Zinc Sulphate as a Chemoprophylactic Agent in Experimental Poliomyelitis. ∗

Abstract

In earlier notes 1 we reported observations on the prophylactic action exercised by picric acid and certain other compounds. In this note we are reporting results which indicate that zinc sulphate applied to the nasal mucosa is even more effective than picric acid. These observations are set forth in Table I, in which the relative efficiency of the respective agents is compared in terms of the approximate per cent of animals which were protected for at least one month against repeated intranasal instillations of poliomyelitis virus.

While the number of animals in individual experiments and the mode of treatment and the intensity of the subsequent virus inoculations are not all strictly comparable, certain experiments are sufficiently alike to reveal important differences in the degree of protection, For example, in Experiment 4, in which 8 monkeys were treated with 0.5% picric, and in Experiment 7, in which 9 monkeys were treated with 0.5% zinc sulphate, but otherwise were dealt with in the same way, there is a difference amounting to 88% in favor of ZnSO₄. Furthermore, the addition of zinc sulphate to picric acid (Experiment 6) enhanced its protective value somewhat more than did the addition of alum (Experiment 5). Of significance also is the fact that zinc sulphate when used alone has afforded over 95% protection in a total of 53 animals (Experiments 7 to 13). Thus far, only 2 animals treated with zinc sulphate alone have succumbed to poliomyelitis. Six animals have survived repeated virus instillations for 3 months.

It will be noted that the protection afforded by picric acid is distinctly greater in Experiment I than in Experiments 2, 3, and 4. This is accounted for by the fact that in the latter experiments, virus was instilled intranasally almost daily during the entire month; an exposure which brought down 100% of the controls.