Thoughts on cats, rats, and a day in Jerusalem
April 26, 2007
Jacob Schor, ND
Subject: Chronic infection with Toxoplasma gondii may cause personality shifts to the degree that they change cultural behavior in areas of high incidence of infection.
On August 7, 2000, Manuel Berdoy presented a paper to the Royal Society of London on the protozoan, Toxoplasma gondii.
This parasite spends the early portion of its life living in rats but must transfer to a cat's body to reproduce and complete its lifecycle. Jumping from a rat to a cat is not easy, as rats tend to avoid cats. However, this parasite has a vested interest in a cat catching and eating the rat it's living in, and has figured out a way to make it happen.
Apparently, the Toxoplasma parasite has learned to make a host rat unafraid of cats and increase the rat's chance of getting eaten. Berdoy and his fellow researchers watched rats as they exposed them to cat odors. Normal rats avoid cat smells. Yet Toxoplasma infected rats lost their wariness and were even attracted to the cat fragrance. This is an example of a parasite manipulating its victim mammal. [i]
Just a few weeks ago, on April 10, 2007, Ajai Vyas and his colleagues at Stanford University in California explained how Toxoplasma pulls this off. The parasite reverse the rat's innate fear by interfering with the amygdala, the seat of conditioned responses in the brain. The parasites congregate in the amygdala of infected rats so that there were twice as concentrated as in other tissue. They damage the amygdala leaving all other neurological fear mechanisms for avoiding danger intact. The rats know how to survive the other hazards of being a rat, except for one, being eaten by a cat. [ii]
In the six years since I first chanced upon this information, it has often been the subject of my rumination. If Toxoplasma can make a cat look attractive to a rat, how much could our own thinking be the result of other living things influencing our thoughts? We are outnumbered in our own bodies. If you performed a census counting all the parasites, bacteria, fungi, and viruses that live within your body, you would find ‘yourself' outnumbered nine to one. Clearly, we do not want our bodies to operate as a democracy where each entity gets a vote. We would prefer to limit decision making power to cells that share our genes and our goal for survival.
Toxoplasma can infect many types of mammals, including people. Researchers began to speculate that low-grade infections might produce subtle mental changes in people and cause odd behavior. When Berdoy presented his paper in London, others were quick to point out that about 28% of the English population [iii] was infected with Toxoplasma but almost triple that number were infected in Paris. [iv] At first glance, this sounded like a joke the English would find amusing.
Kevin Lafferty took this question of Toxoplasma's effect on human populations a few steps further. Lafferty is with the United States Geological Survey at the University of California, Santa Barbara . His research specialty is costal marine biology and as a result knew a lot about Toxoplasma. Toxaplasma infects other mammals besides cats and rats. Though it can't reproduce successfully, it still may affect the animal's behavior. Almost 10% of the sea otters deaths along the coast of California are blamed on Toxoplasma infections that result from cat feces getting into washed into the ocean.
In September 2006, Lafferty presented a paper correlating human behavior with Toxoplasma infection at the Royal Society in London. Lafferty took this English versus French joke seriously. He started with the assumption,
The number of people infected by Toxoplasma varies widely in different parts of the world. In some areas, it is rare and in others almost everyone is infected. Lafferty reviewed and compared published data on culture and personality from countries where data on Toxoplasma incidence is available. Pregnant women are routinely tested in some countries for antibodies against Toxoplasma because of the risk the parasite poses to fetuses.
Comparing the data, Lafferty concluded that, “….the parasite's subtle effect on individual personality appears to alter the aggregate personality at the population level.”
Countries with high Toxoplasma levels had a higher aggregate neuroticism score, and Western nations with high prevalence also scored higher in the "neurotic" cultural dimensions of "masculine" sex roles and uncertainty avoidance.
"There could be a lot more to this story. Different responses to the parasite by men and women could lead to many additional cultural effects that are, as yet, difficult to analyze," said Lafferty. [vi]
Climate affects how long Toxoplasma lasts in the environment and how many people get infected. The parasite's eggs live longer in humid, low-altitude regions, especially at mid latitudes where they do not freeze. Rates of infection will vary with cultural sanitation practices but especially with how many cats are around.
This brings back memories of watching cats with my daughter from an apartment window in Jerusalem several years ago. In many Mediterranean countries, feral cats are everywhere. Whereas in Denver squirrels are so ubiquitous we hardly notice them, in Jerusalem, it is the same with cats. They are everywhere. Our daughter was just learning to count at the time and counted upwards of 27 cats prowling the refuse cans in the back courtyard.
