How Come I Have Never Heard of T. gondii?

Toxoplasma gondii (T. gondii) parasite lives inside you (intracellular). This single-celled protozoan organism causes a disease known as toxoplasmosis and is arguably the most successful protozoan parasite on Earth. Between 15 and 85% of the world adult human population is chronically infected with Toxoplasma gondii depending on geographical location. Why have you never heard of the parasite T. gondii and toxoplasmosis? One major reason is that most people who are infected with the parasite do not have obvious symptoms. And when symptoms of a new infection do occur, they are usually flu-like and are often misdiagnosed. In any event, the symptoms of the acute infection generally clear up within several weeks, without the infected person’s even knowing what caused them.

Recent studies have suggested that Toxoplasma gondii is able to effect behavioral change in humans

This parasite influences human culture when parasitizing the brain. According to Kevin Lafferty, a USGS scientist at the University of California, Santa Barbara, people infected with T. gondii experience a wide range of long term personality changes.

A more detailed look provides my thesis, my concern of the danger of leadership with no accountability. Consider, the personalities of T. gondii infected men showed lower superego strength (rule consciousness) and higher vigilance (factors G and L on Cattell’s 16PF). Thus, the men were more likely to disregard rules and were more expedient, suspicious, jealous, and dogmatic. The personality of infected women, by contrast, showed higher warmth and higher superego strength (factors A and G on Cattell’s 16PF), suggesting that they were more warm-hearted, outgoing, conscientious, persistent, and moralistic. Both men and women had significantly higher apprehension (factor O) compared with the uninfected controls.

Humans with latent infections of the common protozoan parasite Toxoplasma gondii appear to experience a variety of long-term personality changes (Webster 2001). For instance, in infected women, intelligence, superego strength (rule-conscious, dutiful, conscientious, conforming, moralistic, staid and rule-bound) and affectothymia (warm, outgoing, attentive to others, kindly, easy-going, participating and likes people) are higher, while infected men have lower intelligence, superego strength and novelty-seeking (low novelty-seeking indicates rigid, loyal, stoic, slow-tempered and frugal personalities); both infected men and women have higher levels of guilt-proneness (they tend to be more apprehensive, self-doubting, worried, guilt prone, insecure, worrying and self-blaming; Flegr & Hrdy 1994; Flegr et al. 1996, 2000, 2003).

The seroprevalence (percentage of people with antibodies to latent infections) of T. gondii varies geographically nearly from 0 to 100% (Tenter et al. 2000), suggesting that T. gondii could lead to variation in aggregate personality among populations (Lafferty 2005). In other words, the average personality of a population might be shifted if a higher proportion of individuals are infected with T. gondii. The ability to detect statistically an effect of T. gondii on aggregate personalities of populations will depend on how strongly the parasite affects individual personality, the extent of variation in prevalence among populations and the consistency of the personality change between men and women. This begs the question: could aspects of human culture result from a parasite selected to predispose its host to predation by cats (Lafferty 2005)? The report indicates associations between the prevalence of T. gondii infection and aggregate personality that could explain some of the variation in cultural dimensions among human populations.

Scientists estimate that the parasite has infected about 3 billion people, or about half of the human population. Studies by researchers in the Czech Republic have suggested T. gondii might have subtle but long-term effects on its human hosts. The parasite is thought to have different, and often opposite effects in men versus women, but both genders appear to develop a form of neuroticism called “guilt proneness.”

Facts about T. Gondii (Toxoplosmosis)

There is no CURE! No Vaccine!

The T. gondii parasite was discovered in 1908. In 1939 T. gondii was identified in tissues of a congenitally infected infant, and veterinary importance became known when it was found to cause abortion storms in sheep in 1957. In 1948 the recognition that T. gondii is a common parasite of warm-blooded hosts with a worldwide distribution. 1970 was when it was found that felids (cats) are the definitive host and an environmentally resistant stage (oocyst – eggs) is excreted in feces of infected cats. The recent discovery of its common infection in certain marine wildlife (sea otters) indicates contamination of our seas with T. gondii oocysts washed from land. Hygiene remains the best preventive measure because currently there is no vaccine to prevent toxoplasmosis in humans.

