Toxoplasmosis is a parasitic disease
Parasitic disease
A parasitic disease is an infectious disease caused or transmitted by a parasite. Many parasites do not cause diseases. Parasitic diseases can affect practically all living organisms, including plants and mammals...

 caused by the protozoan Toxoplasma gondii
Toxoplasma gondii
Toxoplasma gondii is a species of parasitic protozoa in the genus Toxoplasma. The definitive host of T. gondii is the cat, but the parasite can be carried by many warm-blooded animals . Toxoplasmosis, the disease of which T...

. The parasite infects most genera
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of warm-blooded
The term warm-blooded is a colloquial term to describe animal species which have a relatively higher blood temperature, and maintain thermal homeostasis primarily through internal metabolic processes...

 animals, including humans, but the primary host is the felid (cat) family
Felidae is the biological family of the cats; a member of this family is called a felid. Felids are the strictest carnivores of the thirteen terrestrial families in the order Carnivora, although the three families of marine mammals comprising the superfamily pinnipedia are as carnivorous as the...

. Animals are infected by eating infected meat, by ingestion of feces
Coprophagia or coprophagy is the consumption of feces, from the Greek κόπρος copros and φαγεῖν phagein . Many animal species practice coprophagia as a matter of course; other species do not normally consume feces but may do so under unusual conditions...

 of a cat
The cat , also known as the domestic cat or housecat to distinguish it from other felids and felines, is a small, usually furry, domesticated, carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests...

 that has itself recently been infected, or by transmission from mother to fetus. Cats are the primary source of infection to human hosts, although contact with raw meat, especially pork, is a more significant source of human infections in some countries. Fecal contamination of hands is a significant risk factor.

Up to one third of the world's human population is estimated to carry a Toxoplasma infection. The Centers for Disease Control and Prevention
Centers for Disease Control and Prevention
The Centers for Disease Control and Prevention are a United States federal agency under the Department of Health and Human Services headquartered in Druid Hills, unincorporated DeKalb County, Georgia, in Greater Atlanta...

 notes that overall seroprevalence
Seroprevalence is the number of persons in a population who test positive for a specific disease based on serology specimens; often presented as a percent of the total specimens tested or as a proportion per 100,000 persons tested...

 in the United States as determined with specimens collected by the National Health and Nutritional Examination Survey (NHANES
National Health and Nutrition Examination Survey
The National Health and Nutrition Examination Survey is a survey research program conducted by the National Center for Health Statistics to asses the health and nutritional status of adults and children in the United States, and to track changes over time. The survey combines interviews and...

) between 1999 and 2004 was found to be 10.8%, with seroprevalence among women of childbearing age (15 to 44 years) 11%.

During the first few weeks post-exposure, the infection typically causes a mild flu-like illness or no illness. Thereafter, the parasite rarely causes any symptoms in otherwise healthy adults. However, those with a weakened immune system
Immunodeficiency is a state in which the immune system's ability to fight infectious disease is compromised or entirely absent. Immunodeficiency may also decrease cancer immunosurveillance. Most cases of immunodeficiency are acquired but some people are born with defects in their immune system,...

, such as AIDS patients or pregnant women, may become seriously ill, and it can occasionally be fatal. The parasite can cause encephalitis
Encephalitis is an acute inflammation of the brain. Encephalitis with meningitis is known as meningoencephalitis. Symptoms include headache, fever, confusion, drowsiness, and fatigue...

 (inflammation of the brain) and neurologic diseases, and can affect the heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...

, liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...

, inner ear
Inner ear
The inner ear is the innermost part of the vertebrate ear. In mammals, it consists of the bony labyrinth, a hollow cavity in the temporal bone of the skull with a system of passages comprising two main functional parts:...

s, and eye
Human eye
The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...

s (chorioretinitis
Chorioretinitis is an inflammation of the choroid and retina of the eye. It is also known as choroid retinitis.-Causes:...

). Recent research has also linked toxoplasmosis with brain cancer.

Acute toxoplasmosis

During acute toxoplasmosis, symptoms are often influenza
Influenza, commonly referred to as the flu, is an infectious disease caused by RNA viruses of the family Orthomyxoviridae , that affects birds and mammals...

-like: swollen lymph node
Lymph node
A lymph node is a small ball or an oval-shaped organ of the immune system, distributed widely throughout the body including the armpit and stomach/gut and linked by lymphatic vessels. Lymph nodes are garrisons of B, T, and other immune cells. Lymph nodes are found all through the body, and act as...

s, or muscle aches
Myalgia means "muscle pain" and is a symptom of many diseases and disorders. The most common causes are the overuse or over-stretching of a muscle or group of muscles. Myalgia without a traumatic history is often due to viral infections...

 and pains that last for a month or more. Rarely, a patient with a fully functioning immune system
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...

 may develop eye damage from toxoplasmosis. Young children and immunocompromised
Immunodeficiency is a state in which the immune system's ability to fight infectious disease is compromised or entirely absent. Immunodeficiency may also decrease cancer immunosurveillance. Most cases of immunodeficiency are acquired but some people are born with defects in their immune system,...

 patients, such as those with HIV/AIDS, those taking certain types of chemotherapy
Chemotherapy is the treatment of cancer with an antineoplastic drug or with a combination of such drugs into a standardized treatment regimen....

