TRENCH FEVER 187 



take place inside the epithelial cells of the insect. This organism 

 has been found in the blood and tissues of typhus patients also. 



A great deal of dispute concerning the relationship of Rickett- 

 sia prowazeki to typhus has arisen from the fact that Rickettsia 

 also occurs in lice which could not have been infected from typhus 

 patients. It is now generally believed that there is a distinct 

 species or variety of Rickettsia, named R. pediculi, which is an 

 inhabitant of the gut of the body louse, but which is non-patho- 

 genic to man, in fact probably limited to the insect host. 



Trench Fever. This disease, which was unknown before the 

 great war, but which was one of the most important diseases 

 afflicting troops participating in it, was shown in 1918 by a com- 

 mission of the Medical Research Committee of the American 

 Red Cross and also by a British committee to be normally trans- 

 mitted by body lice (see p. 399), although the possibility of trans- 

 mission by body excretions also exists. A form of the disease 

 occurring in Central Europe was known as Volhynian fever. 



After an incubation period which is probably usually between 

 14 and 30 days, there is a sudden onset of fever accompanied by 

 headache, dizziness, muscular pains and other symptoms. The 

 fever may last continuously for several weeks, or it may be more 

 or less definitely relapsing. In most cases the spleen is enlarged, 

 and there is a rash on the back, chest and abdomen. Usually 

 the patient recovers in from five to six weeks, but the illness may 

 be greatly prolonged. 



In 1916 Toepfer first described a species of Rickettsia, R. quin- 

 tana, as occurring in lice fed on trench fever patients. This or- 

 ganism closely resembles that of typhus fever but is more con- 

 stantly rounded or diploid in form, and most writers agree that it 

 does not occur inside the epithelial cells of the gut of the louse. 

 This parasite may be merely a pathogenic variety of R. pediculi, 

 mentioned in the preceding section, which has acquired the ability 

 to thrive in human blood. In infected lice the organisms are 

 found attached to the surface of the cells of the midgut. They 

 gradually fill the lumen, and are eventually voided with the faeces. 



According to Hindle, who is inclined to regard the organisms 

 as bacteria rather than protozoa, no distinct portion of the life 

 cycle occurs in the louse, this insect merely acting as a culture 

 tube as does the flea for the bacilli of plague. The negative period 

 of four or five days after a louse becomes infected until it is ca- 



