From Wikipedia, the free encyclopedia
ICD9 = | ICDO = | OMIM = | MedlinePlus = 000637 | eMedicineSubj = med | eMedicineTopic = 2294 |Toxoplasmosis is a parasitic disease caused by the protozoan Toxoplasma gondii. The parasite infects most warm-blooded animals, including humans, but the primary host is the felid (cat) family. Animals are infected by eating infected meat, by contact with cat feces, or by transmission from mother to fetus. Cats have been shown as a major reservoir of this infection. While this is true, contact with infected undercooked meat seems to be a more important cause of human infection in many countries.Up to one third of the world's population is estimated to carry a Toxoplasma infection. The Centers for Disease Control and Prevention notes that overall seroprevalence in the United States as determined with specimens collected by the third National Health and Nutritional Assessment Survey (NHANES III) between 1988 and 1994 was found to be 22.5%, with seroprevalence among women of childbearing age (15 to 44 years) of 15%. 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 HIV, and fetuses, 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).
History The protozoan was first discovered by Nicolle & Manceaux, who in 1908 isolated it from the African rodent Ctenodactylus gundi, then in 1909 differentiated the disease from Leishmania and named it Toxoplasmosis gondii [http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6W7G-4J55654-3-3&_cdi=6626&_user=427455&_orig=search&_coverDate=03%2F31%2F2006&_sk=999779996&view=c&wchp=dGLbVzb-zSkzS&md5=10087511e28d0e025255efed0d310bdf&ie=/sdarticle.pdf]. 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.http://www.pamf.org/serology/clinicianguide.html#toxosero
Transmission Transmission may occur through:
Pregnancy precautionsCongenital toxoplasmosis is a special form in which an unborn child is infected via the placenta. This is the reason that pregnant women should be checked for Toxoplasma antibodies. A positive titer indicates previous exposure and immunity and largely ensures the unborn baby's safety. If a woman receives her first exposure to Toxoplasma 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.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 antiprotozoans, an infection can be very serious in the young.Transplacental transmission:(a) infection in 1st trimester - incidence of transplacental infection is low (15%) but disease in neonate is most severe. (b) infection in 3rd trimester - incidence of transplacental infection is high (65%) but infant is usually asymptomatic at birth.
Clinical manifestations Infection has two stages:
Acute toxoplasmosisDuring 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 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 or the eyes. Only a small percentage of infected newborn babies have serious eye or brain damage at birth.
Latent toxoplasmosisMost 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.[http://www.futurepundit.com/archives/001675.html]
TreatmentTreatment is often only recommended for people with serious health problems, because the disease is most serious when one's immune system is weak. Medications that are prescribed for acute Toxoplasmosis are:
Biological modifications of the host The parasite itself can cause various effects on the host body, some of which are not fully understood.
Reproductive changesA recent study Jaroslav Flegr. Women infected with parasite Toxoplasma have more sons, Naturwissenschaften, August 2006. full text has indicated Toxoplasmosis correlates strongly with an increase in boy 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 0.60 to 0.65 (as opposed to the normal 0.51) for Toxoplasma positive mothers.
Behavioral changesIt has been found that the parasite has the ability to change the behavior of its host: infected rats 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 will be able to sexually reproduce if its host is eaten by a cat.Berdoy M, Webster J, Macdonald D (2000). Fatal Attraction in Rats Infected with Toxoplasma gondii. Proceedings of the Royal Society of London, B267:1591-1594. CiteULike The mechanism for this change is not completely understood, but there is evidence that toxoplasmosis infection raises dopamine levels in infected mice.The findings of behavioral 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. Toxoplasma is one of a number of parasites that may alter their host's behaviour as a part of their life cycle. therefore acting similarly to dopamine reuptake inhibitor type antidepressants and stimulants.
"In populations where this parasite is very common, mass personality modification could result in cultural change. in the prevalence of Toxoplasma gondii may explain a substantial proportion of human population differences we see in cultural aspects that relate to ego, money, material possessions, work and rules." — Kevin Lafferty Kevin Lafferty [http://newswire.ascribe.org/cgi-bin/behold.pl?ascribeid=20060803.110303&time=11%2035%20PDT&year=2006&public=0]Correlations have been found between latent Toxoplasma infections and various characteristics: Carl Zimmer, The Loom. A Nation of Neurotics? Blame the Puppet Masters?, 1 Aug. 2006
Toxoplasma's role in schizophreniaThe possibility that toxoplasmosis is one cause of schizophrenia has been studied by scientists since at least 1953. free full text These studies had attracted little attention from U.S. researchers until they were publicized through the work of prominent psychiatrist and advocate E. Fuller Torrey. 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).
Human prevalence The U.S. NHANES (2004-2005) national probability sample found that 33.1% of U.S. persons above 12 years of age had Toxoplasma-specific IgG antibodies, indicating that they had been infected with the organism. This prevalence has significantly increased from the 1999-2000 data.It is estimated that between 30% and 65% of all people worldwide are infected with Toxoplasmosis. However, there is large variation countries: in France, for example, around 88% of the population are carriers, probably due to a high consumption of raw and lightly cooked meat.
David Adam, Guardian Unlimited. Can a parasite carried by cats change your personality?, 25 Sep. 2003
Germany, the Netherlands and Brazil also have high prevalences of around 80%, over 80%
Toxoplasmosis in the Netherlands by the Laboratory for Diagnoses for Infectious Diseases and Screening; RIVM Bilthoven
[http://www.nvkc.nl/tijdschrift/content/1999/nr%201/p65/1999-1-p65.pdf] and 67% respectively. In Britain, about 22% are carriers, and South Korea's rate is only 4.3%.Two risk factors for contracting toxoplasmosis are:
Animal prevalence A University of California, Davis study of dead sea otters 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 were a major risk factor. Ingestion of oocysts from cat feces is considered to be the most likely ultimate source.
Notable people with toxoplasmosis
This article is based on an article from Wikipedia, the free encyclopedia and is available under the terms of GNU Free Documentation License.
In the Wikipedia there is a list with all authors of this article available.