What is toxoplasmosis?

A single-celled parasite called Toxoplasma gondii causes a disease known as toxoplasmosis. While the parasite is found throughout the world, more than 60 million people in the United States may be infected with the Toxoplasma parasite. Of those who are infected, very few have symptoms because a healthy person's immune system usually keeps the parasite from causing illness. However, pregnant women and individuals who have compromised immune systems should be cautious; for them, a Toxoplasma infection could cause serious health problems.

How do people get toxoplasmosis?

A Toxoplasma infection occurs by:
*Eating undercooked, contaminated meat (especially pork, lamb, and venison).
*Accidental ingestion of undercooked, contaminated meat after handling it and not washing hands thoroughly (Toxoplasma cannot be absorbed through intact skin).
*Eating food that was contaminated by knives, utensils, cutting boards and other foods that have had contact with raw, contaminated meat.
*Drinking water contaminated with Toxoplasma gondii.
*Accidentally swallowing the parasite through contact with cat feces that contain Toxoplasma. This might happen by
*Mother-to-child (congenital) transmission.
*Receiving an infected organ transplant or infected blood via transfusion, though this is rare.

What are the signs and symptoms of toxoplasmosis?

Symptoms of the infection vary.Most people who become infected with Toxoplasma gondii are not aware of it.
Some people who have toxoplasmosis may feel as if they have the "flu" with swollen lymph glands or muscle aches and pains that last for a month or more.
Severe toxoplasmosis, causing damage to the brain, eyes, or other organs, can develop from an acute Toxoplasma infection or one that had occurred earlier in life and is now reactivated. Severe cases are more likely in individuals who have weak immune systems, though occasionally, even persons with healthy immune systems may experience eye damage from toxoplasmosis.
Signs and symptoms of ocular toxoplasmosis can include reduced vision, blurred vision, pain (often with bright light), redness of the eye, and sometimes tearing.
Ophthalmologists sometimes prescribe medicine to treat active disease. Whether or not medication is recommended depends on the size of the eye lesion, the location, and the characteristics of the lesion (acute active, versus chronic not progressing).
An ophthalmologist will provide the best care for ocular toxoplasmosis.Most infants who are infected while still in the womb have no symptoms at birth, but they may develop symptoms later in life. A small percentage of infected newborns have serious eye or brain damage at birth.

Who is at risk for developing severe toxoplasmosis?

People who are most likely to develop severe toxoplasmosis include:
Infants born to mothers who are newly infected with Toxoplasma gondii during or just before pregnancy.
Persons with severely weakened immune systems, such as individuals with AIDS, those taking certain types of chemotherapy, and those who have recently received an organ transplant.

What should I do if I think I am at risk for severe toxoplasmosis?

If you are planning to become pregnant, your health care provider may test you for Toxoplasma gondii.
 If the test is positive it means you have already been infected sometime in your life. There usually is little need to worry about passing the infection to your baby. If the test is negative, take necessary precautions to avoid infection (See below).
If you are already pregnant, you and your health care provider should discuss your risk for toxoplasmosis. Your health care provider may order a blood sample for testing.
If you have a weakened immune system, ask your doctor about having your blood tested for Toxoplasma.
If your test is positive, your doctor can tell you if and when you need to take medicine to prevent the infection from reactivating. If your test is negative, it means you need to take precautions to avoid infection. (See below).

What should I do if I think I may have toxoplasmosis?

If you suspect that you may have toxoplasmosis, talk to your health care provider.
Your provider may order one or more varieties of blood tests specific for toxoplasmosis. The results from the different tests can help your provider determine if you have a Toxoplasma gondii infection and whether it is a recent (acute) infection.

What is the treatment for toxoplasmosis?

Once a diagnosis of toxoplasmosis is confirmed, you and your health care provider can discuss whether treatment is necessary.
In an otherwise healthy person who is not pregnant, treatment usually is not needed.
If symptoms occur, they typically go away within a few weeks to months. For pregnant women or persons who have weakened immune systems, medications are available to treat toxoplasmosis.

How can I prevent toxoplasmosis?

There are several general sanitation and food safety steps you can take to reduce your chances of becoming infected with Toxoplasma gondii.
Cook food to safe temperatures. A food thermometer should be used to measure the internal temperature of cooked meat.
Do not sample meat until it is cooked. USDA recommends the following for meat preparation. For Whole Cuts of Meat (excluding poultry) Cook to at least 145° F (63° C) as measured with a food thermometer placed in the thickest part of the meat, then allow the meat to rest* for three minutes before carving or consuming.
For Ground Meat (excluding poultry) Cook to at least 160° F (71° C); ground meats do not require a rest* time.For All Poultry (whole cuts and ground) Cook to at least 165° F (74° C), and for whole poultry allow the meat to rest* for three minutes before carving or consuming.
*According to USDA, "A 'rest time' is the amount of time the product remains at the final temperature, after it has been removed from a grill, oven, or other heat source. During the three minutes after meat is removed from the heat source, its temperature remains constant or continues to rise, which destroys pathogens."
More on: Fight BAC: Safe Food HandlingFreeze meat for several days at sub-zero (0° F) temperatures before cooking to greatly reduce chance of infection.
Peel or wash fruits and vegetables thoroughly before eating.
Do not eat raw or undercooked oysters, mussels, or clams (these may be contaminated with Toxoplasma that has washed into sea water).
Do not drink unpasteurized goat's milk.
Wash cutting boards, dishes, counters, utensils, and hands with hot soapy water after contact with raw meat, poultry, seafood, or unwashed fruits or vegetables.
Wear gloves when gardening and during any contact with soil or sand because it might be contaminated with cat feces that contain Toxoplasma.
Wash hands with soap and warm water after gardening or contact with soil or sand.
Teach children the importance of washing hands to prevent infection.
If you have a weakened immune system, please see guidelines for Immunocompromised Persons.
For further information on safe food handling to help reduce foodborne illness visit the Fight BAC! ® Web site.

