Localized Rabies Infection in Mice 1

Abstract

The common belief that rabies infection of man and animals is always fatal has been challenged recently by numerous observations. Although it has been known for many years (1, 2) that vampire bats can be carriers of rabies for long periods of time, and are able to transmit infection through bites while remaining symptomless themselves, it was considered a peculiarity of that host. Several authors (3–7) have observed that in large numbers of mice inoculated with rabies virus, a few infected ones remained well, or survived with paralysis, tremors, or general malaise. The term “abortive rabies infection,” which was first introduced by Koch (8), was adopted by Bell (6) to describe animals that survived experimental rabies infection after developing symptoms of the disease.

The first well-documented case of rabies infection in man followed by recovery was recently reported (9), that of a 6-year-old boy who was bitten by a rabid bat.

In the course of investigating survival, after inoculation with fixed or street rabies viruses, of mice previously vaccinated with the nonpathogenic Flury HEP strain of rabies, we noted that a number of animals developed a permanent paralysis of the inoculated limb, but survived for periods of over 1 year; this report presents the findings of a study of this phenomenon.

Materials and Methods. Animals. Swiss white female mice, 4–6 weeks old, were used throughout this study except for the detection and titration of HEP virus, for which newborn animals, 3–4 days old, were used.

Virus strains. Standard challenge virus (CVS), a fixed strain of rabies virus propagated in mouse brain, was obtained from the National Institutes of Health, Bethesda, Maryland. A pool of virus was prepared as a 10% mouse brain suspension in 50% serum-water.