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Toxoplasmosis: An infection with the protozoal organism Toxoplasma gondii.

July 26, 2013

By Dr. Tekla Lee-Fowler, Dr. James Wright

Auburn, Alabama —

What is toxoplasmosis?

Toxoplasmosis is an infection with the protozoal organism Toxoplasma gondii. People that become infected for the first time experience varying degrees of illness; in most individuals, symptoms may go unnoticed or be very mild while some experience symptoms such as swollen lymph nodes, fever, muscle stiffness, joint pain, or upper abdominal discomfort. For most people, the symptoms resolve within 2 weeks and they only occur the first time you are infected. Toxoplasmosis is more serious in people who are immunocompromised or pregnant women who have never been exposed to the organism. The disease is of particular concern during pregnancy because a first time infection early in pregnancy could result in miscarriage or stillbirth. Additionally, children infected in the womb could experience varying degrees of blindness (often much later in life) and/or neurological abnormalities. While the most commonly discussed source for exposure to this organism is cats, they are not the most important source for people. We will discuss some of the other ways humans can become infected with toxoplasmosis, what the concerns regarding infection are, and steps you can take to reduce your risk from exposure to this organism.

How can I come in contact with Toxoplasma gondii?

It’s first necessary to tell you a bit about this organism’s life cycle. Cats are hunters by nature, and when they eat a mouse, bird, etc. that is infected with Toxoplasma gondii, they become infected. Rates of infection vary significantly, with outdoor cats or cats with outdoor access having higher rates of infection than their indoor counterparts. For several weeks after the cat becomes infected, it may shed the organisms in its feces. Young cats shed the organism for a longer period of time and in higher numbers. Older cats that have been exposed previously and are healthy will shed toxoplasma for only a brief time. After  cats stop shedding , the organism becomes sequestered in the muscle tissue, and is typically not “infectious” unless their immune system later becomes suppressed (i.e. Feline leukemia infection, feline immunodeficiency virus infection, medications). During the initial shedding phase, the cat’s feces contains the toxoplasma organisms. Importantly, it takes 24-48 hours before the feces is truly “infectious” to other animals and people. Consuming cat feces or things contaminated with cat feces (i.e. plant material or soil) is how animals such as mice and birds (and even farm animals or deer later used for food) become infected. When these animals become infected, the organism is incorporated into the muscle tissue. So, what are some sources of infection for people?

  1. Cat feces in the litter box

This one seems obvious, right? However, remember that not every cat is infected with Toxoplasma gondii, the feces would be infectious mainly for a few weeks after the initial infection or possibly if they become immune compromised, and it takes about 24 hours from the time the cat uses the litter box for the feces to become “infectious.”    

  1. Environment/Soil contamination

Exposure can occur from coming into contact with soil or other substrate contaminated with cat feces (i.e. gardening, sandboxes, etc.).

  1. Eating improperly cooked or processed meat

This is the most important source for exposure of people to toxoplasmosis. Farm animals such as pigs, sheep, goats, cattle, etc. and wild game like deer can all become infected with Toxoplasma gondii from the environment. In these animals, the organism becomes incorporated into the muscle tissue (aka meat). Eating undercooked or improperly processed cured meats can result in exposure. People are most often exposed through meat from pigs, sheep, and deer.  Remember that good hygiene when preparing meat is also important to reduce exposure. As feeding raw meat diets to dogs and cats has become more frequent, it is also important to realize that feeding your cat raw meat could result in infection of your cat and consequently increase your exposure risk as described above.  

  1. Consuming raw goat’s milk

When these animals become infected, the organisms can also be passed into the milk. Therefore, consuming raw (aka unpasteurized) goat’s milk is a potential source of infection.

  1. Eating raw oysters, clams or mussels

These shellfish may become infected if exposed to water contaminated with cat feces. This is possible if water emptying into rivers (an eventually the ocean) either bypasses a sewage treatment facility or the organism survives the water treatment.

What steps can I take to reduce my risk?

People can reduce their risk of exposure through good pet care, good hygiene, and consuming properly prepared and cooked food.

For cat owners, a few rules apply:

  1. Practice good hygiene (i.e. handwashing)
  2. Clean the litterbox regularly (at least every 24 hours)
  3. Don’t feed your cat raw meat
  4. Don’t allow dogs or other household pets to consume cat feces
  5. Try to prevent the ingestion of potentially infected rodents or birds by cats
  6. Maintain good pet health (routine vaccinations, deworming, routine veterinary care). Remember that ill or immunocompromised cats could potentially begin shedding the organism again.
  7. If you are pregnant or immunocompromised, have someone else clean the litterbox. If you must clean the litterbox yourself, wear gloves and a mask, and practice good hygiene. Also, avoid handling unknown or stray cats.

For reducing other exposure:

  1. Practice good hygiene
  2. Wear gloves when gardening
  3. Wear gloves when field dressing deer
  4. Cover sandboxes
  5. Don’t drink untreated water
  6. Properly cook meat
  7. Wash produce before consumption
  8. Avoid consumption of unpasteurized dairy products

More information on toxoplasmosis can be found at the following link: