Is there a relation between the manipulative activity of Toxoplasma and personalized medicine?
Flegr, J.
Expert Review of Anti-Infective Therapy 2018; 16: 1-3
Do differences in Toxoplasma gondii prevalence influence global variation in secondary sex ratio? Preliminary ecological regression study
Dama, S.M., Martinec Nováková, L., Flegr, J.
Parasitology 2016; 143, 1193–1203 doi:10.1017/S0031182016000597
Click for abstract
Sex of the fetus is genetically determined such that an equal number of sons and daughters are born in large populations.
However, the ratio of female to male births across human populations varies signi
fi
cantly. Many factors have been impli-
cated in this. The theory that natural selection should favour female o
ff
spring under suboptimal environmental conditions
implies that pathogens may a
ff
ect secondary sex ratio (ratio of male to female births). Using regression models containing
13 potential confounding factors, we have found that variation of the secondary sex ratio can be predicted by seropreva-
lence of
Toxoplasma
across 94 populations distributed across African, American, Asian and European continents.
Toxoplasma
seroprevalence was the third strongest predictor of secondary sex ratio,
β
=
−
0·097,
P
< 0·01, after son pref-
erence,
β
= 0·261,
P
< 0·05, and fertility,
β
=
−
0·145,
P
< 0·001. Our preliminary results suggest that
Toxoplasma gondii
in-
fection could be one of the most important environmental factors in
fl
uencing the global variation of o
ff
spring sex ratio in
humans. The e
ff
ect of latent toxoplasmosis on public health could be much more serious than it is usually supposed to be.
Schizophrenia and Toxoplasma gondii: an undervalued association?
Flegr, J.
Expert Review of Anti-infective Therapy 2015; 13: 817-820
Click for abstract
The existence of an association between schizophrenia and an infection by the
protozoan parasite
Toxoplasma gondii
has been suspected since the 1950s. Two
significant phenomena first garnered the attention of the psychiatric community
toward toxoplasmosis, the illness precipitated by an infection of the parasite.
Transient symptoms of acute toxoplasmosis sometimes resemble the clinical
picture of paranoid schizophrenia. Many studies have also found an increased
seroprevalence of toxoplasmosis in clients of mental health institutions in
comparison with members of control populations. We have had to wait until the
first decade of our millennium for several independent research teams to make
discoveries that would shed light on he possible mechanisms that link the
Toxoplasma
parasite to schizophrenia.
The influence of latent toxoplasmosis on women’s reproductive function: four cross-sectional studies
Kankova, S., Flegr, J., Calda, P.
Folia Parasitologica 2015; 62:
Click for abstract
Several studies have investigated the association between infection with Toxoplasma gondii (Nicolle et Manceaux, 1908), pregnancy and fertility, but the results of studies focused on the fertility are rather ambiguous. Here we report results of four new cross-sectional studies. The studies were performed in the General University Hospital, Prague (study A with n = 1 165, and study C with n = 317), in private clinics of the Centre of Reproductive Medicine, Prague (study B with n = 1 016), and in a population of Czech and Slovak volunteers from the Facebook page 'Guinea Pigs' willing to participate in various basic science studies (study D with n = 524). In studies A and B, the clinical records were used to assess the fertility problems, whereas in studies C and D, the women were asked to rate their fertility problems using a six-point scale. Pregnant T. gondii-infected women were older than T. gondii-free women (study A: 33.1 vs 31.2, P < 0.001; study B: 30.6 vs 29.6, P = 0.012) and more often used assisted reproductive technology to conceive (study A: 17.2% vs 12.4%, P = 0.041; study B: 13.4% vs 9.2%, P = 0.317). Pregnant T. gondii-infected primiparous women were older than T. gondii-free primiparas (study A: 31.1 vs 29.5, P < 0.001; study B: 29.7 vs 28.9, P = 0.064) and more often used assisted reproductive technology to conceive (study A: 24.7% vs 14.4%, P = 0.010; study B: 15.9% vs 15.5%, P = 0.888). T. gondii-infected women reported to take a longer time to conceive than T. gondii-free women (P = 0.015). They also claimed to have more fertility problems than T. gondii-free women (P < 0.0001). Our results suggest that 'asymptomatic' latent toxoplasmosis could be a more serious source of fertility problems and health-associated burden than more severe but far rarer congenital toxoplasmosis.
Latent Toxoplasma gondii infection leads to deficits in goal-directed behavior in healthy elderly
Beste, C., Getzmann, S., Gajewski, P. D., Golka, K., Falkenstein, M
Neurobiology of Aging 2014; 35: 1037-1044.
