Few diseases are at once more widespread and more baffling than the parasitic infection called toxoplasmosis. It afflicts as many as 75 million Americans (along with an astonishing half a billion persons worldwide), and though the vast majority of victims never even know they have it (the symptoms in adults are similar to those of a mild case of the flu), the effects can be devastating when the disease is contracted by a pregnant woman and passed on to her unborn child.

The reason fetuses are susceptible while their mothers are not is because they do not develop the immunity that makes the affliction relatively harmless to adults. But in unborn children, toxoplasmosis can cause severe skull deformities, total blindness and hopeless brain damage. Even worse is the fact that in some of the 500 or more babies in the U.S. each year with toxoplasmosis, the disease has a delayed-action effect. The victims may appear perfectly normal until they reach their early 20’s, when the toxoplasma cysts which have been lying dormant burst open and release thousands of parasites that can attack and destroy the cells of the eye.

When the eye is affected, the macular area of the retina is often attacked, for this seems to be the preferred site for the parasite’s multiplication. There have even been a few rare cases, notably in patients already suffering from other diseases, in which toxoplasmosis has attacked the brain and other vital organs.

For two decades, doctors have known that a major source of toxoplasmosis is raw or undercooked meat containing the cysts. Although undercooked lamb or pork are the most common hosts for toxoplasma parasite, beef seems to be a major source of contamination, particularly because of the growing popularity in many areas of “steak tartare” (ingredients: raw chopped beef, a raw egg, chopped onions, capers, and freshly ground black pepper – a kind of uncooked spicy meatball). Eating ordinary hamburgers rare may also spread the disease.

Doctors, however, have been persistently puzzled by the fact that many cases were also diagnosed in persons who had never eaten meat of any kind. Now, simultaneous evidence from researchers in the U.S. and Scotland has finally pinpointed what seems to be another relay point in the transmission of toxoplasmosis. It is the common house cat.

The intestinal tract of the cat provides not only a potential host for the tiny organisms, but a virtual breeding ground as well. Inside the feline intestine, the one celled parasites do not merely divide and attack; rather they produce male and female cells which join together to form an egg called an oocyst, inside of which eight new toxoplasma parasites develop. The oocysts remain viable in the cat’s expelled feces for an indefinite period of time and can readily contaminate the hands of gardeners, children playing in sandboxes, and particularly cat owners changing their pet’s litter boxes.

Since the only effective drugs against toxoplasmosis are extremely dangerous to the fetus, precaution seems to be the one sure way to avoid the heartbreak of losing a child, having a deformed baby, or a child who may become blind at age 20. Every pregnant woman should at all costs avoid eating raw meat. And if there is a cat in the house, send it away for a nine-month vacation.

Scientists are currently testing the possibility of giving every pregnant woman a blood test for toxoplasmosis, which could be performed routinely in late adolescence or at the time that pregnancy is first suspected.

Preliminary work has also begun on the development of a vaccine. Further research is necessary, however, before either could be applied on a widespread basis.