Neurotropic response of Spiroplasma mirum following peripheral inoculation in the rat.

Spiroplasma mirum experimentally produces a persistent brain infection in suckling rats when administered intracerebrally. In order to examine spiroplasma infection induced by a more natural route, suckling rats were inoculated both intraperitoneally and subcutaneously with strain GT-48. No mortality was recorded over a 50-day study period. Rats developed localized alopecia and showed a significant reduction in body weight. Minimal pathological alterations were observed in brain tissues, in addition to cataracts, retinal degeneration and panophthalmitis. Spiroplasmas were recovered from brain and spleen on day 2 following peripheral inoculation with highest titres in the spleen. Spleen titres significantly declined (p less than 0.022) during the 50-day study period. On day 50, brain titres exceeded those in the spleen. The attraction of spiroplasma to central nervous system tissues may be related to its nutritional dependence on sterols.