Click for abstract
The parasite Toxoplasma gondii has been found to manipulate the behavior of its secondary hosts to increase its own dissemination which is commonly believed to be to the detriment of the host (manipulation hypothesis). The manipulation correlates with an up-regulation of dopaminergic neurotransmission. In humans, different pathologies have been associated with T. gondii infections but most latently infected humans do not seem to display overt impairments. Since a dopamine plus does not necessarily bear exclusively negative consequences in humans, we investigated potential positive consequences of latent toxoplasmosis (and the presumed boosting of dopaminergic neurotransmission) on human cognition and behavior. For this purpose, we focused on action cascading which has been shown to be modulated by dopamine. Based on behavioral and neurophysiological (EEG) data obtained by means of a stop-change paradigm, we were able to demonstrate that healthy young humans can actually benefit from latent T. gondii infection as regards their performance in this task (as indicated by faster response times and a smaller P3 component). The data shows that a latent infection which is assumed to affect the dopaminergic system can lead to paradoxical improvements of cognitive control processes in humans.
Latent Toxoplasma gondii infection leads to improved action control
Stock, A. K., von Heinegg, E. H., Kohling, H. L., Beste, C.
Brain Behavior and Immunity 2014; 37: 103-108
Click for abstract
The parasite Toxoplasma gondii has been found to manipulate the behavior of its secondary hosts to increase its own dissemination which is commonly believed to be to the detriment of the host (manipulation hypothesis). The manipulation correlates with an up-regulation of dopaminergic neurotransmission. In humans, different pathologies have been associated with T. gondii infections but most latently infected humans do not seem to display overt impairments. Since a dopamine plus does not necessarily bear exclusively negative consequences in humans, we investigated potential positive consequences of latent toxoplasmosis (and the presumed boosting of dopaminergic neurotransmission) on human cognition and behavior. For this purpose, we focused on action cascading which has been shown to be modulated by dopamine. Based on behavioral and neurophysiological (EEG) data obtained by means of a stop-change paradigm, we were able to demonstrate that healthy young humans can actually benefit from latent T. gondii infection as regards their performance in this task (as indicated by faster response times and a smaller P3 component). The data shows that a latent infection which is assumed to affect the dopaminergic system can lead to paradoxical improvements of cognitive control processes in humans. (C) 2013 Elsevier Inc. All rights reserved.
Does prevalence of latent toxoplasmosis correlate with nation-wide rate of traffic accidents?
Flegr, J., Dama, M.
Folia Parasitologica 2014; 6, 485-494
Click for abstract
Latent toxoplasmosis is probably the most common protistan parasitic disease with many indirect negative impacts on
human health. One of the important impacts is impaired psychomotor function leading to reduced driving efficiency in
Toxoplasma
-
seropositive subjects. Numerous case-control studies have established a positive relation between the seroprevalence of
Toxoplasma
gondii
(Nicolle et Manceaux, 1908) and probability of traffic accidents in study populations. The prevalence of toxoplasmosis varies
between populations according to local geographical conditions, hygienic practices and kitchen habits. Similarly, we see a striking
variation in the incidence of traffic accidents across countries. Hence, we compiled the largest ever data set on the seroprevalence
of toxoplasmosis
and tried to understand its role in traffic accident-related deaths and disabilities across 87 countries. Simple non
-
parametric analysis showed a
positive and strong relation of
T. gondii
seroprevalence and traffic accident related disabilities. Further,
we conducted multivariate analysis to control for confounding factors. After controlling for wealth, geographical latitude, health of
population, length of roads and number of vehicles, the correlation disappeared. When the frequency of RhD negativity and its in
-
teraction with toxoplasmosis were included into the model, the effects of toxoplasmosis seemingly returned. However, the analysed
data suffered from the problem of multicollinearity. When a proper method of analysis, ridge regression, was applied, the effects
of toxoplasmosis prevalence and RhD negativity frequency disappeared again. The existence of a strong correlation between the
prevalence of toxoplasmosis and health of population in particular countries, which was the probable cause of multicollinearity and
possible reason for the negative result of the present study, suggests that ‘asymptomatic’ latent toxoplasmosis could have a large impact on public health
Difference of neuro- and immunomodulatory steroids and selected hormone and lipid concentrations between Toxoplasma-free and Toxoplasma-infected schizophrenia patients
Flegr, J., Hampl, R., Bicíková, M., Ripova, D., Mohr, P.
Neuroendocrinology Letters 2014; 35: 20-27
Click for abstract
OBJECTIVES
:
Toxoplasma gondii
, the protozoan parasite infecting about 30%
population worldwide, is suspected to be the etiological agent of certain form
of schizophrenia disease.
