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Toxoplasmosis: Who’s at risk?

By David Jimison, DVM

Toxoplasma Gondii is a small protozoal parasite that most commonly affects our feline friends. Clinical signs of toxoplasmosis in cats will primarily involve the organ system that the parasite has infected. Most commonly we see either no clinical signs, or mild fever, lethargy, and gastrointestinal signs such as diarrhea.  Other affected body systems include inflammation in the eye, respiratory problems, muscle pain, or neurologic disease with trouble walking or seizures.  If you are concerned that your cat may be experiencing any of these problems related to toxoplasmosis, please consult with your veterinarian for the appropriate care and laboratory testing.

Life Cycle

Cats are the definitive host for the Toxoplasma parasite, where reproduction and replication of the parasite occurs.  Although other species can be infected with Toxoplasma, the parasite will only be able to complete its lifecycle within the cat.  Once infected with Toxoplasma, the organism will enter the reproductive stage and produce oocysts (eggs), which will then be released into the environment through the cat’s stool.  Shedding of these oocysts typically lasts several weeks.

Once in the environment, Toxoplasma oocysts will be ingested by small animals, such as rodents, birds, or cockroaches. As seen in the diagram from the CDC (Centers for Disease Control and Prevention), most cats can then become infected through ingestion of these small animals, termed intermediate hosts, and the lifecycle repeats.  Because the lifecycle most commonly involves this intermediate host, toxoplasmosis is more commonly seen in cats that are spending all or part of their lives outside.

Public Health

Toxoplasma is considered a zoonotic organism, meaning it is transmissible between animals and people.  The good news is the risk for human infection is low when the proper precautions are taken. Additionally, in people with healthy immune systems, toxoplasmosis typically results in fever, malaise, and flu-like symptoms, which can be self-limiting. In rare cases, severe infection can results in damage to the eyes, respiratory tract, brain, or other organs. Severe reactions are more common in individuals with a compromised immune system.  Please consult with your doctor if you have concern for human infection of this parasite.

Sources of human infection of toxoplasmosis include:

  • Ingestion of undercooked meat (especially lamb, pork, or venison).
  • Ingestion after handling undercooked meat and improper handwashing or improper washing of utensils, dishes, cutting boards, etc.
  • Ingestion after handling cat feces, such as cleaning the cat litter box and improper handwashing.
  • Ingestion of oocysts after gardening where cat feces may be present with improper handwashing.
  • Ingestion of unwashed fruits and vegetables.
  • Transmission from mother to child during pregnancy.

In order to reduce human infection of toxoplasmosis, all meat should be cooked thoroughly before ingestion. Peel or wash all fruits and vegetables before eating.  Wash all cutting boards, dishes, utensils, etc. after contact with raw or undercooked meat.  Wear gloves when gardening or handling cat feces, and wash hands thoroughly afterward.  Regular cleaning of the litter box can also help reduce transmission. Toxoplasma oocysts need to remain present in the environment for at least 24 hours before becoming infectious. Therefore, prompt and regular cleaning of the litterbox will prevent any oocysts if present from becoming infectious.  Proper hygiene and preparation of food are key to reducing the risk for transmission of not just Toxoplasma, but all other foodborne pathogens as well.


If you are considering starting a family or expanding an existing family and have questions or concerns about your risk for toxoplasmosis, please consult with your doctor for recommendations on testing and prevention.  Some people wonder if it is safe to keep their cat when immune compromised or pregnant.  You do not need to give up your feline companion.  With the proper precautions, you can take steps to greatly minimize risk for disease.  First, cats should be kept indoors to minimize contraction of infectious organisms such as Toxoplasma from the outside. Cats should be fed a balanced commercial cat food, and avoid raw cat food preparations that could contain infectious diseases. Ensure that the litterbox is cleaned daily; it takes around 1-5 days for Toxoplasma parasite to become infectious once passed from the cat.  Avoid changing the litterbox if possible. You can have a spouse or family member clean the litterbox for you.  If it is not possible for someone else to do so, then make sure to wear disposable gloves, and thoroughly wash your hands afterward.

We need to remember that although cats are the definitive host for this parasite and can serve as a source, they are not to be blamed.  We, as guardians for our pets, can take a proactive role in limiting the exposure that our feline companions experience, and thereby limiting our own personal exposure.  With the proper hygiene, meal preparation, and maintenance of our environment we can greatly reduce the risk for infectious disease to protect ourselves, our family, and our four-legged friends.

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