rats
Can offspring sex ratios help to explain the endocrine effects of toxoplasmosis infection on human behaviour?
James, W. H., Grech, V.
Early Human Development 2018; 122: 42-44
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Humans infected with the parasite Toxoplasma gondii display a wide variety of abnormal behaviours, from suicide and depression to stuttering. These behaviours have been seen as so serious as to constitute a public health problem. It is not clear to what extent the parasite is a cause of, or merely a marker for, these behaviours, but there is evidence for both. Some of these behaviours are associated with changes in steroid hormones, that is, estrogen in women and testosterone in men. It is suggested here that these endocrine-related states of infected people may be better understood by studying their offspring sex ratios.
Toxoplasma gondii impairs memory in infected seniors
Gajewski, P. D., Falkenstein, M., Hengstler, J. G., Golka, K.
Brain Behavior and Immunity 2014; 36: 193-199
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lmost 30% of humans present a Toxoplasma gondii positive antibody status and its prevalence increases with age. The central nervous system is the main target. However, little is known about the influence of asymptomatic i.e. latent Toxoplasmosis on cognitive functions in humans. To investigate neurocognitive dysfunctions in asymptomatic older adults with T. gondii positive antibody status a double-blinded neuropsychological study was conducted. The participants were classified from a population-based sample (N = 131) of healthy participants with an age of 65 years and older into two groups with 42 individuals each: Toxoplasmosis positive (T-pos; IgG > 50 IU/ml) and Toxoplasmosis negative (T-neg; IgG = 0 IU/ml). The outcome measures were a computer-based working-memory test (2-back) and several standardized psychometric tests of memory and executive cognitive functions. T-pos seniors showed an impairment of different aspects of memory. The rate of correctly detected target symbols in a 2-back task was decreased by nearly 9% (P = 0.020), corresponding to a performance reduction of about 35% in working memory relative to the T-neg group. Moreover, T-pos seniors had a lower performance in a verbal memory test, both regarding immediate recall (10% reduction; P = 0.022), delayed recognition (6%; P = 0.037) and recall from long-term memory assessed by the word fluency tests (12%; P = 0.029). In contrast, executive functions were not affected. The effects remained mostly unchanged after controlling for medication. The impairment of memory functions in T-pos seniors was accompanied by a decreased self-reported quality of life. Because of the high prevalence of asymptomatic Toxoplasmosis and an increasing population of older adults this finding is of high relevance for public health
Masterpiece of epigenetic engineering – how Toxoplasma gondii reprogrammes host brains to change fear to sexual attraction
Flegr, J., Markos, A.
Molecular Ecology 2014; 23:5934-5936
Toxoplasma gondii exposure affects neural processing speed as measured by acoustic startle latency in schizophrenia and controls
Pearce, B. D., Hubbard, S., Rivera, H. N., Wilkins, P. P., Fisch, M. C., Hopkins, M. H., Hasenkamp, W., Gross, R., Bliwise, N., Jones, J. L., Duncan, E.
Schizophrenia Research 2013; 150: 258-261
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The prevalence of Toxoplasma gondii (TOXO) infection in schizophrenia (SCZ) is elevated compared to controls (odds ratio = 2.73). TOXO infection is associated with psychomotor slowing in rodents and non-psychiatric humans. Latency of the acoustic startle response, an index of neural processing speed, is the time it takes for a startling stimulus to elicit the reflexive response through a three-synapse subcortical circuit. We report a significant slowing of latency in TOXO seropositive SCZ vs. seronegative SCZ, and in TOXO seropositive controls vs. seronegative controls. Latency was likewise slower in SCZ subjects than in controls. These findings indicate a slowing of neural processing speed with chronic TOXO infection; the slowest startle latency was seen in the TOXO seropositive SCZ group
The neurotropic parasite Toxoplasma gondii increases dopamine metabolism
Prandovszky, E., Gaskell, E., Martin, H., Dubey, J. P., Webster, J. P., McConkey, G. A.
