Etiology.—In cases similar clinically to the seven-day fever of Rogers, Ido, Ito and Wani have found a spirochaete resembling that of infectious jaundice and designated Leptospira hebdomadalis. It can be differentiated from L. icterohaemorrhagiae by immunity reactions. It is found in the blood during the fever period and young guinea pigs can be infected by such blood either subcutaneously or by mouth. The organism can be cultured by Noguchi’s method. The spirochaete is to be found in the urine towards the end of the disease and the urine is probably the source of infection. In Japan field mice seem to be the carriers of this spirochaete. In about 3% of such rodents the spirochaete can be found in the urine and the disease is limited to the sections in which the field mice are found. There is practically no mortality and the treatment is symptomatic.
Sand-fly fever, and Three-day Fever
These dengue-like fevers of India are practically identical clinically with phlebotomus fever. The usual idea is that dengue epidemics are far more explosive in character than is true of epidemics transmitted by the sand-fly.
The strongest point in differentiation of sand-fly fever and dengue is that neither confers any immunity for the other disease.
The distinctions of enlarged glands and break-bone pains are often advanced as characteristic of dengue and not of sand-fly fever. I have never observed other than slight glandular enlargement in dengue cases.
Six-day Fever
Deeks has described a disease from Panama with a dengue-like clinical course.
There were but slight changes from normal in the pulse rate or blood findings. Some of the cases showed a late scarlatiniform eruption.
It was considered that the continuous fever for six days and the enlargement of the spleen, which accompanied the disease, differentiated it from dengue.