Behavior
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
Click for abstract
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.
Pattern of money allocation in experimental games supports the stress hypothesis of gender differences in Toxoplasma gondii-induced behavioural changes
Lindová, J., Kubena, A.A., Sturcová, H., Krivohlavá, R., Novotná, M., Rubesová, A., Havlícek, J., Kodym, P. , Flegr, J.
Folia Parasitologica 2010; 57: 136-142
Click for abstract
Latent toxoplasmosis has been previously found to cause behavioural and personality changes in humans, which are
specific for each gender. Here we tested the stress hypothesis of these gender differences based on the assumption that latent toxo
-
plasmosis causes long-term subliminal stress. In line with this hypothesis, the gender difference will appear specifically in situations
with interpersonal context because in contrast to the typical individualistic coping style of men, women have a tendency to express
elevated prosocial behaviour under stress. Altogether 295 biology students (29/191 females and 27/104 males infected by
T. gondii
)
played a modified version of the Dictator Game and the Trust Game. As predicted, a gender difference in the effect of latent toxo
-
plasmosis was found for the measure of reciprocal altruism in the Trust Game (
p
= 0.016), but both genders appeared less generous
when infected in the Dictator Game modified to minimize social connotation (
p
= 0.048).
Toxoplasma gondii antibody titers and history of suicide attempts in patients with recurrent mood disorders
Arling, T. A., Yolken, R. H., Lapidus, M., Langenberg, P., Dickerson, F. B., Zimmerman, S. A., Balis, T., Cabassa, J. A., Scrandis, D. A., Tonelli, L. H., Postolache, T. T.
The Journal of Nervous and Mental Disease 2009; 3:905-908
Click for abstract
Toxoplasma gondii (T.gondii) is an obligate intracellular protozoan parasite infecting one-third of the world population, residing relatively silently in the brain of the immunocompetent host. We hypothesized that T.gondii seropositivity and serointensity are associated with having a history of attempting suicide and, in those attempting suicide, a greater number of attempts. T.gondii seropositivity and antibody titers were compared between (a) patients with recurrent mood disorders with history of suicide attempt (99 individuals) versus (b) patients with recurrent mood disorders without history of suicide attempt (119 individuals), and (c) healthy controls (39 individuals). Diagnosis was made using the Structured Clinical Interview for DSM-IV. Statistical methods included chi square, analysis of variance, and linear and logistic regression analyses. Suicide attempters had higher T.gondii antibody titers than nonsuicide attempters (p = 0.004). The logistic regression analysis revealed a predictive association between titers of anti- T.gondii antibodies and history of suicide attempt with OR = 1.55 (1.14-2.12), p = 0.006. No significant relationship was found between T.gondii seropositivity and suicide attempt status, number of prior suicide attempts, and recurrent mood disorder diagnosis. Although preliminary and bearing replication, this is the first report, to our knowledge, of an association between attempting suicide and T. gondii.
Higher prevalence of toxoplasmosis in victims of traffic accidents suggest increased risk of traffic accident in Toxoplasma-infected inhabitants of Istanbul and its suburbs.
Kocazeybek, B., Oner, Y. A., Turksoy, R., Babur, C., Cakan, H., Sahip, N., Unal, A., Ozaslan, A., Kilic, S., Saribas, S., Asian, M., Taylan, A., Koc, S., Dirican, A., Uner, H. B., Oz, V., Ertekin, C., Kucukbasmaci, O., Torun, M. M.
Forensic Science International 2009; 187: 103-108
Click for abstract
Reflexes of drivers who have toxoplasmosis have been shown to deteriorate from the actions of the parasitic cysts. The cysts can change the level of the neurotransmitters such as dopamine in the brain and by doing so extend the muscle response time and change personality profiles. In this Study, we aimed to determine the frequency of the latent toxoplasmosis (LT) in the driver population who were either injured or died in traffic accidents reported in Istanbul and its suburbs.
We compared the results with a control group and discussed the relationship between the LT and the traffic accidents. We included 218 (89.7%) non-fatal, 25 (10.3%) fatal cases in our study as study groups. A total 243 subjects, 234 (96%) male, 9 (4%) female (who were alcohol negative) compared with 191 (95.5%) male and 9 (4.5%) female Subjects (control group) who had a traffic accident before but no history of toxoplasmosis were studied.