, or those who have recently received an organ transplant
Organ transplant
Organ transplantation is the moving of an organ from one body to another or from a donor site on the patient's own body, for the purpose of replacing the recipient's damaged or absent organ. The emerging field of regenerative medicine is allowing scientists and engineers to create organs to be...

, may develop severe toxoplasmosis. This can cause damage to the brain (encephalitis) or the eyes (necrotizing retinochoroiditis). Infants infected via placental transmission may be born with either of these problems, or with nasal malformations, although these complications are rare in newborns.

Swollen lymph nodes are more commonly found in the neck followed by axillae and then groin. Swelling may occur at different times after the initial infection, persist, and/or recur for various times independently of antiparasitic treatment. It is usually found at single sites in adults, but in children multiple sites may be more common. Enlarged lymph nodes will resolve within one to two months in 60% of patients. However, a quarter of patients take 2–4 months to return to normal and 8% take 4–6 months. A substantial number of patients (6%) do not return to normal until much later.

Latent toxoplasmosis

It is easy for a host to become infected with Toxoplasma gondii
Toxoplasma gondii
Toxoplasma gondii is a species of parasitic protozoa in the genus Toxoplasma. The definitive host of T. gondii is the cat, but the parasite can be carried by many warm-blooded animals . Toxoplasmosis, the disease of which T...

 and develop toxoplasmosis without knowing it. In most immunocompetent patients, the infection enters a latent phase, during which only bradyzoites are present, forming cyst
A cyst is a closed sac, having a distinct membrane and division on the nearby tissue. It may contain air, fluids, or semi-solid material. A collection of pus is called an abscess, not a cyst. Once formed, a cyst could go away on its own or may have to be removed through surgery.- Locations :* Acne...

s in nervous
Nervous tissue
Nervous tissue is one of four major classes of vertebrate tissue.Nervous tissue is the main component of the nervous system - the brain, spinal cord, and nerves-which regulates and controls body functions...

 and muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...

 tissue. Most infants who are infected while in the womb have no symptoms at birth but may develop symptoms later in life.

Cutaneous toxoplasmosis

While rare, skin lesions may occur in the acquired form of the disease, including roseola and erythema multiforme-like eruptions, prurigo
Prurigo is a general term used to describe itchy eruptions of the skin.Specific types include:* Prurigo nodularis* Actinic prurigo* Besnier's prurigo ....

-like nodules, urticaria
Urticaria is a kind of skin rash notable for pale red, raised, itchy bumps. Hives is frequently caused by allergic reactions; however, there are many non-allergic causes...

, and maculopapular lesions. Newborns may have punctate macules, ecchymoses, or “blueberry muffin” lesions.
Diagnosis of cutaneous toxoplasmosis is based on the tachyzoite form of T. gondii being found in the epidermis. It is found in all levels of the epidermis, is about 6 μm by 2 μm , bow-shaped, the nucleus being one-third of its size. It can be identified by electron microscopy or by Giemsa
Giemsa stain
Giemsa stain, named after Gustav Giemsa, an early German microbiologist, is used in cytogenetics and for the histopathological diagnosis of malaria and other parasites.-Uses:...

 staining tissue where the cytoplasm shows blue, the nucleus red.

Possible link to psychiatric disorders

Studies have been conducted that show the toxoplasmosis parasite may affect behavior and may present as or be a causative or contributory factor in various psychiatric disorders such as depression, anxiety and schizophrenia
Schizophrenia is a mental disorder characterized by a disintegration of thought processes and of emotional responsiveness. It most commonly manifests itself as auditory hallucinations, paranoid or bizarre delusions, or disorganized speech and thinking, and it is accompanied by significant social...

. In 11 of 19 scientific studies, T. gondii antibody levels were found to be significantly higher in individuals affected by first-incidence schizophrenia than in unaffected persons. Individuals with schizophrenia are also more likely to report a clinical history of toxoplasmosis than those in the general population. Recent work at the University of Leeds
University of Leeds
The University of Leeds is a British Redbrick university located in the city of Leeds, West Yorkshire, England...

 has found that the parasite produces an enzyme with tyrosine hydroxylase
Tyrosine hydroxylase
Tyrosine hydroxylase or tyrosine 3-monooxygenase is the enzyme responsible for catalyzing the conversion of the amino acid L-tyrosine to dihydroxyphenylalanine . It does so using tetrahydrobiopterin as a coenzyme. DOPA is a precursor for dopamine, which, in turn, is a precursor for norepinephrine ...

 and phenylalanine hydroxylase
Phenylalanine hydroxylase
Phenylalanine hydroxylase is an enzyme that catalyzes the hydroxylation of the aromatic side-chain of phenylalanine to generate tyrosine. PheOH is one of three members of the pterin-dependent amino acid hydroxylases, a class of monooxygenase that uses tetrahydrobiopterin and a non-heme iron for...

 activity. This enzyme may contribute to the behavioral changes observed in toxoplasmosis by altering the production of dopamine
Dopamine is a catecholamine neurotransmitter present in a wide variety of animals, including both vertebrates and invertebrates. In the brain, this substituted phenethylamine functions as a neurotransmitter, activating the five known types of dopamine receptors—D1, D2, D3, D4, and D5—and their...

