Most infected pregnant women do not have symptoms. People infected through ingestion of oocysts may be listless and have fever, enlarged lymph nodes and less commonly, inflammation of the heart. I've heard all kinds of stories about how people can get toxoplasmosis. Neither people who own cats nor veterinarians have a significantly higher risk of being infected with T. gondii than the rest of the population. In the United States, people are much more likely to become infected through eating raw meat than from handling cat feces.
People also become infected by eating unwashed fruits and vegetables.
It is unlikely you will become infected by petting an infected cat. The oocysts do not tend to stick to the fur like roundworm eggs might. The cat while grooming would generally remove any oocysts on the fur, before they become infective. It is unlikely that you can become infected through cat bites or scratches. As odd as it may seem, a healthy cat that tests positive is probably safer than a cat that tests negative.