Toxoplasmosis is a common infectious disease
Toxoplasmosis is an infectious disease caused by a parasite that animals transmit to humans. It is a common disease that is rarely recognized, since most people infected show no signs or symptoms. It is usually transmitted to humans by pets, especially cats, or by ingesting undercooked meat.
It is a mild illness for most people, but it can sometimes cause certain flu-like symptoms.
The disease can be dangerous for people with weakened immune systems or for pregnant women, as it can affect the development of the fetus (congenital toxoplasmosis).
Although toxoplasmosis cannot be caught from an infected adult or child, the disease can be contracted:
- contact with cat feces that contain the parasite. For example, if the parasite touches the hands, then the mouth, while gardening or cleaning a litter box;
- by ingestion of contaminated water or meat (most frequently lamb, pork or game). By contact with knives, boards or kitchen utensils that have touched raw meat;
- by the consumption of fruits, vegetables or certain non-pasteurized products;
- very rarely, during an organ transplant or blood transfusion.
Symptoms of toxoplasmosis
The incubation period of toxoplasmosis is poorly understood. It is estimated to last between five to ten days after being contaminated by the parasite.
In more than 80% of cases, toxoplasmosis goes unnoticed.
Otherwise, various symptoms appear:
- moderate fever (below 38°C or 100.4°F);
- the presence of lymph nodes (especially in the neck and at the base of the skull);
- skin rashes (small pink pimples) all over the body;
- frequent prolonged fatigue (several weeks or months);
- headache ;
- pain in joints and muscles.
Acquired ocular involvement (chorioretinitis) with a tendency to relapse is occasionally observed in foreign-acquired toxoplasmosis (Latin America, Africa) and is caused by more virulent parasites.
After an illness, the toxoplasmosis parasite remains in the body (mainly in the nerve and muscle tissue) for years. However, it does not cause symptoms because the infected person’s immune system keeps it in an inactive form.
Complications of toxoplasmosis
In people whose immune system is weakened, especially in cases of AIDS / HIV, toxoplasmosis can lead to seizures or encephalitis (severe infections of the nervous system) which can be fatal.
Women who contract toxoplasmosis shortly before or during their pregnancy have a 30% risk of infecting their baby, even if they have no symptoms of the disease. The baby is more likely to contact the infection if the mother is newly infected during the third trimester than if she is infected during the first trimester.
Infections in early pregnancy can cause miscarriage. Moreover, serious consequences for the baby are rarer in the third trimester.
Some of them may develop:
- abnormal enlargement of the liver and spleen (hepato/splenomegaly);
- jaundice (yellowing of the skin and the whites of the eyes caused by an abnormality in the elimination of bilirubin by the liver);
- severe eye infections (ocular toxoplasmosis).
In the majority of cases, children infected during pregnancy will show no symptoms at birth and during the first year of life. Those who are not treated could develop the symptoms of the disease in adolescence or when they are young adults:
- loss of sight or hearing;
- mental retardation;
- severe eye infections.
How do you get contaminated with the toxoplasmosis parasite?
Before contaminating humans, the parasite (Toxoplasma gondii) affects animals (called “hosts”):
In herbivores and omnivores (pigs, cattle, sheep, goats, etc.) as well as in birds, the parasite is present in inactive forms (cysts). These animals are therefore intermediate hosts that show no symptoms.
On the other hand, humans can develop toxoplasmosis if they ingest the cysts contained in undercooked contaminated meat from these animals (mainly pork, beef). Undercooking does not kill cysts.
The parasite (Toxoplasma gondii) can also be transmitted to cats and other felines called “definitive hosts”: it takes an active form (oocysts). These animals eliminate parasites (oocysts) in their excrement and can thus contaminate humans.
The sources of contamination are:
- direct contact with a cat or its litter box. Only cats that hunt for food can carry the parasite. An urban apartment cat, fed with industrial food does not present any danger of contamination of humans,
- soil or river water soiled with excrement,
- soiled and poorly washed raw fruits and vegetables…
- The parasite is able to cross the barrier of the placenta when a pregnant woman has toxoplasmosis during her pregnancy. It then contaminates the fetus.
- The parasite is not transmitted from person to person. Toxoplasmosis is therefore not contagious.
Diagnosis of toxoplasmosis in immunocompetent subjects, including pregnant women
The indications for the biological diagnosis of toxoplasmosis in immunocompetent subjects are as follows: pregnant women (systematic screening), subjects suspected of ocular toxoplasmosis and patients presenting with non-specific symptoms, in particular if the latter are severe.