Plos One 2011; 6: ARTN e23866 10.1371/journal.pone.0023866
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The highly prevalent parasite Toxoplasma gondii manipulates its host's behavior. In infected rodents, the behavioral changes increase the likelihood that the parasite will be transmitted back to its definitive cat host, an essential step in completion of the parasite's life cycle. The mechanism(s) responsible for behavioral changes in the host is unknown but two lines of published evidence suggest that the parasite alters neurotransmitter signal transduction: the disruption of the parasite-induced behavioral changes with medications used to treat psychiatric disease (specifically dopamine antagonists) and identification of a tyrosine hydroxylase encoded in the parasite genome. In this study, infection of mammalian dopaminergic cells with T. gondii enhanced the levels of K+-induced release of dopamine several-fold, with a direct correlation between the number of infected cells and the quantity of dopamine released. Immunostaining brain sections of infected mice with dopamine antibody showed intense staining of encysted parasites. Based on these analyses, T. gondii orchestrates a significant increase in dopamine metabolism in neural cells. Tyrosine hydroxylase, the rate-limiting enzyme for dopamine synthesis, was also found in intracellular tissue cysts in brain tissue with antibodies specific for the parasite-encoded tyrosine hydroxylase. These observations provide a mechanism for parasite-induced behavioral changes. The observed effects on dopamine metabolism could also be relevant in interpreting reports of psychobehavioral changes in toxoplasmosis-infected humans.
May Toxoplasma gondii increase suicide attempt – preliminary results in Turkish subjects?
Yagmur, F., Yazar, S., Temel, H. O., Cavusoglu, M.
Forensic Science International 2010; 199: 15-17
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Suicide attempts are one of the risk factors of suicide. Possible mechanisms by which Toxoplasma gondii may affect human behavior and it may also cause humans to attempt suicide. The aim of this study is to find out whether or not T. gondii is one of the reasons in suicide attempts. We investigated the seropositivity level for anti-Toxoplasma IgG and IgM antibodies by enzyme-linked immunosorbent assay in subjects who have attempted to suicide to find out whether there is a probable relationship between T. gondii and suicide attempts. In our study, we selected 200 cases of suicide attempts and 200 healthy volunteers. The sero-positivity level for anti-Toxoplasma IgG antibodies among suicide attempts (41%) was significantly higher than the control group (28%). This signifies that there might be a causal relationship between toxoplasmosis and the etiology of suicide attempt. (c) 2010 Elsevier Ireland Ltd. All rights reserved.
Toxoplasma gondii infection in first-episode and inpatient individuals with schizophrenia
Hamidinejat, H., Ghorbanpoor, M., Hosseini, H., Alavi, S. M., Nabavi, L., Jalali, M. H., Borojeni, M. P., Jafari, H., Mohammadaligol, S.
International Journal of Infectious Diseases 2010; 14: E978-E981
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Background: A high seroprevalence of Toxoplasma gondii infection has been detected in psychiatric patients, particularly in schizophrenia cases.
Methods: In the present study 98 patients suffering from schizophrenia (58 inpatients and 40 first-episode patients) and 96 control patients (50 healthy volunteers and 46 with a depressive disorder) were examined for the presence of both IgG and IgM antibodies against T. gondii by enzyme-linked immunosorbent assay (ELISA). We applied the Bradford Hill criteria to identify the weight of causal inference.
Results: The positivity rate of anti-T. gondii IgG antibodies among individuals with schizophrenia (57.1%) was significantly higher than in healthy controls (29.2%). There were no associations between immune status ratio (ISR) values and the risk of schizophrenia. The weight of evidence approach using the Bradford Hill criteria revealed a 92% probability of a causal association.
Conclusion: Our results show that exposure to T. gondii may lead to schizophrenia. (C) 2010 International Society for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.
Toxoplasma gondii: host-parasite interaction and behavior manipulation
da Silva, R.C., Langoni, H.