Serologic tests, enzyme immunoassay (EIA) for IgG and IgM, and microimmunoflorescence (MIF) for IgG were used as the reference test, the Sabin-Feldman Dye test (SFDT) was used. According to serologic test results, LT seroprevalence in the study groups was 130 (53.5%) and in the control group 56 (28%) (p < 0.0001). A LT was present in 126 out of 234 (53.8%) males in the study groups, and 54 out of 191 (28.3%) males in the control group (p < 0.0001). In the 31-44 year age group, there was a significant difference with regard to toxoplasmosis between the study subjects and control groups (p < 0.0001). This difference was statistically very significant in (recent and former) cases with middle-aged men (31 44 years old). The results of this retrospective study Suggest that LT in drivers, especially those who are between 31 and 44 years might increase the risk for getting involved in a car accident. In a prospective study, Toxoplasma positive and negative subjects can be monitored before they are involved in a traffic accident to clarify the cause and result relationship. (C) 2009 Elsevier Ireland Ltd. All rights reserved.
The effect of Toxoplasma gondii on host behaviour: studies on mechanism of action using psychotropics, anti-parasite medication and parasite genes
Webster, J. P., McConkey, G. A.
European Neuropsychopharmacology 2009; 19: 179-179
Increased incidence of traffic accidents in Toxoplasma-infected military drivers and protective effect RhD molecule revealed by a large-scale prospective cohort study
Flegr, J., Klose, J., Novotná, M., Berenreitterová, M., Havlíček, J.
Bmc Infectious Diseases 2009; 9: Artn 72 10.1186/1471-2334-9-72
Click for abstract
Background: Latent toxoplasmosis, protozoan parasitosis with prevalence rates from 20 to 60% in most populations, is known to impair reaction times in infected subjects, which results, for example, in a higher risk of traffic accidents in subjects with this life-long infection. Two recent studies have reported that RhD-positive subjects, especially RhD heterozygotes, are protected against latent toxoplasmosis-induced impairment of reaction times. In the present study we searched for increased incidence of traffic accidents and for protective effect of RhD positivity in 3890 military drivers.
Methods: Male draftees who attended the Central Military Hospital in Prague for regular entrance psychological examinations between 2000 and 2003 were tested for Toxoplasma infection and RhD phenotype at the beginning of their 1 to 1.5-year compulsory military service. Subsequently, the data on Toxoplasma infection and RhD phenotype were matched with those on traffic accidents from military police records and the effects of RhD phenotype and Toxoplasma infection on probability of traffic accident was estimated with logistic regression.
Results: We confirmed, using for the first time a prospective cohort study design, increased risk of traffic accidents in Toxoplasma-infected subjects and demonstrated a strong protective effect of RhD positivity against the risk of traffic accidents posed by latent toxoplasmosis. Our results show that RhD-negative subjects with high titers of anti-Toxoplasma antibodies had a probability of a traffic accident of about 16.7%, i.e. a more than six times higher rate than Toxoplasma-free or RhD-positive subjects.
Conclusion: Our results showed that a common infection by Toxoplasma gondii could have strong impact on the probability of traffic accident in RhD negative subjects. The observed effects could provide not only a clue to the long-standing evolutionary enigma of the origin of RhD polymorphism in humans (the effect of balancing selection), but might also be the missing piece in the puzzle of the physiological function of the RhD molecule.
Sex-dependent toxoplasmosis-associated differences in testosterone concentration in humans
Flegr, J., Lindová, J., Kodym, P.
Parasitology 2008; 135: 427-431
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Several lines of indirect evidence suggest that subjects with latent infection of the coccidian parasite Toxoplasma gondii have a higher concentration of testosterone than uninfected controls. Here, we searched for direct evidence of latent toxoplasmosis-associated differences in testosterone concentration among a Population of 174 female and 91 male students screened for Toxoplasma infection. We have found Toxoplasma-infected men to have a higher concentration of testosterone and Toxoplasma -infected women to have a lower concentration of testosterone than Toxoplasma -free controls. The opposite direction of the testosterone shift in men compared to women can explain the observed gender specificity of behavioural shifts in Toxoplasma- infected subjects.
Brief communication: Latent toxoplasmosis and salivary testosterone concentration-important confounding factors in second to fourth digit ratio studies
Flegr, J., Lindova, J., Pivonkova, V., Havlicek, J.
