What is Toxoplasmosis?
Toxoplasmosis is an infection caused by a protozoan (Toxoplasma gondii).
Infected individuals may be asymptomatic (have no symptoms), may present with a mild, flu-like illness, or may be subject to a widespread, rapidly fatal disease.
The infection has three forms.
- The trophozoite is the invasive, multiplying form that is seen in tissue and body fluids in the active (acute) stage of the illness.
- A cyst, containing live trophozoite, is the non-active (latent) form that can persist indefinitely as a chronic infection found in muscles and nerve tissue.
- The oocyst, encapsulated egg form, is passed only in the feces of the cat family.
Found worldwide, humans acquire the infection through eating oocysts from soil or by eating a cyst in raw or undercooked meat, through improper handling of cat litter, through the placenta (transplacentally) during pregnancy, and rarely through direct inoculation (blood transfusion).
Symptoms of Toxoplasmosis
The disease can be divided into four categories:
- congenital infection (present at birth),
- infection in the healthy host,
- infection in the immunocompromised individual,
- ocular (eye) infection.
In congenital infection, symptoms may be present at birth or not until years later. Although most infected newborns have no symptoms at birth, they later develop symptoms including seizures, feeding problems, respiratory distress, and diarrhea.
In healthy individuals, over 80% of toxoplasmosis infections are asymptomatic (without symptoms). If symptoms are present, they may include fever, fatigue, headache, sore throat, muscle or joint pain, and an occasional rash.
In the immunocompromised individual (AIDS, cancer, or those taking immunosuppressive drugs), the symptoms of toxoplasmosis are widespread. It usually affects the central nervous system (brain and spinal cord) and can also affect the lung, heart, and liver. Symptoms include fever, headache, cough, shortness of breath, chest pain, weakness, seizures, psychosis (loss of reality), and cognitive (reasoning, memory) impairment.
Ocular toxoplasmosis is usually a congenital condition (present at birth) of the eye, and is usually without symptoms (asymptomatic latent chorioretinal scar). If eye infection does occur or is reactivated, an inflammatory condition (retinochoroiditis) may occur, causing visual disturbances such as blurring or island-like gaps in the visual field. It is possible for ocular toxoplasmosis to progress resulting in glaucoma or blindness.
How is it diagnosed?
- In congenital infection, symptoms may include fever, rash, or jaundice (yellow coloring to skin). Abdominal palpation (exam done by pressing with hands on abdomen) may reveal enlarged spleen or liver.
- In healthy individuals, lymph nodes in the neck region may be swollen but not tender. Other symptoms may include fever, rash, and muscle tenderness. Abdominal palpation may reveal enlarged spleen or liver.
- Immunocompromised individuals may present with interstitial pneumonia (inflammation of the tissues surrounding the air passages), myocarditis (inflammation of the heart) and evidence of neurologic disease (altered mental status, seizures, cranial nerve involvement).
Tests: Diagnosis depends principally on serologic tests (blood tests) that are sensitive and reliable. Tachyzoites in blood or body fluids confirm active infection. The presence of cysts in the placenta, fetus, or newborn indicates congenital infection. Diagnosis is occasionally made by histologic (microscopic examination) of tissue cells or by isolating the organism from a tissue culture.
How is Toxoplasmosis treated?
Asymptomatic individuals and individuals with chronic latent infections are usually not treated. When symptoms are present, the individual is usually treated with a combination of anti-malarial and antibiotic drugs.
Individuals who are immunocompromised will require drug maintenance treatment for life.
- Pyrimethamine, sulfadiazine or trisulfapyrimidines for 3 to 4 weeks and folinic acid to reduce the side effects of pyrimethamine are often prescribed.
- Corticosteroids, if necessary, for inflammation.
What might complicate it?
Complications may include glaucoma, blindness, interstitial pneumonia (inflammation of the tissues surrounding the air passages), myocarditis (inflammation of the heart), partial paralysis, cranial nerve disturbances, and seizures.
Most individuals have a non-life threatening, self-limited disease. Symptoms, if present, usually resolve within a few months. Rarely, they may last up to a year. If diagnosed early, the survival rate in immunocompromised individuals is greater than fifty percent. However, recurrence of the infection is these individuals is common.
Conditions with similar symptoms include CMV, infectious mononucleosis, sarcoidosis, tuberculosis, tularemia, lymphoma, metastatic cancer, herpes simplex, multifocal leukoencephalopathy, fungal encephalitis, vascular stroke, and CNS lymphoma.
Infectious disease specialist, internist and parasitologist.
Notify your physician if
- You or your child has symptoms of toxoplasmosis.
- Symptoms worsen or don't improve after diagnosis and treatment.
Last updated 4 October 2011