What is Toxoplasmosis
Toxoplasmosis is a disease caused by a protozoan parasite called Toxoplasma gondii, named after the African rodent on which it was found. This parasite infects a very large variety of species and very many cellular types of the host.
Hosts can be probably all warm-blooded animals, including humans and domestic animals. Of great importance is the cat, felid family member, the primary hosts of the parasite.
For healthy adults in terms of immunity, infection with this parasite does not have great importance, most cases of infection with Toxoplasmosis Gondii are asymptomatic. Occasionally, various mild symptoms can be observed, lymphadenopathy (swollen lymph nodes) is the most significant clinical manifestation. Other manifestations are headache, nausea, tiredness, fever, muscle aches, irritated throat. Severe forms in immunologic competent adults are extremely rare.
Knowing the conditions in which Toxoplasmosis occurs and the treatment, however, are extremely important for two categories of people:
– Immunosuppressed adults – those with Hodgkin’s lymphoma, cancer, systemic lupus erythematosus, immunosuppressive treatment, AIDS;
– Pregnant women who are infected for the first time during pregnancy. At them the parasite can be transmitted to the child, with worst consequences.
Transmission to humans
Toxoplasma gondii is transmitted to humans by three principal routes:
1. First, man may become infected by eating raw or insufficiently cooked meat, especially pork, lamb, hunted animals, or inadequately cooked food that came in contact with raw meat;
2. Secondly, a person can ingest cysts that cats have eliminated trough their feces, oocysts originating from manure boxes or soil (by gardening or unwashed fruits and vegetables or unfiltered water);
3. Thirdly, women can transmit Toxoplasmosis transplacental to the fetus.
The infection in pregnant women
It is estimated that the chances of women of childbearing age to come in contact with the parasite (and have Toxoplasmosis) are between 25 and 99% (Paris25%, Brussels 47%, West of Scotland 75%, U.S. 85%, Oslo 99%). Overall average risk for a woman to make an acute infection with Toxoplasma gondii during pregnancy is between 20 and 50%. These differences are occurring due to various socio-cultural and geographical conditions (eating habits, animals in the region, temperature, etc.).
Congenital Toxoplasmosis – the disease transmitted by the mother to baby
In immunocompetent hosts, infection with Toxoplasma gondii is followed in most cases by immunity to Toxoplasmosis, for life. Because of this, if the primary infection occurs in 4-6 months before conception, or earlier, the mother immunity will prevent the usual transmission to the fetus in the case of the mother’s subsequent exposures. The exception is the immunocompromised women who have lupus erythematosus, or AIDS, on which congenital transmission it was found, although exposure to the parasite had occurred before conception.
But if Toxoplasma gondii infection was contracted during pregnancy, the parasite can be transmitted to the fetus even by immunocompetent women. The probable mechanism involves the transmission of the parasite in the blood and then passing it to the fetus through the placenta. Congenital Toxoplasmosis can cause abortion, neonatal death or fetal malformations, with consequences for the fetus. It can also significantly reduce quality of life for children who survived prenatal infection.
The risk of fetal intrauterine infection, Congenital Toxoplasmosis manifestation risk and severity of Toxoplasmosis depends on:
– the moment when the infection occurred during pregnancy,
– Immunological competence of the mother during acute infection,
– The number and virulence of parasites transmitted to the fetus,
– Fetal age at the time of transmission.
If the Toxoplasmosis is not treated, the risk of intrauterine transmission to the fetus increases as pregnancy progresses in age, which is about 14% in the first quarter and 59% in the third trimester of pregnancy.
I. While the risk of intrauterine fetal infection increases with the age of pregnancy, the effects on fetus are even more severe as infection occurs earlier. Approximately 10% of prenatal infections are followed by abortion or fetal death at birth. Other 10-23% of infants infected prenatally, show clinical signs of Toxoplasmosis at birth. Approximately 12-16% of these infants die because the disease. Children who survive suffer from progressive mental retardation or other neurological deficits and require most often inclusion in a special education system or institutionalization.
II. If transmission of the parasite occurs in a more advanced stage of pregnancy, the effects on fetus are less severe, most children infected during the third quarter are asymptomatic at birth. In total, the infection in approximately 67-80% of children who have acquired prenatal disease is subclinical at birth and can only be diagnosed using serological or other laboratory investigations. Although these children appear healthy at birth, they may develop clinical symptoms and deficiencies throughout life. This mainly affects the eyes (retinochoroiditis, strabismus, blindness), central nervous system (neurological and mental impairments, seizures, mental retardation) or ear (deafness). It is estimated that approximately one third of infected children will develop a prenatal deficiency of vision later in life.
Possible signs of Congenital Toxoplasmosis infection, occurred during childhood or later in life: anemia, chorioretinita, convulsions, deafness, fever, slow growth, increase in volume of liver and spleen, hydrocephalus, jaundice, learning difficulties, lymphadenopathy, mental retardation , microcephaly, impaired vision.
How to prevent infection with Toxoplasma gondii
Some tips to avoid threatening the child’s development:
1. To prevent Toxoplasmosis and other diseases caused by food, food should be prepared at a higher temperature: 63-71°C (145-160°F). Heating food should be uniform, watch out at low-power microwaves!
2. Fruits and vegetables should be washed thoroughly before being used.
3. Tables or boards used for cutting meat, cooking surfaces, utensils and hands shall be washed with hot soapy water after coming in contact with raw meat red or white or unwashed vegetables or fruits. Do not use knives which you have used to cut meat before wash them, to cut other foods.
4. Tasting raw meat or insufficient cooked is completely forbidden.
5. Pregnant women should wear gloves when working in the garden or when coming in contact with soil or sand because of the possibility of infection with cat feces. After activities that involve contact, hands should be washed carefully.
6. If possible, pregnant women should avoid to clean cat litter. If there is no one available to replace that, pregnant women will wear gloves and wash afterwards carefully. Cat litter required to be cleaned daily. Cats shall be kept indoors in order not to be infected outdoors and will be fed only dry food, canned or cooked. Pregnant women should not adopt stray cats.
Opinions on the value of analysis that can detect possible Toxoplasmosis infection in pregnant women are divided. In Austria and France, prenatal screening programs are mandatory being established in 1975 respectively 1978. More recently, prenatal screening has been introduced in parts of Italy while in Denmark, Poland (Poznan region) and parts of the U.S., neonatal screening programs were started.
In some areas of the U.S. with very low incidence of Toxoplasmosis, is considered that screening is recommended only for women with very high risk (HIV, SLE, malignancy) or those in which routine echography detected hydrocephaly in the fetus, intracranial calcifications, microcephaly, delay in the fetal development, ascites or hepatosplenomegaly, because false positive results can lead to unnecessary treatments or unnecessary abortions.
In areas where seroprevalence is high, serologic screening of pregnant women is recommended, at least in weeks 10-12 of pregnancy and should be repeated in weeks 20 to 22 if the initial result is negative.
Agneta Paul (1992) showed that “The real morbidity of this disease is far from being known. The figures provided represent just the tip of the iceberg of this phenomenon.”
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