Toxoplasmosis

Toxoplasmosis

Toxoplasmosis is a parasitic disease caused by the protozoan Toxoplasma gondii.[1] The parasite infects most genera of warm-blooded animals, including humans, but the primary host is the felid (cat) family. Animals are infected by eating infected meat, by ingestion of faeces of a cat that has itself recently been infected, or by transmission from mother to fetus. Cats have been shown as a major reservoir of this infection.[2]

Up to one third of the world's human population is estimated to carry a Toxoplasma infection.[3] The Centers for Disease Control and Prevention notes that overall seroprevalence in the United States as determined with specimens collected by the National Health and Nutritional Examination Survey (NHANES) between 1999 and 2004 was found to be 10.8%, with seroprevalence among women of childbearing age (15 to 44 years) of 11%.[4]

During the first few weeks, the infection typically causes a mild flu-like illness or no illness. After the first few weeks of infection have passed, the parasite rarely causes any symptoms in otherwise healthy adults. However, people with a weakened immune system, such as those infected with advanced HIV disease or those who are pregnant, may become seriously ill, and it can occasionally be fatal. The parasite can cause encephalitis (inflammation of the brain) and neurologic diseases and can affect the heart, liver, and eyes (chorioretinitis).

Toxoplasmosis Symptoms

Infection has two stages:

Acute toxoplasmosis: During acute toxoplasmosis, symptoms are often influenza-like: swollen lymph nodes, or muscle aches and pains that last for a month or more. Rarely, a patient with a fully functioning immune system may develop eye damage or nasal lesions from toxoplasmosis. Young children and immunocompromised patients, such as those with HIV/AIDS, those taking certain types of chemotherapy, or those who have recently received an organ transplant, may develop severe toxoplasmosis. This can cause damage to the brain (encephalitis) or the eyes (necrotizing retinochoroiditis). Only a small percentage of infected newborn babies have serious eye and brain damage or nasal malformations at birth.

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.[5] 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.[6]

Latent toxoplasmosis: Most patients who become infected with Toxoplasma gondii and develop toxoplasmosis do not know it. In most immunocompetent patients, the infection enters a latent phase, during which only bradyzoites are present, forming cysts in nervous and muscle tissue. Most infants who are infected while in the womb have no symptoms at birth but may develop symptoms later in life.[7]

Possible link to psychiatric disorders

The toxoplasmosis parasite may also trigger the development of schizophrenia, bipolar disorders, Parkinson’s Disease and attention deficit disorders.[citation needed] The University of Leeds’ Faculty of Biological Sciences has shown a statistical link between toxoplasmosis infections and incidences of schizophrenia. Research finds that a person with schizophrenia is more likely to have toxoplasmosis than the general population.[8] The parasite produces an enzyme called tyrosine hydroxylase which may contribute to the development of these psychological disorders by affecting the production of dopamine. These changes in the chemistry of the brain can significantly affect behaviour. Well documented is dopamine’s role in mood, sociability, attention, and motivation and sleep patterns. Schizophrenia has long been associated with dopamine, which is targeted by all currently available schizophrenia drugs. Research is ongoing to confirm whether or not there is a causal link, which is proving difficult because there are many factors involved. Health risks of toxoplasmosis include occasional fatalities.[9]

Toxoplasmosis Diagnosis

Detection of Toxoplasma gondii in human blood samples may be achieved by using the polymerase chain reaction (PCR).[10] Inactive cysts may exist in a host which would evade detection.

Transmission

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. Oocysts 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.[11]
Ingestion of contaminated cat feces. This can occur through hand-to-mouth contact following gardening, cleaning a cat's litter box, contact with children's sandpits, or touching anything that has come into contact with cat faeces.
Drinking water contaminated with Toxoplasma.
Transplacental infection in utero.
Receiving an infected organ transplant or blood transfusion, although this is extremely rare.[11]

The cyst form of the parasite is extremely hardy, capable of surviving exposure to freezing down to −12 degrees Celsius (10 degrees Fahrenheit), moderate temperatures and chemical disinfectants such as bleach, 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.[12]