A fair percentage of those cats were probably infected. The rate of feline infection varies by neighborhood. In one study, only 16% of cats in Jewish neighborhoods were infected compared to 34 % in Arab neighborhoods. [vii] Another Israeli study compared infection rates between Arab villagers and Jewish kibbutzim. On average 22% of the kibbutz members were infected compared to 58% of the villagers. Infection rates of both groups increased with age so that 43% of the kibbutz members over 60 years old were infected and over 74% of the Arab villagers were infected by age 40. [viii]
How does this stack up to the rest of the world? About one quarter of the US population tests positive for Toxoplasma infection. [ix] Infections rates typically run at about 78-80% in northern Iran . [x] In Croatia they average about 36% [xi] while in rural Korea , only 6 to 7% [xii] of the population is infected. In Iceland , the infection rate is about 10% while it can go as high as 50% in parts of Sweden where evidence suggests that infection increases risk of developing asthma. [xiii] In Mexico, 29 % of schizophrenic patients in a psychiatric hospital were infected compared to just 9% of a control group of blood donors from the same area. [xiv]
In humans, the parasite commonly causes mild flu-like symptoms, after which it supposedly remains dormant in the brain and other tissues. At least that has been the general medical opinion until recently. A February 2007 paper, suggests though that Toxoplasma infection is possibly the culprit behind chronic inflammatory headaches. [xv]
No one is ready to read conclusions into these numbers, but clearly, this gives me more to consider. How much of the way we see the world results from a microscopic parasite bending out thoughts to its own needs? How many of our views and perceptions are some other organism's agenda masquerading as our own thoughts. And, how much of what appears to be irrational human behavior is a result of these distorted thought processes?
[i] Proc Biol Sci. 2000 Aug 7;267(1452):1591-4.
Fatal attraction in rats infected with Toxoplasma gondii.Berdoy M, Webster JP, Macdonald DW.
Oxford University Veterinary Services, UK . firstname.lastname@example.org
We tested the hypothesis that the parasite Toxoplasma gondii manipulates the behaviour of its intermediate rat host in order to increase its chance of being predated by cats, its feline definitive host, thereby ensuring the completion of its life cycle. Here we report that, although rats have evolved anti-predator avoidance of areas with signs of cat presence, T. gondii's manipulation appears to alter the rat's perception of cat predation risk, in some cases turning their innate aversion into an imprudent attraction. The selectivity of such behavioural changes suggests that this ubiquitous parasite subtly alters the brain of its intermediate host to enhance predation rate whilst leaving other behavioural categories and general health intact. This is in contrast to the gross impediments frequently characteristic of many other host parasite systems. We discuss our results in terms of their potential implications both for the epidemiology of toxoplasmosis and the neurological basis of anxiety and cognitive processes in humans and other mammals.
PMID: 11007336 [PubMed - indexed for MEDLINE]
[ii] Proc Natl Acad Sci U S A. 2007 Apr 10;104(15):6442-7. Epub 2007 Apr 2. s
Behavioral changes induced by Toxoplasma infection of rodents are highly specific to aversion of cat odors.Vyas A, Kim SK, Giacomini N, Boothroyd JC, Sapolsky RM.
*Department of Biological Sciences, Stanford Universit , Stanford , CA 94305 .
The protozoan parasite Toxoplasma gondii blocks the innate aversion of rats for cat urine, instead producing an attraction to the pheromone; this may increase the likelihood of a cat predating a rat. This is thought to reflect adaptive, behavioral manipulation by Toxoplasma in that the parasite, although capable of infecting rats, reproduces sexually only in the gut of the cat. The "behavioral manipulation" hypothesis postulates that a parasite will specifically manipulate host behaviors essential for enhancing its own transmission. However, the neural circuits implicated in innate fear, anxiety, and learned fear all overlap considerably, raising the possibility that Toxoplasma may disrupt all of these nonspecifically. We investigated these conflicting predictions. In mice and rats, latent Toxoplasma infection converted the aversion to feline odors into attraction. Such loss of fear is remarkably specific, because infection did not diminish learned fear, anxiety-like behavior, olfaction, or nonaversive learning. These effects are associated with a tendency for parasite cysts to be more abundant in amygdalar structures than those found in other regions of the brain. By closely examining other types of behavioral patterns that were predicted to be altered we show that the behavioral effect of chronic Toxoplasma infection is highly specific. Overall, this study provides a strong argument in support of the behavioral manipulation hypothesis. Proximate mechanisms of such behavioral manipulations remain unknown, although a subtle tropism on part of the parasite remains a potent possibility.
