Toxoplasmosis and risks to pregnant women

Toxoplasmosis is a parasitic disease which can affect cats and all other warm blooded animals, including humans. In both cats and humans its effects are usually mild and the parasite is easily kept under control by the body’s natural defenses. However there are exceptions:

• In pregnant women, the parasite may cause severe damage to the unborn baby.
• In humans with a weakened immune system, the disease can sometimes be fatal.

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Toxoplasmosis is caused by an infection with a tiny single-celled creature called Toxoplasma gondii. This is a very common parasite in mammals and birds but it can only live through every stage of its complicated life cycle in cats. Toxoplasma lives and multiplies inside the intestines of an infected cat. Its offspring pass out of the cat’s body in the cat’s feces (droppings) as an egg-like form which hatches after a few days releasing several spores. The spores can survive for months in the soil until they are picked up and swallowed by a mouse or bird where they hatch, burrow through the gut wall and enter the bloodstream. Then they are carried all over the body and form tiny inactive cysts buried in muscle. Cats are reinfected through hunting and eating the host, eg mice or birds.

Surveys show that up to six out of ten cats have been infected with Toxoplasma at some stage. It is more common in stray cats than pet animals because they are more dependent on hunting for their food. In most cases the infection is harmless, there are no symptoms and it lasts for about two weeks. But in some animals, usually kittens and young cats, the immune system is weak and signs of disease may develop. Also in some cats an inactive infection will flare up again if the animal is weakened by another disease, eg Feline Immunodeficiency Virus. Kittens can be infected inside their mother’s womb and in these cases the toxoplasmosis may be severe.

Cats infected with Toxoplasma rarely show any symptoms of disease. In the early stages a cat shows symptoms which could be caused by many other diseases – it seems lethargic, depressed, loses interest in food and may have a fever. Later symptoms might be:

• Breathlessness because of pneumonia
• Jaundice due to liver damage
• Blindness, changed behavior and paralysis due to damaged eyes and brain.

Most affected cats recover if treated early enough. Veterinarians will use a drug which prevents the bug from multiplying any further. There is no vaccine available yet for use in cats so there is no way to protect your cat from infection.

One in every two people will be infected with Toxoplasma during their lifetime. Toxoplasmosis usually causes a brief flu-like infection in humans but it can cause serious problems if a woman comes into contact with it for the first time when she is pregnant. It may cause her to lose her baby or her child may be born with damage to the eyes or brain. However, only about half of women pass on the infection through the placenta and in these only perhaps one in ten cases results in serious damage. Toxoplasmosis can also be dangerous for people whose immune system is weakened by AIDS, or following cancer or organ-transplant treatment.

In Western countries the most likely way that people will be infected is through undercooked (rare) meat, unpasteurized dairy products or unwashed vegetables. But care should also be taken to avoid accidental contact with contaminated cat feces (droppings).

• Cook all meat thoroughly. The infective cysts are destroyed if heated to 158°F for at least 15 minutes. Other types of food processing (freezing, salting, pickling, etc) are not guaranteed to kill them.
• Wash all cooking utensils and surfaces after handling uncooked meat.
• Don’t feed your cat uncooked meat, commercially prepared foods are much healthier for your cat. If possible, try to discourage them from hunting rodents and birds.
• Wash vegetables thoroughly to remove any traces of soil.
• Use rubber gloves when gardening and wash your hands afterwards.
• Cover children’s sandpits when not in use to stop them being used by cats as a toilet.
• Remove droppings from a cat’s litter tray every day.
• Disinfect litter trays regularly using hot water.

Any woman who is pregnant or hopes to become pregnant in the near future should take extra care. They should avoid foods, listed above, which can pass on the infection and should ask someone else to clean out cat litter trays. You will not become infected through touching your cat – pet owners are no more at risk of catching toxoplasmosis than anyone else. The disease is not passed on by stroking your cat or through cat scratches and bites.