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Year : 2019  |  Volume : 8  |  Issue : 1  |  Page : 42-46

Association between Toxoplasma gondii and mental disorders in Taif region

1 College of Medicine, Taif University, Taif, Saudi Arabia
2 Department of Pathology and Cytopathology, Taif University; Laboratory and Blood Bank, King Abdul Aziz Hospital, Taif, Saudi Arabia
3 Department of Microbiology, College of Medicine, Taif University, Taif, Saudi Arabia; Department of Parasitology, Suez Canal University, Ismailia, Egypt

Date of Web Publication16-May-2019

Correspondence Address:
Dr. Hind Mohammed Alshehri
College of Medicine, Taif University, Taif
Saudi Arabia
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/sjhs.sjhs_144_18

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Background: Around 30% of the population of both developing and developed countries are infected by Toxoplasma gondii. Research has shown that in the Toxoplasma infection's initial stage, changes are made in the infected human physiology, behavior, as well as in the animals that are infected artificially. Changes in personality shifts were observed in simple response times and psychiatric diseases and intelligence consisting of schizophrenia, dementia, and suicidal tendencies. Correspondingly, changes in behavior such as raised attraction toward feline odors and reduction in neophobia were observed in experimental studies. Aims: The aim of our study is to investigate the association between latent T. gondii infection and various mental illnesses in the city of Taif, KSA. Settings and Design: A cross-sectional study involving patients who are receiving medical care for various mental disorders in a psychiatric health hospital in Taif, KSA, and a control group of patients not suffering from any previous mental disorders. Materials and Methods: Blood samples were drawn from patients with different mental disorders and a control group. T. gondii-IgG ELISA was performed. Statistical Analysis Used: Statistical tests data were analyzed using a Chi-square test. Statistical analyses were carried out using SPSS version 11. Results and Conclusions: A statistically significant association between mental disorders and latent Toxoplasma infection (IgG positive) was observed. 60% of the study group were positive for Toxoplasma IgG compared to only 30% of the control group. The most frequent mental disorder observed in the positive cases was schizophrenia (55%), followed by depression with suicidal tendencies (22%). Moreover, 66% of the study group reported having owned a cat or had come into close contact in their history. Our results support the hypothesis of major involvement between latent T. gondii infection and mental disorders. We recommend that Toxoplasma-IgG test routinely be performed to all patients with mental disorders and considering administering anti-Toxoplasma drugs to all positive cases.

Keywords: Association, depression, schizophrenia, Taif, Toxoplasma gondii

How to cite this article:
Alshehri HM, Almathami JA, Alsumairi RA, Binabdulrahman BA, Nemenqani DM, Soliman RH. Association between Toxoplasma gondii and mental disorders in Taif region. Saudi J Health Sci 2019;8:42-6

How to cite this URL:
Alshehri HM, Almathami JA, Alsumairi RA, Binabdulrahman BA, Nemenqani DM, Soliman RH. Association between Toxoplasma gondii and mental disorders in Taif region. Saudi J Health Sci [serial online] 2019 [cited 2023 Jun 9];8:42-6. Available from: https://www.saudijhealthsci.org/text.asp?2019/8/1/42/256783

  Introduction Top

Toxoplasma gondii is a prevalent parasite that can account for infecting almost 30% of individuals of both developing and developed countries. Toxoplasma prevalence rates can reach 80% of any population.[1] It is considered one of the most accomplished of all protozoan parasites due to its surprisingly wide range of mammalian hosts.[2] Individuals might be infected by T. gondii through eating food which is either undercooked or can be considered as raw meat containing the infective stage, in this case, tissue cysts or by accidentally ingesting oocytes after manipulation of cat feces,[3] or if the oocysts in cat feces have contaminated drinking water.[4]

Since 1994, numerous studies have demonstrated that the initial stage of Toxoplasma infection was historically taken as an asymptomatic disease from the perspective of medicine, in particular, modifications are made in the infected humans' physiology and behavior and in animals that have been infected artificially. Over the past two decades, several studies have demonstrated the ability of the latent Toxoplasma infection, which was earlier regarded as having nonmedical significance, to result in behavioral and physiological alterations in both infected humans and experimental animals.[5],[6]

Some researchers have explained these behavioral alterations as being a result of the parasite's manipulative actions to ascertain its spread from the wide range of animals acting as intermediate hosts to their ultimate definitive host, the cat;[6],[7] moreover, it has also been suggested by others that such changes are the primary reason for Toxoplasma infection on the infected human physiology that will grow under light stress.

