Toxoplasmosis is a parasitic infection that may cause flu-like symptoms. The organism that causes toxoplasmosis — Toxoplasma gondii — is one of the world's most common parasites. Most people affected never develop signs and symptoms. But for infants born to infected mothers and for people with compromised immune systems, toxoplasmosis can cause extremely serious complications. If you're generally healthy, you probably won't need any treatment for toxoplasmosis. If you're pregnant or have lowered immunity, certain medications can help reduce the infection's severity. The best approach, though, is prevention.
Complications of Toxoplasmosis
Causes of Toxoplasmosis
Toxoplasma gondii (T. gondii) is a single-celled parasitic organism that can infect most animals and birds. But because it reproduces sexually only in cats, wild and domestic felines are the parasite's ultimate host. T. gondii's complex life cycle begins when a cat eats infected prey, usually a mouse or bird. Cats can also become infected if they are fed raw, contaminated meat or eat infected soil. Once ingested, T. gondii burrows into the walls of the cat's small intestine, forming early-stage cells called oocysts that the cat eliminates in its feces, usually for a period of two to three weeks. A single stool may contain millions of oocysts. Most healthy cats won't shed oocysts after this initial acute stage. Within a few days, the oocysts develop into mature, highly infectious cells that under certain conditions can survive in the soil for months. If they're ingested by another animal, they multiply rapidly inside the host, eventually forming inactive cysts that lodge mainly in the brain or muscles. Although the new host animal usually remains symptom-free and won't excrete oocysts, it can still transmit the parasite to any predator that eats it.
What happens in humans
In many respects, the pattern is similar in humans. After you're infected with T. gondii, the parasite forms cysts that can affect almost any part of the body, but often affects your brain and muscles, including the heart. If you're generally healthy, your immune system keeps the parasites at bay, and they remain in your body in an inactive state for life. This provides immunity so that you can't become infected with the parasite again. But if your resistance is weakened by disease or certain medications, the infection can be reactivated, leading to serious complications. Although you can't "catch" toxoplasmosis from an infected child or adult, you can become infected if you come in contact with:
Signs & Symptoms of Toxoplasmosis
Most often, you won't know that you've contracted toxoplasmosis, although some people may develop toxoplasmosis symptoms similar to those of the flu or mononucleosis, such as:
If you are living with HIV/AIDS, are receiving chemotherapy or have recently had an organ transplant, you're more likely to develop signs and symptoms of severe toxoplasmosis infection, including:
Signs in babies
Most pregnant women with toxoplasmosis don't have signs or symptoms of the disease, but if you become infected for the first time just before or during your pregnancy, you have about a 30 percent chance of passing the infection to your baby (congenital toxoplasmosis), even if you aren't having signs and symptoms yourself.
The risk and severity of your baby's infection often depend on when in your pregnancy you were infected. Your baby is most at risk of contracting toxoplasmosis if you become infected in the third trimester and least at risk if you become infected during the first trimester. On the other hand, the earlier in your pregnancy infection occurs, the more serious the outcome for your baby. Many early infections end in stillbirth or miscarriage, and children who do survive are likely to be born with serious problems, such as:
Only a small number of babies who have toxoplasmosis show signs of the disease at birth. Instead, many infected newborns don't develop signs and symptoms of the disease until they're in their teens or later. Those signs and symptoms include:
Diagnosis of Toxoplasmosis
Most pregnant women in the United States aren't routinely screened for toxoplasmosis, and most states don't screen infants for the infection. Without specific screening, toxoplasmosis is often difficult to diagnose because signs and symptoms, when they occur, are similar to those of more common illnesses such as the flu and mononucleosis.
Testing in pregnancy
If your doctor suspects you have the infection, you may have several blood tests that check for antibodies to the parasite. Antibodies are proteins produced by your immune system in response to the presence of foreign substances, including viruses, bacteria, parasites, drugs and toxins. Because these antibody tests can be difficult to interpret, the Centers for Disease Control and Prevention (CDC) recommends that all positive results be confirmed by a laboratory that specializes in diagnosing toxoplasmosis.
What test results mean
Sometimes you may be tested early in the course of the disease before your body has a chance to produce antibodies. In that case, you may have a negative result, even though you're infected. If your doctor is still suspicious, you'll need to be retested in several weeks. In most cases, though, a negative toxoplasmosis test result means you've never been infected and therefore aren't immune to the disease. If you're at high risk, you can take certain precautions so that you don't become infected in the future. A positive result, on the other hand, doesn't necessarily mean you're actively infected. In many cases, it's a sign that you were infected at some time in your life and are now immune to the disease. Further tests can help determine when the infection occurred, based on the types of antibodies in your blood, and whether the levels of these antibodies are rising or falling. This is especially important if you're pregnant or living with HIV/AIDS.
Testing your baby
If you're pregnant and have a current toxoplasmosis infection, the next step is to determine whether your baby also is infected. Tests your doctor may recommend include:
Testing in severe cases
If you've developed a life-threatening illness such as toxoplasmic encephalitis, you may need one or more imaging tests to check for lesions or cysts in your brain. These include:
Treatments of Toxoplasmosis
Most healthy people don't require toxoplasmosis treatment. But if you're otherwise healthy and have signs and symptoms of acute toxoplasmosis, your doctor may prescribe the following drugs:
Treating people with HIV/AIDS
If you are living with HIV/AIDS and have toxoplasmosis, the treatment of choice is also pyrimethamine and sulfadiazine, along with folic acid. An alternative is pyrimethamine in conjunction with clindamycin (Cleocin) — an antibiotic that can sometimes cause severe diarrhea. Normally, you'll need to take these medications for life, although in some cases, your doctor may consider stopping toxoplasmosis therapy if your CD4 count remains very high for at least three to six months. Side effects of most drugs can be more severe in people with HIV/AIDS.
Treating pregnant women and babies
If you're pregnant and currently infected with toxoplasmosis but your baby isn't affected, you may be given the antibiotic spiramycin. Use of this drug can reduce the likelihood that your baby will become infected, without posing a risk to you or your child. Although routinely used to treat toxoplasmosis in Europe, spiramycin is still considered an experimental drug in the United States. Your doctor can obtain it from the Food and Drug Administration. When tests indicate that your unborn child has toxoplasmosis, your doctor may suggest treatment with pyrimethamine and sulfadiazine. Because these drugs can have serious side effects for both women and babies, they're normally not used during pregnancy, but doctors sometimes prescribe them in extreme circumstances. Drug treatment can lessen the severity of congenital toxoplasmosis, but it won't undo any damage that's already been done.
Prevention of Toxoplasmosis
Although effective therapy is available for toxoplasmosis, all treatments have side effects and may not protect an unborn child. That's why the best approach is prevention. These precautions can help keep you safe:
For cat lovers
If you are living with HIV/AIDS, or are pregnant or planning to become pregnant, you're right to be concerned about toxoplasmosis. But you don't have to give up your cat. Here are a few simple steps that can keep both you and your animal companion healthy:
When to seek Medical Advice
If you're living with HIV or AIDS or are pregnant or thinking of becoming pregnant, talk to your doctor about being tested. The signs and symptoms of severe toxoplasmosis — blurred vision, confusion, loss of coordination — require immediate medical care, particularly if your immune system has been weakened.