Cats excrete the pathogen in their faeces 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[citation needed]. Studies have shown that only about 2% of cats are shedding oocysts at any one time[citation needed], and that oocyst shedding does not recur even after repeated exposure to the parasite[citation needed]. Although the pathogen has been detected on the fur of cats, it has not been found in an infectious form, and direct infection from handling cats is generally believed to be very rare.[citation needed]

Pregnancy precautions

Congenital toxoplasmosis is a special form in which an unborn child is infected via the placenta. A positive antibody titer 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, 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,[13] France,[14] Austria,[14] and Italy[15] being the exceptions) for reasons of cost-effectiveness and the high number of false positives generated as the disease is so rare (an example of Bayesian statistics). As invasive prenatal testing incurs some risk to the fetus (18.5 pregnancy losses per toxoplasmosis case prevented),[14] postnatal or neonatal screening is preferred. The exceptions are cases where fetal abnormalities are noted, and thus screening can be targeted.[14]

Some regional screening programmes operate in Germany, Switzerland and Belgium.[15]

Treatment is very important for recently infected pregnant 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.

Toxoplasmosis Treatment

Treatment is often only recommended for people with serious health problems, because the disease is most serious when one's immune system is weak.

Acute

Medications that are prescribed for acute toxoplasmosis are:

Pyrimethamine: an antimalarial medication.
Sulfadiazine: an antibiotic used in combination with pyrimethamine to treat toxoplasmosis.
clindamycin: an antibiotic used most often for people with HIV/AIDS.
spiramycin: an antibiotic used most often for pregnant women to prevent the infection of their child.

(Other antibiotics such as minocycline have seen some use as a salvage therapy).

Latent

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: an antibiotic that has been used to kill Toxoplasma cysts inside AIDS patients. [16]
clindamycin: an antibiotic which, in combination with atovaquone, seemed to optimally kill cysts in mice.[17]

However, in latent infections successful treatment is not guaranteed, and some subspecies exhibit resistance.

