The Human Risks and Pet Cats


Cats and risks to pregnant woman

Question: Dear Dr. Richards:

Hello. I am a subscriber of your very informative newsletter and was wondering if you could provide me with some information on the following:

I am aware that women who are pregnant should not be exposed to cat litter (because of a bacteria?). I was wondering to what extent cats in general are a risk factor for birth defects. For example, if I am scratched by a cat that carries this bacteria, do I, two years down the road, have to worry that if I get pregnant my baby is at a higher risk of developing birth defects associated with exposure to the bacteria? Is there a way to "undo" exposure to the bacteria before one becomes pregnant? Thank you for any information you can provide.

Sincerely, Stacy

Answer: Stacy-

The risk to pregnant women, from cats, is primarily due to the disease toxoplasmosis, which is caused by a protozoan, not a bacteria. Protozoans are single celled organisms that sometimes have complex life cycles. In the case of toxoplasmosis, the organism that causes it is Toxoplasma gondii. This parasite is found everywhere that cats are found. Many mammals can be infected with toxoplasmosis, but only cats shed the organism in their stools, where they can be passed to other animals. Oddly enough, though, most humans are not infected because of exposure to Toxoplasma organisms in the soil, litterpan or other source of exposure cat stools. Most humans are infected by eating undercooked meat, especially pork and lamb. Cats actually acquire the infection from eating raw prey most commonly, too. Adult humans who become infected usually are unaware of the infection but may have flu-like symptoms. In humans with immune compromise, such as victims of AIDS, Toxoplasmosis is a much more severe infection, though.

Toxoplasmosis can be very harmful if a pregnant women acquires the infection during a pregnancy. The infection must be new and it must occur during the pregnancy for problems to occur. If a woman has been previously exposed to toxoplasmosis and has antibodies against the organism, her immune system will protect her baby from infection. For this reason, it is best to be very cautious about acquiring a new infection with toxoplasmosis during a pregnancy. These are some rules to follow to avoid this situation:

1) Don't feed your cat raw meat and don't allow your cat to hunt. 2) Don't eat raw or undercooked meat during a pregnancy. 3) Have someone else clean the litter pan during a pregnancy, or if this is not possible, clean the litterpan once a day, since it takes longer than that for the Toxoplasma oocysts shed by the cat to sporulate and become infectious. Preferably, do both of these things. 4) Cover children's sandboxes 5) Wear gloves when gardening and wash hands afterwards, even though you were wearing gloves. 6)Don't handle raw meat (wear gloves if you must). 7) Don't drink water from any source that might be contaminated with Toxoplasma ( water from a spring on a hiking trip, for instance)

Hopefully, this is the information you are looking for.

Mike Richards, DVM 10/9/2000

Pregnancy, Infants and Cats

Q: My wife is three months pregnant and we have three cats in a small, two bedroom apartment. Recently a friend of ours told us quite definitively that, "Only a fool would have cats in the same household as an infant. There are many nasty diseases that cats can transfer to babies". All our cats are indoor cats and always have been. Please advise on the hazards of three cats in the same household as a newborn baby. Thank You, Joe

A: Joe- There are two situations -- having cats when your wife is pregnant and having them after the baby is born.

Toxoplasmosis is a disease that can be transmitted from cats to humans (although other infection routes such as undercooked meat are much more frequent). If a pregnant woman is infected with this parasite for the first time during a pregnancy the effect on the baby can be severe. Your wife should not handle the litterpan during the pregnancy and should wash her hands after handling your cat. There are other suggestions for avoiding this condition in our catinfo section. Toxoplasmosis is much more likely to occur in outdoor cats as it is transmitted to the cat through hunting of small animals.

There are conditions cats can have which are transmissible to infants or even older humans under some circumstances. Ringworm, a fungal infection, is one example of a zoonotic (transmissible to people) disease that affects cats. Toxocara infestation (roundworm infection) is another. The best way to avoid this is to have your vet check your cat's stool for roundworms and treat if they are present. In some cases it is just easier to go ahead and treat for these worms -- such as very young cats. Allergies to cats can occur but it seems more reasonable to wait and see if that is a problem than to get rid of the cats on the off chance that might occur. There is no evidence to support old wive's tales about cats "sucking the breath" from infants but it is a good idea to keep cats from sleeping with an infant. They will sometimes choose to sleep on the infant and that may lead to problems. In addition, children should never be left alone with a cat because either one could be hurt if the child grabs the cat too hard or engages in some activity the cat finds threatening and chooses to retaliate against. Finally, keep your cat's rabies vaccination up to date. This is an unlikely problem in an indoor cat but it is a terrible disease and it is best to be cautious -- and it is also the law in most places now.

There are risks associated with everything. I don't think of the risk of owning a cat and having an infant in the household as especially high. I didn't get rid of my cats when my children were born.

