SEVEN-DAY FEVER 603 
between the time the mosquito })ites the patient (first to third day of 
the cHnical disease) and the period when the mosquito is infective. 
Cleland, Bradley and McDonald/ and Siler, Hall and Kitchens- have 
successfully repeated this observation. They also corroborated the 
filterability of the parasite in accordance with Ashburn and Craig's 
technique. Present indications are that dengue is transmitted l)y the 
yellow fever mosquito, during the first three days of the clinical disease, 
the insect being infective after twelve days, or thereabouts thus resem- 
bling yellow fever quite closely in these respects. The virus seems 
to be filterable, and Craig^ believes that subsequent study will reveal 
it to be a spirochete, probably quite similar to Leptospira icteroides 
which in all probability is the causative organism of yellow fever. 
RAT BITE FEVER. 
Rat bite fever, known in Japan as Sokosho, is a febrile disease 
resembling recurrent fever somewhat in its general clinical manifes- 
tations. The symptoms usually appear after the initial lesion appar- 
ently has healed; not infrequently three to five weeks may elapse 
from the time of the bite to the appearance of the first febrile attack. 
Subsecjuent ulceration at the site of the puncture may or may not occur. 
The attack usually begins with chills, followed soon by vomiting, 
an erythematous eruption, and a fever which persists for from three 
to five days. An afebrile period of equal duration followed by a second 
and even a third recurrence is characteristic. Usually an eosinophilia 
develops. Few cases have been studied postmortem. Blake, ^ how- 
ever, has studied the lesions in great detail. About 80 cases had 
been reported up to 1916. Recently 2 have been reported from New 
Orleans.^ 
Futaki, Takaki, Taniguchi and Osumi,^ and, a few weeks later, 
Ishiwara, Ohtawara and Tamura^ described a spirochete which appears 
to be the etiological agent. The organism was first obtained from a 
swollen gland in a patient bitten several weeks previously by a rat. 
It has been named Spirochseta morsus-murium. It is a rather small 
spiral organism, measuring from 2 to 4 microns in length, and about 
0.5 micron in width. A long, delicate flagellum is found at either end. 
This is best observed by the method of dark-field illumination. Kusama 
Kobayashi and Kasai** have confirmed the transmissibility of the 
organism to rats and guinea-pigs,^ and have studied the distribution 
of the organism in infected animals in great detail. They have foimd 
the spirochete in the blood during the first two weeks after infection 
and note its gradual appearance in connective tissue, the adventitia 
of the large arteries, and the parenchymatous organs. Very few are 
> Jour. Hyg., 1917-1918, 16, 367. ^ jour. Am. Med. Assn., 1925, 84, 1163. 
» Ibid., 1920, 75, 1171. 4 Jour. Exp. Med., 1916, 23, .39. 
5 Rubino: Public Health Reports, 1927, 42, 2097. 
6 Jour. Exp. Med., 1916, 23, 249. ^ Ibid., 1917, 25, 33. 
8 Jour. Infec. Dis., 1919, 24, 366. « Jour. Exp. Med., 1917, 25, 33. 