Several research articles have addressed the changes that can be inflicted by Toxoplasma infection and have demonstrated its association with alterations in intelligence and simple reaction time[6],[8] and personality shifts.[9],[10] Others even went as far as the assumption that Toxoplasma infection can be related to different psychiatric disorders such as suicidal behavior, dementia, and schizophrenia.[11],[12],[13]

Meanwhile, experimental studies have revealed behavioral alterations and decreased aversion to odors of a feline nature.[14],[15] Some studies suggested the capability of the parasite to modify the production of neurotransmitters, mainly dopamine, in infected persons leading to different behavioral alterations.[16]

Although several studies have directly related chronic infection with T. gondii to schizophrenia incidence, several indirect evidence suggest its implication as a cause of schizophrenia.[17],[18] An observation was established that some drugs that are used to treat mental disorders such as haloperidol, a potent antipsychotic drug, and valproic acid which serves as a mood stabilizer, can also hinder behavioral changes observed with chronic toxoplasmosis.[19] On the other hand, many studies disapproved of these findings.[20],[21]


The aim of our study is to investigate the association between latent T. gondii infection and various mental illnesses in the City of Taif, KSA.

  Materials and Methods Top

The study was conducted on 30 female patients receiving medical care for various mental disorders in a psychiatric health hospital in Taif, KSA. The study was approved by the faculty's scientific research committee, and the psychiatric health hospital ethical committee, and written consent was obtained from the patient or their legal guardian before enrolling in this study. There were no negative consequences for patients who refused to participate in the study.

A written questionnaire was completed by the supporting staff including some personal data (optional), patient's diagnosis, and data about owning or handling cats in the previous year.

A control group comprised of 20 age- and sex-matching volunteers, not suffering from any previous mental disorder and coming to perform different laboratory tests in the laboratory department of King Abdel Aziz Hospital.

From every patient, a 5 ml blood sample was taken for serological analysis. The blood samples were centrifuged at 1500 rpm for 10 min to acquire vibrant supernatants. The sera were maintained at −20°C before the examination. IgG antibodies in both the case and control groups were evaluated through the ELISA technique (UDI, KSA) as per the manufacturer's instructions.

A Chi-square test was carried out for the examination of quantitative data tests. A probability level of 0.05 was taken as being statistically important. The examination was done through SPSS version 11 (SPSS Inc., Chicago).

  Results and Discussion Top

The data collected from the participants of the research enrolled in control as well as interventions groups were analyzed statistically. The results of the Toxoplasma IgG test are summarized in [Figure 1]. These results illustrate a significant difference in the study group with the value of P < 0.05. In relation to the intervention or study group, the statistical results were found positive in 18 participants, while negative were in 12 research participants. On the other hand, the research subjects from the control group were also analyzed, in which only 6 participants revealed positive results for Toxoplasma IgG test, while 14 participants revealed negative results for Toxoplasma IgG test. [Table 1] demonstrates the results obtained from 18 participants of research.
Figure 1: Toxoplasma IgG test in the study group versus the control group

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Table 1: Frequency of the positive Toxoplasma IgG cases according to their clinical diagnosis

