Pathogenicity of Spiroplasma sp. strain SMCA in Syrian hamsters: clinical, microbiological, and histological aspects

The intracerebral inoculation of newborn Syrian hamsters with pure cultures of Spiroplasma sp. strain SMCA caused severe, prolonged disease involving the central nervous system, culminating in death. The disease was characterized by spasms, muscular tremors, disturbances in motor control, inability to feed, dramatic loss of weight, and runting. The effect ws dose related, with the largest numbers of viable spiroplasmas producing the highest incidence of disease and death in the shortest period of time. Severe hemorrhaging developed throughout the brain, liver, and spleen, and spiroplasmas were readily recovered from these organs, indicating that the agent disseminated from the initial site of infection to distant host tissues. Newborn animals were susceptible, but adults were resistant; these findings are similar to those reported for newborn mice and rats. Unlike mice and rats, hamsters did not develop cataracts visible to the unaided eye. The histopathological features of eye disease in hamsters were different from those in rats and were characterized by microophthalmia (especially in runted hamsters) and abnormal proliferation, disorientation, and disorganization of corneal, lens, and retinal tissues. The significance of these findings is discussed.