CHAPTER XVIII
JAPANESE RIVER FEVER (SHIMA MUSHI)
Definition.— An acute endemic disease running a definite course and attended with a considerable mortality. It is characterized by the presence on the skin of an initial eschar, supervening on the bite of a species of Trombidium. This is followed by an ulcer, lymphatitis, fever, an exanthematous eruption, bronchitis, and conjunctivitis.
History.— This disease was first described by Palm in 1878, and subsequently, and more fully, by Baelz and Kawakami.
Geographical and seasonal distribution.— So far as known, shima mushi is confined to the banks of two rivers on the west side of the island of Nippon— the Shinanogawa and one of its tributaries, and the Omonagawa. Every spring these rivers inundate large tracts of country. Later in the year hemp is raised on strips of the inundated district. The crop is reaped in July and August, and it is solely among those engaged in harvesting and handling this that the disease occurs. It is not communicable by the sick to the healthy. Although transportable in the hemp to a very slight extent, it is only in limited spots here and there in the endemic districts that the virus originates.
Etiology.— The Japanese attribute this disease to the bite of a larval acarus (locally called aka mushi —red insect) resembling the Leptus autumnalis of Europe. Baelz rejects this idea, but does not explain how otherwise the virus is introduced. Men, women, and children are equally susceptible. New arrivals in infected districts are said to be the most liable. One attack does not confer immunity, although it may render subsequent attacks less