Parasitology Research 2009; 105: 893-898
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Toxoplasma gondii is an obligate intracellular parasite that causes different lesions in men and other warm-blooded animals. Humoral and cellular immune response of the host against the parasite keeps the protozoan in a latent stage, and clinical disease ensues when immunological response is compromised. Brain parasitism benefits the parasite causing behavioral changes in the host, not only in animals but also in humans. Schizophrenia and epilepsy are two neurological disorders that have recently been reported to affect humans coinfected with T. gondii. Further studies based on host-parasite interaction in several wild or domestic warm-blooded species are still necessary in order to better understand parasitism and behavioral changes caused by T. gondii.
Psychosis may be associated with toxoplasmosis
Zhu S.
Medical Hypotheses 2009; 73: 799-801.
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Many parasites induce characteristic changes in their host. The effect of Toxoplasma gondii infection on the cerebrum and neuropsychiatric patients has been increasingly emphasized in recent years. T gondii has a high affinity for brain tissue where tachyzoites may form tissue cysts and persist for a life long time. Some psychiatric symptoms such as schizophrenia and mental retardation may be induced by the infection of T gondii. Furthermore, experiments demonstrated that some antipsychotics and mood stabilizers used to treat psychosis displayed the function of inhibiting T. gondii replication. Investigations from various regions in China in psychotic patients support the hypotheses that psychosis may be linked to T gondii infection. (C) 2009 Elsevier Ltd. All rights reserved.
Selected infectious agents and risk of schizophrenia among US military personnel
Nielbuhr, D.W., Millikan, A. M., Cowan, D. N., Yolken, R., Li, Y. Z., Weber, N. S.
American Journal of Psychiatry 2008; 165: 99-106
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Objective: A number of studies have reported associations between Toxoplasma gondii (T gondii) infection and the risk of schizophrenia. Most existing studies have used small populations and postdiagnosis specimens. As part of a larger research program, the authors conducted a hypothesis-generating case control study of T. gondii antibodies among individuals discharged from the U.S. military with a diagnosis of schizophrenia and serum specimens available from both before and after diagnosis.
Method: The patients (N=180) were military members who had been hospitalized and discharged from military service with a diagnosis of schizophrenia. Healthy comparison subjects (3:1 matched on several factors) were members of the military who were not discharged. The U.S. military routinely collects and stores serum specimens of military service members. The authors used microplate-enzyme immunoassay to measure immunoglobulin G (IgG) antibody levels to T gondii, six herpes viruses, and influenza A and B viruses and immunoglobulin M (IgM) antibody levels to T. gondii in pre- and postdiagnosis serum specimens.
Results: A significant positive association between the T gondii IgG antibody and schizophrenia was found; the overall hazard ratio was 1.24. The association between IgG and schizophrenia varied by the time between the serum specimen collection and onset of illness.
Conclusion: The authors found significant associations between increased levels of scaled T gondii IgG antibodies and schizophrenia for antibodies measured both prior to and after diagnosis.
Prevalence of Toxoplasma infection in first-episode schizophrenia and comparison between Toxoplasma-seropositive and Toxoplasma-seronegative schizophrenia
Wang, H. L., Wang, G. H., Li, Q. Y., Shu, C., Jiang, M. S., Guo, Y.
Acta Psychiatrica Scandinavica 2006; 114: 40-48.
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Objective: To compare the prevalence of Toxoplasma infection between the first-episode schizophrenia and the controls and to compare the clinical features between the Toxoplasma-seronegative and Toxoplasma-seropositive patients with schizophrenia.
Method: The rate of serum reactivity toToxoplasma in 600 schizophrenia, 600 affective disorders, and 400 controls was investigated. The clinical symptoms of the schizophrenia patients were scored and compared.
Results: The rate of IgG antibody, not IgM in the schizophrenia patients, was higher than the control groups, and the odds ratio of schizophrenia associated with IgG antibody was 2.22-5.12. The affective disorders did not differ in the rate of IgG or IgM antibody from the normal or the physical disease control. The seropositive schizophrenia patients had higher scores on the positive subscale and three components of Positive and Negative Symptoms Scale than the seronegative patients.
Conclusion: This study lent further weight to the hypothesis that exposure to Toxoplasma may be a risk factor for schizophrenia.
Look what the cat dragged in: do parasites contribute to human cultural diversity?
Lafferty, K.D.
Behavioural Processes 2005; 68: 279-282