Strep suus is more common than realised in smallholders herds. The pigs respond quickly to penicillin and always recover if treated early, at later stages, the piglet needs to be given plenty of fluids, as dehydration causes most of the damage due to "salt poisoning"
Later stage pigs are often unsteady for several months but always seem to be normal by 6 months old. The herd develops an immunity once the strep infects them, the antibodies pess through the colostrum to the new piglets, the danger in an established herd, is to introduced pigs which are not immune, and cannot pass immunity to their piglets which then contract the disease.
I had a 650 sow commercial herd go down with strep meningitis, it stableised in about 2 monthsand I only lost 6 weaners through the whole transition to immune herd.