To x o p l a s m a
is known to change levels of certain neu-
rotransmitters, cytokines and several hormones in both infected animals and
humans. A common feature of toxoplasmosis and schizophrenia is a disorder of
immune system.
METHODS:
Here we studied the levels of five neuro- and immunomodulatory
steroids, selected hormones and lipids in sera of 173 schizophrenia patients.
RESULTS:
To x o p l a s m a
infected schizophrenia patients expressed only insignifi-
cantly lower concentration of neuro- and immunomodulatory DHEA metabo-
lites. Infected women had higher concentration of glucose while infected men had
higher concentration of cholesterol and LDL cholesterol. No significant effect of
human cytomegalovirus infection on the concentration of the above parameters
was observed. The difference in the concentration of DHEA metabolites faded
with the decrease of the concentration of anti-
To x o p l a s m a
IgG antibodies (i.e.
with the duration of
To x o p l a s m a
infection) while the difference in the concentra-
tion of cholesterol and LDL-cholesterol increased with the decrease of the con-
centration of anti-
To x o p l a s m a
IgG antibodies. The prevalence of toxoplasmosis in
male (53.2%) but not female (29.8%) schizophrenia
patients was unusually high in
comparison with prevalence of toxoplasmosis in a general population.
CONCLUSION:
Our results provided an explanation for seemingly decreasing
prevalence of toxoplasmosis in schizophrenia patients observed in current studies (increased concerns about the rights of patients result-
ing in absence of non-cooperative
To x o p l a s m a
-positive
patients in the study population) and suggest possible
explanation for reported positive correlation between
prevalence of toxoplasmosis and incidence of cardio-
vascular diseases (accelerated atherosclerotic develop-
ment due to increased level of cholesterol and LDL in
To x o p l a s m a
infected humans).
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
Higher extraversion and lower conscientiousness in humans infected with Toxoplasma
Lindová, J., Příplatová, L., Flegr, J.
European Journal of Personality 2012; 26: 285–291
Click for abstract
oxoplasmosis is associated with speci
fi
c differences in the personality
of infected subjects relative to
non-infected subjects. These differences are usually cons
idered to be a side effect of the manipulative activity of
the parasite aimed to increase the probability of its
transmission from the intermediate host to the de
fi
nitive host
by predation. The personality of infected s
ubjects was studied mostly using the Cattell
’
s questionnaire. However,
this questionnaire is now considered outdated and has been mostly substituted with the Neuroticism
–
Extraversion
–
Openness Personality Inventory
—
Revised (NEO-PI-R) questionnaire in clinical practice. Here, we searched for the as-
sociation between toxoplasmosis and the personality by screening a population of students with the NEO-PI-R question-
naire. We found that Toxoplasma-infected male and female students had signi
fi
cantly higher extraversion and lower
conscientiousness. The conscientiousness negatively correlated with the length of infection in men, which suggested that
the toxoplasmosis associated differences were more probably the result of slow cumulative changes induced by latent
toxoplasmosis, rather than transient side effect of acute Toxoplasma infection. The existence of this correlation also sup-
ported (but of course not proved) the hypothesis that Toxoplasma infection in
fl
uenced the personality, rather than the
hypothesis that the personality in
fl
uenced the probability of the infection.
Women infected with parasite Toxoplasma have more sons
Kanková S., Sulc J. ,Nouzová K., Fajfrlík K., Frynta D., Flegr J.
Naturwissenschaften 94: 122-127, 2007
Click for abstract
The boy-to-girl ratio at birth (secondary sex ratio)
is around 0.51 in most populations. The sex ratio varies
between societies and may be influenced by many factors,
such as stress and immunosuppression, age, primiparity, the
sex of the preceding siblings and the socioeconomic status of
the parents. As parasite infection affects many immunolog-
ical and physiological parameters of the host, we analyzed
the effect of latent toxoplasmosis on sex ratios in humans.
Clinical records of 1,803 infants born from 1996 to 2004
contained information regarding the mother
’
s age, concen-
tration of anti-
Toxoplasma
antibodies, previous deliveries
and abortions and the sex of the newborn. The results of
our retrospective cohort study suggest that the presence of
one of the most common parasites (with a worldwide
prevalence from 20 to 80%),
Toxoplasma gondii
,can
influence the secondary sex ratio in humans. Depending
on the antibody concentration, the probability of the birth of
a boy can increase up to a value of 0.72, C.I.