In these indications, the biological diagnosis of toxoplasmosis consists of:
- the search for anti-Toxoplasma serum antibodies of IgG and IgM isotypes, usually carried out by an immunoanalysis technique (immunoenzymatic, chemiluminescence, etc.);
of iteration(s) that can follow this first search in the following situations and according to the following methods:
- the presence of IgM and/or questionable IgG results, which requires confirmation by a different technique (dye-test, IFI, immunoblot, or ISAGA) and from a laboratory expert in toxoplasmosis,
a suspicion of acute toxoplasma infection, which requires the study of the kinetics of IgG with one or two iteration(s) of the initial search two or three weeks apart; successive samples to be titrated during the same series, with the same immunoanalytical technique,
- the extension of the monthly follow-up by a search for IgG and IgM two to four weeks after delivery, which is to be carried out in seronegative mothers throughout pregnancy;
the anti-Toxoplasma IgG avidity measurement test to date the infection in the presence of a suspicion of recent infection (presence of IgM, confirmed by a second technique, and of anti-
- Toxoplasma IgG) in women pregnant woman and the symptomatic subject, this test only allowing to exclude a recent infection in the presence of a high avidity.
In this context of diagnosis of toxoplasmosis in the immunocompetent subject, the search for serum anti-Toxoplasma antibodies of IgA and IgE isotypes is not relevant.
Pre- and postnatal diagnosis of congenital toxoplasmosis
This diagnosis consists of:
The search for Toxoplasma DNA by gene amplification (PCR) on amniotic fluid, specifying the following elements:
- amniocentesis for this research should only be performed after at least 16-18 weeks of pregnancy, and not less than four weeks since the manifestation of the suspected acute maternal infection,
the reporting of the results is qualitative and specifies that a negative PND result does not totally exclude the possibility of congenital toxoplasmosis;
- the search for Toxoplasma DNA by gene amplification (PCR) in cord blood, peripheral blood of the newborn, amniotic fluid and placenta, specifying that a positive result in the placenta should be confirmed by the positivity of another postnatal diagnostic test to establish the diagnosis of congenital toxoplasmosis;
- the search for anti-Toxoplasma serum antibodies in newborns and children under one year of age, as follows:
- search for specific IgM and/or IgA on cord blood or peripheral blood between D0 and D3 of life, by an immunoanalysis technique, checked after 10-15 days of life in the event of positivity of the first search,
- search for neosynthesis of IgG and/or IgM in the cord blood or the peripheral blood of the child by comparison of the mother-child profiles in immunoblot or ELIFA, between D0 and D3, at D15 and D30 (then M2 +/- M3 if the diagnosis remains undetermined at D30),
- monitoring of the specific serum IgG level of the child, measured between D0 and D3, at D15 and D30 then monthly until disappearance of the antibodies to affirm the absence of congenital infection.
Given the complexity of interpreting certain tests, and in order to ensure continuity between the pre- and postnatal diagnosis, the pre- and postnatal biological diagnosis examinations of congenital toxoplasmosis should be carried out by expert laboratories in toxoplasmosis working in a network and in consultation with clinicians.
Diagnosis of ocular toxoplasmosis
Indications for laboratory diagnosis of ocular toxoplasmosis are: Toxoplasmosis-seropositive subjects with atypical ocular lesions, fulminant expression of the disease, uncertain differential diagnosis with other causes of retinochoroiditis, and delayed response to anti-toxoplasma challenge treatment. .
This diagnosis consists of the following tests, the implementation and interpretation of which are the responsibility of expert laboratories in toxoplasmosis:
- detection of Toxoplasma DNA by gene amplification (PCR) in ocular fluids;
- detection of local IgG production by comparison of the immune loads of paired serum-ocular fluid samples;
- detection of local production of IgG and/or IgA by comparison of immunoblot immunological profiles of paired serum-ocular fluid samples.
For all clinical contexts of toxoplasmos (within the scope of this assessment):
- the mouse biological sample inoculation technique is of interest only in the case of symptomatic
- patients for whom a hypervirulent strain is suspected, for the purposes of typing and adaptation of care;
- Toxoplasma cell culture is no longer of interest.
As far as the place of performance is concerned, the diagnostic examinations for toxoplasmosis are carried out either by so-called “polyvalent” or “front-line” laboratories, or by so-called “expert” laboratories in toxoplasmosis. This distinction is based on the particular technicality of the examination in question and/or on the complexity of the clinical situation. An expert laboratory is mainly defined by its mastery of uncommon or manual techniques, its ability to handle complex files, and its integration into a network of reflection and collaboration with the various clinicians and other expert laboratories.
Preventions of Toxoplasmosis
– Wash your hands thoroughly, especially after handling raw meat, raw vegetables soiled with dirt or gardening and before each meal
– Wear gloves for gardening or for any contact with soil
– Have the cat’s litter box washed daily with boiling water by another person or wear gloves
– Thoroughly cook all types of meat (including poultry and game)
– When preparing meals, wash vegetables and aromatic plants with plenty of water, especially if they are earthy and eaten raw
– Wash kitchen utensils and work surfaces with plenty of clean water.
In the event of meals taken outside the home, pregnant women must eat well-cooked meat and “avoid raw vegetables” by “preferring cooked vegetables”.
Freezing food of animal origin at -18°C (-0.4°F) is one of the essential additional measures. As for precautionary measures, they concern foods whose consumption is not recommended, namely raw goat’s milk, marinated, brined or smoked meat and raw molluscs (oils, mussels, etc.).
Information: Cleverly Smart is not a substitute for a doctor. Always consult a doctor to treat your health condition.