RICKETTSIA BODIES 647 
peripheral bloodvessels, transmitted h\- a tick, Dermacentor venustiis, 
and characterized by onset with a chill, continued fever, severe pains in 
the bones and muscles, headache and a macular eruption becoming 
petechial, which ajjpears first on the wrists, ankles aufl back, then over 
the whole surface of the body." The disease possesses many charac- 
teristics in common with typhus fever,i especially from the clinical 
viewpoint. The former, however, is transmitted through the tick, 
the latter by the body louse. Also the Japanese flood or river fever, 
Tsutsugamushi disease, presents many points of resemblance to 
Rocky Mountain spotted fever. The Japanese flood fever, however, 
is transmitted by the bite of the larva of an insect commonly called 
the "akanuishi mite;" the zoological name and position of this insect 
is still a subject of controversy. A principal determining factor at 
the present time of the diagnosis of the three diseases is their respective 
geographical distribution. 
Etiology. — Ricketts,'- in numerous investigations, has shown that 
the \irus of Rocky IMountain spotted fever circulates in the blood 
stream of the patient, and also that infected ticks may transmit the 
disease. He was successful in inducing infection in monkeys (Macacus 
rhesus) and guinea-pigs with the virus. Recovery from an infection 
conferred immunity to subsequent infection in experimental animals, 
and the serum of an immune animal protected a susceptible animal 
from infection. As a curati\'e agent the serum is of real value. ^ 
Ricketts observed minute diplococci or bipolar staining bodies, lan- 
ceolate in shape, and reminiscent of minute pneumococci in the blood 
of man, monkeys and guinea-pigs. Similar organisms were demon- 
strated in the tissues of infected ticks, and in the eggs deposited by 
infected ticks. These bodies were agglutinated by the serum of an 
immune animal. Attempts to cultivate these bodies were unsuc- 
cessful. Xoguchi,'' however, has cultivated bacteria which are 
morphologically similar to the Rickettsia from ticks. They are not 
pathogenic. Wolbach^ has demonstrated the parasite in sections from 
infected animals, and in infected ticks. Ticks known to be non- 
infected have never been found to harbor these parasites.*^ The 
organisms are localized chiefly in the smooth muscle fibers of blood- 
vessels exhibiting the characteristic lesions of the disease. They are 
relatively unconnnon elsewhere in the body. Only rarely are they 
demonstrable in the circulating blood. The lanceolate bodies measure 
about 0.2 to 0.3 micron in diameter, and the pair scarcely exceeds 
1 micron in length. A characteristic staining feature of the parasite 
1 See Wolbach, p. 181. 
2 Jour. Am. Med. Assn., 1906, 47, 33, 358; 1907, 49, 24, 1278. Jour. Infec. Dis., 1908, 
5, 221; Jour. Am. Med. Assn., 1909, 52, 379. 
3 Noguchi: Jour. E.xp. Med., 1923, 37, 383, 605. 
' Jour. Exp. Med., 1926, 43, 515. = Loc. cit. 
« It is stated that non-infected body lice sometimes contain bodies which resemble 
the Rickettsia, commonly believed to be the etiological agent of typhus fever. Noguchi 
(loc. cit.) has apparently cultivated at least some of these. 