, a neurotransmitter
Neurotransmitters are endogenous chemicals that transmit signals from a neuron to a target cell across a synapse. Neurotransmitters are packaged into synaptic vesicles clustered beneath the membrane on the presynaptic side of a synapse, and are released into the synaptic cleft, where they bind to...

 involved in mood, sociability, attention, motivation and sleep patterns. Schizophrenia has long been linked to dopamine dysregulation.


Toxoplasmosis can be difficult to distinguish from that of primary central nervous system lymphoma, and as a result, the diagnosis is made by a trial of therapy (pyrimethamine, sulfadiazine + leucovorin), or a brain biopsy
A biopsy is a medical test involving sampling of cells or tissues for examination. It is the medical removal of tissue from a living subject to determine the presence or extent of a disease. The tissue is generally examined under a microscope by a pathologist, and can also be analyzed chemically...

 if the drugs produce no effect.

Detection of Toxoplasma gondii in human blood samples may also be achieved by using the polymerase chain reaction
Polymerase chain reaction
The polymerase chain reaction is a scientific technique in molecular biology to amplify a single or a few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence....

 (PCR). Inactive cysts may exist in a host which would evade detection.

Toxoplasmosis cannot be detected with immunostaining
Immunohistochemistry or IHC refers to the process of detecting antigens in cells of a tissue section by exploiting the principle of antibodies binding specifically to antigens in biological tissues. IHC takes its name from the roots "immuno," in reference to antibodies used in the procedure, and...

. Lymph nodes affected by toxoplasma have characteristic changes, including poorly demarcated reactive germinal centers, clusters of monocytoid B cells and scattered epithelioid histiocyte
A histiocyte is a cell that is part of the mononuclear phagocyte system . The mononuclear phagocytic system is part of the organism's immune system...



Transmission may occur through:
  • Ingestion of raw or partly cooked meat, especially pork, lamb, or venison containing Toxoplasma cysts. Infection prevalence in countries where undercooked meat is traditionally eaten has been related to this transmission method. Tissue cysts may also be ingested during hand-to-mouth contact after handling undercooked meat, or from using knives, utensils, or cutting boards contaminated by raw meat.
  • Ingestion of contaminated cat feces
    Feces, faeces, or fæces is a waste product from an animal's digestive tract expelled through the anus or cloaca during defecation.-Etymology:...

    . This can occur through hand-to-mouth contact following gardening, cleaning a cat's litter box
    Litter box
    A litter box, sometimes called a sandbox, sand box, litter tray, litter pan, dirt box, catbox, or cat box, is an indoor feces and urine disposal box for cats that are permitted free roam of a home but who cannot or do not always go outside...

    , contact with children's sandpits, or touching a leach, and can survive in the environment for over a year. It is, however, susceptible to high temperatures—above 66 degrees Celsius (150 degrees Fahrenheit), and is thus killed by thorough cooking, and would be killed by 24 hours in a typical domestic freezer.

Cats excrete the pathogen in their feces for a number of weeks after contracting the disease, generally by eating an infected rodent. Even then, cat faeces are not generally contagious for the first day or two after excretion, after which the cyst 'ripens' and becomes potentially pathogenic.

Pregnancy precautions

Congenital toxoplasmosis is a special form in which an unborn child is infected via the placenta
The placenta is an organ that connects the developing fetus to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. "True" placentas are a defining characteristic of eutherian or "placental" mammals, but are also found in some snakes and...

. A positive antibody titer
A titer is a way of expressing concentration. Titer testing employs serial dilution to obtain approximate quantitative information from an analytical procedure that inherently only evaluates as positive or negative. The titer corresponds to the highest dilution factor that still yields a positive...

 indicates previous exposure and immunity and largely ensures the unborn baby's safety. A simple blood draw at the first pre-natal doctor visit can determine whether or not the woman has had previous exposure and therefore whether or not she is at risk. If a woman receives her first exposure to toxoplasmosis while pregnant, the baby is at particular risk. A woman with no previous exposure should avoid handling raw meat
Raw meat
Raw meat generally refers to any type of uncooked muscle tissue of an animal used for food. In the meat production industry, the term ‘meat’ refers specifically to mammalian flesh, while the words ‘poultry’ and ‘seafood’ are used to differentiate between the tissue of birds and aquatic creatures...

