Greg had already given some information. A quick search on the web learns me that "Trench fever" is a moderately serious disease, transmitted by lice, that infected more than a million soldiers during World War I and World War II. The disease persists even today among the homeless.
Trench fever is also called Wolhynia fever, shin bone fever, quintan fever, five-day fever, Meuse fever, His disease and His-Werner disease (after Wilhelm His, Jr. and Heinrich Werner).
It is caused by the organism Bartonella quintana, found in the stomach walls of the body louse.
The disease is classically a 5-day fever, rarely with a contiunous course instead. Latent period is relatively long (circa 2 weeks). The onset of symptoms is usually sudden with high fever, severe headache, back and leg pain and a fleeting rash. Spleen enlargement is very common (50-90% of cases). Recovery takes a month or more. Relapses are common.
Transmission of the disease to people can occur by rubbing feces of infected louse into abraded skin or into the eyes.
The article stated that traces of this disease were found on the bodies of the mass grave in Vilna which is not surprising as the condition of those unfortunate soldiers were quite awful. But I wouldn't call this eventual disease as the primary cause of their death