American Journal of Physical Anthropology 2008; 137: 479-484
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A sexually dimorphic characteristic, the second to fourth digit ratio (2D:4D ratio), has been shown to reflect the prenatal concentration of sex steroid hormones and to correlate with many personality, physiological, and life history traits. The correlations are usually stronger for the right than the left hand. Most studies have shown that the 2D:4D ratio does not vary with age or postnatal concentration of sex steroid hormones. Recently, a strong association between left hand 2D:4D ratio and infection with a common human parasite Toxoplasma has been reported. We hypothesized that the confounding effect of Toxoplasma infection on left hand 2D:4D ratio could be responsible for the stronger association between different traits and right hand rather than left hand 2D:4D ratio. This confounding effect of toxoplasmosis could also be responsible for the difficulty in finding an association between 2D:4D ratio and age or postnatal steroid hormone concentration. To test this hypothesis, we analyzed the association between sex and age and 2D:4D ratio in a population of 194 female and 106 male students with and without controlling for the confounding variables of Toxoplasma infection and testosterone concentration. Our results showed that the relationship between age and sex and 2D:4D ratio increased sharply when Toxoplasma infection and testosterone concentration were controlled. These results suggest that left hand 2D:4D ratio is more susceptible to postnatal influences and that the confounding factors of Toxoplasma infection, testosterone concentration and possibly also age, should be controlled in future 2D:4D ratio studies. Because of a stronger 2D:4D dimorphism in Toxoplasma-infected than Toxoplasma-free subjects, we predict that 2D:4D ratio dimorphism as well as right hand/left hand 2D:4D ratio dimorphism will be higher in countries with a high prevalence of Toxoplasma infection than in those with a low prevalence. Am J Phys Anthropol 137:479-484, 2008. (C) 2008 Wiley-Liss, Inc.
Higher perceived dominance in Toxoplasma infected men – a new evidence for role of increased level of testosterone in toxoplasmosis-associated changes in human behavior
Hodková, H., Kolbeková, P., Skallová, A., Lindová, J. , Flegr, J.
Neuroendocrinology Letters 2007; 28: 110-114
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Toxoplasma
is parasite of cats that uses any warm-blooded animals as intermediate
hosts. It is known to induce shifts in behavior, physiology and even morphology
of its intermediate hosts, including humans. The lower second to fourth digit ratio
(2D:4D ratio) in infected man and women, and higher height in infected man sug
-
gest that sex steroid hormones like testosterone could play a role in these shifts.
Here, we searched for another indirect indication for a higher postnatal testosterone
level, i.e. increased perceived dominance and masculinity in infected men. We
showed portrait pictures of 89 male students of which 18 were
Toxoplasma
-
infected to 109 female students. When we statistically corrected for age, men with
latent toxoplasmosis were perceived as more dominant (p=0.009) and masculine
(p=0.052). These results support the idea that the higher level of testosterone could
be responsible for at least some of the toxoplasmosis-associated shifts in human and
animal behavior.
Effects of Toxoplasma on human behavior
Flegr, J.
Schizophrenia Bulletin 2007; 33: 757-760
Click for abstract
Although latent infection with
Toxoplasma gondii
is among
the most prevalent of human infections, it has been gener-
ally assumed that, except for congenital transmission, it is
asymptomatic. The demonstration that latent
Toxoplasma
infections can alter behavior in rodents has led to a recon-
sideration of this assumption. When infected human adults
were compared with uninfected adults on personality ques-
tionnaires or on a panel of behavioral tests, several differ-
ences were found. Other studies have demonstrated reduced
psychomotor performance in affected individuals. Possible
mechanisms by which
T. gondii
may affect human behavior
include its effect on dopamine and on testosterone.
Can the common brain parasite, Toxoplasma gondii, influence human culture?
Lafferty, K.D.
Proceedings of the Royal Society B-Biological Sciences 2006; 273: 2749-2755.
Click for abstract
The latent prevalence of a long-lived and common brain parasite, Toxoplasma gondii, explains a statistically significant portion of the variance in aggregate neuroticisin among populations, as well as in the 'neurotic' cultural dimensions of sex roles and uncertainty avoidance. Spurious or non-causal correlations between aggregate personality and aspects of climate and culture that influence T gondii transmission could also drive these patterns. A link between culture and T gondii hypothetically results from a behavioural manipulation that the parasite uses to increase its transmission to the next host in the life cycle: a cat. While latent toxoplasmosis is usually benign, the parasite's subtle effect on individual personality appears to alter the aggregate personality at the population level. Drivers of the geographical variation in the prevalence of this parasite include the effects of climate on the persistence of infectious stages in soil, the cultural practices of food preparation and cats as pets. Some variation in culture, therefore, may ultimately be related to how climate affects the distribution of T gondii, though the results only explain a fraction of the variation in two of the four cultural dimensions, suggesting that if T gondii does influence human culture, it is only one among many factors.
