertility and result in infertility. Materials and Methods: Selective infertile males were asked about days of sexual abstinence. Seminal fluid samples were collected following a minimum of 2 days and a maximum of 7 days from abstinence. Every patient was given a clean, wide mouth, sterile, dry, graduated plastic and warm disposable container. The samples were obtained by masturbation in a private room near the semen analysis lab to reduce seminal exposure to temperature fluctuations and control the time from collection to analysis. Results: For the ND1 gene, samples of 8 different fertility groups have been sequenced. These sequences have been compared to reference sequences taken from the NCBI database. Several mutations in various nucleotide positions of the ND1 regions have been detected in samples from multiple groups. The base substitution has been positioned on the nucleotides (nts) 3480, 3567, 3591, 3693, and 4216. The T to C evolution was notorious at nt 3480 in ND1 genes. The SNP was detected in an asthenospermia human (Sample code: 010480). Keywords: Sequence, ND1 gen, Oligospermia Toxoplasmosis, Couples infertility

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.

Comparison of Toxoplasmosis in Narcotic Drug-addicted and Healthy Persons in the Southwest of Iran; A Case-control Study

INTRODUCTION

Toxoplasmosis and narcotic drug addiction are endemic in various regions of Iran. These drugs can provide situations for infections by disrupting the immune system. The current case-control study was designed to determine the prevalence of toxoplasmosis in narcotic drugaddicted persons in comparison with healthy subjects using serology and molecular techniques in the southwest of Iran.

METHODS

A total of 201 subjects (including 101 individuals with drug addiction and 100 control participants) were randomly selected. Chronic and acute toxoplasmosis was detected using the enzymelinked immunosorbent assay (ELISA) IgG avidity. T. gondii immunoglobulin G (IgG) and immunoglobulin M (IgM) were also determined by the ELISA. Moreover, the presence of T. gondii in blood samples was diagnosed using the nested-polymerase chain reaction (Nested-PCR).

RESULTS

For T. gondii IgG, 17 (17.0%) of 100 and 39 (38.6%) of 101 cases were diagnosed in the control participants and drug-addicted people, respectively [P=0.001, OR=3.071, CI= (1.591-5.929)]. Moreover, 16 (15.8) and 5 (5.0%) cases were positive for the B1 gene in the drug-addicted patients and controls by the nested-PCR technique, respectively [P=0.019, OR=3.576, CI= (1.257-10.179)]. However, no significant differences were found between the opium (n=64) and crystal methamphetamine (n=37) groups in terms of T. gondii IgG and IgM antibodies and the presence of the parasite in the blood (P>0.05).

CONCLUSION

The present results demonstrated that the outbreak of the infection was more frequent in narcotic drug-addicted persons than the controls using serology and molecular techniques.

Association between toxoplasmosis and bipolar disorder: A systematic review and meta-analysis

BACKGROUND

The relationship between toxoplasma gondii (T. gondii) infection and bipolar disorder (BD) is poorly understood. This review explores this relationship by estimating the strength of the association between the two conditions using data from published studies.

METHODS

Following PRISMA guidelines, we performed a review and meta-analysis of published articles obtained from a systematic search of PubMed, PsycINFO, EMBASE and the Cochrane library up to January 10th, 2021. We included observational studies that compared seroprevalence of IgG class antibodies against T. gondii in patients with a diagnosis of BD with healthy controls. We excluded studies that included <10 participants in each study arm and patients with a serious concomitant medical illness. Discrepancies between the two independent researchers were resolved by consulting a third experienced researcher. Summary data were extracted from published reports. Analysis was conducted using both fixed-effects and random-effects models. The study is registered with PROSPERO number CRD42021237809.

FINDINGS

The search yielded 23 independent studies with a total of 12690 participants (4021 with BD and 8669 controls). Persons with BD had a greater odd of seropositivity with toxoplasmosis than controls, both in the fixed-effects model (OR = 1.34 [95%CI: 1.19 to 1.51]) and the random-effects model (OR = 1.69 [95%CI: 1.21 to 2.36]). No publication bias was detected but reported results showed a high heterogeneity (I2 = 84% [95%CI:77%-89%]).

