Fielding D. O’Niell, DVM, MS
Diseases that humans contract from animals are termed "zoonotic". The most publicized zoonotic disease, second only to rabies, is toxoplasmosis. This infamy is due, in large part, to the training (or lack of) that physicians receive in animal diseases. Unfortunately, surveys have shown that many physicians provide inappropriate advice to their pregnant patients regarding the risk of contracting toxoplasmosis from cats. Extensive studies have failed to show any connection between toxoplasmosis and contact with cats. Pregnant women do not need to get rid of their cats. If your OB/GYN tells you so, get rid of your OB/GYN - "Free to a Good Home".
Almost fifty percent of Americans test positive for toxoplasmosis. That means we were exposed to it and are now immune. Adults and children infected with toxoplasmosis usually show no signs of illness, unless they are HIV positive or otherwise immune compromised. If a non-exposed woman becomes infected while pregnant, however, the results may be devastating to the unborn child.
Humans, like cats, contract toxoplasmosis in 1 of 3 ways: ingesting contaminated soil or water, congenital transmission to the fetus or eating undercooked meats, mainly pork, lamb or wild game. Cats that hunt are at risk of contracting toxoplasmosis. Indoor cats are not. If a cat is infected, the organism may be shed in the stool for 2 weeks. The stool is not infectious until it incubates for one to five days. After this incubation period, the infectious organism may persist in the environment for up to 8 months. Another source of exposure is gardening since feral cats may use your garden as a litter box. Likewise, children's sand boxes should be covered when not in use.
All epidemiologists that I've consulted with agree that a human's greatest risk of exposure to toxoplasmosis is handling or eating undercooked meat. My advice to pregnant women is to wear gloves when gardening, have another person clean the litter box, only eat well done meat and pet your cat often!
P.S: Mice have always been repelled by the scent of cat urine for obvious survival reasons. It's been discovered that mice infected with toxoplasma actually may be attracted to the scent of cat urine with obvious devastating results to the mouse. How could a single-cell protozoan like toxoplasma gondii engineer such a sophisticated system to ensure its survival in nature?
Darwin vs. Lamarck?