Parasites as causative agents of human affective disorders? The impact of anti-psychotic, mood-stabilizer and anti-parasite medication on Toxoplasma gondii ‘s ability to alter host behaviour
Webster, J.P., Lamberton, P.H.L., Donnelly, C.A., Torrey, E.F.
Proceedings of the Royal Society B-Biological Sciences 2006; 273: 1023-1030
Click for abstract
With increasing pressure to understand transmissible agents, renewed recognition of infectious causation of both acute and chronic diseases is occurring. Epidemiological and neuropathological studies indicate that some cases of schizophrenia may be associated with environmental factors, such as exposure to the ubiquitous protozoan Toxoplasma gondii. Reasons for this include T gondii's ability to establish persistent infection within the central nervous system, its ability to manipulate intermediate host behaviour, the occurrence of neurological and psychiatric symptoms in some infected individuals, and an association between infection with increased incidence of schizophrenia. Moreover, several of the medications used to treat schizophrenia and other psychiatric disease have recently been demonstrated in vitro to possess antiparasitic, and in particular anti-T gondii, properties. Our aim here was thus to test the hypothesis that the anti-psychotic and mood stabilizing activity of some medications may be achieved, or at least augmented, through their in vivo inhibition of T gondii replication and invasion in infected individuals. In particular we predicted, using the epidemiologically and clinically applicable rat-T gondii model system, and following a previously described and neurologically characterized 'feline attraction' protocol that haloperidol (an antipsychotic used in the treatment of mental illnesses including schizophrenia) and/or valproic acid (a mood stabilizer used in the treatment of mental illnesses including schizophrenia), would be, at least, as effective in preventing the development of T gondii-associated behavioural and cognitive alterations as the standard anti-T gondii chemotherapeutics pyrimethamine with Dapsone. We demonstrate that, while T gondii appears to alter the rats' perception of predation risk turning their innate aversion into a 'suicidal' feline attraction, anti-psychotic drugs prove as efficient as anti-T gondii drugs in preventing such behavioural alterations. Our results have important implications regarding the aetiology and treatment of such disorders.
Toxoplasma gondii a potential risk for traffic accidents in Turkey?
Yereli, K., Balcioglu, .IC., Ozbilgin, A.
Forensic Science International 2006; 163: 34-37
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In Turkey, traffic accidents are the major causes of mortality and morbidity. According to the statistics made by Turkish Security Headquarters in the year 2000, 7500 people are killed in the traffic accidents every year. Drivers are mostly blamed for the traffic accidents. Tired, weary, sleepy and absentminded driving are common reasons for traffic accidents due to many reasons. Among these reasons mental and reflex conditions of drivers are significant. Toxoplasmosis is one of the most common zoonoses throughout the world. In immumocomponent adults, toxoplasmosis has no clinical signs or symptoms and infection in such people can only be detected by serological examinations. This kind of latent or dormant toxoplasmosis can be located in neural or muscular tissues and cause prolonged reaction times of the muscles. Extended reaction times also lead to deceleration of the reflexes which could be a major cause of the traffic accidents. By the light of this situation, the incidence of Toxoplasma gondii is investigated among the population who were involved in a traffic accident while driving. A total of 185 people (100 men and 85 women), aged between 21 and 40 years, living in Izmir and Manisa cities, were enrolled in the study group (SG) during a period of 6 months time. Their informed consents were taken initially and the laboratory tests of all these individuals related to blood alcohol levels after the accidents were found negative. The control group (CG) were also consisted 185 people (95 men and 90 women), residents of the same region, in same age group. The people in CG had no clinical signs or symptoms concerning toxoplasmosis. All collected sera were examined using a commercial IgG and IgM ELISA kit. According to the results of serological tests of the SG, 45 (24.32%) sera were IgG positive, six (3.24%) were IgM positive and 10 (5.40%) were both IgG and IgM positive. On the other hand in CG, 12 (6.48%) people found IgG positive, one (0.54%) found IgM positive and three (1.62%) found both IgG and IgM positive. This data was considered as statistically significant by Yates corrected chi(2)-test. (p < 0.05). In conclusion, there is an increased risk for traffic accidents for drivers owing to these high seroprevalence of latent toxoplasmosis. Prospective studies are still necessary on this subject but latent toxoplasmosis of drivers should be taken into account while developing strategies to prevent traffic accidents in Turkey. (c) 2005 Elsevier Ireland Ltd. All rights reserved.