95
=(0.636,
0.805), which means that for every 260 boys born, 100 girls
are born to women with the highest concentration of anti-
Toxoplasma
antibodies. The toxoplasmosis associated with
immunosuppression or immunomodulation might be re-
sponsible for the enhanced survival of male embryos. In
light of the high prevalence of latent toxoplasmosis in most
countries, the impact of toxoplasmosis on the human
population might be considerable
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.
Decreased level of novelty seeking in blood donors infected with Toxoplasma
Skallová, A., Novotná, M., Kolbeková, P., Gasová, Z., Veselý,V., Sechovská, M., Flegr, J.
Neuroendocrinology Letters 2005; 26: 480-486
Click for abstract
OBJECTIVES
:
Toxoplasma gondii
, a parasitic protozoan, infects about 30–60% of
people worldwide.
Toxoplasma
is known to induce behavioral changes and an
increase of dopamine in mice. The presence of anti-
Toxoplasma
antibodies (latent
toxoplasmosis) is also a risk factor for schizophrenia. Latent toxoplasmosis in
men (male soldiers) is associated with lower novelty seeking. As the novelty seek
-
ing is supposed to negatively correlate with level of dopamine, the observed effect
was interpreted as indirect evidence of increased dopamine levels in subjects with
toxoplasmosis. However, it is also possible that the observed effect was caused by
association of both novelty seeking and
Toxoplasma
infection with a third factor,
e.g. size of place of residence.
METHODS
:
Personality profile of 290 blood donors (205 men and 85 women) were
measured by Cloninger’s TCI (Temperament and Character Inventory) and their
blood samples were assayed for the presence of anti-
Toxoplasma
antibodies. Dif
-
ference between
Toxoplasma
-infected and
Toxoplasma
-free subjects was tested
with ANCOVA method with gender, size of place of residence, and age as covari
-
ates.
RESULTS
:
The present analysis revealed that lower novelty seeking was associ
-
ated with latent toxoplasmosis both in men and women. The effect of infection
on novelty seeking remained significant even after adjustment for size of place of
residence (p<0.0).
CONCLUSION
:
Decreased novelty seeking in
Toxoplasma
-infected subjects have
been already confirmed in three independent populations (male soldiers and
male and female blood donors). These findings suggest that the local inflamma
-
tion-induced increase in dopamine in the brain of infected subjects can represent
a missing link between toxoplasmosis and schizophrenia
Decreased level of psychobiological factor novelty seeking and lower intelligence in men latently infected with the protozoan parasite Toxoplasma gondii. Dopamine, a missing link between schizophrenia and toxoplasmosis?
Flegr, J., Preiss, M., Klose, J., Havlíček, J., Vitáková, M, Kodym, P.
Biological Psychology 2003; 63: 253-268
Click for abstract
Toxoplasma gondii
, a parasitic protozoan, infects about 30
/
60% of people worldwide. The
latent toxoplasmosis, i.e. life-long presence of cysts in the brain and muscular tissues, has no
effect on human health. Howe
v
er, infected subjects score worse in psychomotor performance
tests and ha
v
e different personality profiles than
Toxoplasma
-negati
v
e subjects. The
mechanism of this effect is unknown; howe
v
er, it is supposed that presence of parasites’ cysts
in the brain induces an increase of the concentration of dopamine. Here we search for the
existence of differences in personality profile between
Toxoplasma
-positi
v
e and
Toxoplasma
-
negati
v
e subjects by testing 857 military conscripts using a modern psychobiological
questionnaire, namely with Cloninger’s Temperament and Character In
v
entory (TCI).
ANCOVA showed that
Toxoplasma
-positi
v
e subjects had lower No
v
elty seeking (NS) scores(
P
/
0.035) and lower scores for three of its four subscales, namely Impulsi
v
eness (
P
/
0.049),
Extra
v
agance (
P
/
0.056) and Disorderliness (
P
/
0.006) than the
Toxoplasma
-negati
v
e
subjects. Differences between
Toxoplasma
-negati
v
e and positi
v
e subjects in NS was in
v
ersely
correlated with duration of toxoplasmosis estimated on the basis of concentration anti-
Toxoplasma
antibodies (
P
/
0.031). Unexpectedly, the infected subjects had also lower IQ
(
P
2
/
0.003) and lower probability of achie
v
ing a higher education (
P
2
B
/
0.0000). Decrease of
NS suggests that the increase of dopamine in brain of infected subjects can represent a missing
link between toxoplasmosis and schizophrenia
Decrease of psychomotor performance in subjects with latent “asymptomatic” toxoplasmosis
Havlícek, J., Gasová, Z., Smith, A. P. , Zvára, K, J. Flegr, J.