, exposure to cat feces, and gardening (cat feces are common in garden soil). Most cats are not actively shedding oocysts and so are not a danger, but the risk may be reduced further by having the litterbox emptied daily (oocysts require longer than a single day to become infective), and by having someone else empty the litterbox. However, while risks can be minimized, they cannot be eliminated. For pregnant women with negative antibody titer, indicating no previous exposure to T. gondii, as frequent as monthly serology testing is advisable as treatment during pregnancy for those women exposed to T. gondii for the first time decreases dramatically the risk of passing the parasite to the fetus.

Despite these risks, pregnant women are not routinely screened for toxoplasmosis in most countries (Portugal
Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...

, France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

, Austria
Austria , officially the Republic of Austria , is a landlocked country of roughly 8.4 million people in Central Europe. It is bordered by the Czech Republic and Germany to the north, Slovakia and Hungary to the east, Slovenia and Italy to the south, and Switzerland and Liechtenstein to the...

, Uruguay
Uruguay ,officially the Oriental Republic of Uruguay,sometimes the Eastern Republic of Uruguay; ) is a country in the southeastern part of South America. It is home to some 3.5 million people, of whom 1.8 million live in the capital Montevideo and its metropolitan area...

, and Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

 being the exceptions) for reasons of cost-effectiveness and the high number of false positives generated. As invasive prenatal testing incurs some risk to the fetus
A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...

 (18.5 pregnancy losses per toxoplasmosis case prevented), postnatal
Postnatal is the period beginning immediately after the birth of a child and extending for about six weeks. Another term would be postpartum period, as it refers to the mother...

 or neonatal screening is preferred. The exceptions are cases where fetal abnormalities are noted, and thus screening can be targeted.

Some regional screening programmes operate in Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

, Switzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....

 and Belgium
Belgium , officially the Kingdom of Belgium, is a federal state in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters, and those of several other major international organisations such as NATO.Belgium is also a member of, or affiliated to, many...


Treatment is very important for recently infected pregnant
Pregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets...

 women, to prevent infection of the fetus. Since a baby's immune system does not develop fully for the first year of life, and the resilient cysts that form throughout the body are very difficult to eradicate with anti-protozoans, an infection can be very serious in the young.


Treatment is often only recommended for people with serious health problems or with HIV with CD4 count under 200, because the disease is most serious when one's immune system is weak. Trimethoprim/sulfamethoxazole is the drug of choice to prevent Toxoplasma, but is not the drug to treat.


Medications that are prescribed for acute toxoplasmosis are:
  • Pyrimethamine
    Pyrimethamine is a medication used for protozoal infections. It is commonly used as an antimalarial drug , and is also used in the treatment of Toxoplasma gondii infections in immunocompromised patients, such as HIV-positive individuals.-Mechanism of action:Pyrimethamine interferes with...

     — an antimalarial medication.
  • Sulfadiazine
    Sulfadiazine is a sulfonamide antibiotic.-Uses:It eliminates bacteria that cause infections by stopping the production of folic acid inside the bacterial cell, and is commonly used to treat urinary tract infections ....

     — an antibiotic
    An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...

     used in combination with pyrimethamine to treat toxoplasmosis.
    • Combination therapy is usually given with folinic acid supplements to reduce incidence of thrombocytopaenia.
  • clindamycin
    Clindamycin rINN is a lincosamide antibiotic. It is usually used to treat infections with anaerobic bacteria but can also be used to treat some protozoal diseases, such as malaria...

     — an antibiotic used most often for people with HIV/AIDS.
  • spiramycin
    Spiramycin is a macrolide antibiotic. It is used to treat toxoplasmosis. Although used in Europe, Canada and Mexico, spiramycin is still considered an experimental drug in the United States, but can sometimes be obtained by special permission from the FDA for toxoplasmosis in the first trimester of...

     — an antibiotic used most often for pregnant women to prevent the infection of their child.

(Other antibiotics such as minocycline
Minocycline is a broad-spectrum tetracycline antibiotic, and has a broader spectrum than the other members of the group. It is a bacteriostatic antibiotic, classified as a long-acting type...

 have seen some use as a salvage therapy
Salvage therapy
Salvage therapy is a form of treatment given after an ailment does not respond to standard treatment. The most common diseases that require salvage therapy are HIV and various tumors...



In people with latent toxoplasmosis, the cysts are immune to these treatments, as the antibiotics do not reach the bradyzoites in sufficient concentration.

Medications that are prescribed for latent toxoplasmosis are:
  • atovaquone
    Atovaquone is a chemical compound that belongs to the class of naphthalenes. Atovaquone is a hydroxy-1,4-naphthoquinone, an analog of ubiquinone, with antipneumocystic activity. Its average wholesale price is about US$2.13 per standard 250 mg. tablet...