Gender differences in behavioural changes induced by latent toxoplasmosis
Lindová, J., Novotná, M., Havlícek, J., Smídová, E., Skallová, A., Kolbeková, P., Hodný, Z., Kodym, P. , Flegr, J.
International Journal for Parasitology 2006; 36: 1485-1492
Click for abstract
There is growing evidence that the protozoan
Toxoplasma gondii
modifies behaviour of its intermediate hosts, including humans,
where it globally infects about 20–60% of the population. Although it is considered asymptomatic in its latent stage, it was previously
found to have remarkable and gender different effects on the personality factors A (warmth), G (rule consciousness), L (vigilance, mis-
trust) and Q3 (self-control, self-image) from Cattell’s 16PF Questionnaire. We performed a double blind experiment testing 72 and 142
uninfected men and women, respectively, and 20 and 29 infected men and women, respectively, in order to verify these gender differences
using behavioural experiments. Our composite behavioural variables Self-Control and Clothes Tidiness (analogue to the 16PF factors G
– conscientiousness and Q3 – self-control) showed a significant effect of the toxoplasmosis–gender interaction with infected men scoring
significantly lower than uninfected men and a trend in the opposite direction in women. The effect of the toxoplasmosis–gender inter-
action on our composite behavioural variable Relationships (analogue to factor A – warmth) approached significance; infected men
scored significantly lower than uninfected men whereas there was no difference in women. In the composite behavioural variable Mistrust
(analogue to factor L), the pattern was affected by environment (rural versus urban). Possible interpretations of the gender differences are
discussed.
Look what the cat dragged in: do parasites contribute to human cultural diversity?
Lafferty, K.D.
Behavioural Processes 2005; 68: 279-282
Parasitic manipulation: where are we and where should we go?
Thomas, F., Adamo, S., Moore, J.
Behavioural Processes 2005; 68: 185-199
Parasitic manipulation: where else should we go?
Webster, J. P.
Behavioural Processes 2005; 68: 275-277
Increased risk of traffic accidents in subjects with latent toxoplasmosis: a retrospective case-control study
Flegr, J., Havlícek, J., Kodym, P., Malý, M., Smahel, Z.
BMC Infectious Diseases 2002; 2: 11 (1-13)
Click for abstract
Background:
The parasite
Toxoplasma gondii
infects 30–60% of humans worldwide. Latent
toxoplasmosis, i.e., the life-long presence of
Toxoplasma
cysts in neural and muscular tissues, leads
to prolongation of reaction times in infected
subjects. It is not known, however, whether the
changes observed in the laboratory influence the
performance of subjects in real-life situations.
Methods:
The seroprevalence of latent toxoplasmosis in
subjects involved in traffic accidents (N
= 146) and in the general population living in the same area (N = 446) was compared by a Mantel-
Haenszel test for age-stratified da
ta. Correlation between relative risk of traffic accidents and level
of anti-Toxoplasma antibody titre was evaluate
d with the Cochran-Armitage test for trends.
Results:
A higher seroprevalence was found in the traffic accident set than in the general
population (Chi
2
MH
= 21.45, p < 0.0001). The value of the odds ratio (OR) suggests that subjects
with latent toxoplasmosis had a 2.65 (C.I.
95
= 1.76–4.01) times higher risk of an accident than the
toxoplasmosis-negative subjects. The OR significantly increased with level of anti-
Toxoplasma
antibody titre (p < 0.0001), being low (OR = 1.86, C.I.
95
= 1.14–3.03) for the 99 subjects with low
antibody titres (8 and 16), higher (OR = 4.78, C.I.
95
= 2.39–9.59) for the 37 subjects with moderate
titres (32 and 64), and very high (OR = 16.03, C.I.
95
= 1.89–135.66) for the 6 subjects with titres
higher than 64.
