Toxoplasmosis is a disease caused by infection with the protozoan organism called Toxoplasma gondii (T. gondii). This microscopic single-cell protozoal organism is related to coccidia. Virtually all warm-blooded animals (yes people are included) can be infected with this organism. This is a very well adapted parasite and rarely causes significant disease to the individuals when it infects. Cats get and transmit toxoplasmosis. T. gondii is a parasite that needs felines to complete its life cycle. Previously medical health care providers advised pregnant women to get rid of their cats. The fear was this parasitic disease could be transmitted to an unborn fetus. The biggest concern is it can cause severe deformities in unborn babies. Cats are the only animal that transmits this disease directly to people or other animals.
Toxoplasmosis is spread in two ways: by consuming raw or undercooked meat containing the organism, (eating unwashed vegetables has a small chance of transmission) or by ingesting infective eggs (oocysts) shed in the feces of a recently infected cat. Avoiding the first means of catching this disease is simple: don't eat raw or undercooked meat. The freezing process will kill the parasite, so frozen meat is safe to eat (at least from this disorder). Washing your hands will prevent inadvertent direct fecal contact. Understanding how the parasite is spread by cats helps you to avoid contamination from cat feces. This will prevent giving up the feline members of your family during a pregnancy.Cats spread the disease by passing these infective oocysts (eggs) in their feces when they are first infected. Cats shed the eggs only for a few days (approximately 14 days) after the initial infection. This is usually a young cat or a kitten.Once an infected cat passes the eggs in its feces, it takes at least 24 hours for the egg to become infective. Owners who clean the litter box every day will not come into contact with any infective eggs (oocysts). Someone other than a pregnant woman should be delegated to clean the litter box every day. Disposable gloves may be worn to reduce the yuck factor. Always wash your hands after you clean up litter. This principle of hygiene should be followed by anyone who owns a cat. In addition to avoiding cat litter, it's best during pregnancy to avoid gardening and uncovered sand boxes. These are areas where cat feces may be found. If you are unable to avoid these areas, make sure to wear gloves and wash your hands afterwards.Between 30 to 50 percent of all cats, dogs, and people have already been exposed to Toxoplasma gondii. Their bodies have already made antibodies to it. Cats may carry the organism their entire life, they will not shed the disease again unless they becomes immunosuppressed.Your cat may be tested as soon as you find out you are pregnant. If your cat already has antibodies to this disease, then your cat has had the disease and probably will not shed again. The cats that do not have a positive titer for toxoplasmosis: There are measures protecting them from infection, keep them indoors and never feeding them raw meat. Feeding a commercial cat food that has been "cooked" either dry or canned will eliminate transmission to a cat's people.People can also be tested for toxoplasmosis. If a woman with a healthy immune system tests positive to Toxoplasma before becoming pregnant, she cannot pass the disease through the placenta to her fetus. The woman's prior exposure has allowed her immune system to develop a "titer". A pregnancy conceived after a titer will "protect the fetus" during gestation. If there are questions about future immune disorders they should be addressed by your health care provider. It used to be common medical advice for pregnant or immunosuppressed people (AIDS, cancer patients, people with autoimmune disease) to get rid of their cat. Many cat owners consider their cats indispensable members of the family. I have some clients that elevate their cats to better than family.
Cats are usually infected by ingesting organisms present in the tissues (meat) of another infected animal known as an 'intermediate host' which is usually a rodent. The Toxoplasma organism replicates first locally in the intestinal tract of the cat, and is often restricted there. The replication in the intestinal tract results in shedding of oocysts in the feces. The oocysts represent a hardy form of the organism that can survive can survive in the external environment for many months or even years. Other animals can become infected by ingesting these oocysts, but disease will result only if large numbers are ingested.
When some cat's immune system defenses are out of balance and compromised it allows Toxoplasma organisms to invade beyond the intestine and access to various organs of the body. There may be enough damage to cause signs of disease or may Toxo may be become dormant as a tissue cyst. This is not the same as the oocyst form. Such tissue cysts can be infective if the infected tissue is eaten by another animal.
While cats are usually infected by eating infected rodents or more rarely by ingestion of oocysts from the environment, people are most commonly infected through eating contaminated food. Meat is our primary source of infection. Sheep, cattle and pigs grazing on contaminated pastures, or fed oocyst contaminated food; develop the encysted form of the organism in skeletal muscle or other body tissues. If infected meat is not adequately cooked, or if proper hygiene precautions are not followed during handling of uncooked meat, humans can become infected. Ingestion of oocysts from infected cats, for example during gardening in contaminated soil, is a much less common source of human infection.
Toxoplasmosis is a reasonably common parasitic infection that does not cause disease in infected cats with a normal functioning immune system. When a cat's immune system is not working properly Toxoplasma may continue to replicate, spread and damage a cats other tissues. A variety of different clinical signs can develop including ocular (eye) disease, respiratory disease, diarrhea, liver disease and neurological signs. This form of disease may be acute (rapid) in onset or chronic with periods of illness interspersed with periods of some recovery. Toxoplasma is a very rarely a cause of disease in cats.
Toxoplasmosis is difficult to diagnose in cats because signs are variable. Blood tests are available that demonstrate, by the presence of antibodies or immune globulins to the organism. This helps veterinarians to decide whether a cat has been exposed to the organism. These tests help to rule out T Gondii. A "positive" result only means exposure to the organism. Most exposed cats do not develop disease. If a tentative diagnosis of Toxoplasmosis is suspected in a cat, treatment with a course of an appropriate antibiotic resolves most cases.
It turns out Mom and Grandma were right. Wash your hands prior to cooking and before meals. You should wash your vegetables before eating, and cook your meat properly. People may become infected by exposure to and ingestion of oocysts in the environment. Infected meat is a more common source of infection.
There are simple ways to manage yourself and your pets to enjoy pet ownership and ensure that you do not catch this disease:
Cook all meat thoroughly - at least 160 -180°F (70 -82°C) throughout.
Wash hands, utensils and surfaces carefully after handling raw meat.
Wash all vegetables carefully.
Wear gloves when gardening in soil potentially contaminated by cat feces.
Empty cat litter trays daily, dispose of litter carefully, and disinfect with boiling water. If this is done every day, even if a cat is excreting oocysts, they will not have become infectious by the time the litter is changed. It takes more than twenty-four hours from when they are passed in the feces for the oocysts to develop into the infective stage.
Discourage pet cats from hunting, and avoid feeding them raw or undercooked meat.
Cover children's sand boxes to prevent cats using them as a litter box.
Dr Mike Sweet
734-439-1112