Even if the feces are scooped out, the sandbox may remain contaminated with parasites. Feeding commercial cat food and keeping your cat indoors so it cannot catch mice will prevent spread of toxoplasmosis by your cat. Having someone other than a pregnant woman clean out the litter box daily will prevent spread of toxoplasmosis by your cat. Transmission from your cat to you requires that you swallow the toxo oocysts that have incubated in your cat's feces for 1-5 days. Reasonable personal hygiene should be adequate to prevent that from occurring.
Toxoplasmosis is transmitted more commonly in the United States via poorly cooked meat than by cats.
Testing your cat's blood for toxoplasma antibodies is only meaningful if a positive test is followed 2-4 weeks later with another test. Weekly testing of your cat's feces will more directly detect a cat that is capable of transmitting toxoplasmosis.