The recent origin and widespread distribution of the clonal lineages is attributed to the circumvention of the sexual cycle by a new mode of transmission-asexual transmission between intermediate hosts (Khan et al., 2006).

Diagnosis

The diagnosis of toxoplasmosis is usually made by a blood test. The most common test used in the clinical setting is the polymerase chain reaction (PCR) test. This test can detect T. gondii DNA (genetic material of the parasite).

A test that measures antibodies to T. gondii is used to determine if someone has been infected recently or in the past. The diagnosis can also be made by looking for the parasite in stained tissue samples, cerebrospinal fluid (CSF—fluid that circulates around the brain and spinal column), or other material taken by biopsy. (Edvinsson B, Lundquist J, Ljungman P, Ringdén O, Evengård B. A prospective study of diagnosis of Toxoplasma gondii infection after bone marrow transplantation. APMIS. 2008 May;116(5):345-51).

In pregnant women, a sample of amniotic fluid can be obtained to test for the parasite.

Computed tomography (CT) scan or magnetic resonance imaging can be used to look for an abscess in the brain. Abscesses caused by T. gondii typically have the appearance of a dark spot in the brain tissue with a ring around it.

Recent studies have suggested that Toxoplasma gondii is able to effect behavioral change in humans

It is proposed that this parasite influences human culture when parasitizing the brain. According to Kevin Lafferty, a USGS scientist at the University of California, Santa Barbara, people infected with T. gondii experience a wide range of long term personality changes.

A more detailed look provides my thesis, my concern of the danger of leadership with no accountability. Consider, the personalities of T. gondii infected men showed lower superego strength (rule consciousness) and higher vigilance (factors G and L on Cattell’s 16PF). Thus, the men were more likely to disregard rules and were more expedient, suspicious, jealous, and dogmatic. The personality of infected women, by contrast, showed higher warmth and higher superego strength (factors A and G on Cattell’s 16PF), suggesting that they were more warm-hearted, outgoing, conscientious, persistent, and moralistic. Both men and women had significantly higher apprehension (factor O) compared with the uninfected controls.

Humans with latent infections of the common protozoan parasite Toxoplasma gondii appear to experience a variety of long-term personality changes (Webster 2001). For instance, in infected women, intelligence, superego strength (rule-conscious, dutiful, conscientious, conforming, moralistic, staid and rule-bound) and affectothymia (warm, outgoing, attentive to others, kindly, easy-going, participating and likes people) are higher. Infected men have lower intelligence, superego strength and novelty-seeking (low novelty-seeking indicates rigid, loyal, stoic, slow-tempered and frugal personalities); both infected men and women have higher levels of guilt-proneness (they tend to be more apprehensive, self-doubting, worried, guilt prone, insecure, worrying and self-blaming; Flegr & Hrdy 1994; Flegr et al. 1996, 2000, 2003).

Reactivation of latent infection

People who are infected with T. gondii and who later develop a weakened immune system (from conditions such as HIV/AIDS, cancer, or organ transplantation), can experience severe symptoms from reactivation of latent toxoplasmosis. Symptoms of toxoplasmosis depend on where the latent infection has reactivated in the body. In people with HIV/AIDS, reactivation typically occurs in the brain leading to toxoplasma encephalitis. Symptoms can include severe headache, lethargy, trouble thinking, confusion, seizures, weakness in the arms or legs, coma, and death. Other symptoms may occur depending upon which organs are involved in the infection.

