Why Was Malaria Used to Treat Syphilis?

Andrew Scull says doctors infected asylum patients with malaria because general paralysis of the insane, the tertiary stage of syphilis, was invariably fatal, and an Austrian doctor who had long thought fever could treat mental illness claimed the infection cured it. That doctor had tried another fever and a typhoid vaccine without success. Near the end of World War I he took blood from a captured Italian soldier with malaria and injected it into a series of patients. The cure claims were wildly exaggerated, and they were widely accepted anyway. The work won a Nobel Prize in 1927, one of only two Nobel Prizes awarded for psychiatric innovations. The other was lobotomy.

The treatment spread to Britain, Germany, and the United States. Hospitals kept vials of malarial blood, and many kept colonies of malarial mosquitoes, so a patient in a straitjacket could be bitten until malaria developed. One theory was that the fever stimulated the immune system. Another was that heating the parasite to about 105 or 106 degrees killed it. No controlled trial existed yet. Penicillin ended the practice. Once that drug existed, there was no reason to keep treating syphilis with malaria.