     — an antibiotic that has been used to kill Toxoplasma cysts inside AIDS
    Acquired immune deficiency syndrome or acquired immunodeficiency syndrome is a disease of the human immune system caused by the human immunodeficiency virus...

  • clindamycin
    Clindamycin rINN is a lincosamide antibiotic. It is usually used to treat infections with anaerobic bacteria but can also be used to treat some protozoal diseases, such as malaria...

     — an antibiotic which, in combination with atovaquone, seemed to optimally kill cysts in mice.

Biological modifications of the host

The parasite itself can cause various effects on the host body, some of which are not fully understood.

Reproductive changes

A recent study has indicated toxoplasmosis correlates strongly with an increase in male births in humans. According to the researchers, "depending on the antibody concentration, the probability of the birth of a boy can increase up to a value of 0.72 ... which means that for every 260 boys born, 100 girls are born." The study also notes a mean rate of 0.608 (as opposed to the normal 0.51) for Toxoplasma-positive mothers. The study explains that this effect may not significantly influence the actual sex ratio of children born in countries with high rates of latent toxoplasmosis infection because "In high-prevalence countries, most women of reproductive age have already been infected for a long time and therefore have only low titres of anti-Toxoplasma antibodies. Our results suggest that low-titre women have similar sex ratios to Toxoplasma-negative women."

Behavioral changes

It has been found that the parasite has the ability to change the behaviour of its host: infected rat
Rats are various medium-sized, long-tailed rodents of the superfamily Muroidea. "True rats" are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, Rattus norvegicus...

s and mice are less fearful of cats—in fact, some of the infected rats seek out cat-urine-marked areas. This effect is advantageous to the parasite, which is able to proliferate if a cat eats the infected rat and thereby becomes a carrier.
The mechanism for this change is not completely understood, but there is evidence that toxoplasmosis infection raises dopamine
Dopamine is a catecholamine neurotransmitter present in a wide variety of animals, including both vertebrates and invertebrates. In the brain, this substituted phenethylamine functions as a neurotransmitter, activating the five known types of dopamine receptors—D1, D2, D3, D4, and D5—and their...

 levels and concentrates in the amygdala
The ' are almond-shaped groups of nuclei located deep within the medial temporal lobes of the brain in complex vertebrates, including humans. Shown in research to perform a primary role in the processing and memory of emotional reactions, the amygdalae are considered part of the limbic system.-...

 in infected mice.

The findings of behavioural alteration in rats and mice have led some scientists to speculate that Toxoplasma may have similar effects in humans, even in the latent phase that had previously been considered asymptomatic
In medicine, a disease is considered asymptomatic if a patient is a carrier for a disease or infection but experiences no symptoms. A condition might be asymptomatic if it fails to show the noticeable symptoms with which it is usually associated. Asymptomatic infections are also called subclinical...

. Toxoplasma is one of a number of parasites that may alter their host's behaviour as a part of their life cycle.
The behaviors observed, if caused by the parasite, are likely due to infection and low-grade encephalitis
Encephalitis is an acute inflammation of the brain. Encephalitis with meningitis is known as meningoencephalitis. Symptoms include headache, fever, confusion, drowsiness, and fatigue...

, which is marked by the presence of cysts in the human brain
Human brain
The human brain has the same general structure as the brains of other mammals, but is over three times larger than the brain of a typical mammal with an equivalent body size. Estimates for the number of neurons in the human brain range from 80 to 120 billion...

, which may produce or induce production of a neurotransmitter, possibly dopamine,
therefore acting similarly to dopamine reuptake inhibitor
Dopamine reuptake inhibitor
A dopamine reuptake inhibitor is a type of drug that acts as a reuptake inhibitor for the neurotransmitter dopamine by blocking the action of the dopamine transporter...

 type antidepressants and stimulants.

Correlations have been found between latent Toxoplasma infections and various characteristics:
  • Decreased novelty seeking
    Novelty seeking
    In psychology, novelty seeking is a personality trait.It is measured in the Tridimensional Personality Questionnaire as well as the later version Temperament and Character Inventory.NS has been suggested to be related to low dopaminergic activity....

  • Slower reactions
  • Lower rule-consciousness and greater jealousy (in men)
  • Greater warmth, conscientiousness and moralistic behavior (in women)

The evidence for behavioral effects on humans is controversial. No prospective research has been done on the topic, e.g., testing people before and after infection to ensure that the proposed behavior arises only afterwards. Although some researchers have found potentially important associations with Toxoplasma, the causal relationship, if any, is unknown, i.e., it is possible that these associations merely reflect factors that predispose certain types of people to infection. However, many of the neurobehavioral symptoms that are postulated to be due to toxoplasmosis correlate to the general function of dopamine in the human brain, and the fact that toxoplasma encodes the dopamine synthetic enzyme tyrosine hydroxylase enzymes makes it likely that neurobehavioral symptoms can result from infection.

