Tropical Diseases/Chapter 18
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 severe. As yet the virus of the disease, which doubtless enters in the first instance at the site of the primary eschar, has not been discovered. Mizayima states that shima mushi is communicable to the monkey by the bite of the insect, and also by inoculation from a human patient.
Symptoms.— After an incubation period of from four to seven days the disease usually begins with malaise, frontal and temporal headache, anorexia, chills alternating with flushes of heat, and prostration. Presently the patient becomes conscious of pain and tenderness in the lymphatic glands of the groin, armpit, or neck. On inspecting the skin of the corresponding lymphatic area there is discovered— usually about the genitals or armpits— a small (2 to 4 mm.), round, dark, tough, firmly adherent eschar surrounded by a painless livid red areola of superficial congestion. Occasionally two or three such eschars are discovered. Although a line of tenderness may be traced from the sore to the swollen, hard, and sensitive glands, no well-defined cord of lymphatitis can be made out. The superficial lymphatic glands of the rest of the body, especially those on the opposite side corresponding to the glands primarily affected, are also, but more slightly, enlarged.
Fever of a more or less continued type now sets in, the thermometer mounting in the course of five or six days to 40° or 41° C. The conjunctiæ become injected, and the eyes somewhat prominent; at the same time a considerable bronchitis gives rise to harassing cough. The pulse is full and strong, ranging rather low— 80 to 100— for the degree of fever present. The spleen is moderately but distinctly enlarged, and there is marked constipation.
About the sixth or seventh day an eruption of large dark-red papules appears on the face, tending to become confluent on the cheeks. It then extends to the forearms, legs, and trunk, being less pronounced on the upper arms, thighs, neck, and palate. Simultaneously with the papules a minute lichenous eruption breaks out on the forearms and trunk. This lasts usually from four to seven days; if but slightly marked the eruption may fade in twenty-four hours.
The patients during the height of the fever are flushed, and at night, it may be, delirious. They complain incessantly, probably on account of a general hyperæsthesia of skin and muscles. Deafness is also a feature.
As the disease advances, the symptoms become more urgent; the conjunctivitis is intensified, the cough becomes incessant, the tongue dries, the lips crack and bleed, and there may be from time to time profuse perspiration. By the end of the second week— sooner or later according to the severity of the case— the fever begins to remit, the tongue to clean, and, after a few days, temperature falls to normal, and the patient speedily convalesces. Ashburn and Craig have noted a well-marked leucopenia. The red cells are normal. Diarrhoæ or diuresis may occur during the decline of the fever. The circular, sharp-edged, deep ulcer left after the separation of the primary eschar— an event which usually takes place during the second week now begins to heal, and the enlargement of the glands gradually to subside.
Such is the course of a moderately severe case. In some instances, however, the. constitutional disturbance is very slight, although the primary eschar may be well marked and perhaps extensive. On the other hand, the fever may be much more violent, and complications such as parotitis, melæna, coma, mania, cardiac failure, or œdema of the lungs may end in death. Similarly, the duration of the disease varies according to severity from one to four weeks, three weeks being about the average.
Pregnant women contracting shima mushi mostly abort and die.
The mortality in those attacked is approximately about 27 per cent.
Pathological anatomy.— Beyond evidences of bronchial catarrh, hypostatic pneumonia, enlarged spleen, perisplenitis, patchy reddening of the intestine near the ileo-cæcal valve, injection of the peritoneum, and slight enlargement of the mesenteric and superficial lymphatic glands, no noteworthy lesions have been described.
Treatment.— On the supposition that the disease is introduced by an insect, or through a wound of some sort, care should be exercised by those engaged in hemp culture in the endemic district to protect and keep clean the skin, especially that about the genitals and armpits. There is no specific remedy for the disease; treatment must therefore be conducted on general principles.