The seroprevalence (percentage of people with antibodies to latent infections) of T. gondii varies geographically nearly from 0 to 100% (Tenter et al. 2000), suggesting that T. gondii could lead to variation in aggregate personality among populations (Lafferty 2005). In other words, the average personality of a population might be shifted if a higher proportion of individuals are infected with T. gondii. The ability to detect statistically an effect of T. gondii on aggregate personalities of populations will depend on how strongly the parasite affects individual personality, the extent of variation in prevalence among populations and the consistency of the personality change between men and women. This begs the question: could aspects of human culture result from a parasite selected to predispose its host to predation by cats (Lafferty 2005)? The report indicates associations between the prevalence of T. gondii infection and aggregate personality that could explain some of the variation in cultural dimensions among human populations.

Scientists estimate that the parasite has infected about 3 billion people, or about half of the human population. Studies by researchers in the Czech Republic have suggested T. gondii might have subtle but long-term effects on its human hosts. The parasite is thought to have different, and often opposite effects in men versus women, but both genders appear to develop a form of neuroticism called “guilt proneness.”

 

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T. Gondii behavioral changes in humans.

Professor Jaroslav Flegr of Charles University in Prague has discovered evidence that infection by intracellular protozoan parasite toxoplasma gondii (T. gondii) causes changes in human personalities.

Further, consider T. gondii can alter individual personality, and modal personality can shape culture, then T. gondii may be one of the factors that shape culture. (Look what the cat dragged in: do parasites contribute to human cultural diversity. (Kevin D. Lafferty, K.D. Lafferty / Behavioral Processes 68 (2005) 279–282)

T. gondii orchestrates a significant increase in dopamine metabolism in neural cells.  The observed effects on dopamine metabolism could also be relevant in interpreting reports of psycho-behavioral changes in toxoplasmosis-infected humans. (Dubey JP (2010) Toxoplasmosis of animals and humans. Boca Raton,, Florida: CRC Press. 313 p.)

Behavioral Changes Such as:

• Women infected with toxoplasma spent more money on clothes and were consistently rated as more attractive. “We found they were more easy-going, more warm-hearted, had more friends and cared more about how they looked,” he said. “However, they were also less trustworthy and had more relationships with men.”
• Infected men appeared to suffer from the “alley cat” effect: becoming less well groomed undesirable loners who were more willing to fight. They were more likely to be suspicious and jealous. “They tended to dislike following rules,” Flegr said.
• The pathogen is a leading cause of neurological birth defects in children born to mothers who contract the disease during pregnancy and can cause fatal toxoplasmosis encephalitis in immunosuppressed patients.
• Toxoplasma-infected men have a higher level of testosterone.
• Slowed reaction times resulting in an increase in traffic accidents.
• Slowed reaction times resulting in an increase in traffic accidents.
• Men who are infected with T. Gondii tend to gain antisocial tendencies.
• They become more aggressive, jealous, and suspicious.
• Also their desirability to women decreases.
• Women who are infected become more intelligent, and more promiscuous. Unsurprisingly this increases their desirability to men.
• Toxoplasmosis also results in a higher risk of developing schizophrenia or a bipolar disorder. Epidemiologic studies indicate that infectious agents may contribute to some cases of schizophrenia.
• In animals, infection with Toxoplasma gondii can alter behavior and neurotransmitter function.
• In humans, acute infection with T. gondii can produce psychotic symptoms similar to those displayed by persons with schizophrenia.
• T. Gondii is a parasitic protozoan.
• T. Gondii causes the disease toxoplasmosis.
• Toxoplasmosis is linked to slowed reaction time, 2.5 times increased chance of auto accidents, anti-social behavior in men, promiscuity in women, schizophrenia and bipolar disorder.
• 30-85% of the human population is infected with T. Gondii depending on geographical location.
• Toxoplasmosis is a potentially fatal disease of the developing human fetus and immunocompromised (e.g., AIDS and transplant) patients and can cause severe ocular disease in otherwise healthy individuals.
• The third most common source of food borne infection in the USA.
• Most infections remain asymptomatic and treatment is not prescribed, however, toxoplasmosis is strongly linked with development of psychosis, depression, and anxiety disorders, reckless behavior and impulsivity in youth.
• Infected rats and mice exhibit hyperactivity, fearlessness toward cat urine odor, and novelty seeking behavior – types of conduct that most likely make them victims of cat predation. It is speculated that the pathogen targets brain of an intermediate host to increase its exposure and vulnerability to its natural predators.
• T. gondii is listed as a category B Biodefense Agent by National Institute of Allergy and Infectious Diseases (NIAID).