INTERPRETATION

The findings support the relationship between toxoplasmosis infection and BD and suggests a need for studies designed to explore possible causal relationship. Such studies may also improve our understanding of the pathophysiology of BD and open other avenues for its treatment.

FUNDING

P.O.R. Sardegna F.S.E. 2014-2020.

Back to the Future: The Role of Infections in Psychopathology. Focus on OCD

OBJECTIVE

Recently, there has been a resurgence of interest in the relationship between infections and psychopathology, given the increasing data on the neurotropism and neurological/psychiatric morbidity of the SARS-COV2 virus, responsible for the current worldwide pandemic. Although the majority of observations were those obtained in mood and schizophrenic disorders, a few data are also available on the presence of bacterial or viral infections in patients suffering from obsessive-compulsive disorder (OCD). Therefore, given the limited information, the present paper aimed at reviewing the most updated evidence of infections in neuropsychiatric disorders and their possible mechanisms of actions, with a narrow focus on microbes in OCD.

METHOD

This paper is a narrative review. The databases of PubMed, Scopus, Embase, PsycINFO and Google Scholar were accessed to research and collect English language papers published between 1 January 1980 and 31 December 2021. The data on PANDAS/PANS and those observed during severe brain infections were excluded.

RESULTS

Several pathogens have been associated with an increased risk to develop a broad spectrum of neuropsychiatric conditions, such as schizophrenia, mood disorders, autism, attention-deficit/hyperactivity disorder, anorexia nervosa, and post-traumatic stress disorder. Some evidence supported a possible role of infections also in the pathophysiology of OCD. Infections from Herpes simplex virus 1, Borna disease virus, Group A-Beta Hemolytic Streptococcus, Borrelia spp., and Toxoplasma gondii were actually found in patients with OCD. Although different mechanisms have been hypothesized, all would converge to trigger functional/structural alterations of specific circuits or immune processes, with cascade dysfunctions of several other systems.

CONCLUSIONS

Based on the current evidence, a possible contribution of different types of microbes has been proposed for different neuropsychiatric disorders including OCD. However, the currently available literature is meager and heterogeneous in terms of sample characteristics and methods used. Therefore, further studies are needed to better understand the impact of infectious agents in neuropsychiatric disorders. Our opinion is that deeper insights in this field might contribute to a better definition of biological underpinnings of specific clinical pictures, as well as to promote psychiatric precision medicine, with treatments based on altered pathological pathways of single patients. This might be particularly relevant in OCD, a disorder with a high proportion of patients who are resistant or do not respond to conventional therapeutic strategies.

The Association of Toxoplasma gondii IgG and Liver Injury in US Adults

Background: Toxoplasma gondii (T. gondii) is a ubiquitous obligatory intracellular parasite which infects over 40 million Americans and causes toxoplasmosis. Inside the human body, T. gondii can damage tissues and invade vital organs. Methods: This study evaluated the association of T. gondii infection and liver disease using data from the National Health and Nutrition Examination Survey (NHANES) 2009–2010, with a sample size of 3371 participants (age 20–80 years). Toxoplasma infection was determined by the level of T. gondii IgG antibody in serum samples. Liver disease was assessed by liver injury biomarkers and the Fatty Liver Index (US-FLI). The evaluation of the association between T. gondii infection and liver disease included the calculation of the Mantel–Haenszel risk ratio (RRMH), Rho-Scott chi-square bivariate analyses, design-based t-tests, and linear and logistic regression models which were adjusted for demographic and anthropometric covariates. Results: Mean levels of aspartate aminotransferase (AST) and alkaline phosphatase (ALP) were significantly more elevated in the T. gondii IgG-positive (IgG+) participants as compared to T. gondii-negative (IgG−) participants, p = 0.0435 and 0.0310, respectively. In linear regression analysis, exposure to T. gondii IgG+ had statistically significant positive associations with AST (p = 0.0211), alanine aminotransferase (ALT) (p = 0.0221), and gamma-glutamyl transferase (GGT) (p = 0.0258) after adjusting for BMI, age, gender, and race. T. gondii exposure was associated with an elevated relative risk of chronic liver disease (CLD) (RRMH = 1.26, 95% CI: 1.05–1.51). This association was more pronounced in certain occupations, such as construction, agriculture, forestry, and fishing, where Toxoplasma infection is more common (p = 0.0477). Moreover, Toxoplasma infection increased the odds of nonalcoholic fatty liver disease (NAFLD) (OR = 6.99, 95% CI = 1.85–26.32, p = 0.0237). Conclusion: T. gondii IgG+ antibody was significantly associated with liver injury biomarkers (ALT, AST, GGT, and ALP) and an increased risk of CLD and NAFLD. Moreover, the association of Toxoplasma with CLD was more evident in specific occupations where the prevalence of Toxoplasma was high. The findings of this study provide insight into utilizing liver biomarkers and US-FLI to assess the health complications of Toxoplasma when imaging tests are not accessible.