PMID: 17404235 [PubMed - in process]
[iii] Scand J Infect Dis Suppl. 1992;84:65-9.
Epidemiology of toxoplasmosis in the U.K.Joynson DH.
Toxoplasma Reference Laboratory, Singleton Hospital , Swansea , Wales .
The overall rate of toxoplasma infection in the U.K. is between 23-33% though there is evidence of regional variation. Seropositivity increases by 0.5-1.0% per annum to reach about 50% at the age of 60 years. The incidence of acute infection in pregnant women is about 2-2.6% per thousand pregnancies while the transplacental transmission rate is reported to range from 0% to 40%. As there is no official notification of congenital toxoplasma infections within U.K. the true number of cases is not known. However, information relating to the prevalence of infection in the general population in the U.K. is outdated and new studies are urgently required.
PMID: 1290077 [PubMed - indexed for MEDLINE]
[iv] 1: Int J Epidemiol. 1988 Sep;17(3):595-602.
Epidemiology of toxoplasmosis among pregnant women in the Paris area.Jeannel D, Niel G, Costagliola D, Danis M, Traore BM, Gentilini M.
Departement de Parasitologie et Medecine Tropicale, Groupe Hospitalier Pitie Salpetriere, Paris , France .
A survey was performed using a sample of pregnant women selected at one of the biggest test centres in the Paris area. These women were serologically screened for toxoplasmosis between October 1981 and September 1983 (according to the prevention protocol for congenital toxoplasmosis established by the French health ministry). The prevalence rate of specific antibodies for toxoplasmosis was estimated from the 1074 women who were tested for the first time during the study. The prevalence rate among pregnant women in the Paris area was derived by direct standardization according to age and geographical origin. A standardized prevalence rate of 71% +/- 4% among French women, of 51.4% +/- 5% among immigrant women and a global adjusted prevalence rate of 67.3% +/- 3% for pregnant women in the Paris area was found. An incidence rate of 1.6% was estimated for the 2216 non-immune pregnant women included in the sample. There is no significant difference between the probabilities of seroconversion among French and immigrant women (2.3% +/- 1% and 1.6% +/- 0.8% respectively). Comparison of the data with previous study results show a decrease in the prevalence rate of specific antibodies for toxoplasmosis in the Paris area over the last 20 years that cannot be explained by changes in age and geographical origin. No data were available to support an aetiological hypothesis for a decrease in toxoplasma transmission to humans. Since immigration and a decrease in toxoplasma transmission to humans has led to a larger population of women at risk of infection during pregnancy in France , it is therefore important to perform studies to investigate risk factors and markers of acquired toxoplasmosis during pregnancy in order to improve the prevention of congenital toxoplasmosis.
PMID: 3264821 [PubMed - indexed for MEDLINE]
[v] Gloria Maender. Cat Parasite May Affect Cultural Traits in Human Populations. Sound Waves. September 2006
[vi] Proc Biol Sci. 2006 Nov 7;273(1602):2749-55.
Can the common brain parasite, Toxoplasma gondii, influence human culture?
• Lafferty KD.
Western Ecological Research Centre, United States Geological Survey, Marine Science Institute, University of California , Santa Barbara , CA 93106 , USA . email@example.com
The latent prevalence of a long-lived and common brain parasite, Toxoplasma gondii, explains a statistically significant portion of the variance in aggregate neuroticism 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 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.
PMID: 17015323 [PubMed - indexed for MEDLINE]
[vii] Vet Parasitol. 2004 Oct 5;124(3-4):167-77.
A cross-sectional survey of anti-Toxoplasma gondii antibodies in Jerusalem cats.Salant H, Spira DT.
