What is it?

It is an infectious disease caused by a protozoon called Toxoplasma gondii. This protozoon is easily found in the environment and can cause infection in a large number of mammals and birds all across the world.

The infection in humans is asymptomatic in 80-90% of the cases, that is, it doesn´t cause symptoms and may go unnoticed in those patients whose immunity is normal. The immune defenses of a normal individual can render this parasite inactive in the body (without causing any damage) for an undetermined period of time.

However, when this individual becomes immunodepressed (with reduced immune defenses) for any reason (AIDS, secondary to drugs used for transplant patients, or even after a highly disabling illness), symptoms and toxoplasmosis may manifest themselves.

Another particularly risky period for acquiring the infection is the intrauterine one, from the pregnant mother to the fetus (vertical transmission). The fetus may have their formation affected when contaminated.

How is the disease acquired?

By four ways:

Ingestion of cysts present in feces of contaminated animals, particularly cats, which may be available in the ground where the animal is used to wandering about. It´s more common in our environment.;
Ingestion of meat from infected animals (raw or undercooked meat), more common in Asia;
Intrauterine transmission from the pregnant woman to the fetus (vertical).
A fourth means of transmission can occur through contaminated organs which, on being transplanted into people who will have to take medications that reduce immunity (to fight rejection to the received organ), cause the disease..

What does one experience?

Here we must differentiate between:

By four ways:

Immunocompetent people (with normal immunity), and;
Immunodepressed people (with decreased immunity).

In those people that have their immunity preserved occur symptoms only in 10% of the cases. In these cases, the main manifestation is the presence of swollen lymph glands, which may occur in any body site where lymph glands exist (inguinal region, armpit, neck, etc.), but more frequently the neck is the body part affected. The lymph nodes become visible upon simple viewing or palpation and are painless. The manifestations may remain restricted to these and are self-limiting, that is, they disappear spontaneously.

However, some patients can present fever, pain in muscles and joints, tiredness, headache and visual alterations, when compromising of the retina (layer that covers the internal and posterior face of the eye and is rich in light-sensitive nervous terminations) occurs along with a sore throat, appearance of red spots scattered all over the body – as an allergy, urticaria, and enlargement of the liver and spleen; less usually, there is inflammation of the heart muscle. Abdominal pains may occur when there´s compromising of the lymph glands of the posterior abdominal region. Despite disappearing spontaneously most of the time, in some cases the lymph nodes can last for months, as well as the tiredness and fatigue.

A less benign type of presentation in patients with normal immunity is the already mentioned retinal inflammation (chorioretinitis).

Most usually, it results from contamination of the fetus, manifesting itself in adolescence or in the young adult, seldom occurring after the age of forty, but it can – with much less frequency – occur during an acute infection.

People under these conditions show blurred sight and black spots in the visual field that may remain or even lead to blindness in the compromised eye, if not suitably treated.

After an acute phase of infection, whether or not it is with minimal manifestations (swollen lymph glands), the disease remains latent, as it were “sleeping”, remaining thus forever, or being likely to reappear later on spontaneously or as a result of a decline in the immunity level.

The presentation of this disease in those with decreased immunity, as already expected, is far more aggressive. Particularly more common in this group are the patients contaminated with the HIV-1 virus (virus that causes the Acquired Immunodeficiency Syndrome – AIDS).

By and large, it also occurs by reactivation of a latent infection.

The symptoms in these cases are manifestations of compromising of the brain, lungs, eyes and heart.

The most usual presentation stems from the compromising of the brain manifested by headaches, fever, sleepiness, decrease in strength in the whole body or in part of it (the right or the left half) evolving into a progressive drop in clear-headedness to a coma.

If untreated, these cases evolve to rapid progression and death.

How is the diagnosis made?

As it is a disease with very unspecific symptoms and which are common to many other diseases, the diagnosis usually is made by experienced doctors. The confirmation of the diagnosis is achieved by diverse blood tests, the most common being the ones that detect the presence of antibodies to Toxoplasma gondii in the blood.


The need for and the time of treatment are determined by the manifestations, affected sites and, especially, the immune state of the sick individual.

The situations are three:

Immunocompetent patients with acute infection:

Compromising of lymph glands only – in general, treatment is not required.;
Infections acquired by transfusion with contaminated blood (rare, since all donors are tested in blood banks) or accidents with contaminated material (with health care providers) – in general, the condition is severe and must be treated.
Retinal infection (chorioretinitis) – must be treated..

Acute infections in pregnant women:

These must be treated since it´s been proved that the chances for fetal contamination are thereby reduced.;
Fetal contamination being proved – treatment is needed and the treatment regimen can be harmful to the fetus; special surveillance must be maintained hence.

Infections in patients with a compromised immune system:

These individuals must always be treated, and some groups, as those contaminated by HIV-1, must keep on taking a slightly lower dose of the medication used for treating the disease for an undetermined period of time. In this case, the possibility of stopping the maintenance of treatment has been discussed for those that achieve recovery of immune defenses with the so-called AIDS cocktails.

How to prevent it?

As the chief contamination mode is oral, prevention, as a rule, must be performed by:

avoiding raw meat;;
eating only vegetables and fruits properly washed in running water;.
avoiding contact with cat feces.

Pregnant women, in addition to avoiding contact with cats, should subject themselves to suitable medical (prenatal) follow-up. Some countries have been successful in preventing intrauterine contamination by applying laboratory tests to all pregnant women.

For people with immune deficiency, prevention can be necessary with the use of medication depending on an individual analysis of each case.