Fact Sheet Number 517
- WHAT IS TOXOPLASMOSIS?
- HOW IS TOXO TREATED?
- HOW DO I CHOOSE A TREATMENT FOR TOXO?
- CAN TOXO BE PREVENTED?
- THE BOTTOM LINE
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PrintToxoplasmosis (toxo) is an infection caused by the parasite Toxoplasma
gondii. A protozoa is a single-celled animal. A parasite lives
inside another living organism (the host) and takes all of its
nutrients from the host.
The toxo parasite is very common in cat feces, raw meat, raw
vegetables, and the soil. It can get into your body when you breathe
in dust.Up to 50% of the population is infected with toxo. A healthy
immune system will keep toxo from causing any disease. It does
not seem to spread from person to person.
The most common illness caused by toxo is an infection of the
brain (encephalitis).Toxo can also infect other parts of the body.
Toxo can lead to coma and death. The risk of toxo is highest when
your T-cell (CD4+) counts are
below 100.
The first signs of toxo include fever, confusion, headache,
disorientation, personality changes, tremor, and seizures. Toxo
is usually diagnosed by testing for antibodies to toxoplasma gondii.
The toxo antibody test shows whether you have been exposed
to toxo. A positive test does not mean that you have toxo encephalitis.
However, a negative antibody test means that you are not infected
with toxo.
Brain scans by computerized tomography (CT scan) or magnetic
resonance imaging (MRI scan) are also used to diagnose toxo. A
CT scan for toxo can look very similar to scans for other opportunistic
infections. An MRI scan is more sensitive and can make it easier
to diagnose toxo.
Toxo is treated with a combination of pyrimethamine (Daraprim®)
and sulfadiazine. Both drugs can cross the blood-brain barrier.
The toxoplasma protozoa needs vitamin B to live. Pyrimethamine
stops toxo from getting vitamin B. Sulfadiazine prevents toxo
from using it. The normal dosage of these drugs is 50 to 75mg
of pyrimethamine with 2 to 4 grams per day of sulfadiazine.
These drugs both interfere with vitamin B and can cause anemia.
People with toxo usually take Leucovorin, a form of folic acid
(a B vitamin), to prevent anemia.
This combination of drugs is very effective against toxo. Over
80% of people show improvement within 2 to 3 weeks.
Toxo usually comes back after the first episode. People who
have had toxo should keep taking the anti-toxo drugs at a lower,
maintenance dose.
A TREATMENT FOR TOXO?
If you are diagnosed with toxo, your doctor will probably prescribe
pyrimethamine and sulfadiazine. This combination can cause a drop
in white blood cells, and kidney problems.
Also, sulfadiazine is a sulfa drug. Almost half the people
who take it have an allergic reaction. This usually is a skin
rash, sometimes a fever.
Allergic reactions can be overcome using a desensitization
procedure. Patients start with a very small amount of the drug.
They get increasing amounts until they can tolerate the full dose.
People who can not tolerate sulfa drugs can use clindamycin
(Cleocin®) instead of sulfadiazine in the combination.
You can be tested to see if you have been exposed to toxo. If
not, you can reduce your risk of infection by not eating undercooked
meat or fish, and by wearing gloves and a face mask and washing
thoroughly if you clean a cat box.
If you have less than 100 T-cells, you should take medication
to prevent toxo. People with less than 200 T-cells usually take
Bactrim or Septra to prevent pneumocystis carinii pneumonia (PCP).
These drugs also protect you against toxo. See Fact
Sheet 512 for more information on PCP. If you can’t tolerate
Bactrim, your doctor can use other drugs.
THE
BOTTOM LINE
Toxoplasmosis is a serious opportunistic infection. If you have
not been exposed, you can avoid exposure by not eating undercooked
meat or fish, and taking extra precautions if you clean a cat
box.
If your T-cell count falls below 100, talk with your doctor
about taking drugs to prevent toxo.
If you develop headaches, disorientation, seizures, or other
possible signs of toxo, see your doctor immediately. With early
diagnosis and treatment, toxo can be treated effectively.
If you do develop toxo, you should continue to take the anti-toxo
drugs to prevent another episode.
Revised July 27, 2002
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New Mexico AIDS Education and Training Center
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