An Overview of Toxoplasmosis

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Though it's likely that more than 60 million people in the United States are infected with one of the most common parasites, Toxoplasma gondii (T. gondii), the majority never show any symptoms thanks to healthy immune systems that keep the parasite inactive. Toxoplasmosis, the disease that's caused by the parasite, is spread to humans through cat feces and can lead to serious health issues for unborn babies and those with compromised immune systems. Because of this, pregnant women and people with immunosuppression need to stay away from their cat's litter box and be cautious about food preparation and handling.

Symptoms

For most healthy individuals, toxoplasmosis usually has few or no symptoms and the majority of people don't even know they have it. Some people will develop mild flu-like symptoms such as fever, body aches, fatigue, headache, or swollen lymph nodes that can last for several weeks or more and resolve without any treatment.

If you're pregnant and you've become infected with the T. gondii parasite either right before you get pregnant or during your pregnancy, the infection can be passed to your fetus. This can lead to possible miscarriage, stillbirth, or birth abnormalities, including brain or eye damage. In many instances, babies born with toxoplasmosis do not show any symptoms at birth, but can later develop loss of vision, jaundice, serious eye infections, enlargement of the liver and spleen, mental disability, and seizures.

For people with significant immunosuppression, such as those with advanced AIDS or who are receiving high-dose chemotherapy, there is the risk of reactivating T. gondii that was previously controlled by the immune system. This can have serious consequences such as severe encephalitis, a brain inflammation that can cause confusion, weakness, blurred vision, and seizures.

Causes

Toxoplasmosis is caused by the T. gondii parasite, which is able to infect most animals and birds. However, the parasite is only found in cat excrement. Though millions of people are probably infected with the parasite as well, it's contained in an inactive state in those with healthy immune systems. This means that you can't get the disease from a human unless you receive an organ transplant or blood from someone who is infected, which is rare.

Cats are a necessary part of the T. gondii lifecycle, but most infections occur far away from cats. After a cat ingests an infected small animal, such as a rodent or bird, the parasite invades cells of the cat's intestine. The parasite next undergoes several developmental changes to become the infective form or oocyst and is released into the environment in cat feces. The parasite can then invade the body of another animal or human, burying itself into skeletal muscles, heart muscles, and the brain. It forms cysts and can remain there throughout your entire life.

Toxoplasmosis is also spread through:

  • Undercooked meats, especially pork, lamb, and venison that may carry T. gondii cysts
  • Unwashed fruits and vegetables that have been contaminated with T. gondii. Water can contain the parasite as well, though it's not as likely in the United States. Sometimes the transmission of the parasite from kitty litter or feces to soil or water is not as obvious as might be expected. Feral cats or trash disposal may be responsible.
  • Unpasteurized dairy products, though this isn't as common
  • Mother-to-baby transmission in utero, known as congenital infections

The parasite is not infectious until one to five days after being excreted by an infected cat, but it can survive in the environment or litter box for over a year. This is why it's important to carefully change your cat's litter box every day. All fruits and vegetables you eat should also be washed thoroughly.

Diagnosis

Clinical diagnosis of toxoplasmosis can be difficult because the symptoms are generally so similar to other illnesses like influenza and mononucleosis. In general, though, the diagnosis can be made from a blood sample that's sent specifically to check for antibodies against the T. gondii parasite. The specific antibody type can help your doctor estimate when the infection occurred.

Less commonly used methods of diagnosis include microscopic examination of tissues or body fluids for the presence of the parasite. Detection of T. gondii DNA in amniotic fluid can also be used to determine if a fetus is infected.

Treatment

Healthy people tend to recover from toxoplasmosis without any treatment. Most people can be treated with drugs, usually a combination of pyrimethamine, sulfadiazine, and folinic acid, but the parasite cannot be completely eliminated and will stay in the body in an inactive state. There are alternative regimens for people with certain drug allergies.

A Word From Verywell

If you have a cat and you want to get pregnant, you are pregnant, or your immune system is suppressed, there's no need to give up your cat because of fear of toxoplasmosis. Just be sure to take precautions such as making sure you cook all your meat thoroughly; washing all your food preparation dishes, surfaces, and utensils in hot soapy water; thoroughly washing all vegetables and fruit; having someone else change your cat's litter box, or wearing disposable gloves and a face mask and washing your hands afterward if no one else can do it; changing the litter every day; refraining from adopting or touching any new cats while you're pregnant; not feeding your cat raw or undercooked meat; and wearing gloves when you touch soil or sand.

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