Typhus, Body Lice, and DDT (2 of 4)   by Dr. David L. Evans, Department of Natural Sciences Pennsylvania College of Technology    
     Actually, a tiny minority of the lice had a rare characteristic that allowed them
 
 
to destroy the DDT as it entered their tiny bodies. This characteristic could be
 
 
passed from parent to child louse through the genetic material in their eggs and
 
 
sperm. The reason this ability was rare is that until DDT had been invented, it
 
 
was an absolutely useless thing to be able to do!
 
 
     Naturally, when American troops started hosing everyone down with DDT,
 
 
most lice died and typhus could not be easily spread. Water systems were
 
 
restored and people were able to clean themselves properly again and the few
 
 
lice that remained became even rarer. Nobody noticed that there were really still
 
 
a few lice around.