Toxoplasmosis in Treatment-Resistant Obsessive-Compulsive Disorder Patients

BACKGROUND AND OBJECTIVES

The current study was done to evaluate the relationship between T. gondii and obsessive-compulsive disorder (OCD) as well as prevalence rate of toxoplasmosis in treatment-resistant patients with OCD in comparison with treatment-sensitive patients with OCD.

METHODS

A total of 180 subjects were selected, including 90 patients with OCD and 90 control participants. Immunoglobulin G (IgG) and immunoglobulin M (IgM) antibodies against T. gondii were measured by the enzyme-linked immunosorbent assay (ELISA) technique. Detection of acute and chronic toxoplasmosis was carried out using the ELISA IgG avidity. In addition, the presence of this parasite in blood was detected using the nested-polymerase chain reaction (PCR) method.

RESULTS

Regarding T. gondii IgG antibodies 42 (46.7%) and 17 (18.9%) cases were detected in the patients and controls, respectively (P = 0.000). Also, 16 (17.8%) and 5 (5.6%) cases were positive for B1 gene in patients and controls, respectively (P = 0.018). The antibodies were found to be related to risk of OCD [OR (95% CI) = 3.71 (1.88-7.30); P < 0.001]. Moreover, out of 90 patients, 35 and 55 cases were resistant and sensitive to treatment, respectively, so that 24 (68.6%) out of 35 and 18 (32.7%) out of 55 were positive for the antibodies (P = 0.01) as well as 11 (31.4%) out of 35 and 5 (9.1%) out of 55 were positive for B1 gene (P = 0.010). The antibodies were also associated with risk of resistance to treatment in patients with OCD [OR (95% CI) = 3.81 (1.42-10.17); P = 0.008].

CONCLUSION

Our findings showed that toxoplasmosis was more frequent in patients with OCD than the control group. In addition, prevalence rate of toxoplasmosis in treatment-resistant patients with OCD was significantly more than that in treatment-sensitive patients with OCD.

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.

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.

Comprehensive Overview of Toxoplasma gondii-Induced and Associated Diseases

Toxoplasma gondii (T. gondii) is a prevalent protozoan parasite of medical and veterinary significance. It is the etiologic agent of toxoplasmosis, a neglected disease in which incidence and symptoms differ between patients and regions. In immunocompetent patients, toxoplasmosis manifests as acute and chronic forms. Acute toxoplasmosis presents as mild or asymptomatic disease that evolves, under the host immune response, into a persistent chronic disease in healthy individuals. Chronic toxoplasmosis establishes as latent tissue cysts in the brain and skeletal muscles. In immunocompromised patients, chronic toxoplasmosis may reactivate, leading to a potentially life-threatening condition. Recently, the association between toxoplasmosis and various diseases has been shown. These span primary neuropathies, behavioral and psychiatric disorders, and different types of cancer. Currently, a direct pre-clinical or clinical molecular connotation between toxoplasmosis and most of its associated diseases remains poorly understood. In this review, we provide a comprehensive overview on Toxoplasma-induced and associated diseases with a focus on available knowledge of the molecular players dictating these associations. We will also abridge the existing therapeutic options of toxoplasmosis and highlight the current gaps to explore the implications of toxoplasmosis on its associated diseases to advance treatment modalities.

