History.—It is remarkable that so striking and communicable a disease as trench fever should have been an unrecognized entity prior to the recent war. While resembling dengue in some respects, and relapsing fever in others, as well as various well-recognized exotic fevers, there is no satisfactory account of the prior existence of such a type of fever. Werner was of the opinion that a quintan fever of the Middle Ages might have been trench fever, and it has been suggested that a quintan fever described by Hippocrates may have been of this nature, but the evidence is not convincing. Some have thought that the miliary fever reported in France from 1821 to 1855 might have been a type of trench fever since it had no mortality.
Geographical Distribution.—During the war, trench fever was reported not only in Flanders, but also among the troops fighting in Macedonia and Mesopotamia, and in the forces of the Central Powers on the German and Austrian fronts. It is remarkable that since the war this louse-borne disease seems to have disappeared, although other diseases transmitted by lice, as typhus fever and relapsing fever, continue to occur widely in Poland, Russia and the Balkans.
Etiology and Epidemiology
Etiology.—It now seems rather definitely settled that trench fever belongs to the group of diseases caused by Rickettsia bodies, and this species has been named Rickettsia quintana. Like the other organisms of the group, these bodies are very small (0.3 to 0.5 by 1.5 to 2 microns), Gram-negative, nonmotile and stain best by Giemsa’s method. As these bodies with their coccal or bipolar staining characteristics, when observed in the eggs of ticks infected with the virus of spotted fever of the Rocky Mountains, showed the so-called chromatin staining, Ricketts regarded them as chromatin-staining bacteria. Since, however, they are transmitted by an arthropodan host, we believe now that they are probably protozoal in nature.
Bradford and his colleagues stated that they were able to culture these organisms by Noguchi’s method for culturing the organism of syphilis, but Strong failed to obtain growth. As the organism of typhus fever has recently been cultured by the same method, it would appear that the trench fever organism also is cultivable. The virus is present in the whole blood, in the plasma and in the washed erythrocytes; it is nonfilterable, and withstands a temperature of 56°C. for 20 minutes but not one of 80°C. for 10 minutes. These organisms in the alimentary tract of the louse are extracellular, and not contained within the cells of the epithelium of the gut of the louse. The trench fever bodies differ from those of typhus in that they are plumper and stain more deeply with ordinary aniline dyes.
Epidemiology.—The ordinary method of transmission is by the agency of infected lice, but the disease can be produced artificially by the injection of the blood of an infected person. It is probable that urine also may be a factor in transmission, as Strong brought about infection by smearing skin abrasions with urinary sediment from trench fever cases.
It is now considered that the bite of the louse is noninfectious, although Strong succeeded in transmitting the disease by this means in five cases. The accepted explanation of the mechanism of infection is that it takes place through contamination of an abrasion or wound of the skin with louse faeces or with the juices from the crushed bodies of infected lice. In this connection, excoriations of the skin resulting from the scratching of scabies-infested areas makes a scabies patient peculiarly liable to trench fever infection. The louse faeces become infective only after seven days from the time of feeding on trench fever cases, this fact indicating a developmental cycle in the louse.
Pathology
As the disease of itself is never fatal, there have been no opportunities for studying the pathological changes.