Mike Richards, DVM

Asthma, cat allergy and lots of cats

Q: I am trying to help my sister-in-law who has asthma. She is allergic to cats on top of this all. She is trying to avoid having to go to steroids herself and yet spends the days wheezing when home and inhaling things to keep air passages open. She married my brother a few years ago. He lives in downtown Phoenix and had been feeding neighborhood strays for years. He had come to know that there was leukemia on the property and that every cat who comes and stays will eventually die of it. He rescued and bottle fed many kittens and now there are two new kittens. He spays cats when he can catch them and has money on the same day. Some are too wild to catch easily. His wife finally said that the cats could not come into the house and so they opened the basement for them. The cats have found passages up inside the walls of all of the floors of the house and, hopefully, are coming back down to the basement or outside to go to the bathroom. I have not visited in a year. I fear (having lost adult friends to asthma deaths) that I will lose this most wonderful of sister-in-laws to these cats. I know that my brother feels like the parent of the rescued babies and feels that he is running a Hermitage for dying cats (tho' it all seems very Catch-22 to me) and he is almost Hindu in his inability to put them to sleep or to do anything about them, other than to feed and water them and sometimes play with them. His wife loves cats too and loves my brother dearly and so, the family feels that we must come up with outside answers to this dilema. Do you have any suggestions or some thing that I could tell my brother? I will ask him to come to your page and read any answer that you could give us. Thank-you, April who loves her brother and his wife....

A: April- It is not easy to change people's behaviors unless they either want to change them or see the need to change them. This is a particularly tough situation when seeing the need may come too late. My limited understanding of asthma leads me to believe that a severe attack such as you describe is possible and that your sister-in-law actually could die in this situation. But she and your brother have to decide to deal with this situation themselves.

The way I see this, from your note, there are a couple of problems that need to be addressed. First, is your brother really doing these cats a favor - are they better off staying around his house than finding their own way in life? Who knows? My personal opinion is that it is much more responsible to keep one or two cats and care for them well than to keep a dozen and let them develop feline leukemia and become chronically ill and then die. I know for a fact, from numerous conversations with people in similar circumstances, that this is not the opinion of people who collect large numbers of cats or dogs even if they can only provide minimal care. They truly believe they are helping more than hurting. Euthanasia is usually not an acceptable option and discussions along this line are usually fruitless. This belief in life at all costs is like a religious faith and it is as resistant to logical discussion. I suspect that it is necessary to come to a compromise that does not involve euthanasia.

The second problem is the inability to keep the cats out of the house, even though it places your sister-in-law in jeopardy. This situation could be resolved by providing the cats with their own building, such as one of the portable yard buildings sold most places, and then thoroughly blocking entrances to the house. This would be much better for your sister-in-law. The dander concentration in an enclosed space is usually much worse than it is outdoors.

Your brother might even consider the option of spaying the cats and letting them stay outside and establish a territory. This would keep the number of new cats to a minimum and it seems reasonable safe to do this in Arizona, at least from a climate standpoint. Most cats are pretty resistant to heat related problems. One problem with this approach is that the cats will be able to spread the leukemia to other cats in the neighborhood. Another ethical problem.

Your sister-in-law may want to discuss this whole situation carefully with the physician treating her asthma. Perhaps he or she will have some advice on living with this circumstance. Wetting the cats thoroughly with water once or twice a week will keep the dander down and can help with allergies quite a bit but requires cooperation on the part of the cats.

If your brother would consent to it, there is a chance that psychiatric care might help. I know that sounds sort of radical and may not be financially feasible but animal collecting is beginning to be viewed as a sort of compulsive behavior and it might actually help a lot to talk to a trained therapist.

I am not sure if any of this is advice you will find practical to use in this situation. This is a surprisingly common situation.. Some people endanger their families and some people endanger themselves but a lot of people create situations in which their behaviors place someone at risk and often seem to be unwilling or unable to stop. It happens when people keep overly aggressive dogs, when they collect large numbers of cats and keep them in unhealthy situations and it happens when allergies or asthma produce a risk of death from a pet and people choose to keep them, anyway. I wish I had an easy way to help people see the best path to take in situations like this but it is different for every person or family.

Mike Richards, DVM

Michal Response: I'm going to worry more for your sister-in-law then for your brother's feelings in this case. Allergies certainly contribute to chronic pulmonary disease. Acute Asthma attacks certainly can kill. Bottom line - keep the cats in the house..shorten wife's life. With lung disease - you can feel like your breathing through a pillow most of the time..then it get's worse.

I am also aware of how difficult it is to change destructive behaviors.

Perhaps the family can help your brother build an outside kennel for his cats. A small building for shelter and a covered fenced area connected - with climbing material and perches..think small zoo. If the family pools its resources, the cost could be kept down. Any carpenters in the family?

Michael Lebowitz, M.D., Professor of Medicine and Epidemiology at the University of Arizonia, Tucon, has done studies on the role of allergies and lung disease. Perhaps he could provide you with more information.

This is a new study - a different treatment for cat allergy. The Lung Association any be able to get it for you. *"Treatment of Cat Allergy with T cell Reactive Peptides." Philip S. Norman, et al. Am J Respir Crit Care Med 1996;154:1623-1628.

The American Lung association has a very good web site.. - or you can call 1-800-LUNG-USA.

Please don't waste time arguing - go after whatever aspect of this situation you can change.

Last edited 09/17/02


Michael Richards, D.V.M. co-owns a small animal general veterinary practice in rural tidewater Virginia. Dr. Richards graduated from Iowa State University's College of Veterinary Medicine in 1979, and has been in private practice ever since. Dr. Richards has been the director of the PetCare Forum...