Abstract
Unsuccessful attempts to immunize the domestic rabbit against the virus of infectious myxomatosis by means of various vaccines have been reported by Sanarelli, 1 Moses, 2 and Hobbs, 3 In this study 8 rabbits immunized with phenolized and formalized vaccines prepared from the South American myxoma virus also demonstrated no immunity.
Recently a strain of myxoma virus has been encountered in several rabbitries of Southern California (Kessel, Prouty and Meyer 4 ), and this strain has been employed in the accompanying series of vaccination experiments. All of the vaccines were made from virus in the form of fresh sterile blood collected from rabbits showing the symptoms of advanced myxomatosis, and were injected into the experimental animals by the subcutaneous route. Chemically inactivated vaccines were prepared by phenolizing and formalizing 10 and 20% solutions of the myxomatous blood. Heat was also employed as a means of inactivating the virus, and portions of the blood were heated both at 60°C for 30 minutes and at 45°C for 24 hours.
Eight animals vaccinated with heat inactivated virus proved susceptible to subsequent inoculation of living virus. Attempts to immunize rabbits with phenolized and formalized vaccine have yielded more encouraging results, and are summarized in Table I.
In addition to the above 29 control animals, 111 other unvaccinated rabbits have been inoculated with the California strain of virus in other studies in progress. Of these 150 unvaccinated animals, 5, or 3.3%, have shown partial resistance, and 2, or 1.3%, have recovered. No inoculated animals in this series have failed to develop symptoms. Thus a total of 7 unvaccinated animals, or 4.6%, as contrasted with 25.6% of vaccinated animals have exhibited either partial or complete resistance to inoculation.
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