The infestation of rats as well as lice and many other rodents alike, infested the trenches since it was the perfect habitat for them.
INFESTATION
The trenches were thoroughly infested with rats, lice and frogs. These pests continuously sabotaged the soldier’s way of life, eating their food and passing on infections. Soldiers frequently wrote back home, and in many letters, they talked about the pests that inhabited the trenches. One soldier sent a letter home saying, “my hair was crawling with lice most of the men have been scratching and itching almost since the day we got here”.
Also, according to The Great War and Its Aftermath, the usual level of infestation on one soldier was 20 lice, and the more rare level of infestation was anywhere between 100-300 lice. Paul Baumer, a character in All Quiet on the Western Front hates the rats in the trenches. There is a moment when a “mob of fleeting rats” swarm into their dugout. The soldiers “scream and curse and start hitting out” at these rats, which showns the immense frustration that the soldiers had for these pests.
When news and letters like this would reach home, peoples glorified views on trench warfare changed dramatically.