Tuesday, March 10, 2009

Toxoplasmosis and Cats

Dear Dr. Gordon: My doctor has recommended I be extremely careful around my 2 cats. I have just found out that I am pregnant and he is concerned that I could become infected with Toxoplasmosis. Now I am worried that I could become infected and am thinking of finding homes for my cats. Is there any way I can keep my cats? PB

Dear PB: Your OB-GYN is being conscientious about warning you regarding the risks involved with cats and Toxoplasmosis. That being said, I see no reason for you to adopt out your cats if you take some simple precautions around the house.

First, let’s give you some background on this disease, which has been poorly understood for years. It was not uncommon, just a few years ago, that human medical doctors were insisting that cat owners rid themselves of their cats to avoid this disease. Fortunately, they know better now.

Toxoplasma infects virtually all warm-blooded mammals and birds, including about 50% of people worldwide. Transmission from cats to humans can occur if cat owners contaminate their hands while cleaning the litter box and accidentally swallow infectious cysts before washing their hands. Other more likely routes of transmission are underrecognized and include ingestion of contaminated soil or water, eating inadequately washed raw vegetables or fruit and consuming raw or undercooked meat and shellfish

It is true that infection by the protozoan organism, Toxoplasma gondii, can cause a variety of birth defects, especially if the mother is infected in the first trimester. However, avoiding infection throughout the pregnancy is very important because the probability of transplacental transmission increases as the pregnancy progresses.

Pregnant women are not the only individuals who are at risk. Most infected individuals have no clinical disease or only flu like symptoms. But, immuno-compromised individuals may suffer from severe, sometimes, fatal, toxoplasmosis when parasites are released from latent tissue cysts and travel to the brain.

So, how can you avoid being infected? Some of the recommendations require just good hygiene and common sense. You should wash all fruits and vegetables thoroughly before eating. You should never eat raw or undercooked meat , poultry, or fish. Restricting access to the outdoors is a key strategy to prevent cats from acquiring T. gondii and serving as a source of infection for people.

Cats that have access to the outdoors typically hunt and eat small mammals and birds which are the intermediate hosts for this parasite. Domestic cats begin shedding the eggs 3-5 days after ingestion of infected animal tissues, and the shedding period lasts about 8 days but may continue up to 3 weeks.

Another important strategy in minimizing exposure is how you deal with the cat’s feces. First and foremost, have your husband clean the litter box. He may not like doing this but when faced with the possibility of congenital birth defects in his first-born, I bet he will comply. If you must deal with the cat’s feces yourself, be extra careful. Changing the cat’s litter boxes daily as well as wearing disposable plastic gloves and washing hands after cleanup, considerably reduce the risk of contracting the disease from cat litter. Cat litter and feces should not be deposited in toilets or recycled into the soil around the home but instead should be deposited in garbage containers in tightly sealed bags. Proper disposal reduces the risk of ingestion and inhalation by other animals and people.

The domestic cat remains the most important vector in spreading the disease into the environment. Cats rarely exhibit clinical disease as a result of T. gondii infection but are implicated in human outbreaks as well as disease in food and zoo animals. Most cat owners probably do not recognize the potential risks to human and animal health posed by feral and owned cats that roam outdoors.

Until a vaccine is developed to prevent cats from shedding the eggs, the challenge for veterinarians is to educate cat owners about environmentally friendly cat management and safe methods for collection and disposal of cat litter. Strategies to manage feral cat populations, which may include adoption, sterilization, relocation, removal, and/or provision of indoor housing, also are needed. David Gordon, DVM