Toxoplasmosis

Pet Tales  by Barry B. Burtis

Toxoplasmosis

Toxoplasmosis is another zoonotic disease - a disease that is transmitted from animals to people. It is caused by a small parasite called Toxoplasma gondii. When human adults or children, who have healthy immune systems, become infected with this organism, it may cause no symptoms or very mild flu-like illness. As the initial infection subsides, the organisms may form cysts in various body tissues. In healthy people this is not a problem. However, HIV-positive or other immuno-compromised  people may become seriously ill if, as their immune system declines, these cysts become re-activated. Toxoplasmosis is also a serious problem when a pregnant woman becomes first infected when she is pregnant. Abortion, premature birth or neurological damage to the unborn may result.

Cats are the definitive or preferred host for the parasite. Only in cats can the parasite complete its normal life cycle. Cats who have become infected with the parasite pass the infective stage of the organism in their stools. Animals that people consume as food become infected with this stage, called oocysts. These food animals become infected while grazing or from their feed. When such animals become infected, cysts form in their muscles. It is thought that most people become infected with the toxoplasma organism by eating undercooked meat from these animals. Other foods we eat may be contaminated from contact with raw meat. Direct spread from infected cats to people is a less likely but possible route for infection in humans.

In North America, it is felt that fresh pork, meat from sheep and from certain game animals such as deer, bear and moose probably presents the greatest risk for toxoplasmosis infection. The danger occurs when it is not prepared for human consumption properly.

Despite these facts, people often worry about just how much risk there is of contracting toxoplasmosis from their pet cat. The answer seems to be the risk is very small. However, there are a few other points to remember and actions that can be taken to reduce the danger even more.

Feed your pet cat only commercial cat food or other cooked foods. Do not give them raw meat, poultry, internal organs or bones. Keep your cat indoors and prevent it from hunting or scavenging for other food sources. These are the best ways to prevent your cat from becoming infected  with toxoplasmosis in the first place.

If a cat does become infected it can shed toxoplasma oocysts in the feces for about 3 weeks. It is rare for recurrent shedding to occur. It is unlikely you would notice any change in the cat's health or behaviour at this time. It will take a day or so for the oocysts, sitting in the stool in the litter box, to mature and be able to cause infection. Daily removal and proper disposal of feces from the litter box prevents this infective stage from being reached. It is always important to properly wash your hands after performing the litter box cleaning.

What about the danger of handling a cat itself?  If a cat is shedding oocysts, its stools are usually still well formed. This means contamination in the hair is not significant. Also cats are usually very fastidious about thoroughly cleaning themselves after a trip to the litter.

Women who are pregnant, in particular, need to know these facts about toxoplasmosis. Remember to avoid eating undercooked meats.  Toxoplasma cysts are killed by thorough cooking (155 F. or above) or by freezing (-20 F or below) for at least a day. Let your husband or another family member take over cat litter duties. Wear gloves when gardening or if you must perform litter box cleaning. Wash your hands thoroughly after such activities or after handling a cat. These measures mean you are erring on the side of being overly cautious. However, unless you know from blood testing that you are immune to toxoplasmosis because you have been infected earlier, they are recommended. It is wise to do everything possible to reduce the risk of developing a first time infection while pregnant and thereby threatening the health of your baby.