How can the risk of transmission of toxoplasma from other sources be reduced?

These measures are essential in all ‘high risk’ groups of people and are also sensible routine hygiene precautions:

• Gloves should be worn when gardening and hands thoroughly washed after contact with soil which may contain sporulated (infectious) oocysts.
• Gloves should be worn when handling food to prevent exposure to oocysts and tissue cysts.
• Hands should always be washed thoroughly afterwards.
• Fruit and vegetables should be thoroughly washed before eating to remove any oocysts present on their surface.
• All food preparation surfaces and utensils should be cleaned with detergent in warm water before and after use to inactivate any tissue cysts.
• Meat should be cooked to a minimum of 58°C for 10 minutes or 61°C for four minutes to kill the tissue cysts (Dubey et al 1990).
• Microwaving is not a safe way to kill tissue cysts as the heating is uneven. T gondii oocysts can remain infectious when stored in a refrigerator (4°C) for up to 54 months (Dubey 1998).
• Freezing meat at –12°C to -20°C for three days kills tissue cysts as does curing or smoking (Dubey 1988, Lunden and Uggla 1992).
• Gamma irradiated food is free from any risk of infection.
• If drinking a non-mains water supply, boil or filter before drinking to remove oocysts.

 Sources of Human T. gondii Infection:

• Unpasteurized dairy products also may contain the parasite T. gondii.
• There have been rare cases of transmission through unpasteurized goat’s milk and through accidental sticks.
• Use of contaminated knives, cutting boards or other utensils subject to T. gondii infection.
• T. gondii infection may come from an infected organ transplant or transfused blood.
• Epidemiological studies found a significant association between toxoplasmosis (T. gondii) and consumption of meat by human, (Bobic et al., 1998; Baril et al., 1999)
• T. gondii oocysts (capsule, with a hardy shell) can survive in soil for up to 18 months.
• A high prevalence of T. gondii infection was found in pet dogs.
• Ingestion of oocysts from the environment eg, through contact with soil containing sporulated oocysts. This can also occur indirectly through eating contaminated fruit or vegetables.
• Ingestion of meat containing tissue cysts. Fresh meat is most risky since freezing meat for several days will kill most tissue cysts.
• Ingestion of sporulated oocysts through contact with contaminated water.
• Coastal freshwater runoff is a risk factor for Toxoplasma gondii infection of southern sea otters (Enhydra lutris nereis) – International Journal for Parasitology 32 (2002) 997–1006
• Chickens are considered one of the most important hosts in the epidemiology of Toxoplasma gondii infection because may become infected with this parasite after eating undercooked infected chicken meat. The prevalence of T. gondii in backyard chickens and chickens from organic farms reached up to 100%.
• Geese infected with T. gondii may be a source of T. gondii infection for humans and cats. – Zoonoses and Public Health Volume 58, Issue 4, pages 299–302, June 2011
• Toxoplasmosis is now also recognized to be a water-borne zoonosis. This method of transmission occurs where water treatment is ineffective or non-existent and there is a sizeable local felid population that contaminates surface water with oocysts. (DUBEY J.P. (2004).
• Linked to this there is now also an appreciation that sea mammals are becoming infected by waters from contaminated land and from untreated urban sewage. (DUBEY J.P. (2004). Toxoplasmosis – a waterborne zoonosis. Vet. Parasitol., 126, 57–72.
• T. gondii have been detected in body fluids, including saliva, sputum, urine, tears, semen and milk of several intermediate hosts, including sheep, goats, cows and camels (Tenter et al. 2000). An early study reported that T. gondii tachyzoites may be isolated from raw chicken eggs laid by hens with experimentally induced infection (Jacobs & Melton 1966).

