Toxoplasmosis in Pregnancy

Toxoplasmosis is an infection caused by the parasite Toxoplasma gondii. It is a disease that usually goes unnoticed in healthy people, but is serious in immunosuppressed patients and pregnant women.

Before we approach toxoplasmosis in pregnancy, it is worth a review of how the serological diagnosis of the disease is made.

Pregnant woman with cat
Pregnant woman with cat

Diagnosis of prenatal toxoplasmosis: IgM and IgG

During the prenatal care, the obstetrician requests some serologies (blood test that shows the main infections that the pregnant woman has had) to evaluate the immunological state of the pregnant woman. Five infections are of great importance in pregnancy because of the risk of transmission to the fetus:

The great risk to the fetus occurs when a mother without antibodies to toxoplasmosis acquires the disease during pregnancy. To find out which women are susceptible to infection during pregnancy, we request a prenatal serology for toxoplasmosis.

Serology is basically a dosage of specific antibodies. A serology for toxoplasmosis is one that investigates antibodies against Toxoplasma gondii, a parasite that causes the disease. The reasoning is this: our body only creates antibodies against a particular infectious agent if we are exposed to it. Therefore, having antibodies against toxoplasmosis means already having been contaminated by the parasite at some point in life.

To summarize an extremely complex process, we can say that our body basically works with two antibodies, called IgM (immunoglobulin M) and IgG (immunoglobulin G). As soon as a new germ enters our body, our immune system begins to produce the IgM antibody, which is called the acute phase antibody. IgM is a less specific antibody, but it can be produced in a few days. In toxoplasmosis it is possible to identify circulating IgM 5 to 7 days after contamination.

After about 4 weeks, when our immune system has known the invading agent well, the body replaces the IgM antibody with the IgG antibody, which is stronger and more specific against toxoplasmosis. Therefore, after 4 weeks, the patient ceases to have positive IgM and only has IgG positive for toxoplasmosis. This IgG for toxoplasmosis will be positive for the rest of life and will prevent the parasite from multiplying within our body.

In summary, a patient with acute toxoplasmosis has IgM positive, whereas a patient who has had toxoplasmosis and has the parasite inactive in the body will present positive IgG. Those who have never been exposed to Toxoplasma have negative IgM and IgG.

As toxoplasmosis does not cause disease in 90% of people, the only way to know if the patient has ever been exposed to Toxoplasma is through the dosage of IgG to toxoplasmosis.

Toxoplasmosis in pregnancy

It is important to stress that the problem is not in those mothers who acquired toxoplasmosis before they were pregnant. Women who already had IgG positive for toxoplasmosis before being pregnant are not at risk of transmitting it to their fetuses. In these cases, Toxoplasma is dormant in the muscular tissues and the mother's immune system is in charge of keeping it away from the fetus. The only exception is in cases of immunosuppression of the mother, as in pregnant women with AIDS , for example. In these cases, as the immune system is weak, Toxoplasma acquired years before can become active again and infect the fetus during gestation.

The risk of toxoplasmosis in pregnancy occurs in those mothers who have never had previous contact with the parasite, having negative serology, that is, IgM and IgG negative for toxoplasmosis. These are the pregnant women at risk because the congenital toxoplasmosis occurs when women acquire Toxoplasma during pregnancy.

Therefore, if during the prenatal examination the expectant mother already has an IgG positive for toxoplasmosis, she can be at peace because she is not at risk of passing the disease to the fetus. If, however, the mother is found to be a negative IgG, some precautions should be taken to minimize the risk of contamination during pregnancy:
  • Avoid eating undercooked meat, especially pork
  • Wash the fruits and vegetables well before eating them
  • Wash well knives and dishes that had contact with raw meat
  • Freezing the meat for a week before consuming it helps to kill the parasites
  • Do not consume meat of unreliable origin
  • Avoid drinking non-bottled water
  • Do not practice gardening
  • Avoid prolonged contact with cats

Pregnant women and cats

Cats are the only animals that, if contaminated with Toxoplasma, begin to eliminate them in the feces, serving as a source for contamination of the environment and people. In other animals, the parasite is lodged and dormant in the muscles, which is why the intake of raw meat is currently the main risk factor for toxoplasmosis contamination.

Therefore, pregnant women susceptible to toxoplasmosis (IgG negative) should avoid raw meats and close contact with cats.

But I'm a pregnant woman with negative IgG and I have a pet cat. Do I have to get rid of it?

No, you do not. But some care must be taken:
  • Take him to the vet to know his immune status.
  • Ask someone to clean the litter box with cat feces daily. Try not to come in contact with the cat's faeces.
  • Feed it only with rations; never let him eat raw meat.
  • Avoid letting the cat leave the house, so that it does not run the risk of contracting the parasite.
  • Avoid insects at home, especially flies and cockroaches, which can carry the parasite and be eaten by the animal.

If your cat is well cared for, feeds properly and does not usually walk freely down the street, his chance of having toxoplasmosis is very small.

When pregnant women take proper care, the rate of contamination is low. Currently, less than 8 out of 1000 (ie, 0.8%) pregnant women with negative serology for toxoplasmosis become infected during pregnancy.

As with any patient with an intact immune system, toxoplasmosis in pregnancy does not usually cause symptoms. In rare cases where there are symptoms, they are usually mild and nonspecific, such as low fever, tiredness and muscle pain. Therefore, in women with IgG negative, serology should be repeated serially throughout pregnancy so that we are sure that no positive IgM has emerged indicative of recent infection. You can not rely only on the symptoms to tell if someone has been infected with Toxoplasma recently.

Congenital toxoplasmosis

As already explained exhaustively, congenital toxoplasmosis occurs when mothers with negative serology for toxoplasmosis (negative IgG) come in contact with the parasite during pregnancy.

Women who intend to become pregnant but who have just become infected with toxoplasmosis should observe a minimum interval of 6 months between cure and pregnancy in order to avoid risk of transmission of the parasite to the fetus.

The greater the gestational age at the time of infection, the greater the risk of transmitting the parasite to the fetus. Toxoplasmosis acquired at the 13th week, the 26th week or at the 36th week present, respectively, a risk of 15%, 44% and 71% transmission to the fetus.

Symptoms of congenital toxoplasmosis

Most newborns with toxoplasmosis are asymptomatic at birth. Less than 30% are already born with symptoms of congenital toxoplasmosis, such as chorioretinitis, intracranial calcifications, hydrocephalus (accumulation of cerebrospinal fluid inside the skull), dermatological lesions and generalized lymphadenopathy (enlarged lymph nodes throughout the body).

Those born without symptoms, however, if not diagnosed and properly treated, are at high risk of developing later symptoms of congenital toxoplasmosis. In addition to serious eye injuries, these children may experience deafness, mental retardation and epilepsy. More serious cases can progress to death.

Fetal ultrasonography is able to detect those 30% of cases of fetal malformations caused by toxoplasmosis still inside the uterus. In countries that allow abortion, abortion can be indicated because these babies already present severe neurological sequelae and high mortality in the first days of life.

Prevention congenital toxoplasmosis

Mothers who develop toxoplasmosis during pregnancy, regardless of gestational age, should be treated until the end of gestation with an antibiotic cocktail consisting of Pyrimethamine, Sulfamadiazine and Spiramycin.

If, despite treatment, the child is born with toxoplasmosis, symptomatic or not, this should also be treated. The indicated schedule is Pyrimethamine + Sulfamadiazine. The treatment lasts 12 months.

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