What is Toxoplasmosis?

Toxoplasmosis is an infection caused by the parasite Toxoplasma gondii (aka T. gondii).  It is one of the most common parasitic diseases found in pets and humans.  Despite the high prevalence, this parasite rarely causes significant clinical disease, as long as pets and people have healthy immune systems. 

How does trasmission occur?

T. gondii is transmitted to cats that consume infected raw meat (inlcuding store-bought raw meat, infected rodents and other small mammals). Once consumed, the parasite is released into the cat’s digestive tract and will start microscopically shedding in the feces as early as 3-10 days and can continue to shed for up to 2 weeks. After this period, the cat will never shed the parasite again in its lifetime. T. gondii is very resistant and can survive in the environment for over a year! Even though the parasite is shed in the feces for up to 2 weeks, the oocysts (microscopic eggs of T. gondii) in the cat’s feces are not immediately infectious to other cats, dogs or people. The oocysts must go through a process called sporulation which takes 1-5 days, and once this process is complete, oocysts are considered infectious to cats, people and other animals. If people or other animals accidentally ingest the sporulated oocysts, they can develop toxoplasma cysts in their muscle tissues that remain there for life.

What is the risk of transmission to cats and what are the symptoms?

It is very likely that your cat may become infected if the cat is allowed to hunt outdoors or is fed raw meat. About 30% of cats in the United States have been infected with toxoplasma at some point and most infected cats will not show symptoms.  However, if a cat has a suppressed immune system (such as a kitten, or an adult cat on steroids, or one with a virus such as FIV or FELV), symptoms may occur such as fever, poor appetite, diarrhea, or more rarely, pneumonia, eye abnormalities or neurologic disease such as seizures or personality changes.

Should cats be tested for Toxoplasmosis?

Testing healthy cats is generally not recommended since interpretation of the results can be confusing and controversial. In fact, if a healthy cat tests positive, that would indicate it had toxoplasmosis previously in its life and will now be forever immune and is at no risk of transmission.   If a healthy cat tests negative, there is a greater risk of infection if exposed to toxoplasma, and thus prevention in this cat is most important. However, if an unhealthy cat is exhibiting some of the signs of toxoplasmosis, your veterinarian will likely recommend that the cat be tested.

Can cats with toxoplasmosis be treated?

Most cats with toxoplasmosis can recover by treating with certain types of antibiotics.  Treatment must be started as soon as possible and often needs to continue for several weeks.  In most cases, symptoms will start to resolve within 1-2 days of starting therapy.  Unfortunately, no antibiotic can completely eliminate toxoplasma from the body, so relapses may occur with immune-compromised cats.

What is the risk of transmission to people?

The chance of human exposure is small due to the fact that cats only shed toxoplasma in their feces for a short period of time, and only once in their lifetime. People have a greater risk of getting the disease by eating raw or undercooked infected meat or unwashed vegetables that have been contaminated by soil. There is also a risk of transmission if people do not wash their hands after gardening or scooping the litter box.  It is important to note that T. gondii can be transmitted directly from pregnant woman to an unborn child if the mother becomes infected during pregnangy. Other at-risk individuals would be those with compromised immune systems such as people on corticosteroids or chemotherapy, or people with immune conditions such as AIDS.  The elderly and children also have an increased risk.      

What are the symptoms in people?

In healthy people there are often no symtoms or there can be flu-like signs such as fever, malaise or lymph node enlargement or soreness.  If a woman is pregnant, and if and only if it’s her first exposure, birth defects are possible as well as fetal death.  Individuals that have a suppressed immune system can be at risk for possibly life-threatening central nervous system disorders.

Should people be tested for toxoplasmosis?

If there is any question about possible exposure to T. gondii, people should seek advice from their medical doctor and testing can be performed. In general, testing is most important in people with compromised immune systems, the elderly and pregnant women.  If toxoplasmosis is found in an immune-compromised individual, it is likely due to a reactivation of a previous infection.  For those that test positive, a physician may start them on a preventative therapy.  If an immune-compromised individual tests negative, they will be advised to be more cautious about disease prevention.  Important: If a woman initially tests negative for T. gondii, but then becomes infected with toxoplasmosis during pregnancy, there is significant risk of having a baby with birth defects.  If a woman initially tests positive prior to pregnancy, and then becomes pregnant, she will have already built up antibodies to protect her and her baby from infection.

Once infected, can a person get toxoplasmosis a second time?

This is very unlikely. Similar to chicken pox, after the first infection, people generally do not get it again.  But if your immune system becomes compromised, a previous infection can potentially become reactivated.  

How can toxoplasmosis be prevented?

• People or pets should NOT eat raw or undercooked meat
• Meat should be cooked to at least 160 degrees Fahrenheit for 20 minutes
• Thoroughly wash hands after handling raw meats
• Thoroughly wash vegetables and wear gloves while gardening
• Keep your cat healthy with regular annual visits to your veterinarian
• Do not allow your cat to hunt or roam
• Control rodent populations
• Keep children’s sandboxes covered
• Litter Box Management:
  • Change litter boxes every 24 hours. Remember, it takes the toxoplasma oocysts at least 24 hours after they sporulate to become infectious, and that is when it will be contagious to people and other animals.  
  • Use disposable plastic liners and change them each time you change the litter.
  • Do not “dump” litter into the trash. If contaminated dust is inhaled, human infection is possible.
  • Disinfect the litterbox at least once a month by filling it with boiling water and letting it stand for 5 minutes. No other disinfecting method seems to kill the toxoplasma organism.
  • Always wash your hands after cleaning the litter box.
  • *** Pregnant women and people with suppressed immune systems should NOT clean litter boxes. ***

References:

• Cornell University’s Toxoplasmosis in Cats brochure. Website: www.vet.cornell.edu/fhc/Health_Information/brochure_toxo.cfm
• Clinical Veterinary Advisor, 2015 3^rd Edition, pp 1008-1010.
• P.A.W.S. or Pets Are Wonderful Support.  A group of North American non-profit organizations that advocate the value of the bond between humans and their pets as a means to extend a person’s quality of life and life-span, specifically the elderly or disabled persons.