Crazy Cat Lady: Understanding Toxoplasmosis

Posted by TF Oren
cat on cat tree

If you've had contact with cats, you might have heard the term "toxoplasmosis."

Toxoplasmosis is a disease caused by the Toxoplasma gondii (T. gondii) parasite. It is one of the most ubiquitous parasites in the world, and there are a number of ways a person can become infected with it, including consuming undercooked, contaminated meat, fruits, or vegetables, contact with infected cat feces, and transmission from mother to unborn child.

T. gondii is a single cell organism. It can infect most animals and birds, but cats - wild and domestic - are its favorite host because the infectious parasites are excreted exclusively in cat feces.

The life cycle of T. gondii includes several stages. Tachyzoites are the motile forms of the parasite. They are the vehicles of acute infection; they grow and proliferate rapidly, spreading quickly through the tissues in the body. Once they have replicated, the tachyzoites transform into bradyzoites.

Bradyzoites are slow-growing, intracellular tissue cysts that occur mostly in the muscles and the brain. Once formed, these antibiotic-resistant bradyzoites can remain in the tissues for the remainder of the life of the host. Bradyzoites can also convert back into tachyzoites. In a healthy host, the immune system will neutralize the tachyzoites, but in hosts with compromised immune systems or in fetuses, these tachyzoites can cause neurological damage.

Many healthy people who have toxoplasmosis are unaware, as they have no signs or symptoms of the disease. However, for those who do develop symptoms, they include:

  • Aches, including headache
  • Swollen lymph nodes
  • Fever
  • Fatigue
  • Respiratory difficulties
  • Blurry vision (due to retinal inflammation)
  • Confusion
  • Loss of coordination

human and cat

Toxoplasmosis is more likely to affect people with weakened immune systems, including those with HIV/AIDS, receiving chemotherapy, recipients of organ transplants, or taking steroids or other immunosuppressants. Expectant mothers are also at a higher risk of infection.

It is not possible to "catch" toxoplasmosis from an infected individual. Rather, infection happens when the parasite is ingested. This can occur in a number of ways:

  • Inadvertently ingesting the parasite after being exposed to infected cat feces (for example: cleaning a litter box and then touching your mouth)
  • Eating or drinking contaminated food or water. Certain meats (lamb, pork, and venison) are more likely targets of the parasite, and unpasteurized dairy products are also at risk - the parasite can also contaminate water, but this is uncommon in the U.S.
  • Using contaminated kitchen utensils
  • Eating unwashed fruits and vegetables that have come into contact with the parasite
  • Receiving an organ or transfused blood that has been contaminated with the parasite (this method of transmission is unlikely, although it has happened in rare cases)
toxoplasmosis
Image courtesy of CDC/Alexander J. da Silva, PhD/Melanie Moser via Wikipedia

When someone becomes infected, the parasite forms cysts. These cysts can attack any part of the body, from the brain to eyes to muscle tissue.

Healthy individuals who contract toxoplasmosis are unlikely to experience complications, as the immune system will keep the parasite in check. If any symptoms occur, conservative management is likely the extent of the treatment that will be necessary. However, for those with weakened immune systems, toxoplasmosis can wreak havoc on the body and requires immediate medical attention.

The best approach to toxoplasmosis is prevention. Taking the following precautions can drastically reduce your risk of contracting the disease:

  • Wear gloves when working outdoors or gardening/handling soil, and thoroughly wash your hands afterwards
  • Do not eat raw or undercooked meat, including raw cured meat
  • Thoroughly wash all kitchen utensils, including cutting boards in hot, soapy water
  • Thoroughly wash all fruits and vegetables, regardless of whether you plan to eat them raw or cooked - if possible, remove peels after washing
  • Do not consume unpasteurized dairy products
  • If your child has a sandbox, cover it when not in use (this will prevent cats from using it as their personal litter box)

cat

Cat owners and expectant mothers should take the following additional precautions to prevent infection:

  • Keep cats indoors and feed them dry or canned foods rather than raw meat - cats can become infected with toxoplasmosis after eating infected animals or undercooked, contaminated meats
  • Do not invite stray cats or kittens into your home, as most cats do not show any signs of a toxoplasmosis infection and test results can take up to a month
  • If you're expecting, do not change your cat's litter box - have somebody else do it. If that's not possible, wear gloves and a face mask every time you change the litter. Change it daily to prevent the cysts from becoming infections, and wash your hands thoroughly every time you clean the litter box

So, what does toxoplasmosis look like in cats?

Toxoplasmosis manifests in both acute and chronic forms. The latter is usually low-grade and does not produce clinical symptoms. The acute form, however, is much more serious.

The clinical symptoms of toxoplasmosis in cats include but are not limited to:

  • Lethargy
  • Depression
  • Fever
  • Weight loss
  • Respiratory distress
  • Loss of coordination
  • Seizures
  • Muscle weakness
  • Partial or complete paralysis
  • Vomiting
  • Diarrhea
  • Loss of appetite
  • Inflammation of the retina, iris, and cornea

Unborn kittens are most affected by toxoplasmosis and may be stillborn or die shortly after birth. Cats can be treated for toxoplasmosis, although the prognosis for individuals with severe symptoms is very poor. In cats, as with humans, prevention is the best approach to toxoplasmosis.


Cats can be tested for toxoplasmosis but those that test positive are actually less likely to transmit the disease because the positive result means that antibodies to the parasite are present and that the cat has been previously infected.

A cat that has been previously infected is essentially immune to repeat infection for about six years after the initial infection. A cat that tests negative for antibodies is at greater risk of both becoming infected and transmitting the infection, as it has no protective antibodies.

Click here to learn more about toxoplasmosis in humans. And click here for an in-depth look at how the disease affects cats.

Have you had experience with toxoplasmosis? Tell us about it in the comments section.

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Crazy Cat Lady: Understanding Toxoplasmosis