Definition: what is toxoplasmosis?
The Toxoplasmosis is an infection caused by a parasite (we speak of parasitosis ) in order apicomplexa (or sporozoites): The toxoplasma gondii.
This condition is frequent in the population, even if its prevalence has tended to decrease for 40 years. Toxoplasmosis is almost always benign and asymptomatic : “People with the disease may present with some signs but which generally never lead to a consultation”, explains Doctor Alexandre Vivanti, obstetrician gynecologist at the Antoine-Beclère Hospital in Clamart (92).
Toxoplasmosis is contracted by eating contaminated food or water. The foods concerned are meats , raw or undercooked shellfish , and dairy products made from raw milk (generally soft cheeses). Transmission is also caused by contact with the faeces of domestic cats (especially when changing the litter). Organ transplantation is also a passive mode of contamination if the donor’s graft is infested.
Once the subject is contaminated, he is immune : “There cannot be two contaminations. On the other hand, the parasite still exists in the body and can reactivate if the patient is immunocompromised. In this case, it can present much more serious clinical signs such as damage to the brain and various organs, ”adds the specialist.
In addition, two periods present a risk of complications in the case of primary infection with toxoplasmosis.
- During pregnancy : “If the pregnant woman has never been in contact with the parasite, she will not be immune. If she catches it during pregnancy, there is a risk of transplacental contamination ”, according to Dr. Vivanti, gynecologist . In this case, the risk is for the fetus. Toxoplasmosis can lead to developmental abnormalities of the brain or skull, ophthalmic damage to the fetus and miscarriages.
- In case of immunosuppression : these may be patients with HIV, people undergoing organ transplants, patients on long-term corticosteroid treatments or on immunosuppressants. Immunocompromised patients are at risk of severe cerebral, ophthalmic and multiple organ damage.
How common is toxoplasmosis?
Toxoplasmosis is a common condition but it tends to become rare. In fact, in 1995, 54% of pregnant women were immunized against toxoplasmosis (therefore had already encountered the parasite) against only 44% in 2003 and 37% in 2010 (source 1).
Causes: what causes toxoplasmosis?
An infection linked to a parasite
Toxoplasmosis is linked to contamination by a parasite: toxoplasma-gondii . It is a coccidian parasite (microscopic protozoan). Its apicomplex shape allows it to easily enter human cells. Man is an intermediate host for this parasite.
In humans , the parasite will stay to transform into an infesting form for the definitive host, which is the feline (and therefore the cat in a country like France).
In cats, toxoplasm infects the tissues of the intestine. “The cat will have no symptoms or just a little tiredness. He will then reject the eggs in his stool and will be immune to the toxoplasma. These eggs (or oocysts) will then be ingested by other mammals (cows, mice, humans, etc.) which are the intermediate hosts ”. The cycle will be reactivated when another feline ingests a contaminated rodent. Indeed, the intermediate hosts retain in their organism the parasite which encysts itself in various organs: we speak of intra-tissue cysts.
Modes of contamination
There are different modes of toxoplasmosis contamination:
Active modes of contamination:
- Foods contaminated by toxoplasm: these are raw or undercooked meats and seafood, raw milk products (such as soft cheeses) or even cold cuts. “These foods are strictly not recommended during pregnancy in order to prevent a primary toxoplasmosis infection that endangers the fetus”, according to Doctor Alexandre Vivanti.
- Contact with cat faeces: “pregnant women should avoid changing cat litter boxes. “
Passive modes of contamination:
- Transplacental contamination during pregnancy: if the mother has never been in contact with toxoplasma before her pregnancy, she is not immune to it. A primary infection of the mother during pregnancy is a risk of transmission of the parasite to the child through the blood.
- Contaminated organ transplantation or transplantation : if the parasite is encysted inside the donor’s organ, there is a risk of reactivation in the recipient who is then immunosuppressed.
