Parasites or not? Transposable elements in fruit flies

Nearly all organisms contain pieces of DNA that do not really belong to them. These "transposable elements", generally represent a drain on the persons resources and in certain cases may lead directly to disease.
       The findings were dramatic. The fruit flies contain transposable elements at a large number of sites in the genome, although many insertion sites are affected in relatively few individuals.
      most transposable elements are somehow purged before they become established. Schlötterer sums up the results by stating that "the genome is like a record of past wars between hosts and the parasitic DNA. There have been waves of attacks and the majority of them have been repelled, with only few transposable elements managing to survive and spread throughout the population."