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The results mentioned in [Table 2] revealed that the most frequent diagnosis among the positive Toxoplasma IgG study group cases was. Approximately, ten cases of the study group were found to be associated with the symptoms of Schizophrenia, which represents 55% of the Toxoplasma-positive cases. On the other hand, four positive cases were found to be associated with suicidal tendencies followed by depression, representing 11% of the overall Toxoplasma-positive cases. The study also revealed statistically significant results for bipolar cases. Bipolar disorder was found in two positive cases. In addition, the statistical analysis also revealed that only one patient is experiencing adjustment disorders, whereas one patient was found to be associated with psychotic episodes. Other types of psychiatric disorders were not diagnosed in the study group throughout the study period.
Table 2: Toxoplasma IgG results in patients

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[Figure 2] revealed a statistically significant association between having a cat or have exposure with cats in the last year and positive results for Toxoplasma-IgG in the study group with the value of P < 0.05. The findings of the questionnaire revealed that only 3 cases out of 12 cases found to be associated with positive results for Toxoplasma-IgG as compared to the control group. The statistical analysis of responses of the questionnaire revealed that handling or exposure with cat on daily basis is significantly associated with the higher risk of T. gondii in patients. T. gondii is an apicomplexan protozoan that has potentiality to infect host cells through asexual as well as sexual reproduction process. After the infection or reproducing T. gondii cells in the human body, the antibodies are produced in response to the infection and parasite developed in the quiescent phase through changing its cell structure into the form cysts in almost every tissue in the body. However, the most affected tissues by T. gondii cells are brain and muscles.[1]
Figure 2: The association between having or handling a cat and Toxoplasma infection in the study group versus the control group

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The samples cells were taken from benign cells and the results of Toxoplasma-IgG test revealed that T. gondii infection has the potential to influence the human behavior and likely to affect mental state of the individual and thus lead to the instability of the mental state. In the past studies, it is evident that T. gondii infection is less harmful for the humans; however, the recent researches presents major behavioral changes in human in association with the T. gondii infection.[5],[10] In addition to this, the increased traffic accidents have also been found to be associated with the increased prevalence of T. gondii infection in humans.[5]

Over the past several years, different reports has revealed significant association among T. gondii infection and several major changes in behavior in different species, ranging from insects to mammals.[10],[22],[23],[24],[25],[26] The behavioral manipulation theory explains this association in a better way and asserts that the behavior is likely to be manipulated through acquiring infection by protozoa that has the potential to control or change behavior of host cells to the environmental circumstances.[27] This association is explicitly evident in the mice infected by protozoa that cause changes in behavior to feline urine odor.[28],[29]

The findings of the following study supported the findings of several previous studies in relation to the statement that there is a positive association between T. gondii infection and occurrence of different mental illness, specially schizophrenia.[30],[31],[32],[33] On the other hand, few researches revealed the cause of schizophrenia is genetical risk and the prevalence of schizophrenia is common in depressed patients as compared to the people having T. gondii infection.[19],[20],[34] Several previous researches have agreed on the statement that there is an association between T. gondii and schizophrenia and supported their hypothesis by referring to the role of dopamine in schizophrenia. This role was proven by the attributes which present that antipsychotic drugs minimize the brain's dopamine levels, hence minimizing the symptoms of schizophrenia.[35],[36] At the same time, T. gondii replication was inhibited by antipsychotic drugs.[37],[38]T. gondii infection of the brain raises levels of dopamine[39],[40],[41] and causes psychotic symptoms resembling schizophrenia.[18],[42] Artemether, a potent antiparasitic drug, essentially improves symptoms in contrast to schizophrenia controls.[43] Therefore, the hypothesis has been summarized and presented in [Table 3].
Table 3: Summarised hypotheses and decision

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  Conclusions and Recommendations Top

Our results are in accordance with many other studies that support the hypothesis of major involvement between latent T. gondii infection and several different mental disorders. The high percentage of positive undiagnosed cases of Toxoplasma is surprising. Based on our findings, we recommend that Toxoplasma-IgG test routinely be performed on all patients with mental disorders and consider administering anti-Toxoplasma drugs to all positive cases. More elaborate studies on different specific neurotransmitters and their levels in T. gondii-infected groups should be considered.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

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  [Figure 1], [Figure 2]

  [Table 1], [Table 2], [Table 3]


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