Neurological and Neurobehavioral Disorders Associated with Toxoplasma gondii Infection in Humans

The intracellular parasite Toxoplasma gondii is estimated to infect up to 30% of the world population, leading to lifelong chronic infection of the brain and muscle tissue. Although most latent T. gondii infections in humans have traditionally been considered asymptomatic, studies in rodents suggest phenotypic neurological changes are possible. Consequently, several studies have examined the link between T. gondii infection and diseases such as schizophrenia, epilepsy, depression, bipolar disorder, dysphoria, Alzheimer's disease, Parkinson's disease, and obsessive-compulsive disorder (OCD). To date, there is varying evidence of the relationship of T. gondii to these human neurological or neurobehavioral disorders. A thorough review of T. gondii literature was conducted to highlight and summarize current findings. We found that schizophrenia was most frequently linked to T. gondii infection, while sleep disruption showed no linkage to T. gondii infection, and other conditions having mixed support for a link to T. gondii. However, infection as a cause of human neurobehavioral disease has yet to be firmly established.

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.

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.

Social preference is maintained in mice with impaired startle reflex and glutamate/D-serine imbalance induced by chronic cerebral toxoplasmosis

Toxoplasma gondii is an opportunistic protozoan pathogen with a wide geographic distribution. The chronic phase of toxoplasmosis is often asymptomatic in humans and is characterized by tissue cysts throughout the central nervous system and muscle cells. T. gondii and other pathogens with tropism for the central nervous system are considered risk factors in the etiology of several neuropsychiatric disorders, such as schizophrenia and bipolar disorder, besides neurological diseases. Currently, it is known that cerebral toxoplasmosis increases dopamine levels in the brain and it is related to behavioral changes in animals and humans. Here we evaluate whether chronic T. gondii infection, using the cystogenic ME-49 strain, could induce behavioral alterations associated with neuropsychiatric disorders and glutamatergic neurotransmission dysfunction. We observed that the startle amplitude is reduced in the infected animals as well as glutamate and D-serine levels in prefrontal cortical and hippocampal tissue homogenates. Moreover, we did not detect alterations in social preference and spontaneous alternation despite severe motor impairment. Thus, we conclude that behavioral and cognitive aspects are maintained even though severe neural damage is observed by chronic infection of C57Bl/6 mice with the ME-49 strain.

Toxoplasma gondii: A possible etiologic agent for Alzheimer's disease

Toxoplasma gondii (T. gondii) is one of the most pervasive neurotropic pathogens causing different lesions in a wide variety of mammals as intermediate hosts, including humans. It is estimated that one-third of the world population is infected with T. gondii; however, for a long time, there has been much interest in the examination of the possible role of this parasite in the development of mental disorders, such as Alzheimer's disease (AD). T. gondii may play a role in the progression of AD using mechanisms, such as the induction of the host's immune responses, inflammation of the central nervous system (CNS), alteration in the levels of neurotransmitters, and activation of indoleamine-2,3-dyoxigenase. This paper presents an appraisal of the literature, reports, and studies that seek to the possible role of T. gondii in the development of AD. For achieving the purpose of the current study, a search of six English databases (PubMed, ScienceDirect, Web of Science, Scopus, ProQuest, and Google Scholar) was performed. The results support the involvement of T. gondii in the induction and development of AD. Indeed, T. gondii can be considered a risk factor for the development of AD and requires the special attention of specialists and patients. Furthermore, the results of this study may contribute to prevent or delay the progress of AD worldwide. Therefore, it is required to carry out further studies in order to better perceive the parasitic mechanisms in the progression of AD.