Toxoplasmosis
Campylobacter Infections Pneumonia Carcinoid Tumors Spleen Diseases Bacterial vaginosis Toxoplasmosis Meningococcal Disease Vaginal Diseases Stomach cancer Ingrown Nail Giardiasis Cardiogenic shock Scoliosis Chronic Diarrhea Urinary Tract And Bladder Infections Aortic Stenosis Mitral Valve Prolapse Colorectal cancer Liver cancer Yersinia Enterocolitica Kaposi's Sarcoma Leukemia, Adult Acute Shigellosis Sickle-cell disease Adenoviridae Coming Soon	Toxoplasmosis Toxoplasmosis is a parasitic disease caused by the protozoan Toxoplasma gondii.[1] The parasite infects most genera of warm-blooded animals, including humans, but the primary host is the felid (cat) family. Animals are infected by eating infected meat, by ingestion of faeces of a cat that has itself recently been infected, or by transmission from mother to fetus. Cats have been shown as a major reservoir of this infection.[2] Up to one third of the world's human population is estimated to carry a Toxoplasma infection.[3] The Centers for Disease Control and Prevention notes that overall seroprevalence in the United States as determined with specimens collected by the National Health and Nutritional Examination Survey (NHANES) between 1999 and 2004 was found to be 10.8%, with seroprevalence among women of childbearing age (15 to 44 years) of 11%.[4] During the first few weeks, the infection typically causes a mild flu-like illness or no illness. After the first few weeks of infection have passed, the parasite rarely causes any symptoms in otherwise healthy adults. However, people with a weakened immune system, such as those infected with advanced HIV disease or those who are pregnant, may become seriously ill, and it can occasionally be fatal. The parasite can cause encephalitis (inflammation of the brain) and neurologic diseases and can affect the heart, liver, and eyes (chorioretinitis). Toxoplasmosis Symptoms Infection has two stages: Acute toxoplasmosis: During acute toxoplasmosis, symptoms are often influenza-like: swollen lymph nodes, or muscle aches and pains that last for a month or more. Rarely, a patient with a fully functioning immune system may develop eye damage or nasal lesions from toxoplasmosis. Young children and immunocompromised patients, such as those with HIV/AIDS, those taking certain types of chemotherapy, or those who have recently received an organ transplant, may develop severe toxoplasmosis. This can cause damage to the brain (encephalitis) or the eyes (necrotizing retinochoroiditis). Only a small percentage of infected newborn babies have serious eye and brain damage or nasal malformations at birth. 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.[5] 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.[6] Latent toxoplasmosis: Most patients who become infected with Toxoplasma gondii and develop toxoplasmosis do not know it. In most immunocompetent patients, the infection enters a latent phase, during which only bradyzoites are present, forming cysts in nervous and muscle tissue. Most infants who are infected while in the womb have no symptoms at birth but may develop symptoms later in life.[7] Possible link to psychiatric disorders The toxoplasmosis parasite may also trigger the development of schizophrenia, bipolar disorders, Parkinson’s Disease and attention deficit disorders.[citation needed] The University of Leeds’ Faculty of Biological Sciences has shown a statistical link between toxoplasmosis infections and incidences of schizophrenia. Research finds that a person with schizophrenia is more likely to have toxoplasmosis than the general population.[8] The parasite produces an enzyme called tyrosine hydroxylase which may contribute to the development of these psychological disorders by affecting the production of dopamine. These changes in the chemistry of the brain can significantly affect behaviour. Well documented is dopamine’s role in mood, sociability, attention, and motivation and sleep patterns. Schizophrenia has long been associated with dopamine, which is targeted by all currently available schizophrenia drugs. Research is ongoing to confirm whether or not there is a causal link, which is proving difficult because there are many factors involved. Health risks of toxoplasmosis include occasional fatalities.[9] Toxoplasmosis Diagnosis Detection of Toxoplasma gondii in human blood samples may be achieved by using the polymerase chain reaction (PCR).[10] Inactive cysts may exist in a host which would evade detection. Transmission 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. Oocysts 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.[11] Ingestion of contaminated cat feces. This can occur through hand-to-mouth contact following gardening, cleaning a cat's litter box, contact with children's sandpits, or touching anything that has come into contact with cat faeces. Drinking water contaminated with Toxoplasma. Transplacental infection in utero. Receiving an infected organ transplant or blood transfusion, although this is extremely rare.[11] The cyst form of the parasite is extremely hardy, capable of surviving exposure to freezing down to −12 degrees Celsius (10 degrees Fahrenheit), moderate temperatures and chemical disinfectants such as bleach, 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.[12] Cats excrete the pathogen in their faeces 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[citation needed]. Studies have shown that only about 2% of cats are shedding oocysts at any one time[citation needed], and that oocyst shedding does not recur even after repeated exposure to the parasite[citation needed]. Although the pathogen has been detected on the fur of cats, it has not been found in an infectious form, and direct infection from handling cats is generally believed to be very rare.[citation needed] Pregnancy precautions Congenital toxoplasmosis is a special form in which an unborn child is infected via the placenta. A positive antibody titer 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, 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,[13] France,[14] Austria,[14] and Italy[15] being the exceptions) for reasons of cost-effectiveness and the high number of false positives generated as the disease is so rare (an example of Bayesian statistics). As invasive prenatal testing incurs some risk to the fetus (18.5 pregnancy losses per toxoplasmosis case prevented),[14] postnatal or neonatal screening is preferred. The exceptions are cases where fetal abnormalities are noted, and thus screening can be targeted.[14] Some regional screening programmes operate in Germany, Switzerland and Belgium.[15] Treatment is very important for recently infected pregnant 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. Toxoplasmosis Treatment Treatment is often only recommended for people with serious health problems, because the disease is most serious when one's immune system is weak. Acute Medications that are prescribed for acute toxoplasmosis are: Pyrimethamine: an antimalarial medication. Sulfadiazine: an antibiotic used in combination with pyrimethamine to treat toxoplasmosis. clindamycin: an antibiotic used most often for people with HIV/AIDS. spiramycin: an antibiotic used most often for pregnant women to prevent the infection of their child. (Other antibiotics such as minocycline have seen some use as a salvage therapy). Latent 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: an antibiotic that has been used to kill Toxoplasma cysts inside AIDS patients. [16] clindamycin: an antibiotic which, in combination with atovaquone, seemed to optimally kill cysts in mice.[17] However, in latent infections successful treatment is not guaranteed, and some subspecies exhibit resistance.
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