Department of Parasitology, Hebrew University-Hadassah Medical School, P.O. Box 12272, Ein Kerem, Jerusalem 91120, Israel. firstname.lastname@example.org
A cross-sectional seroprevalence study of anti-Toxoplasma gondii IgG antibodies was performed in Jerusalem domestic and stray cats. An enzyme ed immunosorbent assay (ELISA) immunodiagnostic technique was used and results analyzed according to specific variables. The overall seroprevalence was 16.8%. After an initial high seroprevalence of 29.7% in kittens after 1-10 days of age, average positive titers dropped to a low of 7.0% at ages 11-60 days. Thereafter, average positivity increased continuously and was observed in 50% of cats more than 5 years of ag e (P = 0.0081). Toxoplasma seroprevalence was highest in the month of summer (25.1%, P < 0.0001); domestic indoor cats had a higher seropositivity (39.0%) than stray cats (14.2%, P = 0.0004). On average, c ats from the mainly Arab inhabited areas of Jerusalem showed a higher positive seroprevalence to Toxoplasma than Jewish inhabited areas (34.1% and 16.0%, respectively, P = 0.0032). There were no significant differences in positivity rates between sexes, and between rates of those with the presence/absence of clinical symptoms similar to those of the disease.
PMID: 15381297 [PubMed - indexed for MEDLINE]
[viii] Isr J Med Sci. 1993 Oct;29(10):636-9.
Seroprevalence of antibodies against Toxoplasma gondii among two rural populations in northern Israel.Raz R, Nishri Z, Mates A, Sartani G, Hadad N, Reichman N, Miron D, Flatau E.
Infectious Disease Unit, Central Emek Hospital , Afula , Israel .
The prevalence of antibodies against Toxoplasma gondii was measured in two rural populations in northern Israel --Jewish kibbutz members and Arab villagers. The respective prevalences in these two populations were 22.2% and 55.8% (P < 0.001). No correlation was found between the presence of antibodies and sex, occupation, contact with cats, a history of fever and/or lymphadenopathy, eye disease, abortions or delivery of children with congenital malformations. In contrast to Jewish children who were not found to have antibodies in the first decade of life, 20.5% of Arab children tested positive. A gradual increase in the prevalence of antibodies with age was seen in both groups, with the Jews reaching a prevalence of 42.6% at age 60+ and the Arabs reaching 74% at age 40. The difference between the two groups probably stems from different eating habits, namely ingestion of raw meat and unpasteurized milk and milk products.
PMID: 8244662 [PubMed - indexed for MEDLINE]
[ix] Am J Epidemiol. 2001 Aug 15;154(4):357-65.
Toxoplasma gondii infection in the United States: seroprevalence and risk factors.Jones JL, Kruszon-Moran D, Wilson M, McQuillan G, Navin T, McAuley JB.
Division of Parasitic Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta , GA 30341-3724 , USA . email@example.com
Infection with Toxoplasma gondii can cause severe illness when the organism is contracted congenitally or when it is reactivated in immune-suppressed persons. To determine the prevalence of T. gondii infection in a representative sample of the US population, the authors tested sera from participants in the Third National Health and Nutrition Examination Survey (1988-1994) for immunoglobulin G antibodies to T. gondii. Of 27,145 persons aged > or =12 years, 17,658 (65%) had sera tested. The overall age-adjusted seroprevalence was 22.5% (95% confidence interval (CI): 21.1, 23.9); among women aged 15-44 years, seroprevalence was 15.0% (95% CI: 13.2, 17.0). Age-adjusted seroprevalence was higher in the Northeast (29.2%) than in the South (22.8%), Midwest (20.5%), or West (17.5%) (p < 0.05). In multivariate analysis, risk for T. gondii infection increased with age and was higher among persons who were foreign-born, persons with a lower educational level, those who lived in crowded conditions, and those who worked in soil-related occupations, although in subset analyses risk categories varied by race/ethnicity. Nearly one quarter of adults and adolescents in the United States have been infected with T. gondii. Most women of childbearing age in the United States are susceptible to acute infection and should be educated about ways to minimize exposure to T. gondii.
PMID: 11495859 [PubMed - indexed for MEDLINE]
[x] Res Dev Disabil. 2007 May-Jun;28(3):219-24. Epub 2006 May 2.
Seroepidemiological study of toxoplasmosis in intellectual disability children in rehabilitation centers of northern Iran.Sharif M, Ziaei H, Daryani A, Ajami A.