Serum Tyrosine Level in Acute Murine Toxoplasmosis

Background

Toxoplasmosis is a zoonotic disease caused by the obligate intracellular parasite, Toxoplasma gondii. This global infectious disease has been associated with behavioral changes in rodents and can result in humans' neuropsychiatric symptoms. Since the neurotransmitters alteration can cause a behavioral change, in this study, tyrosine level, as a precursor of dopamine, was evaluated in acute murine toxoplasmosis during 2015 and 2016 in Shiraz, Iran.

Methods

At the first, 10⁵ tachyzoites of T. gondii were subcutaneously inoculated to 50 BALB/c mice as experimental groups and 10 mice inoculated by PBS considered as the control group. After that, daily, one group of mice was bled, and sera were collected. Then, their serum tyrosine level was evaluated by HPLC method.

Results

After data analysis, the maximum mean serum tyrosine level was seen at 2^th day of post parasite inoculation (0.0194 mg/ ml), with a significant difference compared to the control group (0.0117 mg/ ml, P=0.025). Moreover, the least quantity of serum tyrosine (0.076 mg/ml) was seen on the 5^th day, after parasite inoculation, however, no significant difference was seen.

Conclusion

Serum tyrosine level increased in 2 d after inoculation of Toxoplasma, but the level regularly decreased in successive days. Tyrosine level increased by phenylalanine hydroxylase 2 days after inoculation, then tyrosine decreased by tyrosine hydroxylase in the next days. Toxoplasma tyrosine hydroxylase enzymes, at primary days of toxoplasmosis, effect on tyrosine production, and after that, the most effect on tyrosine consumption.

Latent Toxoplasma gondii infections are associated with elevated biomarkers of inflammation and vascular injury

BACKGROUND

Toxoplasma gondii is a protozoan parasite that infects cats as definitive hosts and other warm-blooded animals including humans as intermediate hosts. It forms infectious cysts in the brain, muscle and other tissues establishing life-long latent infection. Approximately 10% of the US population is infected. While latent infections are largely asymptomatic, they are associated with neurological deficits and elevated risks of neuropsychiatric diseases.

METHODS

This cross-sectional epidemiological study investigated associations of T. gondii infections with biomarkers of inflammation and vascular injury: soluble intercellular adhesion molecule 1 (ICAM-1), soluble vascular cell adhesion molecule 1 (VCAM-1), C-reactive protein (CRP), and serum amyloid A (SAA). Serum samples from 694 adults in the Raleigh-Durham-Chapel Hill, North Carolina metropolitan area were tested for IgG antibody response to T. gondii, and for the above biomarkers using commercially available assays.

RESULTS

T. gondii seroprevalence rate in this sample was 9.7%. Seropositivity was significantly associated with 11% (95% confidence limits 4, 20%) greater median levels of VCAM-1 (p = 0.003), and marginally significantly with 9% (1, 17%), and 36% (1, 83%) greater median levels of ICAM-1, and CRP, respectively (p = 0.04 for each) after adjusting for sociodemographic and behavioral covariates, while the 23% (- 7, 64%) adjusted effect on SAA was not statistically significant (p = 0.15).

CONCLUSIONS

Latent infections with T. gondii are associated with elevated biomarkers of chronic inflammation and vascular injury that are also known to be affected by ambient air pollution.

Potential risk factors associated with seropositivity for Toxoplasma gondii among pregnant women and HIV infected individuals in Ethiopia: A systematic review and meta-analysis

BACKGROUND

Toxoplasma gondii is an obligate intracellular and neurotropic apicomplexan protozoan parasite infecting almost all warm-blooded vertebrates including humans. To date in Ethiopia, no systematic study has been investigated on the overall effects of potential risk factors associated with seropositivity for Toxoplasma gondii among pregnant women and HIV infected individuals. We intended to determine the potential risk factors (PRFs) associated with seropositivity for Toxoplasma gondii from published data among pregnant women and HIV infected individuals of Ethiopia.

METHODOLOGY

An systematic review of the previous reports was made. We searched PubMed, Science Direct, African Journals Online, and Google Scholar for studies with no restriction on the year of publication. All references were screened independently in duplicate and were included if they presented data on at least two risk factors. Meta-analysis using the random or fixed-effects model was made to calculate the overall effects for each exposure.