T. gondii Infection from Rural Drinking Water

Occurrence of Toxoplasma gondii in water from wells located on farms. Toxoplasma gondii and Cyclospora cayetanensis are two coccidian protozoan parasites that are increasingly recognized as having potential for waterborne transmission to humans. The environmental stage for both organisms is an oocyst, shed in the faeces of the infected host and capable of surviving in the environment for months or longer, more than enough time to be transported into a drinking water supply. The infectious dose is believed to be low for both parasites, suggesting that despite massive dilution in water there is still the possibility for people to be exposed and become infected. Similar to another coccidian, Cryptosporidium spp., the oocysts of T. gondii and C. cayetanensis are resistant to disinfection by chlorination. All these life history traits are favourable for waterborne transmission, presenting the drinking water profession with yet another set of emerging pathogens with which to contend. Journal of Applied Microbiology ISSN 1364-5072

Abstract from: US National Library of Medicine National Institutes of Health

Authors: Sroka J, Wójcik-Fatla A, Dutkiewicz J.

Source:

Department of Occupational Biohazards, Institute of Agricultural Medicine, P.O. Box 185, 20-950 Lublin, Poland. jack@galen.imw.lublin.pl

Abstract

Drinking water samples were taken, 80 samples from shallow household wells with a windlass, 16Among various species of parasitic protozoans which may contaminate drinking water, Toxoplasma gondii is of a special importance due to the high incidence of infections with this parasite noted in animals and humans. The objective of this study was to determine the frequency of occurrence of T. gondii in drinking water on farms in the area of the Lublin province (eastern Poland) with respect to health risk among the inhabitants, and to assess the role of water in the transmission of Toxoplasma infections in the rural environment. Studies were conducted on 87 farms located in the Lublin province, 14 of which were classified as possessing a good hygienic state, and 73 as possessing a poor hygienic state. A total number of 114 from deep wells with a pump, and 18 from the water supply system. In microscopic and PCR examinations of 114 water samples, T. gondii was found in 15 (13.2%) and 31 (27.2%) of samples, respectively. The presence of T. gondii DNA detected by PCR test was found significantly more frequently in water samples from the shallow windlass-operated wells than in those from deep wells (p < 0.05) and water supply system (p < 0.01). Water samples collected from shallow wells located on farms of poor hygienic state contained significantly more frequently DNA of T. gondii than samples from shallow wells located on farms of good hygienic state (43.1% vs. 13.3%, p < 0.05). In 26.3% of water samples, oocysts of other protozoans were found belonging to Isospora, Eimeria, and Cryptosporidium. Serologic examinations for the presence of anti-Toxoplasma antibodies conducted among 99 inhabitants of the farms where household wells were used showed 64.6% of seropositive results in IgG class antibodies and 1.0% in IgM class antibodies. Clinical cases of toxoplasmosis were also noted. In the total population examined, a positive correlation was observed between the consumption of unboiled well water and the presence of antibodies against T. gondii (p < 0.05), this correlation being especially strong on farms of poor hygienic state enclosing shallow wells (p < 0.001). In conclusion, the recorded presence of T. gondii in well water provides an evidence of the potential risk of waterborne infection for humans and animals. Therefore, it seems necessary to implement prophylactic actions on the endangered farms.