Department of Parasitology and Mycology, School of Medicine , Mazandaran University of Medical Sciences, PC 48168-95475, Sari , Iran . firstname.lastname@example.org
Serological studies revealed that toxoplasmosis has world wide distribution. Although the infection by Toxoplasma gondii is widely prevalent in humans and animals, the disease is uncommon and most of the acquired infections are asymptomatic. The important aspect of this parasitic infection is the probable danger of congenital transmission and its severe effects on the fetus. There have been many reports about the prevalence of anti-T. gondii antibody among different groups of people in Iran ; however the epidemiological data in intellectual disability (ID) persons are rare. This study was performed to evaluate the seroprevalence of toxoplasmosis among the inhabitants of rehabilitation centers of northern Iran . A total of 336 serum samples (161 males, 175 females) were examined for the IgG antibodies by indirect immunofluorescense technique. First of all, 1:50 titer dilution was tested, in the cases of positive result, further dilutions (1:100, 1:200, 1:400, 1:800, 1:1600, and 1:3200) were prepared and the last dilution was recorded. Among 336 sera, 77.4% showed seropositivit y by IFAT. The positive rates of males and females were 77.6% (125/161) and 80% (140/175), respectively. However, there were no significant differences between sexes. Comparing the age groups, the highest seropositive rate showed in 19 or higher, and their rates had a tendency to increase with age. Prevalence of the infection in 10 rehabilitation centers was not significant either. Nevertheless, our data (77.4%) in rehabilitation centers in northern Iran suggest that infection is the same as in many other reports in normal population in this area, therefore toxoplasmosis is not a major problem in rehabilitation centers of this geographical area.
PMID: 16650733 [PubMed - in process]
[xi] Lijec Vjesn. 2002 Jan-Feb;124(1-2):19-22.
[Occurrence of Toxoplasma gondii antibodies in the population of Split-Dalmatia County ][Article in Croatian]
Tonkic M, Punda-Polic V, Sardelic S, Capkun V.
Klinicka bolnica Split , Odjel za klinicku mikrobiologiju i parazitologiju.
The prevalence of antibodies reactive with Toxoplasma gondii in the population of the Split-Dalmatia county (southern Croatia ) was investigated by enzyme ed immunosorbent assay (ELISA). Of a total of 1464 serum samples collected from persons aged 2-84 years 36.4% reacted with Toxoplasma gondii. The frequency of positive sera increased significantly with age (p < 0.001). Prevalence of specific antibodies to T. gondii does not vary significantly according to gender, except, among children younger than 10 years (boys 14.0%; girls 28.2%; p < 0.01). Of a total of 398 pregnant women tested 31.4% were seropositive. According to increase in seroprevalence among the pregnant women of different age the theoretical incidence of congenital toxoplasmosis was calculated.
PMID: 12038093 [PubMed - indexed for MEDLINE]
[xii] Korean J Parasitol. 2000 Dec;38(4):251-6.
Seroepidemiological study of Toxoplasma gondii infection in the rural area Okcheon-gun, Korea.Lee YH, Noh HJ, Hwang OS, Lee SK, Shin DW.
Department of Parasitology, College of Medicine , Chungnam National University , Taejon 301-131, Korea . email@example.com
There have been some reports about the prevalence of anti-Toxoplasma gondii antibody among Koreans, and most of all data were taken from patients visiting hospitals. However, the epidemiological data of the community-based study in Korea are rare. This study was performed to evaluate the seroprevalence of toxoplasmosis among the inhabitants of the rural area Okcheon-gun , Korea . A total of 1,109 serum samples (499 males, 610 females) were examined for the IgG antibodies by ELISA. To set up the cut-off point for ELISA, we used a commercial latex agglutination (LA) kit. The sensitivity and specificity of ELISA against LA test were 89.5%, and 98.6% respectively. Among 1,109 sera, 6.9% showed seropositivity by ELISA. The positive rates of males and females were 6.0% and 7.2%, respectively. However, there were no significant differences between sexes. Comparing the age groups, the highest seropositive rate showed in the seventies or higher, and their rates had a tendency to increase with age (0.05 < p < 0.3). These results revealed that the seroprevalence of toxoplasmosis in rural inhabitants is similar to previous reports in Korea ; however we need further investigation to clarify the prevalence of toxoplasmosis in the general population.
PMID: 11138318 [PubMed - indexed for MEDLINE]
[xiii] Scand J Infect Dis. 2006;38(8):625-31.
Seroprevalence of Toxoplasma gondii in Sweden, Estonia and Iceland.Birgisdottir A, Asbjornsdottir H, Cook E, Gislason D, Jansson C, Olafsson I, Gislason T, Jogi R, Thjodleifsson B.
Faculty of Medicine, University of Iceland .
