Studies on Rocky Mountain spotted fever / U.S. Treasury Department, Public Health Service.

Date:
[1930]
Catalogue details

Licence: Public Domain Mark

Credit: Studies on Rocky Mountain spotted fever / U.S. Treasury Department, Public Health Service. Source: Wellcome Collection.

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    tions can not be taken as absolute evidence of the absence of rickett- sie from the entire tick. However, it is at least reasonable to be- lieve that they were few in number, since the test ticks had all ingested blood and the rickettsia had thus been afforded, as we have shown, the most favorable conditions for multiplication and distribution throughout the various tissues. There is, of course, the possibility that they were present in an unrecognized form. CERTAIN CHARACTERISTICS OF BLOOD VIRUS 17 By R. R. SPENCER, Surgeon, and R. R. PARKER, Special Expert, United States Public Health Service The experiments outlined below suggest that some of the virus in the blood of animals infected with Rocky Mountain spotted fever is inseparable from the red and white blood cells, that it has a strong affinity for the same cells of normal animals, that it can be easily separated from the platelets, and that it exists in a form not readily demonstrated by our present methods of staining. In this connection - it is interesting to note that Kusama (quoted by Segal) and Segal (Segal, 1922), reported that the virus of typhus fever was not asso- ciated with leucocytes or erythrocytes, but with the platelets. The apparent disparity between the number of demonstrable organ- isms in the blood of animals infected with Rocky Mountain spotted fever, and the high degree of infectiousness of the same blood has often been noted. Ricketts (Ricketts 1909a), for example, saw in the blood serum of infected man, monkeys, and guinea pigs an occasional “ diplococcus- like body with an eosin-staining intermediate substance.” These bodies could be “ found in any preparation of infected blood during a search of not more than a half hour’s duration.” Ricketts has also shown that 0.7 c. c. of red cells after the tenth washing was infec- tious, while 10 c. c: of the supernatant fluid after the tenth washing was not infectious. White cells after the third washing were infec- tious in 5 c. c. amounts. Smaller amounts of cell suspensions were not injected and the amount of the dilution after each washing was not given. Wolbach (Wolbach 1919b) states that “the demonstration of the parasite in the circulating blood is extremely difficult.” . ~ Connor (Connor 1924c) by diluting spotted-fever serum five times with salt solution and centrifuging (2,000 revolutions per minute) for six hours was able to demonstrate in smears of the residue a few organisms identical with forms in tick and animal tissue described by Wolbach and Nicholson (Nicholson 1923). Connor says: “The unusual virulence of the blood (0.001 ¢. c. often being infectious) 17 Reprint No. 1105 from the Public Health Reports, vol. 41, No. 35, Aug. 27, 1926, pp. 1817-1822.