RESULTS

Of the 216 records identified, twenty-four reports met our eligibility criteria, with a total of 6003 individuals (4356 pregnant women and 1647 HIV infected individuals). The pooled prevalences of anti-Toxoplasma gondii antibodies were found at 72.5% (95% CI: 58.7% - 83.1%) in pregnant women and 85.7% (95% CI: 76.3% - 91.8%) in HIV infected individuals. A significant overall effect of anti-Toxoplasma gondii seropositivity among pregnant women (p < 0.05) was witnessed with age, abortion history, contact with cats, cat ownership, having knowledge about toxoplasmosis, being a housewife and having unsafe water source. Age, cat ownership, and raw meat consumption were also shown a significant effect (p < 0.05) to anti-Toxoplasma gondii seropositivity among HIV infected individuals.

CONCLUSIONS

This review showed gaps and drawbacks in the earlier studies that are useful to keep in mind to design accurate investigations in the future. The pooled prevalence of anti-Toxoplasma gondii antibodies was found to be higher among pregnant women and HIV infected individuals. This suggests that thousands of immunocompromised individuals (pregnant women and HIV infected patients) are at risk of toxoplasmosis due to the sociocultural and living standards of the communities of Ethiopia. Appropriate preventive measures are needed to reduce the exposure to Toxoplasma gondii infection. Further studies to investigate important risk factors are recommended to support the development of more cost-effective preventive strategies.

Effects of Toxoplasma gondii infection and schizophrenia comorbidity on serum lipid profile: A population retrospective study from Eastern China

INTRODUCTION

Toxoplasma gondii (T. gondii), a parasitic protozoa that is associated with various psychiatric disorders. Both T. gondii infection and disturbed host's lipid profile are common in schizophrenia patients. However, the underlying pathophysiological mechanisms remain speculative. Also, the characteristics of serum lipid levels in schizophrenia patients comorbid with T. gondii infection are not clear. Therefore, it is necessary to explore the influence of chronic T. gondii infection on the characteristic physiological indexes of schizophrenia patients so as to provide some insights into finding target therapeutic drugs.

METHODS

In this study, the effect of chronic T. gondii infection on serum lipid profile was retrospectively analysed in 1719 schizophrenic patients and 1552 healthy subjects from Eastern China.

RESULTS

The overall prevalence of Immunoglobulin G (IgG) antibodies against T. gondii (17.98%) in schizophrenia patients was significantly higher than healthy controls (7.35%, χ2 = 81.831, P = 0.000). Compared to T. gondii IgG-seronegative schizophrenia patients, IgG-seropositive group had higher high-density lipoprotein (HDL) (P = 0.000) and triglycerides (TG) (P = 0.000) levels, while total cholesterol (TC) (P = 0.000) levels showed an opposite tendency in IgG-seropositive cases. We also found significant correlation between T. gondii seropositivity and increased TG (P = 0.000) and TC levels (P = 0.000) in schizophrenia patients. Binary regression analysis also showed that decreased TC level was more common among schizophrenia patients with T. gondii seropositivity compared to seronegative subjects (OR = 0.617, 95%CI = 0.509-0.749, P = 0.000).

CONCLUSION

Patients with chronic T. gondii infection and comorbid schizophrenia had higher HDL and TG levels, while cholesterol levels showed an opposite trend. To the best of our knowledge, this is the first report focus on the host's lipid profile of chronic T. gondii infection and comorbid schizophrenia patients.

