Cerebral Toxoplasmosis Fast Facts

Cerebral toxoplasmosis is a brain infection caused by a common single-celled parasite.

Antibodies for Toxoplasma gondii, the organism that causes the infection, are present in the bloodstream of about 30% of people worldwide.

People with a healthy immune system usually don’t experience any symptoms of the infection.

Having a compromised immune system can put you at risk of developing a life-threatening Toxoplasma gondii infection. People with HIV/AIDS or other conditions that affect the immune system and those using immune-suppressant drugs are at increased risk.

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People with a healthy immune system usually don’t experience any symptoms of the infection.

What is Cerebral Toxoplasmosis?

Cerebral toxoplasmosis is an infection of the brain or spinal cord caused by a single-celled parasite called Toxoplasma gondii. The parasite is extremely common, and it infects approximately a third of all people worldwide. However, people with a healthy immune system can usually fight off the infection and experience no symptoms.

Cerebral toxoplasmosis can be life-threatening for people with a compromised immune system, especially those with HIV/AIDS. The condition occurs in as many as 15% of AIDS patients in the United States, and infection rates are much higher in some African and European countries. Cases of toxoplasmosis in AIDS patients are usually the result of a reactivation of old Toxoplasma gondii infections.

The condition is sometimes called neurotoxoplasmosis, toxoplasmic encephalitis, or central nervous system (CNS) toxoplasmosis.

Symptoms of Cerebral Toxoplasmosis

Symptoms of the condition can include:

  • Headache
  • Fever and/or chills
  • Vomiting
  • Seizures
  • Sleepiness, fatigue, or loss of consciousness
  • Confusion or disorientation
  • Weakness on one side of the body
  • Speech difficulties
  • Vision difficulties
  • Movement difficulties
  • Changes in personality or behavior

What Causes Cerebral Toxoplasmosis?

A brain abscess develops when the parasite invades brain tissue, and the area of infection is contained by surrounding tissue. This causes an expanding capsule of pus and fluid to put pressure on healthy tissue.

Toxoplasma gondii is found worldwide, and infections by the parasite are very common. It infects birds, shellfish, and mammals, especially cats, and contact with infected animals can pass the parasite to humans.

Common sources of the infection are:

  • Eating undercooked meat or shellfish
  • Handling infected meat or shellfish
  • Using contaminated utensils or cooking tools
  • Drinking contaminated water
  • Having contact with contaminated cat feces (e.g., while cleaning a litter box)
  • Passing the infection from mother to child during pregnancy

Is Cerebral Toxoplasmosis Hereditary?

Toxoplasmosis arises from external environmental sources, and family history plays no part in developing an infection.

How Is Cerebral Toxoplasmosis Detected?

Early detection of toxoplasmosis is essential because long-term damage is more likely to occur if treatment is delayed until symptoms are advanced. Unfortunately, early diagnosis of the condition is difficult because the first symptoms are usually vague and may be caused by various problems other than an infection.

For many patients, the first sign is a dull headache. Sometimes the headache is confined to one side of the head, and it is often the only symptom that occurs during the early stages of the problem. As the infection grows, the headache usually becomes more severe, and over-the-counter pain relievers typically don’t eliminate the pain.

Another common early symptom of an infection is a low-grade fever.

If the infection is left untreated, more severe symptoms, such as vomiting, stiff neck, seizures, personality changes, and weakness on one side of the body may develop. Eventually, an untreated infection will lead to coma and death.

How Is Cerebral Toxoplasmosis Diagnosed?

When your doctor suspects toxoplasmosis may be present, they may follow a diagnostic procedure that includes:

  • Medical history questions. Your doctor will look for signs that you may be at increased risk for certain infections.
  • Blood tests. These laboratory tests will look for signs of infection in your bloodstream.
  • Lumbar puncture (spinal tap). This test will look for evidence of T. gondii in the cerebral spinal fluid (CSF).
  • Imaging tests. Magnetic resonance imaging (MRI) and computerized tomography (CT) scans can be used to produce an image of your brain. An infection is likely to show up on these scans.
  • Biopsy of brain lesions. Doctors may remove a sample of the infected tissue using a fine needle. Tests of this sample can identify the source of the infection and allow for more effective treatment.

How Is Cerebral Toxoplasmosis Treated?

Treatment of cerebral toxoplasmosis involves drugs aimed at eliminating the infection source and relieving the pressure caused by the growing infection.

  • Anti-parasitic medications such as pyrimethamine, sulfadiazine, and folinic acid are typically used to treat the infection.
  • Corticosteroids are sometimes used to reduce inflammation and swelling caused by the abscess.
  • Anti-seizure medications may be used to treat or prevent seizures.

Drainage of abscesses is often necessary. This will require surgery, and the abscess is usually removed, if possible, during the surgery. If the abscess is not easily accessible, it may be drained using a needle guided by CT or MRI imaging.

How Does Cerebral Toxoplasmosis Progress?

Treatment of toxoplasmosis is usually successful, but the condition is fatal when left untreated.

Treatment of cerebral toxoplasmosis in immune-compromised patients usually continues even after the infection is under control. This is because long-term treatment aims to prevent the reactivation of the infection while the immune system is still unable to fight it effectively. However, patients who don’t follow their long-term treatment plan are vulnerable to relapse.

