Abstract
Albino mice of an isolated colony in which murine lymphocytic choriomeningitis (LCM) of natural origin has been congenitally transmitted for many years were used to simulate wild house mice with a persistent tolerant infection (PTJ) in investigations on possible routes of infection of LCM-free (SPF) colonies.
For 50% of SPF contact mice to acquire infection from PTI donors of the same sex, at least a week of close contact was required when they were docile weanlings or young adults. With older aggressive mice a contact period of only 30 minutes was sufficient for 70% of the SPF contacts to become infected if involved in a fight. Bites made artificially and contamination of scarified skin with the urine or saliva of PTI mice regularly transmitted infection to SPF mice of all ages. The SPF female of an SPF x SPF mating may give birth to tolerantly infected mice if she acquires an infection early in pregnancy. This could occur through a bite or contact, and both these routes could introduce tolerant infection into a colony of SPF mice from wild PTI mice. The tolerant form of infection would then be perpetuated in the progeny of PTI females. Horizontal transmission would occur between mixed new-born PTl and SPF mice, thus introducing the risk of post-partum mated SPF foster-mothers becoming infected in early pregnancy. None of these natural infections of adults or young were clinically recognisable.