698 TRENCH FEVER 



lar action of the heart, and a tendency to alight febrile attacks, 

 and may become chronically disabled. 



Extensive observations carried out on this affection failed to 

 show the presence of any bacterium. The first important step 

 in the elucidation of its pathology was made by M'Nee and 

 Renshaw, who showed that the disease could be transmitted to 

 a healthy individual by the intramuscular or intravenous in- 

 jection of the blood of a patient in the acute stage. In these 

 experiments the period of incubation varied considerably, namely, 

 from six to twenty-two days. They found also that the disease 

 was not transmissible by the separated serum, whereas the red 

 corpuscles repeatedly washed in saline were still infective. 

 They accordingly concluded that the infective agent was an 

 intra-corpuscular parasite which could not be demonstrated by 

 microscopic methods. 



It has recently been shown by the independent investigations 

 of a British War Office Committee working in this country and 

 an American Research Committee in France, that trench fever 

 is transmitted by means of lice, the first actual publication of 

 positive results being made by the British Committee in March 

 1918. The results of the two committees are in close agree- 

 ment, the chief point of difference being as to the exact 

 mechanism by which the louse produces the infection. The 

 British Committee made numerous attempts to transmit the 

 disease by the bites of lice which had previously fed on trench 

 fever patients, but without success. If, however, the excreta 

 of such lice were collected and dried, and inoculation with the 

 excreta was then made by scarification of the skin of healthy men, 

 they found that trench fever resulted in a considerable number 

 of cases, the period of incubation being on an average about 

 eight days. After lice are allowed to feed on a trench fever 

 patient, a period of five days at least elapses before their faeces 

 become infective, this period suggesting a cycle of development 

 in the louse, or indicating the time during which the organisms 

 multiply sufficiently to produce infection. The lice remain 

 infective for a period of at least twenty-three days after being 

 infected. It was also found that the bodies of infected lice 

 when crushed on the broken skin are capable of giving rise to 

 trench fever. Even as late as eleven weeks after the onset of 

 the disease the blood during a febrile attack may contain the 

 organism of the disease, as was shown by its capacity of infecting 

 lice — a fact in accordance with the protracted character of the 

 disease in some cases and the recrudescence of typical symptoms. 

 It was found impossible to produce infection by the excreta of 



