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.
Sero-prevalence of anti- Toxoplasma gondii antibodies among patients with neuropsychiatric disorders: Epilepsy and depression
Abd El-Aal, N. F., Saber, M., Fawzy, N., Ashour, W. R.
Journal of the Egyptian Society of Parasitology 2016; 46: 729-736
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Toxoplasma gondii infection is concerned to have an association with epilepsy and depression either as a cause or a potential risk factor for their occurrence. Nevertheless, there has been long-standing interest in investigating this possible association, the evidence for such relationship is yet not conclusive. The current study correlated between T. gondii infection and Neuropsychiatric disorders: epilepsy and depression, through serological valuation of anti-Toxoplasma immunoglobulin (Ig) G antibodies. In the current study, 112 patients suffered from epilepsy (72 cryptogenic and 40 non-cryptogenic), 118 had depression and 60 healthy volunteers that had no history of any neuropsychiatric disorders in their first degree relatives were enrolled. Full history taking, complete physical examination, cranial magnetic resonance imaging (MRI), scalp electroencephalography (EEG), a structured questionnaire and T. gondii specific IgG antibody ELISA were performed to all groups. The results showed that the anti-Toxoplasma IgG antibodies were detected among cases with cryptogenic epilepsy 34.7% (25 out of 72 cases), non-cryptogenic epilepsy 2.5% (1 out of 40) and depression 20.3% (24 out of 118) groups compared to healthy. control group (11.7%). There were significant associations between T. gondii seropositivity of epilepsy and depression groups in age, residence, contact with pets and social class compared to control healthy group (p<0.05). Youth and adults had the highest sero-T. gondii infection especially male in rural areas with low social class.
Toxoplasma gondii: A potential role in the genesis of psychiatric disorders
Fond, G., Capdevielle, D., Macgregor, A., Attal, J., Larue, A., Brittner, M., Ducasse, D., Boulenger, J. P.
Encephale-Revue De Psychiatrie Clinique Biologique Et Therapeutique 2013; 39: 38-43.
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INTRODUCTION: Toxoplasma gondii is the most common protozoan parasite in developed nations. Up to 43% of the French population may be infected, depending on eating habits and exposure to cats, and almost one third of the world human's population may be infected. Two types of infection have been described: a congenital form and an acquired form. Although the medical profession treats these latent cases as asymptomatic and clinically unimportant, results of animal studies and recent studies of personality profiles, behavior, and psychomotor performance have led to reconsider this assumption. PRECLINICAL DATA: Among rats: parasite cysts are more abundant in amygdalar structures than those found in other regions of the brain. Infection does not influence locomotion, anxiety, hippocampal-dependent learning, fear conditioning (or its extinction) and neophobia in rats. Rats' natural predator is the cat, which is also T. gondii's reservoir. Naturally, rats have an aversion to cat urine, but the parasite suppresses this aversion in rats, thus influencing the infection cycle. Tachyzoites may invade different types of nervous cells, such as neurons, astrocytes and microglial cells in the brain, and Purkinje cells in cerebellum. Intracellular tachyzoites manipulate several signs for transduction mechanisms involved in apoptosis, antimicrobial effectors functions, and immune cell maturation. Dopamine levels are 14% higher in mice with chronic infections. These neurochemical changes may be factors contributing to mental and motor abnormalities that accompany or follow toxoplasmosis in rodents and possibly in humans. Moreover, the antipsychotic haloperidol and the mood stabilizer valproic acid most effectively inhibit Toxoplasma growth in vitro with synergistic activity. CLINICAL DATA: The effects of the parasite are not due to the manipulation in an evolutionary sense but merely due to neuropathological or neuroimmunological effects of the parasite's presence. Toxoplasmosis and schizophrenia: epidemiological studies point to a role for toxoplasmosis in schizophrenia's etiology, probably during pregnancy and early life, this association being congruent with studies in animal models indicating that animal exposures of the developing brain to infectious agents or immune modulating agents can be associated with behavioral changes that do not appear until the animal reaches full maturity. Psychiatric patients have increased rates of toxoplasmic antibodies, the differences between cases and controls being greatest in individuals who are assayed near the time of the onset of their symptoms. The increase of dopamine in the brain of infected subjects can represent the missing link between toxoplasmosis and schizophrenia. Toxoplasmosis and Obsessive Compulsive Disorder (OCD): the seropositivity rate for anti-T. gondii IgG antibodies among OCD patients is found to be significantly higher than the rate in healthy volunteers. Infection of basal ganglia may be implicated in the pathogenesis of OCD among Toxoplasma seropositive subjects. Toxoplasmosis and personality: infected men appear to be more dogmatic, less confident, more jealous, more cautious, less impulsive and more orderly than others. Conversely, infected women seem warmest, more conscientious, more insecure, more sanctimonious and more persistent than others. It is possible that differences in the level of testosterone may be responsible for the observed behavioral differences between Toxoplasma-infected and Toxoplasma-free subjects. CONCLUSION: In the future two major avenues for research seem essential. On one hand, prospective studies and research efforts must still be carried out to understand the mechanisms by which the parasite induces these psychiatric disorders. On the other hand, it has not yet been demonstrated that patients with positive toxoplasmic serology may better respond to haloperidol's or valproic acid's antiparasitic activity. These results may appear as a major issue in the drug's prescribing choices and explain variability in response to the treatment of patients with schizophrenia that is not explained by the genetic polymorphism.
Onset of ocular complications in congenital toxoplasmosis associated with immunoglobulin M antibodies to Toxoplasma gondii
Sibalic, D., Djurkovic-Djakovic, O., Bobic, B.
European Journal of Clinical Microbiology &Infectious Diseases 1990; 9: 671-674
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Four patients with congenital toxoplasmosis serologically diagnosed by the Sabin-Feldman test (SFT) and the IgM-indirect fluorescent antibody test (IgM-IFAT) in the first year of life presented with eye disease between the age of 21 months and ten years. Repeated serological testing revealed increasing levels of specific antibodies as measured by the SFT. IgM antibodies to Toxoplasma gondii were detected in all four patients by the immunosorbent agglutination assay, in two by the IgM-IFAT and in three by the IgM-indirect haemagglutination test. Findings suggest that specific IgM antibodies reappear at the time of reactivation of congenital toxoplasmosis later in life, or possibly persist for an extraordinary long period (up to ten years)
A study to determine causal relationships of toxoplasmosis to mental retardation
Mackie MJ, Fiscus AG, Pallister P.
American Journal of Epidemiology 1971; 94: 215-221
Relationship of central nervous system neoplasms to Toxoplasma gondii infection
Schuman LM, Choi NW, Gullen WH
. American Journal of Public Health and the Nations Health 1967; 57: 848-&.
Frontiers of neurological diagnosis in acquired toxoplasmosis
Psychiatria, Neurologia, Neurochirurgia 1966; 69: 43-64.