How Is Cerebral Toxoplasmosis Prevented?

People who are known to have T. gondii antibodies in their bloodstream and whose immune systems are compromised are advised to undergo preventive treatment with anti-parasitic medications.

Ways to reduce your risk of T. gondii infection include:

  • Avoid undercooked meats. Always wash your hands, cooking tools, and surfaces thoroughly when handling or preparing raw meat or shellfish.
  • Wash your hands thoroughly after contact with cats, their feces, or soil from outdoors.
  • If you have HIV, use antiviral medications to decrease your susceptibility to infections, and take the medicines regularly as prescribed.
  • Go to your doctor if you have a headache that lasts (and/or gets worse) for days or weeks.
  • Seek emergency treatment if you have seizures, vomiting, nausea, muscle weakness, or personality changes.

Cerebral Toxoplasmosis Caregiver Tips

If you are a caregiver for a loved one with toxoplasmosis, keep these tips in mind:

  • Attend doctor appointments with your loved one to understand the diagnosis, the treatment plan, and the expectations for recovery.
  • During recovery, provide a comfortable space for the sufferer free from noise, excessive stimulation, and stress.
  • After treatment, work with your loved one’s medical providers to learn how you can best support them as they recuperate. Understand the goals of any long-term therapies, and be realistic about expectations.
  • Call upon family and community to help out whenever possible. Don’t try to take sole responsibility for caregiving.

Cerebral Toxoplasmosis Brain Science

A recent study looked at the advances made in the diagnosis and treatment of brain abscesses over the past several years to determine whether or not medical advances have positively impacted the treatment of the disease. The survey concluded that advances in imaging technologies, antibiotic therapies, and neurosurgery techniques have significantly improved brain abscess patients’ prognoses.

Cerebral Toxoplasmosis Research

Title: A Study of Pyrimethamine in the Treatment of Infection by a Certain Parasite in HIV-Positive Patient

Stage: Completed

Memorial Sloan-Kettering Cancer Center

New York, NY

Encephalitis caused by Toxoplasma gondii has emerged as the most frequent cause of focal central nervous system infection in patients with AIDS. Untreated, the encephalitis is fatal. The best treatment for this disease has not been determined. Presently it is standard practice to administer a combination of pyrimethamine and sulfadiazine. Little is known about the pharmacokinetics of pyrimethamine in patients with AIDS receiving AZT. Furthermore, there are reports that patients already exposed to toxoplasmosis may not have uniform absorption of pyrimethamine.

Patients receive the study treatment for a total of 22 days. Patients are given an initial dose of pyrimethamine followed by a lower dose given as a single oral daily dose for 21 days. Patients continue to receive AZT at the dose prescribed before enrollment in the study. Patients receive leucovorin calcium once a day. Neither the leucovorin calcium nor the AZT is provided through the study.


Title: A Randomized Prospective Study of Pyrimethamine Therapy for Prevention of Toxoplasmic Encephalitis in HIV-Infected Individuals With Serologic Evidence of Latent Toxoplasma Gondii Infection

Stage: Completed

National Institute of Allergy and Infectious Diseases (NIAID) 

Toxoplasmic encephalitis is a major cause of illness and death in AIDS patients. The standard treatment for toxoplasmic encephalitis is to combine pyrimethamine and sulfadiazine. Continuous treatment is necessary to prevent recurrence of the disease, but constant use of pyrimethamine/sulfadiazine is associated with toxicity. Clindamycin has been shown to be effective in treating toxoplasmic encephalitis in animal studies. This study evaluates pyrimethamine as a preventive treatment against toxoplasmic encephalitis (per 3/26/91 amendment, clindamycin arm was discontinued).

Patients are randomized to receive pyrimethamine or a placebo three times a week. All patients must be on aerosolized pentamidine, trimethoprim/sulfamethoxazole (T/S), or dapsone for Pneumocystis carinii pneumonia prophylaxis. Patients will be evaluated bi-weekly for the first month and then every other month for at least 24 months.


Title: A Pilot Study of Oral Clindamycin and Pyrimethamine for the Treatment of Toxoplasmic Encephalitis in Patients With AIDS

Stage: Completed

National Institute of Allergy and Infectious Diseases (NIAID) 

Toxoplasmic encephalitis (encephalitis caused by Toxoplasma gondii) is the most frequent cause of focal central nervous system infection in patients with AIDS. If untreated, the encephalitis is fatal. At present, it is standard practice to give a combination of pyrimethamine and sulfadiazine to treat toxoplasmic encephalitis. The high frequency of sulfonamide-induced toxicity in AIDS patients often makes completing a full course of therapy difficult. There is some information that high doses of parenteral (such as by injection) clindamycin used with pyrimethamine may be as effective as pyrimethamine plus sulfadiazine in the management of the acute phase of toxoplasmic encephalitis in patients with AIDS. However, the administration of parenteral clindamycin for prolonged periods is costly, requires hospitalization, and is inconvenient for the patient. There is some indication that the treatment of AIDS patients with acute toxoplasmic encephalitis with oral clindamycin may be effective. Leucovorin calcium is useful in preventing pyrimethamine-associated bone marrow toxicity.

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