Conclusion:
The subjects with latent toxoplasmosis have
significantly increased risk of traffic
accidents than the noninfected subjects. Relative
risk of traffic accidents decreases with the
duration of infection. These results suggest that
'asymptomatic' acquired toxoplasmosis might in
fact represent a serious and highly underestimated public health problem, as well as an economic problem
The schizophrenia-rheumatoid arthritis connection: Infectious, immune, or both?
Torrey, E. F. , Yolken, R. H.
Brain Behavior and Immunity 2001; 15: 401-410
Click for abstract
Schizophrenia and rheumatoid arthritis share an impressive number of similarities. Both are chronic, relapsing diseases of unknown etiology. Both became prominent in the early 19th century and have prevalences of approximately 1% in North America and Europe. Both run in families, have pairwise concordance rates of approximately 30% among monozygotic twins, and are more common among individuals born in urban areas. For both diseases, studies have reported greater exposure to cats in childhood than in controls. Both diseases have been associated with similar class II HLA antigens. Both have also been suspected of having infectious etiology, with similar agents-retroviruses, herpesviruses including EBV, and Toxoplasma gondii-having been associated in some cases. Since there is also a well-documented inverse correlation between these two diseases, it is possible that they share a common infectious and/or immune etiology and that once a person gets one of the diseases then they are relatively immune to the other. (C) 2001 Elsevier Science.
Rats, cats, people and parasites: the impact of latent toxoplasmosis on behaviour
Webster, J. P.
Microbes and Infection 2001; 3: 1037-1045
Click for abstract
The manipulation hypothesis states a parasite may alter host behaviour for its own benefit, often by enhancing its transmission rate through the food chain. This paper reviews studies on the potential impact of one parasite, Toxoplasma gondii, on host behaviour, both on rodents, where altered responses may be proposed to benefit the parasite, and humans, where altered responses may arise as a side-effect of infection with no current adaptive significance. (C) 2001 Editions scientifiques et medicales Elsevier SAS.
Toxo: The parasite that is manipulating human behavior
Sapolsky, R.
In: The Mind Edited by John Brockman. The Edge Foundation Inc. 2001
Toxoplasmosis, behaviour and personality
Holliman, R. E.
Journal of Infection 1997; 35: 105-110
Click for abstract
The clinical sequelae of acute and congenital toxoplasmosis are well established, but that of chronic toxoplasma infection remains uncertain. In rodents, chronic toxoplasma infection is associated with altered behaviour leading to an enhanced risk of feline predation and a putative selective advantage to the parasite. It is proposed that neurotropic cysts of toxoplasma exert an effect on animal behaviour, either directly or via the release of metabolic products. Long-standing toxoplasma infection in humans has been linked to cerebral tumour formation and personality shift. In view of the vast population with chronic toxoplasma infection, further studies of the clinical sequelae of this condition are required.
Induction of changes in human behaviour by the parasitic protozoan Toxoplasma gondii
Flegr, J., Zitková, Š., Kodym, P., Frynta, D.
Parasitology 1996; 113: 49 - 54
Click for abstract
Toxoplasma gondii, the coccidian parasite, is known to induce changes in the behaviour of its intermediate hosts. The high prevalence of this parasite in the human population (20-80%) offers the opportunity of studying the influence of the parasite on human behaviour by screening of a normal population.
Two hundred and twenty-four men and one hundred and seventy women were tested for toxoplasmosis and their personality profiles were measured by Cattell's questionnaire. Highly significant differences between Toxoplasma infected and uninfected subjects were observed (p < 0.01). For men the factors G (low superego strength, p<0.02), and possibly L (protension), O (guilt proneness), and A (sizothymia) prevailed in infected subjects. For women the prevailing factors were A (afectothymia, p<0.01), and possibly L (alaxia) and N (shrewdness). To reveal whether toxoplasmosis induces personality factor-shifts or whether certain combinations of personality factors influence the probability of acquiring Toxoplasma infection, we examined the personality profiles of 164 male patients diagnosed with acute toxoplasmosis during the past 13 years. The existence of a positive correlation between the duration of latent toxoplasmosis and the intensity of superego strength decrease (p<0.02) suggested that the decrease of superego strength (the willingness to accept group moral standards) was induced by T. gondii infection.
Behavioral alterations caused by parasitic infection in case of latent toxoplasma infection
Piekarski, G.
ZentralblBakteriolMikrobiolHyg[A] 1981; 250: 403-406