Syrian hamsters were shown to be susceptible to infection by the
Lyme disease spirochete Borrelia burgdorferi. Although these spirochetes did not cause any outward signs of illness in these animals, they did cause a generalized infection. Spirochetemia was present during the first 6 days of infection. At 14 days postinfection, spirochetes could be isolated from one or more of the following organs: spleen, eyes, kidneys, liver, testes, and brain. Spirochetes were isolated from the eyes and kidneys of one animal 52 days postinfection, suggesting that these organisms may cause a persistent infection. Virulence of B. burgdorferi is maintained by animal passage but is lost upon prolonged in vitro cultivation.