Studies have found that toxoplasmosis is associated with an increased car accident rate in people with Rh-negative
Rhesus blood group system
The Rh blood group system is one of thirty current human blood group systems. Clinically, it is the most important blood group system after ABO. At Present, the Rh blood group system consists of 50 defined blood-group antigens, among which the 5 antigens D, C, c, E, and e are the most important...

 blood. The chance of an accident relative to uninfected people is increased roughly 2.5 times.

This may be due to the slowed reaction times that are associated with infection. "If our data are true then about a million people a year die just because they are infected with Toxoplasma," the researcher Jaroslav Flegr
Jaroslav Flegr
Jaroslav Flegr is a professor of biology at Charles University in Prague. He is a parasitologist, evolutionary biologist, the author of the book Frozen Evolution and member of the editorial board of Neuroendocrinology Letters....

 told The Guardian.
The data shows that the risk decreases with time after infection, but is not due to age. Ruth Gilbert, medical coordinator of the European Multicentre Study on Congenital Toxoplasmosis, told BBC News Online these findings could be due to chance, or due to social and cultural factors associated with Toxoplasma infection. However there is also evidence of a delayed effect which increases reaction times.

Other studies suggest that the parasite may influence personality. There are claims of Toxoplasma causing antisocial attitudes in men and promiscuity
(or even "signs of higher intelligence"
) in women, and greater susceptibility to schizophrenia
Schizophrenia is a mental disorder characterized by a disintegration of thought processes and of emotional responsiveness. It most commonly manifests itself as auditory hallucinations, paranoid or bizarre delusions, or disorganized speech and thinking, and it is accompanied by significant social...

 and bipolar disorder
Bipolar disorder
Bipolar disorder or bipolar affective disorder, historically known as manic–depressive disorder, is a psychiatric diagnosis that describes a category of mood disorders defined by the presence of one or more episodes of abnormally elevated energy levels, cognition, and mood with or without one or...

 in all infected persons. A 2004 study found that Toxoplasma "probably induce[s] a decrease of novelty seeking."
According to Sydney University of Technology infectious disease researcher Nicky Boulter in an article that appeared in the January/February 2007 edition of Australasian Science magazine, Toxoplasma infections lead to changes depending on the sex of the infected person.

The study suggests that male carriers have shorter attention span
Attention span
Attention span is the amount of time that a person can concentrate on a task without becoming distracted. Most educators and psychologists agree that the ability to focus one's attention on a task is crucial for the achievement of one's goals....

s, a greater likelihood of breaking rules and taking risks, and are more independent, anti-social, suspicious, jealous and morose. It also suggests that these men are deemed less attractive to women. Female carriers are suggested to be more outgoing, friendly, more promiscuous, and are considered more attractive to men compared with non-infected controls. The results are shown to be true when tested on mice, though it is still inconclusive. A few scientists have suggested that, if these effects are genuine, prevalence of toxoplasmosis could be a major determinant of cultural differences.

Toxoplasmas role in schizophrenia

The possibility that toxoplasmosis is one cause of schizophrenia has been studied by scientists since 1953.
These studies attracted little attention from U.S. researchers until they were publicized through the work of prominent psychiatrist and advocate E. Fuller Torrey
E. Fuller Torrey
Edwin Fuller Torrey, M.D. , is an American psychiatrist and schizophrenia researcher. He is Executive Director of the Stanley Medical Research Institute and founder of the Treatment Advocacy Center , a nonprofit organization with the goals of eliminating legal and clinical obstacles to the...

. In 2003, Torrey published a review of this literature, reporting that almost all the studies had found that schizophrenics have elevated rates of Toxoplasma infection. A 2006 paper has even suggested that prevalence of toxoplasmosis has large-scale effects on national culture.
These types of studies are suggestive but cannot confirm a causal relationship (because of the possibility, for example, that schizophrenia increases the likelihood of Toxoplasma infection rather than the other way around).
  • Acute Toxoplasma infection sometimes leads to psychotic symptoms not unlike schizophrenia.
  • Several studies have found significantly higher levels of Toxoplasma antibodies in schizophrenia patients compared to the general population.
  • Toxoplasma infection causes damage to astrocyte
    Astrocytes , also known collectively as astroglia, are characteristic star-shaped glial cells in the brain and spinal cord...

    s in the brain, and such damage is also seen in schizophrenia .

In humans

National Health and Nutrition Examination Survey
The National Health and Nutrition Examination Survey is a survey research program conducted by the National Center for Health Statistics to asses the health and nutritional status of adults and children in the United States, and to track changes over time. The survey combines interviews and...

 (1999–2004) national probability sample found that 10.8% of U.S. persons 6–49 years of age, and 11.0% of women 15–44 years of age, had Toxoplasma-specific IgG antibodies, indicating that they were infected with the organism. This prevalence has significantly decreased from the NHANES
National Health and Nutrition Examination Survey
The National Health and Nutrition Examination Survey is a survey research program conducted by the National Center for Health Statistics to asses the health and nutritional status of adults and children in the United States, and to track changes over time. The survey combines interviews and...

