Horses immunized with cultures of Spirochæta icterohæmorrhagiæ yield an immune serum having therapeutic properties.
With rare exceptions the serum destroys completely the spirochetes contained in the circulating blood.
The development of antibodies is promoted by the serum injections.
The number of spirochetes in the organs is reduced by the treatment.
Secondary manifestations due to the serum are slight and disappear promptly.
The ultimate effects of the serum treatment on the symptoms and final outcome of the disease have still to be determined.