Observations Upon the Nature of the Virus of Hog Cholera.

Abstract

Although hog cholera has been the subject of extensive investigation by immunological methods, little has appeared in the literature concerning the nature of the specific virus, aside from the discovery of DeSchweinitz and Dorset that the causal agent is filtrable through Berkefeldt and Chamberlain candles. This paper records certain observations made with the virus in the course of an experimental study. The virus in the blood of hog cholera withstands rapid desiccation over sulphuric acid, unslacked lime or other hygroscopic agents in vacuo at O° C., without its infectiousness and antigenic property being apparently affected. The resulting virus-powder may be kept in sealed glass containers for years and probably indefinitely without loss in viability, virulence and antigenicity. Though the virus in the powdered form keeps indefinitely, after it is redissolved in a suitable solvent such as normal physiological salt solution, it loses in viability and antigenic property at the same rate and under like conditions as is the case with the undesiccated virus-blood. The desiccated virus-serum can be utilized in conjunction with immune serum (desiccated or fresh) to produce an active immunity in the hog. The virus-powder is first thoroughly dissolved in the fresh immune serum or in the dissolved desiccated immune serum in the proportion of one part virus to 2 parts serum. This in vitro admixture of virus and immune sera in no way prevents the production of an active immunization of the host following its subcutaneous injection, and gives rise to no objective symptoms of infection. It has been determined by animal experiment that the virus of hog cholera at no period during the infection is intracellular, in so far as the blood cells are concerned. Repeated injections into young non-immune hogs of large quantities of the freshly washed blood cells have failed to infect.