Parasitology 2001; 122: 515-520
Click for abstract
Toxoplasma gondii
is known to induce speciÆc behavioural changes in its intermediate hosts. This is usually considered
to be an evolutionary adaptation aimed to increase the probability of transmission of the parasite into its deÆnitive host,
the cat, by predation. In rodents an increase of reaction time as well as many other speciÆc behavioural patterns have been
observed. Here we report the results of our double blind study showing the signiÆcantly longer reaction times of 60
subjects with latent toxoplasmosis in comparison with those of 56 controls. Moreover, the existence of a positive correlation
between length of infection and mean reaction time suggested that slow and cumulative effects of latent toxoplasmosis
rather than a one-step (and possibly transient) effect of acute toxoplasmosis disease are responsible for the decrease of
psychomotor performance of infected subjects. To our knowledge, this is the Ærst study conÆrming the existence of such
parasite-induced changes in human behaviour that could be considered in evolutionary history of the human species as
adaptive from the point of view of parasite transmission.
Correlation of duration of latent Toxoplasma gondii infection with personality changes in women
Flegr, J., Kodym, P.,Tolarová, V.
Biological Psychology 2000; 53: 57-68
Click for abstract
Many parasites induce characteristic changes in behavior of their hosts. In humans latent
toxoplasmosis is associated with changes in personality profiles. It has been already shown
that a decrease in superego strength is correlated with duration of toxoplasmosis in men.
Here we studied changes in personality profiles with Cattell’s 16 PF questionnaire in
Toxoplasma
-infected women. The changes were measured as differences in personality
factors between
Toxoplasma
-infected subjects and uninfected controls of the same age. The
low-rate changes were studied in 230 women diagnosed with acute toxoplasmosis during past
14 years. The results showed the correlation between duration of toxoplasmosis and level of
factors G (high superego strength) and Q3 (high strength of self sentiment). The high-rate
changes were estimated by measuring the correlation between level of
Toxoplasma
-antibody
titers (which rapidly decline after the end of acute phase of toxoplasmosis) and personality
factors in an experimental set of 55 young mothers with latent toxoplasmosis. Again, certain
factors, namely A (affectothymia), F (surgence), G (high superego strength), H (parmia), and
L (protension), correlated with the length of the infection. We suggest that the parasite
induced the changes in the personality profiles of the women because of our observation of
an increasingly different personality profile over time between women with latent infection
and controls. The same evidence questions the view that women with a particular personality profile are more prone to acquisition
Differences in personality profiles of Toxoplasma gondii infected and uninfected biologist
Flegr, J., Hrdá, Š, Havlíček, J.
Remedia-Klinická mikrobiologie 1999, 3: 268-273
Click for abstract
Parasitic protozoan Toxoplasma gondii induces specific changes the behavior of its intermediate hosts. Human latent toxoplasmosis (presence of anti-Toxoplasma immunity in subjects without any clinical symptoms of acute toxoplasmosis) is known to be associated with specific changes of personality profiles of infected subjects. I the present work we studied the toxoplasmosis-associated differences in personality profiles (monitored by Cattell's 16PF questionnaire) in a population of 443 university students and teachers of biology. Our results show that the factors A, G, L, N and Q3 were shifted in the opposite direction in men and women; the factor O was shifted in the same direction, however, the intensity of the shift in women was relatively low. The men with latent toxoplasmosis had lower factor G (had higher tendency to disregard rules) p=0.049, higher factor L (were more suspecting, jealous, dogmatic) p=0.015, and higher factor O (were more apprehensive, self-reproaching, insecure) p=0.046. The Toxoplasma-infected women had higher factor A (warm-hearted, outgoing, easygoing) p=0.001. Several personality factors were shifted (both in men and women) from extreme values toward the middle of the psychological scales. Therefore, the Toxoplasma-infected subjects expressed less extreme personality attitudes in factors F, M, Q1 and Q4.
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.
Influence chronic toxoplasmosis on some personality factors
Flegr, J., Hrdy, I.
Folia Parasitologica 1994; 41: 122-126
Click for abstract
Abstract. An effect of parasites on host behaviour was tested on the toxoplasma-human model. Three hundred and thirty-eight (338)
people were assessed with Cattell's personality questionnaire and then tested for Toxoplasma gondii infection with a delayed type hypersensitivity
test for Toxoplasma. A highly significant correlation between chronic toxoplasmosis and two personality factors (G- Low
Superego Strength and L- Protension) was found (p =0.0032 and 0.0020, respectively). A correlation of the intensity of the personality
factor-shifts with the duration of the infection (estimated from antibody titer) suggests that toxoplasmosis induces the shift in human personality, rather than the personality factors G and L influence an acquisition rate of Toxoplasma gondii infection.