If I am at risk, can I keep my cat?

Yes, you may keep your cat if you are a person at risk for a severe infection (e.g., you have a weakened immune system or are pregnant); however, there are several safety precautions to avoid being exposed to Toxoplasma gondii :
Ensure the cat litter box is changed daily.
The Toxoplasma parasite does not become infectious until 1 to 5 days after it is shed in a cat's feces.If you are pregnant or immunocompromised:
Avoid changing cat litter if possible. If no one else can perform the task, wear disposable gloves and wash your hands with soap and warm water afterwards.Keep cats indoors.
Do not adopt or handle stray cats, especially kittens.
Do not get a new cat while you are pregnant.
Feed cats only canned or dried commercial food or well-cooked table food, not raw or undercooked meats.
Keep your outdoor sandboxes covered.
Your veterinarian can answer any other questions you may have regarding your cat and risk for toxoplasmosis. 

Once infected with Toxoplasma is my cat always able to spread the infection to me?

No, cats only spread Toxoplasma in their feces for a few weeks following infection with the parasite. Like humans, cats rarely have symptoms when infected, so most people do not know if their cat has been infected.
The Toxoplasma shedding in feces will go away on its own; therefore it does not help to have your cat or your cat's feces tested for Toxoplasma.

Acute toxoplasmosis:

Acute infection is usually asymptomatic, but 10 to 20% of patients develop bilateral, nontender cervical or axillary lymphadenopathy. A few of these also have a mild flu-like syndrome of fever, malaise, myalgia, hepatosplenomegaly, and less commonly, pharyngitis, which can mimic infectious mononucleosis. Atypical lymphocytosis, mild anemia, leukopenia, and slightly elevated liver enzymes are common. The syndrome may persist for weeks but is almost always self-limited.

CNS toxoplasmosis:

Most patients with AIDS or other immunocompromised patients who develop toxoplasmosis present with encephalitis and ring-enhancing intracranial mass lesions.
Risk is greatest among those with CD4 counts of < 50/μL; toxoplasmic encephalitis is rare when CD4 counts are > 200/μL. These patients typically have headache, altered mental status, seizures, coma, fever, and sometimes focal neurologic deficits, such as motor or sensory loss, cranial nerve palsies, visual abnormalities, and focal seizures.

Congenital toxoplasmosis:

This type results from a primary, often asymptomatic infection acquired by the mother during pregnancy. Women infected before conception ordinarily do not transmit toxoplasmosis to the fetus unless the infection is reactivated during pregnancy by immunosuppression.
Spontaneous abortion, stillbirth, or birth defects may occur.
The percentage of surviving fetuses born with toxoplasmosis depends on when maternal infection is acquired; it increases from 15% during the 1st trimester to 30% during the 2nd to 60% during the 3rd.
Disease in neonates may be severe, particularly if acquired early in pregnancy; symptoms include jaundice, rash, hepatosplenomegaly, and the characteristic tetrad of abnormalities: bilateral retinochoroiditis, cerebral calcifications, hydrocephalus or microcephaly, and psychomotor retardation.
Prognosis is poor.Many children with less severe infections and most infants born to mothers infected during the 3rd trimester appear healthy at birth but are at high risk of seizures, intellectual disability, retinochoroiditis, or other symptoms developing months or even years later.

Ocular toxoplasmosis:

This type usually results from congenital infection that is reactivated, often during the teens and 20s, but rarely, it occurs with acquired infections. Focal necrotizing retinitis and a secondary granulomatous inflammation of the choroid occur and may cause ocular pain, blurred vision, and sometimes blindness.
Relapses are common.

Disseminated infection and non-CNS involvement:

Disease outside the eye and CNS is much less common and occurs primarily in severely immunocompromised patients.
They may present with pneumonitis, myocarditis, polymyositis, diffuse maculopapular rash, high fevers, chills, and prostration. In toxoplasmic pneumonitis, diffuse interstitial infiltrates may progress rapidly to consolidation and cause respiratory failure, whereas endarteritis may lead to infarction of small lung segments. Myocarditis, in which conduction defects are common but often asymptomatic, may rapidly lead to heart failure.
Untreated disseminated infections are usually fatal.

Diagnosis

Serologic testingFor CNS involvement, CT or MRI and lumbar puncture

The diagnosis is usually made serologically using an indirect fluorescent antibody (IFA) test or enzyme immunoassay (EIA) for IgG and IgM antibodies
Specific IgM antibodies appear during the first 2 wk of acute illness, peak within 4 to 8 wk, and eventually become undetectable, but they may be present for as long as 18 mo after acute infection.
IgG antibodies arise more slowly, peak in 1 to 2 mo, and may remain high and stable for months to years.
Assays for toxoplasma IgM lack specificity.

The diagnosis of acute toxoplasmosis during pregnancy and in the fetus
or neonate can be difficult, and consultation with an expert is recommended.
If the patient is pregnant and IgG and IgM are positive, an IgG avidity test should be done. High avidity antibodies in the first 12 to 16 wk of pregnancy essentially rules out an infection acquired during gestation. But a low IgG avidity result cannot be interpreted as indicating recent infection because some patients have persistent low IgG avidity for many months after infection. Suspected recent infection in a pregnant woman should be confirmed before intervention by having samples tested at a toxoplasmosis reference laboratory. If the patient has clinical illness compatible with toxoplasmosis but the IgG titer is low, a follow-up titer 2 to 3 wk later should show an increase in antibody titer if the illness is due to acute toxoplasmosis, unless the host is severely immunocompromised.