 III (1988–1994).

It is estimated that between 30% and 65% of all people worldwide are infected with toxoplasmosis. However, there is large variation between countries: in France, for example, around 88% of the population are carriers, probably due to a high consumption of raw and lightly cooked meat.

Germany, the Netherlands and Brazil also have high prevalences of around 68%, over 80% and 67% respectively. In Britain about 22% are carriers, and South Korea's rate is 4.3%.

Two risk factors for contracting toxoplasmosis are:
  • Infants born to mothers who became infected with Toxoplasma for the first time during or just before pregnancy.
  • Persons with severely weakened immune systems, such as those with AIDS. Illness may result from an acute Toxoplasma infection or reactivation of an infection that occurred earlier in life.

In other animals

A University of California, Davis
University of California, Davis
The University of California, Davis is a public teaching and research university established in 1905 and located in Davis, California, USA. Spanning over , the campus is the largest within the University of California system and third largest by enrollment...

 study of dead sea otter
Sea Otter
The sea otter is a marine mammal native to the coasts of the northern and eastern North Pacific Ocean. Adult sea otters typically weigh between 14 and 45 kg , making them the heaviest members of the weasel family, but among the smallest marine mammals...

s collected from 1998 to 2004 found that toxoplasmosis was the cause of death for 13% of the animals. Proximity to freshwater outflows into the ocean was a major risk factor. Ingestion of oocysts from cat faeces is considered to be the most likely ultimate source. Runoff
Run-off or runoff may refer to:* Surface runoff, the flow of water, from rain, snow melt, or other sources, over land* Runoff model , a mathematical model describing the rainfall-runoff relations of a rainfall catchment area or watershed...

 containing wild cat faeces and litter from domestic cats flushed down toilets are possible sources of oocysts. According to an article in New Scientist
New Scientist
New Scientist is a weekly non-peer-reviewed English-language international science magazine, which since 1996 has also run a website, covering recent developments in science and technology for a general audience. Founded in 1956, it is published by Reed Business Information Ltd, a subsidiary of...

 the parasites have been found in dolphins and whales. Researchers Black and Massie believe that anchovies, which travel from estuaries into the open ocean, may be helping to spread the disease.


The protozoan was first discovered by Nicolle & Manceaux, who in 1908 isolated it from the African rodent Ctenodactylus gundi
Gundis are a group of small, stocky rodents found in Africa. They live in rocky deserts across the northern parts of the continent. The family comprises 4 living genera and 5 species , as well as numerous extinct genera and species...

, then in 1909 differentiated the disease from Leishmania
Leishmania is a genus of Trypanosomatid protozoa, and is the parasite responsible for the disease leishmaniasis. It is spread through sandflies of the genus Phlebotomus in the Old World, and of the genus Lutzomyia in the New World. Their primary hosts are vertebrates; Leishmania commonly infects...

 and named it Toxoplasma gondii. The first recorded congenital case was not until 1923, and the first adult case not until 1940. In 1948, a serological dye test was created by Sabin & Feldman, which is now the standard basis for diagnostic tests.

Notable people

  • Arthur Ashe
    Arthur Ashe
    Arthur Robert Ashe, Jr. was a professional tennis player, born and raised in Richmond, Virginia. During his career, he won three Grand Slam titles, putting him among the best ever from the United States...

     (tennis player) developed neurological problems from toxoplasmosis (and was later found to be HIV-positive).
  • Merritt Butrick
    Merritt Butrick
    Merritt R. Butrick was an American actor, known for his roles on the 1982 teen sitcom Square Pegs, in two Star Trek feature films, and a variety of other acting roles in the 1980s.-Early life and career:...

     (actor) was H.I.V positive. Died from toxoplasmosis as a result of his already weakened immune system.
  • Prince François, Count of Clermont (pretender to the Throne of France); his disability has caused him to be overlooked in the line of succession.
  • Leslie Ash
    Leslie Ash
    Leslie Ash is an English actress, best known for her role in the sitcom Men Behaving Badly. Her book My Life Behaving Badly: The Autobiography was published in 2007....

     (actress) contracted toxoplasmosis in the second month of pregnancy.
  • Sebastian Coe (British middle distance runner)
  • Martina Navrátilová (tennis player) retired from a competition in 1982 with symptoms of a mystery 'virus' that were later found to be due to toxoplasmosis.
  • Louis Wain
    Louis Wain
    Louis Wain was an English artist best known for his drawings, which consistently featured anthropomorphised large-eyed cats and kittens. In his later years he suffered from schizophrenia, which, according to some psychologists, can be seen in his works.- Life and work :Louis William Wain was...

     (artist) was famous for painting cats; he later developed schizophrenia, which some believe was due to toxoplasmosis resulting from his prolonged exposure to cats.