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Detection of Toxoplasma gondii Oocysts in Municipal Drinking Water

Source:

Judith Isaac-Renton, William R. Bowie, Arlene King, G. Stewart Irwin, Corinne S. Ong, C. P. Fung, M. Omar Shokeir, and J. P. Dubey*

Department of Pathology and Laboratory Medicine and Division of Infectious Diseases, Department of Medicine, University of British Columbia, and Epidemiology Services and Provincial Laboratory, British Columbia Centre for Disease Control, British Columbia Ministry of Health, Vancouver, and Water Department, Capital Regional District, Victoria, British Columbia, Canada, and Parasite Biology and Epidemiology Laboratory, Livestock and Poultry Sciences Institute, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, Maryland

*Corresponding author. Mailing address: Division of Microbiology and Infection Control, Department of Pathology and Laboratory Medicine, Laurel Street Pavilion, Vancouver General Hospital, 855 West 12th, Vancouver, British Columbia, Canada V5Z 1M9. Phone: (604) 875-4631. Fax: (604) 875-4359. E-mail: isaacren@unixg.ubc.ca .

ABSTRACT

The world’s largest outbreak of waterborne toxoplasmosis occurred in a municipality in the western Canadian province of British Columbia. When drinking water emerged as a possible source of infection during the outbreak investigation, a laboratory method was needed to attempt detection of the parasite, Toxoplasma gondii. The method developed was based on the current U.S. Environmental Protection Agency method for detection of Cryptosporidium oocysts. Collection of large-volume drinking water samples and cartridge filter processing were unchanged, although identification of Toxoplasma oocysts in the filter retentate was carried out by using a previously described rodent model. Validation of the method developed was tested by using oocysts from a well-characterized Toxoplasma strain.

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T. gondii Infection is in the Ocean!

The geographic prevalence of T. gondii varies from 0 to 100 percent. It is controlled by a number of factors: climate (which affects the persistence of infectious stages in the soil), cultural practices of food preparation, and how commonly cats are kept as pets. “There is a tendency towards higher prevalence of infections in tropical areas,” Lafferty notes, “because they’re more humid and don’t freeze. Low-risk areas are places that have lots of freezing, high altitude, a dry climate, really good hygiene, or very few cats. (Kevin Lafferty, Ecological Parasitology Laboratory, Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara)                         

Human toxoplasmosis acquired through the consumption of infective Toxoplasma gondii oocysts in contaminated drinking water is an increasing public health risk worldwide. Currently, there are no specific recommendations or approved methods to inactivate T. gondii in public water supplies, and limited research indicates that oocysts may be difficult to destroy in water by conventional disinfection methods . Although T. gondii oocysts can be inactivated by exposure to boiling, freezing, and gamma irradiation the effect of UV radiation on these oocysts has not been evaluated. Central California cities are dumping sewer water into the drinking water of 23 million people in Los Angeles area. See: http://dallas93444.hubpages.com/hub/Why-Is-California-State-Water-Project-Dumping-Parasite-Infection-Into-Water

Sewage Treatment Plants: These plants traditionally treat sewage to kill harmful bacteria, remove the waste solids, and pump the resultant “safe” effluent directly into a freshwater source that eventually drains into ocean bays. Unfortunately present means of sewage treatment do not kill the T. Gondii parasite. Cat owners using flushable litters, may be unwittingly contributing to the ultimate deaths of sea otters.

Storm Drain Runoff: Rain, lawn and garden surface water, and anything you manually put into that storm drain in the street near your house eventually runs off into a creek or river which flows directly into an ocean bay.

Scientists and researchers have recently discovered a correlation between Toxoplasma gondii and the decrease in the sea otter population off the California Coast. Since cats are the only creatures that shed the T. gondii parasite, through their feces, there seems to be a direct link.

The recent recognition of numerous fatal Toxoplasma gondii brain infections in southern sea otters from California has prompted concerns about the emergence of Toxoplasma gondii as a significant marine pathogen.

“Toxoplasma infection has appeared in a variety of sea mammals including beluga whales, dolphins, sea lions and seals. It has also become a major cause of death in Californian sea otters living. It is estimated that approximately 17 percent of sea otter deaths can be attributed to toxoplasma. While many believe fresh water runoff contaminated with cat feces is to blame, there is no definitive evidence on the source of infection.” says Gloeta Massie, a graduate student who conducted the research with Associate Professor Michael Black.

