Duration and patterns of transmission of Theiler's mouse encephalomyelitis virus infection.

The duration and patterns of Theiler's murine encephalomyelitis virus (TMEV) transmission were studied in eight index mice inoculated orally. Transmission was monitored by testing for seroconversion to TMEV in sentinel mice in direct contact with index mice and in other sentinel mice in contact with bedding soiled by index mice. For the first 14 weeks after inoculation, two contact sentinels were housed with each index mouse for 1 week, then replaced with two new sentinels. For the remaining 16 weeks, contact sentinels were changed monthly. All index mice transmitted TMEV continuously (weekly) for 4 to 9 weeks. Thereafter, six index mice transmitted virus intermittently. All index mice ceased transmitting TMEV 7 to 22 weeks post-inoculation. Results obtained from sentinel mice in contact with bedding soiled by index mice were 86% concordant with those using contact sentinel mice. Seven index mice were treated with cyclophosphamide or hydrocortisone 30 weeks post-inoculation. One cyclophosphamide treated mouse reinitiated virus shedding.