Literature and film

  • The effects of Toxoplasmosis on human behavior is central to the plot of Kitty Kitty, a film directed by Michael Medaglia in 2011.
  • Toxoplasmosis is referred to at the end of the British TV series Doc Martin
    Doc Martin
    Doc Martin is a British television comedy drama series starring Martin Clunes in the title role. It was created by Mark Crowdy, Craig Ferguson and Dominic Minghella. The show is filmed on location in the fishing village of Port Isaac, Cornwall, United Kingdom, with filming of most interior scenes...

    , Series 4, Episode 6: "MidWife Crisis", first broadcast on 25 October 2009. This was in relation to eating roadkill, including "Badger Burgers".
  • Toxoplasmosis is referred to in the seventeenth episode of the first season of House M.D.
    House (season 1)
    The first season of House premiered November 16, 2004 and ended May 25, 2005. The season followed Dr. House and his team as they solve a medical case each episode, the season's sub-plot revolved around billionaire Edward Vogler making a $100 million donation to the hospital...

     entitled "Role Model
    Role Model (House)
    "Role Model" is the seventeenth episode of the first season of House, which premiered on the Fox network on April 12, 2005. The episode follows a presidential candidate, Senator Gary H. Wright , following a stroke, while continuing the feud that has developed between Vogler and House...

  • Toxoplasmosis is often referenced in Peeps
    Peeps (novel)
    Peeps is a 2005 novel by Scott Westerfeld revolving around a parasite which causes people to become cannibalistic and repelled by that which they once loved. It follows the protagonist, Cal Thompson, as he lives with this parasite and tries to uncover a possible threat to the whole population of...

    , a 2005 novel by Scott Westerfeld.
  • In the 1996 film Trainspotting
    Trainspotting (film)
    Trainspotting is a 1996 British satirical/drama film directed by Danny Boyle based on the novel of the same name by Irvine Welsh. The movie follows a group of heroin addicts in a late 1980s economically depressed area of Edinburgh and their passage through life...

    , the character Tommy, a heroin addict
    Substance use disorder
    Substance use disorders include substance abuse and substance dependence. In DSM-IV, the conditions are formally diagnosed as one or the other, but it has been proposed that DSM-5 combine the two into a single condition called "Substance-use disorder"....

     with AIDS, acquires toxoplasmosis and dies.
  • Toxoplasmosis is referenced in And The Band Played On
    And the Band Played On (film)
    And the Band Played On is a 1993 American television film docudrama directed by Roger Spottiswoode. The teleplay by Arnold Schulman is based on the best-selling 1987 non-fiction book And the Band Played On: Politics, People, and the AIDS Epidemic by Randy Shilts.The film premiered at the Montreal...

    , a 1993 American television film docudrama
    In film, television programming and staged theatre, docudrama is a documentary-style genre that features dramatized re-enactments of actual historical events. As a neologism, the term is often confused with docufiction....

     directed by Roger Spottiswoode
    Roger Spottiswoode
    Roger Spottiswoode is a Canadian-born film director and writer, who began his career as an editor in the 1970s. He was born in Ottawa, Ontario. He has directed a number of notable films and television productions, including Under Fire and the 1997 James Bond film Tomorrow Never Dies starring...

    . The teleplay
    A screenplay or script is a written work that is made especially for a film or television program. Screenplays can be original works or adaptations from existing pieces of writing. In them, the movement, actions, expression, and dialogues of the characters are also narrated...

     by Arnold Schulman
    Arnold Schulman
    Arnold Schulman is an American playwright, screenwriter, producer, a songwriter and novelist. He was a stage actor long associated with the American Theatre Wing and the Actors Studio....

     is based on the best-selling 1987 non-fiction book And the Band Played On: Politics, People, and the AIDS Epidemic by Randy Shilts
    Randy Shilts
    Randy Shilts was a pioneering gay American journalist and author. He worked as a freelance reporter for both The Advocate and the San Francisco Chronicle, as well as for San Francisco Bay Area television stations....

  • Toxoplasmosis was the subject of a controversial story line in the early years of the American television soap opera "All My Children
    All My Children
    All My Children is an American television soap opera that aired on ABC from January 5, 1970 to September 23, 2011. Created by Agnes Nixon, All My Children is set in Pine Valley, Pennsylvania, a fictitious suburb of Philadelphia. The show features Susan Lucci as Erica Kane, one of daytime's most...

    " (1973–1974) in which a then-teenage Erica Kane (Susan Lucci
    Susan Lucci
    Susan Victoria Lucci is an American actress and entrepreneur, best known for portraying Erica Kane on the daytime drama All My Children. The character is considered an icon, and Lucci has been called "Daytime's Leading Lady" by TV Guide, with New York Times and Los Angeles Times citing her as the...

    ) developed a nearly fatal case of Toxoplasmosis after an abortion. It was later explained to have been caused by the changing of a cat litter box.
  • Toxoplasmosis was referenced in an episode of "Law and Order: SVU" in which an AIDS-denier who is infected with the HIV virus dies of complications stemming from toxoplasmosis.

See also

External links

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