(Photocredit: Morguefile.com)

(Photocredit: Morguefile.com)

(Photocredit: Morguefile.com)

A human with an acute Toxoplasma infection experiences varying degrees of illness: fever, swollen lymph nodes, muscle stiffness, joint pain, swollen liver and/or spleen (manifested as a sore upper abdomen). These symptoms may be so mild as to go unnoticed. Illness lasts 1-12 weeks and is often dismissed as a bad cold or mononucleosis.

However, if the person infected is a pregnant woman, the Toxoplasma organism may cross the placenta. The amount of damage done depends on the stage of pregnancy at the time of infection. Infection in early pregnancy may result in miscarriage or stillbirth. Infection in mid-pregnancy may result in a child with varying degrees of blindness (due to inflamed retina - the most common result of congenital infection) and/or various severe neurological conditions including hydrocephalus or microcephaly. Sometimes problems are not evident at birth and show up later in life.

(Photocredit: Public Domain Image U.S. Dept of Agriculture)

There are two basic forms of Toxoplasma organism: the "oocyst," which is shed in the cat feces, and the Toxoplasma tissue stages, which live in the flesh of such food animals as hogs and lambs. A person who inadvertently eats either of these forms of Toxoplasma is liable to become infected. Raw goat’s milk is also an important source of infection.

When might one inadvertently consume an oocyst? Usually by putting a contaminated hand or finger in one's mouth. Where would a hand get contaminated? Changing a litter box used by an actively infected cat, gardening or handling soil contaminated by the feces of an actively infected cat, or touching cat feces that is at least a day or two old. A cat must be in an active stage of infection to transmit the infection to you.

When might one inadvertently consume a Toxoplasma tissue stage? Tasting meat while it is cooking, eating under cooked meat, handling raw meat and getting tissue in one's mouth accidentally, eating food prepared on a cutting board contaminated with raw meat.

Washing one's hands regularly, wearing gloves while gardening, and having someone else change the litter box can eliminate infection. Most people are infected by eating under-cooked meats.

(Photocredit: CDC Public Health Image Library)

The cat has probably been over-emphasized as a carrier of Toxoplasma; most human infections result from eating tissue stages of Toxoplasma in undercooked meat.

Usually a cat will only shed oocysts after the first infection of Toxoplasma; a cat that has already had a Toxoplasma infection usually will not re-shed the oocysts unless its immune system has been compromised (as through the feline leukemia virus infection or drugs.) Cats shedding oocysts generally do so for 5-14 days.

Oocysts require 24-48 hours to sporulate --- that is, grow into a form which is dangerous to people. For this reason, the cat's litter box should be changed daily or twice daily so the cysts will be thrown out before they reach an infectious stage. Dangerous oocysts can be contacted when gardening. Note that freezing weather will not reliably kill dangerous oocysts in soil nor will freezing meat kill the dangerous tissue forms.

Dogs that eat cat feces can also shed oocysts that they have eaten for 2 days.

Your cat may be tested to see if he/she has already had Toxoplasmosis; a cat that has already been infected is unlikely to shed dangerous oocysts in the future.

The cat itself is not a source of oocyts, only its feces are.