Toxoplasmosis is a disease caused by the intracellular protozoan parasite, Toxoplasma gondii which infects up to one-third of the world human population. Toxoplasmosis in neonates and immunocompromised patients can lead to severe disease and death. We investigated the prevalence and risk factors for T. gondii infection in Iceland , Sweden and Estonia , and tested the hypothesis that T. gondii infection causes systemic inflammation and protects against atopy. Blood samples were collected from 1277 randomly selected subjects. The presence of T. gondii IgG antibodies was determined by an ELISA method and levels of Hs-CRP by immunoturbidimetric assay. The prevalence of T. gondii antibodies was 54.9% in Tartu , 23% in Uppsala and 9.8% in Reykjavik (p<0.0001). The risk of positive T. gondii antibodies increased with the number of siblings and with age in Sweden . T. gondii infection was associated with asthma related symptoms and increased Hs-CRP (p = 0.02). No association was found with IgE-sensitization and lung function. We concluded that risk factors for T. gondii infection suggested that soil exposure was 1 of the mechanisms in all 3 countries and a meat-associated infection route is a risk in Sweden .
PMID: 16857606 [PubMed - indexed for MEDLINE]
[xiv] BMC Infect Dis. 2006 Dec 19;6:178.
Seroepidemiology of Toxoplasma gondii infection in psychiatric inpatients in a northern Mexican city.Alvarado-Esquivel C, Alanis-Quinones OP, Arreola-Valenzuela MA, Rodriguez-Briones A, Piedra-Nevarez LJ, Duran-Morales E, Estrada-Martinez S, Martinez-Garcia SA, Liesenfeld O.
Faculty of Medicine, Juarez University of Durango State (UJED), Durango , Mexico . firstname.lastname@example.org
BACKGROUND: Patients with psychiatric disorders were found to show a high seroprevalence of Toxoplasma gondii infection. There is scarce information about the epidemiology of T. gondii infection in psychiatric patients in Mexico . Therefore, we sought to determine the prevalence of T. gondii infection and associated socio-demographic, clinical and behavioural characteristics in a population of psychiatric patients in Durango City , Mexico . Seroprevalence in patients was compared with that obtained in a control population. METHODS: One hundred and thirty seven inpatients of a public psychiatric hospital and 180 controls were examined for the presence of IgG and IgM antibodies against T. gondii by enzyme- ed immunoassay (Diagnostic Automation Inc., Calabasas , CA , USA ). The control population consisted of blood donors of a public blood bank and elderly persons attending a senior center in the same city. Age in controls (42 years +/- 20.2) was comparable with that of the psychiatric patients (43.7 years +/-13.8) (p = 0.42). Socio-demographic, clinical and behavioral characteristics from the patients were also obtained. RESULTS: Anti-T. gondii IgG antibodies indicating latent infection with T. gondii was found in 25 (18.2%) of 137 psychiatric inpatients and 16 (8.9%) of 180 controls (p = 0.02). Ten (26.3%) of 38 schizophrenic patients had latent infection and this prevalence was also significantly higher than that observed in controls (p = 0.005). Prevalence of anti-T. gondii IgM antibodies was comparable among patients and controls (4.4% vs 2.2%, respectively, p = 0.22). Multivariate analysis showed that T. gondii infection in inpatients was positively associated with sexual promiscuity (adjusted OR = 15.8; 95% CI: 3.8-64.8), unwashed raw fruit consumption (adjusted OR = 5.19; 95% CI: 2.3-11.3), and a history of surgery (adjusted OR = 6.5; 95% CI: 2.6-16), and negatively associated with lamb meat consumption (adjusted OR = 0.26; 95% CI: 0.10-0.63). CONCLUSION: In the present study, psychiatric inpatients in Durango , Mexico , in general and schizophrenia inpatients in particular had a significantly higher prevalence of T. gondii infection than the control group. Results suggest that unwashed raw fruit consumption might be the most important route of T. gondii transmission in our psychiatric inpatients while lamb meat consumption the less important. Additional studies will have to elucidate the causative relation between infection with T. gondii and psychiatric disorders.
[xv] Am J Ther. 2007 Jan-Feb;14(1):63-105.
Recurrent headache as the main symptom of acquired cerebral toxoplasmosis in nonhuman immunodeficiency virus-infected subjects with no lymphadenopathy: the parasite may be responsible for the neurogenic inflammation postulated as a cause of different types of headaches.