Toxoplasma immunity and encystment
In a primary infection with toxoplasma , a healthy patient will usually have no symptoms. The toxoplasm will multiply within its reticulo-histiocytic cells. It will then spread to the whole body about 15 days after contamination. This dissemination takes place during the primary infection or during the reactivation of the virus. Indeed, after the first infection, the patient will be immune to toxoplasma. But the latter will become encysted in orgasm. It will be likely to reactivate in the event of a period of immunosuppression (HIV infection, taking corticosteroids or long-term immunosuppressants, organ transplants, etc.).
Immune reaction following contamination
After the primary infection, the patient presents a peak of immunoglobulins (observable during a serological test): IgM then IgG. It is then protected from reinfection but not from reactivation of the parasite. The IgM peak occurs 3 weeks after contamination and therefore makes it possible to date the primary infection. the peak of IgG is reached around 2 months after the primary infection. In pregnancy, unlike IgM, IgG crosses the placenta.
Encystment of toxoplasm
After the primary infection, the toxoplasms become encysted in the muscles (hence the risk of infection when the individual consumes the muscle of the meat). Reactivation in the muscles is mild, causing muscle pain. However, encystment can also be observed in the brain: reactivation in the event of immunosuppression then generates a risk of cerebral abscess or even in the eye (the risk is then that of chorioretinitis ). Preventive treatment for reactivation is usually prescribed in cases of immunosuppression and toxoplasmosis seropositivity.
What are the symptoms of toxoplasmosis?
The symptoms depend on the context of the contamination: healthy subject, pregnancy, immunocompromised patients, etc. They can sometimes occur when the parasite reactivates.
These are contaminations that take place during life (and therefore after birth).
– In healthy subjects: ” healthy patients are asymptomatic in 80% of cases”, according to the expert. Symptoms usually do not require medical attention. “The patient may present with an influenza-like illness, that is to say a change in general condition and fever ”. Some patients also have swollen neck nodes (cervical lymphadenopathy) and sometimes painful. More rarely, some patients have ophthalmic involvement or chorioretinitis which can cause visual disturbances (such as reduced visual acuity).
The latter may require treatment.
It should be noted that in Guyana, cases of severe toxoplasmosis have been recorded in healthy subjects who presented in particular severe pulmonary symptoms.
– In patients with the AIDS virus: in this case, the patient who has already been contaminated by toxoplasma is at risk of reactivation of the latter. The parasitic invasion can be local or generalized to the organism. Symptoms can be:
- neurological signs : convulsions, epilepsy…;
- ophthalmic involvement or chorioretenitis : the patient has impaired vision;
- lung damage (or pneumonia ): the patient may then have breathing difficulties or chest pain ;
- a brain abscess is a possible clinical sign. It is detectable with a scanner. Symptoms include headache, drowsiness, dizziness, nausea, vomiting, and sometimes coma.
– In the transplant patient: the donor of the transplant may present toxoplasms encysted in the organ to be transplanted. The recipient patient, then treated with immunosuppressants, is at risk of reactivation of the parasite present in the graft. Symptoms are similar to immunosuppression by the HIV virus.
These are infections that occur during pregnancy: the fetus can then present sometimes severe abnormalities.
We consider that the risk of transmitting toxoplasmosis to the fetus in the case of primary infection of the mother is on average 30%. It is low at the very beginning of pregnancy (around 10%) then rises over the latter to reach its maximum (60%) at the end of it (source 2). However, the severity of fetal repercussions is high in the case of primary infection in early pregnancy and much lower at the end.
– If the primary infection occurs during the first trimester: this is rare but can cause very serious abnormalities in the fetus. There are two possible clinical pictures:
- the first associating one of the cerebral and cranial damage (macrocephaly, hydrocephalus , intracranial calcifications) and an ocular damage (pigmentary chorioretinitis);
- the second presents with fever , jaundice (jaundice) and hepato-splenomegaly (enlargement of the liver and spleen).
– If the primary infection occurs during the second trimester: the damage is less significant. But a risk of brain and eye damage remains.
– If the primary infection occurs during the last months of pregnancy: the clinical signs for the child are generally minor.
Whatever the time of the primary infection, if toxoplasmosis in utero is suspected, the child generally obtains regular ophthalmologic follow-up from birth. The ophthalmic disorders present from birth are numerous: microphthalmia, strabismus, nystagmus, chorioretinitis …
What prevention advice against this parasitosis?
