Dear Dr. Roach: My neighbor is battling cancer for the third time. The medical personnel she sees when she goes for her chemotherapy treatments are urging her to get rid of her two cats. They claim the cats are a danger to her health. Wearing gloves and a mask while cleaning litter boxes will not help. Why? What do the cats have that can hurt someone going through chemotherapy?
A: Cancer chemotherapy frequently causes damage to the body's immune system. Many types of chemotherapy work against fast-growing cells, and while cancer cells are fast-growing, your neighbor's healthy immune system cells, especially white blood cells, are also fast-growing and can be damaged by the chemotherapy. Avoiding potentially infectious agents is therefore wise advice for people going through chemo.
There are several potential infections that can be transmitted from cats to humans. The one we worry about most is probably toxoplasmosis, a protozoan infection. Toxoplasmosis is a big concern in people with HIV, but also can be an issue in people who have recurrent chemotherapy or have a more prolonged reduction in immune system function. However, toxoplasmosis can be effectively avoided by wearing gloves while changing the litter box, keeping the cats indoors and feeding them only high-quality cat food and never raw meat.
Cat bites or scratches can be very serious, especially to someone with an immune system that is less than perfect. If her cats occasionally bite or scratch, that would be a problem.
The risks from a healthy indoor cat are very small. Risks must always be balanced against the very strong feelings people have for their pets, especially at a vulnerable time. I would not recommend separating a person from her cats without very good reason.