“The question that drives our research is how are marine mammals from the Arctic Circle to Australia infected by a parasite that is spread primarily through the consumption of infectious cat feces and infected meat? Based on the global prevalence of T. gondii infections, we hypothesize that migratory filter feeders, specifically northern anchovies, are serving to spread T. gondii throughout the ocean,” says Gloeta Massie, a graduate student who conducted the research with Associate Professor Michael Black.

Results show natural exposure of European harbor and grey seals to T. gondii oocysts in the Atlantic Ocean. To the best of our knowledge, this is the first serological survey of T. gondii in European grey and harbor seals. US National Library of Medicine National Institutes of Health – Vet Parasitol. 2011 Jun 30;179(1-3):253-6. Epub 2011 Feb 2.

Toxoplasma gondii infection in marine mammals is intriguing and indicative of contamination of the ocean environment and coastal waters with oocysts. In previous serological surveys, 90% of bottlenose dolphins (Tursiops truncatus) from the coasts of Florida, South Carolina, and California had antibodies to T. gondii. – J. P. Dubey, P. A. Fair, N. Sundar, G. Velmurugan, O. C. H. Kwok, W. E. McFee, D. Majumdar, and C. Su, Animal Parasitic Diseases Laboratory, Animal and Natural Resources Institute, Beltsville Agricultural Research Center, United States, Department of Agriculture, Beltsville, Maryland 20705. e-mail: jitender.dubey@ars.usda.gov

T. gondii was identified in a Hawaiian monk seal (Monachus schauinslandi) – American Society of Parasitologists

Recent research by Drs. Marina Collins and David Lindsay, Virginia Tech, Blackburg Campus, has expanded the understanding of the interaction between Toxoplasma gondii and oysters in the marine environment. T. gondii is prevalent in the marine environment, and it has previously been determined that Eastern oysters (Crassostrea virginica) can remove sporulated T. gondii oocysts from seawater and that the oocysts retain their infectivity for some time.

US National Library of Medicine National Institutes of Health

Surface properties of Toxoplasma gondii oocysts and surrogate microspheres.

Shapiro K, Largier J, Mazet JA, Bernt W, Ell JR, Melli AC, Conrad PA.

Source:

Department of Pathology, Microbiology and Immunology, One Shields Avenue, School of Veterinary Medicine, University of California, Davis, CA 95616, USA. kshapiro@ucdavis.edu

Abstract

The physical properties that govern the waterborne transmission of Toxoplasma gondii oocysts from land to sea were evaluated and compared to the properties of carboxylated microspheres, which could serve as surrogates for T. gondii oocysts in transport and water treatment studies. The electrophoretic mobilities of T. gondii oocysts, lightly carboxylated Dragon Green microspheres, and heavily carboxylated Glacial Blue microspheres were determined in ultrapure water, artificial freshwater with and without dissolved organic carbon, artificial estuarine water, and artificial seawater. The surface wettabilities of oocysts and microspheres were determined using a water contact angle approach. Toxoplasma gondii oocysts and microspheres were negatively charged in freshwater solutions, but their charges were neutralized in estuarine water and seawater. Oocysts, Glacial Blue microspheres, and unwashed Dragon Green microspheres had low contact angles, indicating that they were hydrophilic; however, once washed, Dragon Green microspheres became markedly hydrophobic. The hydrophilic nature and negative charge of T. gondii oocysts in freshwater could facilitate widespread contamination of waterways. The loss of charge observed in saline waters may lead to flocculation and subsequent accumulation of T. gondii oocysts in locations where freshwater and marine water mix, indicating a high risk of exposure for humans and wildlife in estuarine habitats with this zoonotic pathogen. While microspheres did not have surface properties identical to those of T. gondii, similar properties shared between each microsphere type and oocysts suggest that their joint application in transport and fate studies could provide a range of transport potentials in which oocysts are likely to behave.

