Contributions to the Experimental Study of Epidemiology: The Effect of Vaccination on Herd Mortality

Abstract

IN several previous reports we have described the behaviour of communities of mice, submitted over long periods of time to the risks attendant on the epidemic prevalence of a bacterial infection. These communities have been recruited in ways varying both as regards the rate of immigration and the nature of the immigrants.The present report deals with an experiment in which we have studied the effect of prophylactic immunisation, with a suitable bacterial vaccine, in modifying the course of events in our experimental herds.As in many of our previous experiments, the infection selected for study was mouse typhoid, due to infection with Bact. aertrycke. There is abundant evidence that the active immunisation of mice with killed suspensions of this organism results in an increased resistance to subsequent experimental infection with living cultures (

Contributions to the Experimental Study of Epidemiology. Further Observations on the Effect of Vaccination on Herd Mortality

“…These observations are in general accord with those of Pijper and Dau (1930), who noted the development of "O," but not of "H" agglutinins in human subjects who had received typhoid vaccine by the mouth. Since, as will be seen, the advantage of the mice vaccinated per os was but little inferior to that of those vaccinated by the intraperitoneal route, the results of this experiment afford additional evidence of the preponderating role of the " " antibodies in immunity.…”

“…IN the last memoir of this series (Greenwood, Topley and Wilson, 1931) we discussed at some length the modifications of the course of herd sickness effected by immunisation of entrants to the herds. Briefly, these were our conclusions: efficient artificial immunisation (the criteria of efficiency being the usual standardising methods of a laboratory) confers a considerable temporary advantage upon mice entering an infected herd.…”

“…A certain number of mice were vaccinated each week, over and above those required for the daily additions; these were anaesthetised, bled to death from the jugular vein, and their sera tested for the presence of agglutinins. As it was known from previous experience (Topley 1929) that "H" agglutinins would almost invariably be present, 45 out of 67 specimens of serum were put up against the "0 " antigen of Bact. aertrycke only, so that it was possible to start at a low dilution of serum (1 in 5).…”

An Antigenic Basis for Virulence in Strains of Salmonella Typhimurium

“…The second category and of more immediate interest is one in which despite non-specific stimulation, which raises the titre of opsonins, and attempts at specific immunisation, the host is still susceptible to infection by the parasite. This is particularly so in the case of S. typhimurium infections of mice where the degree of protection afforded by non-specific stimuli such as lipopolysaccharides from Gram-negative bacteria, or even specific immunisation is of a very low order, and in most cases may be measured in terms of survival time rather than differences in over-all mortality (32,33). It would seem that in this latter instance there is a failure on the part of the host to respond in an immune fashion to some of the antigens of the parasite.…”

Mechanisms of Acquired Resistance in Mouse Typhoid

“…In the normal mouse rapid growth occurred, but in the vaccinated animals bacterial numbers in the peritoneal cavity declined during the first 24 hr after injection. It is interesting in this connection to review the findings of MacLeod (27) and of Greenwood, Topley, and Wilson (28) who showed that mice immunized with a heat-killed vaccine of S. typkimurium, though partially resistant to intraperitoneal challenge (27,29), were not protected against an experimental infection by the oral route (27) or a naturally acquired infection under epidemic conditions (28). These results, and the finding of ~rskov et al (30), and Seiffert et al (31) that peritonitis is not a feature of the early stages of mouse typhoid acquired by natural means, suggest that protection tests based upon intraperitoneal challenge have limited significance.…”