Evolutionary puzzle of Toxoplasma gondii with suicidal ideation and suicide attempts: An updated systematic review and meta-analysis

The World Health Organization has reported an annual global suicide rate of 14.5 per 100,000 people. On the other hand, it is estimated that approximately one-third of the global population are infected with Toxoplasma gondii (T. gondii) parasite. It is widely assumed that microbial pathogens, such as T. gondii, are probably associated with affective and behavioural modulation. The present article aimed to assess the proposed role of toxoplasmosis in raising the risk of suicidal ideation (SI) and suicide attempts (SA) using the available epidemiological data. Seven major electronic databases and the Internet search engine Google were searched for all the studies published between the 1st of January 1950 and 31st of October 2019. The heterogeneity and the risk of bias within and across studies were assessed. Following data extraction, pooled odds ratios (ORs) with 95% confidence interval (CI) across studies were calculated using the random-effects models. A total number of 9,696 articles were screened and 27 studies were regarded as eligible in our systematic review (SI with five papers and 22 papers on SA). A significant association was detected between antibodies against T. gondii with TA (ORs = 1.57; 95% confidence interval [CI] 1.23-2.00, p = .000). Exploration of the association between T. gondii and SA yielded a positive effect of seropositivity for IgG antibodies but not IgM. Despite the limited number of studies, a statistical association was detected between suicidal behaviours and infection with latent T. gondii.

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.

The influence of exposure to Toxoplasma Gondii on host lipid metabolism

BACKGROUND

Mounting evidence suggested a complex correlation between host lipid metabolism and Toxoplasma gondii (T. gondii) infection. However, the inherent association between T. gondii infection and host lipid state remains elusive either in mice or in human hosts.

METHODS

Through a study in a sample of 1045 healthy participants from eastern China, we determined the association of T. gondii infection and host lipid levels using serological methods. We then examined the host lipid levels in C57BL/6 J mice at both acute and chronic T. gondii infection stages (for a period up to 36 weeks post infection).

RESULTS

In our case-control study, T. gondii seropositive individuals had higher low-density lipoproteins (LDL) (P = 0.0043) and total cholesterol (TC) (P = 0.0134) levels compared to seronegative individuals. Furthermore, individuals with LDL (OR = 3.25; 95% CI:1.60-6.61) and TC (OR = 2.10; 95% CI:1.22-3.63) levels above the upper limit of normal range had higher odds ratio to be T. gondii IgG positive. Consistently, in vivo data revealed that a significantly increased LDL level was first observed at early acute stage but plateaued to later time (chronic infection with T. gondii).

CONCLUSIONS

In both healthy population and T. gondii-infected mice, seropositive individuals had higher LDL level. Individuals with positive T. gondii IgG had more odds of being with LDL and TC abnormality. Latent T. gondii infection is common worldwide, potential medical interventions to host lipid metabolism may be a breakthrough point to the prevention and control of this parasite infection.

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.

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

BACKGROUND

Toxoplasma gondii (T. gondii) is an obligate intracellular opportunistic parasite that is the causative agent of toxoplasmosis. This parasite accounts for mental disorders; however, the relationship between T. gondii infection and depressive disorder is unclear. Regarding this, the present systematic review and meta-analysis was conducted to investigate the scientific evidence regarding the potential association between major depression disorder (MDD) and Toxoplasma infection.

METHODS

For the purpose of the study, the articles related to the subject of interest were systematically searched in seven electronic databases. Special attention was given to the studies examining T. gondii seropositivity level in depressed patients and controls.

RESULTS

The search process resulted in the identification of a total of 30 publications meeting the inclusion criteria and published up to April 2018 for the systematic review. Furthermore, 29 studies met the inclusion criteria to be entered into meta-analysis. Our meta-analysis involved the review of cross-sectional studies including 1657 depressed patients and 19565 individuals as controls and case-control studies entailing 1311 depressed cases and 6015 controls without depression. 1582 depressed people participated in cross-sectional studies whose results were reported as odds ratio (OR). In addition, the total number of participants was 15068 in this type of studies. Statistical analysis indicated that the pooled OR of the risk of anti-T. gondii IgG antibody in depressed individuals in case-control and cross-sectional studies was 1.15 (95% confidence interval (CI): 0.95-1.39).

CONCLUSIONS

As the findings of the reviewed articles indicated, toxoplasmosis is not a risk factor for MDD. However, it is necessary to perform further research to clarify the detailed association between T. gondii and dysthymia or mild and moderate depression. Furthermore, it is recommended to better investigate the effect of antibody titers on the relationship between depression and T. gondii infection.