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More Suicide Attempts with T. gondii Infection

US National Library of Medicine National Institutes of Health

J Nerv Ment Dis. 2009 Dec;197(12):905-8.

Toxoplasma gondii and history of suicide attempts in patients with recurrent mood disorders.

Arling TA, Yolken RH, Lapidus M, Langenberg P, Dickerson FB, Zimmerman SA, Balis T, Cabassa JA, Scrandis DA, Tonelli LH, Postolache TT.

Source

Mood and Anxiety Program, Department of Psychiatry, University of Maryland School of Medicine, Baltimore, MD 21201, USA.

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.

PMID: 20010026 [PubMed - indexed for MEDLINE]

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Toxoplasma gondii parasites can invade your bloodstream, break into your brain and prompt behavioral changes from recklessness to neuroticism. These highly contagious protozoa infect more than half the world’s population, and most people’s immune systems never purge the intruders.

Cornell researchers recently discovered how T. gondii evades our defenses by hacking immune cells, making it the first known parasite to control its host’s immune system. Immunologists from the College of Veterinary Medicine published the study Sept. 8 in PLoS Pathogens, describing a forced partnership between parasite and host that challenges common conceptions of how pathogens interact with the body.

“Toxoplasma is an especially promiscuous parasite,” said Eric Denkers, professor of immunology. “It infects nearly all warm-blooded species, most nucleated cell types and much of the human population. Although it lives in vital brain and muscle tissues, it usually causes no obvious reaction. Infection can seriously harm people with weak immune systems, yet most hosts experience no overt symptoms because Toxoplasma has found a way to coerce cooperation.”

Famous for its manipulative powers, T. gondii has been shown to alter the brain chemistry of rodents so that they fearlessly pursue cats. Cats eat the rodents, delivering the parasites to their breeding ground in feline intestines. Similar manipulations have surfaced in human studies linking T. gondii infections to behavioral and personality shifts, schizophrenia and population variations, including cultural differences and skewed sex ratios. Denkers’ study maps T. gondii‘s newfound ability to manipulate cells in the immune system at the molecular level.

“We found that Toxoplasma quiets its host’s alarm system by blocking immune cells from producing certain cytokines, proteins that stimulate inflammation,” said Denkers. “Cytokines are double-edged swords: They summon the immune system’s reinforcements, but if too many accumulate they can damage the body they’re trying to defend. An unregulated immune response can kill you.”

When immune cells meet intruders, they release cytokines that summon more immune cells, which produce more cytokines, rapidly causing inflammation. T. gondii must allow cytokines to trigger enough of an immune response to keep its own numbers in check and ensure host survival. But too many cytokines cause an overwhelming immune response that could damage the host or eliminate the parasites.

“Toxoplasma hijacks immune cells to enforce a mutually beneficial balance,” Denkers said. “Until recently we thought it walled itself away inside cells without interacting with its environment. It’s now clear that the parasite actively releases messages into cells that change cell behavior.”

To prove this, Barbara Butcher, a senior research associate working with Denkers, exposed immune cells in the lab to bacterial factors that typically stimulate the release of inflammatory cytokines.

“Cells infected with Toxoplasma produced no messages to trigger inflammation,” Denkers said. “Our colleagues at Stanford University found that Toxoplasma produces a specific protein called ROP16 to suppress inflammatory responses. Collaborating with parasitologists at Dartmouth Medical School, we found that Toxoplasma sends ROP16 to infiltrate communication channels in immune cells, causing them to lower cytokine production.

“We are excited to have found the first non-bacterial pathogen able to exert this kind of control,” said Denkers. “If Toxoplasma can do this, maybe other parasites can too. This is the first case where the whole process of immune system manipulation is close to being completely mapped out at the molecular level.”

That map may help steer future investigations into how pathogens interact with hosts, unveiling the inner workings of a spectrum of infectious diseases.

Source: Cornell University

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