Marina was 26 weeks pregnant when she had her routine prenatal blood test. The result showed a change in antibodies for toxoplasmosis. She had never heard much about it, only vaguely knew that "it had something to do with cats". At the appointment, several questions came to mind: is this serious? Is my baby at risk? Should I have gotten rid of my cat? This account brings together the answers that she, and anyone in the same situation, needs to hear.

"The data and clinical case cited in this article are fictitious and are merely illustrative, serving to facilitate understanding of the topic addressed."

What is toxoplasmosis

Toxoplasmosis is an infection caused by a parasite called Toxoplasma gondii. It is one of the most common parasitic infections in the world. In many countries, a good part of the adult population has had contact with this parasite at some point in their lives, often without ever realising it.

The parasite completes part of its life cycle inside cats, but contamination of people usually happens in other ways, which we will detail shortly.

How we get infected

The main forms of transmission are:

  • Eating raw or undercooked meat (mainly pork, lamb and game meat), which may contain parasitic cysts.
  • Eating fruits, vegetables and vegetables that are poorly washed, contaminated by soil or water with faeces from an infected cat.
  • Having contact with contaminated cat faeces, either when cleaning the litter box or when digging in garden soil.
  • Drinking contaminated water, something rarer, but possible in regions without adequate water treatment.
  • In much rarer situations, blood transfusion or organ transplant.

It is important to make clear: direct contact with the cat (petting it, sleeping near it) does not transmit the disease. The risk is in the animal's faeces, especially when it is young and has had a recent infection.

In a healthy person: what usually happens

In the vast majority of people with a well-functioning immune system, toxoplasmosis goes almost unnoticed. About 80 to 90% of cases cause no symptoms at all.

When signs do appear, they tend to be quite subtle and similar to a mild viral infection:

  • Tiredness
  • Low-grade fever
  • Headache
  • Muscle pain
  • Swollen glands (lymph nodes), mainly in the neck

These symptoms usually go away on their own within a few weeks, without need for treatment, and the person is left with a kind of "immune memory" that protects them from new infections by the same parasite.

The situation changes for people with low immunity (for example, those undergoing cancer treatment, living with uncontrolled HIV, or using immunosuppressive medications). In these cases, the infection can be more serious and affect the brain, eyes or lungs, requiring close medical monitoring.

Why pregnancy changes everything

During pregnancy, the concern is not so much with the health of the mother, who usually follows the mild pattern described above, but with the possibility of the parasite crossing the placenta and reaching the baby. This is called congenital toxoplasmosis.

The risk of transmission to the baby varies depending on the stage of pregnancy:

  • In early pregnancy (first trimester), the chance of the parasite passing to the baby is lower, but if this happens, the consequences tend to be more serious.
  • At the end of pregnancy (third trimester), transmission is more frequent, but the effects tend to be milder.

This is why, contrary to what seems intuitive, the greater risk of damage is not always linked to the moment of greatest chance of infection.

A reassuring point: if the woman has already had contact with the parasite before becoming pregnant (which appears on the blood test), she is usually already protected, and the risk to the baby in this pregnancy is quite low.

What can happen to the baby

When the infection passes to the baby, the picture is quite variable. Some babies are born without any apparent signs, and the problem is only noticed later, sometimes years later. Others may present, right at birth:

  • Visible changes on brain imaging scans, such as calcifications
  • Build-up of fluid in the brain (hydrocephalus)
  • Inflammation in the retina of the eye (chorioretinitis), which can affect vision
  • Head smaller than expected (microcephaly)
  • Jaundice, enlargement of the liver and spleen

In more serious and less frequent cases, there may be pregnancy loss or stillbirth. It is important to emphasise that, with proper prenatal monitoring and early diagnosis, most infected pregnant women receive treatment in time to significantly reduce these risks.

What are the first signs? And why is it so hard to notice

Here is the great challenge of toxoplasmosis in pregnancy: in most cases, the infected pregnant woman feels nothing different. When there are symptoms, they are the same as already described (tiredness, swollen glands, low-grade fever), easy to confuse with any common viral infection during pregnancy.

This is exactly why toxoplasmosis is not a disease that you "notice", but rather a disease that you screen for. The routine blood test during prenatal care (toxoplasmosis serology) is what allows you to discover the infection before it gives any visible sign, and this is why it is usually repeated throughout pregnancy in women who have not yet had contact with the parasite.

How to prevent it

The good news is that prevention is simple and within the reach of any pregnant woman, or anyone else, in everyday life:

  • Cook meat well, avoiding any raw or undercooked parts.
  • Wash fruits, vegetables and vegetables thoroughly before eating, and peel them when possible.
  • Wear gloves when handling garden soil or working in the vegetable patch, and wash your hands afterwards.
  • Avoid cleaning the cat's litter box during pregnancy. If you do not have someone to do it for you, use gloves and a mask, and clean the litter box every day (the parasite takes at least 24 hours to become infectious after being shed in faeces).
  • Keep the cat indoors and feed it cat food, preventing it from hunting and eating raw animals.
  • Wash your hands and kitchen utensils thoroughly after handling raw meat.
  • Avoid unpasteurised milk and its derivatives.

Diagnosis and treatment

Diagnosis is made by blood test, which shows whether the person has already had contact with the parasite before (which is usually reassuring) or whether the infection is recent (which requires greater attention). When infection is identified during pregnancy, there is specific medication treatment, which changes depending on the stage of pregnancy, and which aims to reduce the chance of transmission to the baby and, if it has already occurred, to reduce the severity of the effects. This is why regular prenatal monitoring is the most important tool in this whole story.

If you are pregnant or planning to become pregnant, talk to your doctor about toxoplasmosis screening and about the precautions that make sense for your routine.

This content is educational and informative in nature and does not replace individualised medical consultation, diagnosis or treatment. Always seek a healthcare professional to assess your case.

Dr. Rebeca Soares Andrade CRM - GO 39335