Screening for toxoplasmosis
The detection of toxoplasmosis made it possible to better anticipate the onset of the disease. In 1978, prenuptial screening was added to the prenuptial certificate (which was no longer compulsory from 2008). Prenuptial screening for toxoplasmosis was abolished in 2007. In 1992, the possibility of monthly serological monitoring was introduced. In 1994, screening became systematic in the event of organ transplantation.
As for the pregnant woman : the latter is invited to carry out a serological test at the beginning of the pregnancy. If the latter is positive, we consider that the fetus is out of danger because the mother is immune to toxoplasmosis.
On the other hand, if the serological test is negative, it is because the mother has never been in contact with the parasite. Thus in the event of primary infection during pregnancy, the fetus runs risks. The test is carried out again during pregnancy and if it is still negative, the pregnant woman must apply the hygieno-dietetic rules to the letter to avoid contamination. If the test turns positive, doctors will try to date the infection so they can know the risk to the fetus.
The hygiene and dietetic measures to be observed in pregnant women
In 2009, the High Authority for Health drew up recommendations to prevent contamination of pregnant women (source 3):
- Avoid contact with the animal or wear gloves to touch the cat:
- Do not change the litter.
Hygiene rules :
- hand washing should be frequent and especially before meals;
- washing seafood;
- washing of raw vegetables with alcohol vinegar;
- washing dishes and kitchen utensils.
- Do not eat raw meat or fish (tartars, carpaccio) and cook the food well;
- Avoid oysters, mussels, and other raw shellfish.
- Avoid raw goat’s milk.
Examinations: how do you know if you have toxoplasmosis?
Diagnostic tests are only performed in two cases:
- in the event of suggestive symptoms in an immunocompromised patient;
- systematically at the start of pregnancy.
This is a blood sample in order to perform:
– an immunoglobulin assay (IgG and IgM) which allows to know if the patient has already been in contact with the toxoplasm.
– the avidity index which makes it possible to date the infection more precisely.
– the Western Blot which allows to know if the fetus has produced IgM: which would prove that it has been contaminated.
Note that if the pregnant woman has a negative serological test at the beginning of the pregnancy, she is therefore not immune: she will therefore have to repeat tests throughout the pregnancy and strictly respect the hygieno-dietetic rules.
These tests can also be carried out on the newborn at birth: they are carried out by drawing blood from the cord or from the newborn.
This involves looking for the presence of a parasite by direct examination under a microscope or by PCR test . If the PCR test is positive, the toxoplasma is activated in the patient. This examination is to be carried out at:
- an immunocompromised patient who presents suggestive signs;
- a fetus from the moment the pregnant woman seroconversion during pregnancy (if the serological tests turn positive when they were negative at the beginning of the pregnancy). The test consists of a sample of amniotic fluid.
Treatments: how to treat toxoplasmosis?
In pregnant women
In case of primary infection during pregnancy, the pregnant woman should immediately take spyramicin treatment . An ultrasound should be done to check that there is no brain damage.
The prenatal diagnosis by amniocentesis (amniotic fluid puncture) is performed to determine if the child is affected with toxoplasma. “If this test is positive, the parents are informed of the risks to the baby.
Treatment with sulfadiazine, pyrimethamine and folinic acid will be started instead of spyramicin. Ultrasounds should be done twice a month to check for signs of the brain. A medical termination of pregnancy (IMG) may be requested by a patient in the event of severe lesions on ultrasound ”, explains Dr Vivanti.
In immunocompromised patients
In immunocompromised patients with positive serological results, preventive chemoprophylaxis is performed to prevent reactivation of toxoplasma:
treatment includes sulfamethoxazole and trimethoprim (or cotrimoxazole).
Interview with Doctor Alexandre Vivanti, obstetrician gynecologist at the Antoine-Béclère Hospital in Clamart.
Source 3: “ Serological surveillance and prevention of toxoplasmosis and rubella during pregnancy and prenatal screening for hepatitis B – Relevance of implementation methods”, Haute Autorité de santé, December 16, 2009.