A Method of Obtaining Large Amounts of Rickettsia Provaceki by X-ray Radiation of Rats

Abstract

Eventual interepidemic control of typhus fever will depend upon the effective sanitary utilization of the epidemiological facts now available. Even with our almost complete knowledge of transmission and animal reservoir, however, the circumstances under which typhus epidemics occur usually exclude any hope of adequate control. Students of typhus, therefore, have long felt that in this disease particularly a method of specific prophylaxis was needed.

The Rickettsia provaceki may now be accepted as the established etiological agent, and all rational methods of vaccination must be based on (1) active immunization with Rickettsia, killed, attenuated or in subinfectious doses; (2) immunization with living Rickettsia, sensitized or neutralized with convalescent or immune serum; and (3) passive prophylaxis with such serum alone.

The ideal method at which first attempts should be aimed is active immunization with killed Rickettsia material. The first fact to be ascertained is whether or not such a thing is possible.

Active immunization of guinea pigs with carbolized Rickettsia was first accomplished by da Rocha-Lima, 1 confirmed by Weigl, 2 Breinl, 3 and Rosenberger. 4 Doerr and Schnabel 5 obtained negative results, possibly, as Otto, 6 suggests, because of deterioration of their vaccines. This is rendered likely by Kemp, 7 who found that our own early vaccine material lost potency within about 4 weeks. The above writers, as well as Otto, believe that the results obtained with louse vaccines, in contrast to the negative attempts made with virulent tissues—brain, blood, etc.,—are attributable to the high concentration of Rickettsia in the louse vaccines.

In our first vaccinations with formalinized tunica material of Mexican typhus with Batchelder 8 we were encouraged chiefly by the results of Spencer and Parker 9 and of Conner 10 with Rocky Mountain Spotted Fever, which favored the belief that active immunization with dead Rickettsia was feasible provided a sufficient concentration could be attained.