Toxoplasmosis
How can toxoplasmosis be prevented? Information on causes, symptoms, treatments, and risks associated with this infection.
Symptoms and causes
Toxoplasmosis is a parasitic infection caused by Toxoplasma gondii, which usually presents as asymptomatic or with mild symptoms. In general, it does not pose a significant health risk, but it can lead to serious complications in fetuses, newborns, and immunocompromised individuals.
Toxoplasma gondii is an obligate intracellular parasite, meaning it must reside within a host to reproduce. This microorganism uses humans, pigs, sheep, and birds as intermediate hosts for asexual reproduction. Its definitive host is the feline species—particularly domestic cats—where the parasite completes its sexual reproduction cycle.
There are two primary types of toxoplasmosis based on the mode of transmission:
- Acquired toxoplasmosis: transmitted through the consumption of contaminated water or undercooked food containing parasite eggs (oocysts) shed in cat feces.
- Congenital toxoplasmosis: transmitted vertically from mother to fetus via the placenta.
Once oocysts are ingested, they release tachyzoites within the human body, which rapidly multiply inside cells and may cause tissue damage. The immune system responds by converting them into bradyzoites, which replicate slowly and remain encysted in tissues. These latent cysts can reactivate and cause disease when immune function is compromised.
Symptoms
Toxoplasmosis symptoms vary depending on the patient’s immune status and individual characteristics:
- Immunocompetent individuals:
- Often asymptomatic
- Low-grade fever
- Fatigue
- General malaise
- Headache
- Lymphadenopathy (swollen lymph nodes)
- Immunocompromised individuals:
- Ocular toxoplasmosis: eye redness, pain, inflammation, blurred vision, diplopia, floaters, photophobia, blindness
- Cerebral toxoplasmosis: fever, headache, severe fatigue, confusion, poor coordination, muscle weakness, gait disturbances, balance issues, seizures, hemiplegia
- Pulmonary toxoplasmosis: fever, cough, chest pain, respiratory failure
- Toxoplasmosis during pregnancy: in most cases, infected pregnant women do not develop severe symptoms, but vertical transmission to the fetus can occur, though it is not common.
- First trimester: may result in spontaneous miscarriage
- Newborns: hydrocephalus, hepatosplenomegaly, cerebral malformations, ocular infection
- Infants with severe disease: rash, blindness, hearing impairment, jaundice, heart disease, seizures, motor dysfunction, cognitive disability
- Children and adolescents: recurrent ocular infections, developmental delays, poor motor coordination, learning difficulties, growth retardation, early puberty, hearing loss
Causes
Risk Factors
The risk of developing toxoplasmosis increases in immunosuppressed individuals, particularly in the following conditions:
- HIV/AIDS.
- Certain cancers.
- Immunosuppressive therapy following organ transplantation.
- Long-term steroid or corticosteroid use.
- Chemotherapy treatment.
Complications
While most individuals with toxoplasmosis remain asymptomatic or develop mild flu-like symptoms, some may experience severe complications, such as:
- Neurological damage.
- Blindness.
- Hearing loss.
- Congenital anomalies.
- Spontaneous miscarriage.
- Preterm birth.
Prevention
Preventive strategies for toxoplasmosis include:
- Cooking meat to an internal temperature of ≥60°C for at least 3 minutes.
- Cooking poultry to an internal temperature of ≥74°C.
- Avoiding consumption of raw meat, seafood, or fish; if consumed, they should be previously frozen at −20°C for 2 days or −10°C for 3 days.
- Thorough washing of fruits and vegetables before consumption.
- Avoiding unpasteurized milk and dairy products.
- Drinking only potable water.
- Minimizing contact with cats, especially cat feces.
- Wearing gloves when gardening or handling soil.
Which Specialist Manages Toxoplasmosis?
Toxoplasmosis is initially detected by Gynecology and Obstetrics or Family and community medicine. If treatment is required, it is typically managed by Internal medicine.
Diagnosis
The primary diagnostic method for toxoplasmosis is a blood test. This test determines whether the infection is active, through the detection of specific IgM antibodies, or whether the patient has been exposed to the parasite in the past and has developed immunity, through the presence of IgG antibodies.
In Spain, serological testing for toxoplasmosis is included as part of routine prenatal screening. If the results suggest a recent or active infection, additional tests are performed in specialized laboratories to confirm the diagnosis. In some cases, histological studies and amniotic fluid analysis may also be required.
When ocular toxoplasmosis is suspected, specific ophthalmological examinations are conducted to assess eye lesions. To rule out or confirm cerebral toxoplasmosis, diagnostic imaging techniques such as computed tomography (CT) or magnetic resonance imaging (MRI) of the head may be useful, as well as lumbar puncture.
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Treatment
The treatment of toxoplasmosis consists of the administration of the following medications:
- Pyrimethamine combined with sulfadiazine: used during the acute phase of the infection, as it prevents the rapid replication of the parasite.
- Calcium leucovorin (folinic acid): prescribed during pregnancy to counteract the folic acid inhibition caused by pyrimethamine.
- Hydroxynaphthoquinone or azithromycin: these are alternative treatments when the above medications cannot be used or are not sufficiently effective. They also have activity against encysted forms of the parasite.
The required dosage and duration of treatment vary depending on the severity of the disease and the patient's overall health status.
